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Summary Background Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a global threat. We therefore analysed the bacterial characteristics of CRKP infections and the clinical outcomes of patients with CRKP infections across different countries. Methods In this prospective, multicentre, cohort study (CRACKLE-2), hospitalised patients with cultures positive for CRKP were recruited from 71 hospitals in Argentina, Australia, Chile, China, Colombia, Lebanon, Singapore, and the USA. The first culture positive for CRKP was included for each unique patient. Clinical data on post-hospitalisation death and readmission were collected from health records, and whole genome sequencing was done on all isolates. The primary outcome was a desirability of outcome ranking at 30 days after the index culture, and, along with bacterial characteristics and 30-day all-cause mortality (a key secondary outcome), was compared between patients from China, South America, and the USA. The desirability of outcome ranking was adjusted for location before admission, Charlson comorbidity index, age at culture, Pitt bacteremia score, and anatomical culture source through inverse probability weighting; mortality was adjusted for the same confounders, plus region where relevant, through multivariable logistic regression. This study is registered at ClinicalTrials.gov , NCT03646227 , and is complete. Findings Between June 13, 2017, and Nov 30, 2018, 991 patients were enrolled, of whom 502 (51%) met the criteria for CRKP infection and 489 (49%) had positive cultures that were considered colonisation. We observed little intra-country genetic variation in CRKP. Infected patients from the USA were more acutely ill than were patients from China or South America (median Pitt bacteremia score 3 [IQR 2–6] vs 2 [0–4] vs 2 [0–4]) and had more comorbidities (median Charlson comorbidity index 3 [IQR 2–5] vs 1 [0–3] vs 1 [0–2]). Adjusted desirability of outcome ranking outcomes were similar in infected patients from China (n=246), South America (n=109), and the USA (n=130); the estimates were 53% (95% CI 42–65) for China versus South America, 50% (41–61) for the USA versus China, and 53% (41–66) for the USA versus South America. In patients with CRKP infections, unadjusted 30-day mortality was lower in China (12%, 95% CI 8–16; 29 of 246) than in the USA (23%, 16–30; 30 of 130) and South America (28%, 20–37; 31 of 109). Adjusted 30-day all-cause mortality was higher in South America than in China (adjusted odds ratio [aOR] 4·82, 95% CI 2·22–10·50) and the USA (aOR 3·34, 1·50–7·47), with the mortality difference between the USA and China no longer being significant (aOR 1·44, 0·70–2·96). Interpretation Global CRKP epidemics have important regional differences in patients’ baseline characteristics and clinical outcomes, and in bacterial characteristics. Research findings from one region might not be generalisable to other regions. Funding The National Institutes of Health.

Highlights • Due to the rapidly emerging SARS-CoV-2 pandemic and its tremendous public health challenges worldwide, there is a critical demand for rapid and easy to perform diagnostic assays. • The evaluated rapid antigen detection test had a high diagnostic sensitivity and specificity in respiratory samples obtained from patients who mainly presented during the first week of Covid-19. • Rapid antigen detection has the potential to become an important tool for the early diagnosis of SARS-CoV-2, particularly in situations with limited access to molecular methods., Objectives In the context of the Covid-19 pandemic, the development and validation of rapid and easy-to-perform diagnostic methods are of high priority. We evaluated a novel rapid antigen detection test (RDT) for SARS-CoV-2 in respiratory samples. Methods The fluorescence immunochromatographic SARS-CoV-2 antigen test (Bioeasy Biotechnology Co., Shenzhen, China) was evaluated using universal transport medium with nasopharyngeal (NP) and oropharyngeal (OP) swabs from suspected Covid-19 cases. Diagnostic accuracy was determined in comparison to SARS-CoV-2 real time (RT)-PCR. Results A total of 127 samples were included; 82 were RT-PCR positive. Median patients’ age was 38 years, 53.5% were male, and 93.7% were from the first week after symptom onset. Overall sensitivity and specificity were 93.9% (CI95% 86.5–97.4) and 100% (CI95% 92.1–100), respectively, with a diagnostic accuracy of 96.1% and Kappa coefficient of 0.9. Sensitivity was significantly higher in samples with high viral loads. Conclusions The evaluated RDT showed a high sensitivity and specificity in samples mainly obtained during the first week of symptoms and with high viral loads, despite the use of a non-validated sample material. The assay has the potential to become an important tool for early diagnosis of SARS-CoV-2, particularly in situations with limited access to molecular methods.

Objective. To identify socioeconomic factors associated with antimicrobial resistance of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli in Chilean hospitals (2008–2017). Methods. We reviewed the scientific literature on socioeconomic factors associated with the emergence and dissemination of antimicrobial resistance. Using multivariate regression, we tested findings from the literature drawing from a longitudinal dataset on antimicrobial resistance from 41 major private and public hospitals and a nationally representative household survey in Chile (2008–2017). We estimated resistance rates for three priority antibiotic–bacterium pairs, as defined by the Organisation for Economic Co-operation and Development; i.e., imipenem and meropenem resistant P. aeruginosa, cloxacillin resistant S. aureus, and cefotaxime and ciprofloxacin resistant E. coli. Results. Evidence from the literature review suggests poverty and material deprivation are important risk factors for the emergence and transmission of antimicrobial resistance. Most studies found that worse socioeconomic indicators were associated with higher rates of antimicrobial resistance. Our analysis showed an overall antimicrobial resistance rate of 32.5%, with the highest rates for S. aureus (40.6%) and the lowest for E. coli (25.7%). We found a small but consistent negative association between socioeconomic factors (income, education, and occupation) and overall antimicrobial resistance in univariate (p < 0.01) and multivariate analyses (p < 0.01), driven by resistant P. aeruginosa and S. aureus. Conclusion. Socioeconomic factors beyond health care and hospital settings may affect the emergence and dissemination of antimicrobial resistance. Preventing and controlling antimicrobial resistance requires efforts above and beyond reducing antibiotic consumption.

Background Antimicrobial resistance is a global health emergency. Persons colonized with multidrug-resistant organisms (MDROs) are at risk for developing subsequent multidrug-resistant infections, as colonization represents an important precursor to invasive infection. Despite reports documenting the worldwide dissemination of MDROs, fundamental questions remain regarding the burden of resistance, metrics to measure prevalence, and determinants of spread. We describe a multi-site colonization survey protocol that aims to quantify the population-based prevalence and associated risk factors for colonization with high-threat MDROs among community dwelling participants and patients admitted to hospitals within a defined population-catchment area. Methods Researchers in five countries (Bangladesh, Chile, Guatemala, Kenya, and India) will conduct a cross-sectional, population-based prevalence survey consisting of a risk factor questionnaire and collection of specimens to evaluate colonization with three high-threat MDROs: extended-spectrum cephalosporin-resistant Enterobacteriaceae (ESCrE), carbapenem-resistant Enterobacteriaceae (CRE), and methicillin-resistant Staphylococcus aureus (MRSA). Healthy adults residing in a household within the sampling area will be enrolled in addition to eligible hospitalized adults. Colonizing isolates of these MDROs will be compared by multilocus sequence typing (MLST) to routinely collected invasive clinical isolates, where available, to determine potential pathogenicity. A colonizing MDRO isolate will be categorized as potentially pathogenic if the MLST pattern of the colonizing isolate matches the MLST pattern of an invasive clinical isolate. The outcomes of this study will be estimates of the population-based prevalence of colonization with ESCrE, CRE, and MRSA; determination of the proportion of colonizing ESCrE, CRE, and MRSA with pathogenic characteristics based on MLST; identification of factors independently associated with ESCrE, CRE, and MRSA colonization; and creation an archive of ESCrE, CRE, and MRSA isolates for future study. Discussion This is the first study to use a common protocol to evaluate population-based prevalence and risk factors associated with MDRO colonization among community-dwelling and hospitalized adults in multiple countries with diverse epidemiological conditions, including low- and middle-income settings. The results will be used to better describe the global epidemiology of MDROs and guide the development of mitigation strategies in both community and healthcare settings. These standardized baseline surveys can also inform future studies seeking to further characterize MDRO epidemiology globally.

Background Carbapenem-resistant Klebsiella pneumoniae (CRKp) have become an increasing public health problem worldwide. While most CRKp around the world harbour a carbapenemase enzyme, the clinical relevance of non-carbapenemase-producing CRKp (non-CP-CRKp) is increasingly recognized. Selective digestive decontamination (SDD) has been proven successful as a decolonization strategy for patients colonized with Gram-negatives in the ICU. However, it is not regularly used to treat invasive infections. Objectives To report the use of SDD as a useful strategy for managing recalcitrant CRKp bloodstream infections. Patients and methods We present a neutropenic patient with a recalcitrant bloodstream infection with non-CP-CRKp treated with SDD. Besides, genomic analyses of five isolates of non-CP-CRKp was performed. Results After 11 days of SDD treatment with oral colistin and gentamicin, bacteraemia was successfully eradicated. Genomic analysis indicates a fully carbapenem-resistant phenotype evolved in vivo and suggests that the mechanism of carbapenem resistance in our strains relates to gene amplification of narrow-spectrum β-lactamases. Conclusions Our report highlights that SDD might be a useful strategy to manage CRKp bloodstream infections, when intestinal translocation is the likely source of the bacteraemia. In addition, the development of a resistant phenotype during therapy is worrisome as therapies directed against these organisms are likely to favour the amplification process.

Coccidioides is a primary pathogenic fungus, which infects humans through highly infectious arthroconidia, causing substantial morbidity including life-threatening disseminated infections. Due to the low infectious dose, laboratory personnel might become infected during diagnostic procedures. Accordingly, coccidioidomycosis is reported as the most frequent laboratory-acquired systemic mycosis worldwide. This risk is aggravated in non-endemic countries, where the diagnosis may not be suspected. We report on an inadvertent exposure of 44 persons to Coccidioides posadasii in a clinical microbiology laboratory in Chile, the measures of containment after rapid diagnosis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and the lessons learnt in a non-endemic setting.

Background Healthcare workers (HCWs) are at high risk of exposure to SARS-CoV-2. Cross-sectional studies have provided variable rates of seroprevalence in HCWs. Longitudinal assessments of the serological response to Covid-19 among HCWs are crucial to understanding the risk of infection and changes in antibody titers over time. We aimed to investigate seroprevalence and risk factors associated with seroconversion in a prospective cohort of HCWs during the peak of the first wave of the Covid-19 pandemic. Methods We conducted a longitudinal study among 446 front-line HCWsin a tertiary-care hospital in Chile from April to July 2020. IgG was determined monthly using two different ELISAs in serum samples of HCWs, during the three-month period. In each visit, demographic data, symptoms, risk factors, and exposure risks were also assessed. Results The overall seroprevalence at the end of the study period was 24% (95% CI20.2–28.3), with 43% of seropositive HCWs reporting no prior symptoms. Seroconversion rates significantly differed over the study period, from 2.1% to as high as 8.8% at the peak of the epidemic. There were no statistically significant differences observed between HCWs in direct clinical care of patients with Covid-19 and those working in low risk areas. Antibody titers appeared to wane over time. Conclusions HCWs were severely affected with a high rate of seroconversion that appeared to mirror the local epidemiological situation. A significant amount of participants underwent an asymptomatic infection, highlighting the need for improved surveillance policies. Antibody titers appear to wane over time; further studies to understand this finding’s impact on the risk of reinfection are warranted.

Antibiotic-resistant bacteria of critical importance for global health such as extended-spectrum beta-lactamases-producing (ESBL)-Escherichia coli have been detected in livestock, dogs, and wildlife worldwide. However, the dynamics of ESBL-E. coli between these animals remains poorly understood, particularly in small-scale farms of low and middle-income countries where contact between species can be frequent. We compared the prevalence of fecal carriage of ESBL-E. coli among 332 livestock (207 cows, 15 pigs, 60 horses, 40 sheep, 6 goats, 4 chickens), 82 dogs, and wildlife including 131 European rabbits, 30 rodents, and 12 Andean foxes sharing territory in peri-urban localities of central Chile. The prevalence was lower in livestock (3.0%) and wildlife (0.5%) compared to dogs (24%). Among 47 ESBL-E. coli isolates recovered, CTX-M-group 1 was the main ESBL genotype identified, followed by CTX-M-groups 2, 9, 8, and 25. ERIC-PCR showed no cluster of E. coli clones by either host species nor locality. To our knowledge, this is the first report of ESBL-E. coli among sheep, cattle, dogs, and rodents of Chile, confirming their fecal carriage among domestic and wild animals in small-scale farms. The high prevalence of ESBL-E. coli in dogs encourages further investigation on their role as potential reservoirs of this bacteria in agricultural settings.

Objective:To assess the impact of antimicrobial stewardship programs (ASPs) in adult medical–surgical intensive care units (MS-ICUs) in Latin America.Design:Quasi-experimental prospective with continuous time series.Setting:The study included 77 MS-ICUs in 9 Latin American countries.Patients:Adult patients admitted to an MS-ICU for at least 24 hours were included in the study.Methods:This multicenter study was conducted over 12 months. To evaluate the ASPs, representatives from all MS-ICUs performed a self-assessment survey (0–100 scale) at the beginning and end of the study. The impact of each ASP was evaluated monthly using the following measures: antimicrobial consumption, appropriateness of antimicrobial treatments, crude mortality, and multidrug-resistant microorganisms in healthcare-associated infections (MDRO-HAIs). Using final stewardship program quality self-assessment scores, MS-ICUs were stratified and compared among 3 groups: ≤25th percentile, >25th to Results:In total, 77 MS-ICU from 9 Latin American countries completed the study. Twenty MS-ICUs reached at least the 75th percentile at the end of the study in comparison with the same number who remain within the 25th percentile (score, 76.1 ± 7.5 vs 28.0 ± 7.3; P < .0001). Several indicators performed better in the MS-ICUs in the 75th versus 25th percentiles: antimicrobial consumption (143.4 vs 159.4 DDD per 100 patient days; P < .0001), adherence to clinical guidelines (92.5% vs 59.3%; P < .0001), validation of prescription by pharmacist (72.0% vs 58.0%; P < .0001), crude mortality (15.9% vs 17.7%; P < .0001), and MDRO-HAIs (9.45 vs 10.96 cases per 1,000 patient days; P = .004).Conclusion:MS-ICUs with more comprehensive ASPs showed significant improvement in antimicrobial utilization.

Made available in DSpace on 2021-06-25T12:38:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) FONDECYT National Agency for Research and Development (ANID) FONDECYT Iniciacion ANID Millennium Science Initiative/Millennium Initiative for Collaborative Research on Bacterial Resistance, MICROB-R The extensive use of antibiotics is a leading cause for the emergence and spread of antimicrobial resistance (AMR) among dogs. However, the impact of using antibiotics to treat viral infections on AMR remains unknown. In this study, we compared the prevalence of extended-spectrum cephalosporin-resistant Enterobacterales (ESCR-E) between dogs with a suspected infection of canine parvovirus (CPV) and canine distemper (CDV) before and after treatment with third-generation cephalosporins. We found a higher prevalence of ESCR-E faecal carriage in dogs suspected of CPV (37%) and CDV (15%) compared to dogs with noninfectious pathologies (9%) even prior to the start of their treatment. A 7-day course of ceftriaxone or ceftiofur administrated to CPV and CDV-suspected dogs substantially increased their ESCR-E faecal carriage during treatment (85% for CPV and 57% for CDV), and 4 weeks after the treatment ended (89% for CPV and 60% for CDV) when dogs were back in their households. Most of the observed resistance was carried by ESCR-E. coli carrying bla(CTX-M) genes. Our results suggest the need to optimize prophylactic antibiotic therapy in dogs treated for a suspected viral infection to prevent ESCR-E emergence and spread in the community. Sao Paulo State Univ, Sch Vet Med & Anim Sci, Dept Anim Prod & Prevent Vet Med, BR-18618000 Botucatu, SP, Brazil Millennium Initiat Collaborat Res Bacterial Resis, Santiago 7550000, Chile Pontificia Univ Catolica Chile, Escuela Med Vet, Santiago 8940000, Chile Univ Cayetano Heredia Peru, Fac Vet Med & Zootech, Lima 15102, Peru Univ Desarrollo, Fac Med Clin Alemana, Genom & Resistant Microbes Grp, Santiago 7550000, Chile Univ Andres Bello, Fac Ciencias Vida, Dept Ecol & Biodiversidad, Santiago 8320000, Chile Univ Andres Bello, Fac Ciencias Vida, Ctr Invest Sustentabilidad, Santiago 8320000, Chile Sao Paulo State Univ, Sch Vet Med & Anim Sci, Dept Anim Prod & Prevent Vet Med, BR-18618000 Botucatu, SP, Brazil CAPES: 001 FONDECYT: 1181167 National Agency for Research and Development (ANID) FONDECYT Iniciacion: 11181017 ANID Millennium Science Initiative/Millennium Initiative for Collaborative Research on Bacterial Resistance, MICROB-R: NCN17_081

Gut microbiota is known to be transferred from the mother to their offspring. This study determines whether the innate microbiota of rats selectively bred for generations as high alcohol drinkers play a role in their alcohol intake. Wistar-derived high-drinker UChB rats (intake 10-g ethanol/kg/day) administered nonabsorbable oral antibiotics before allowing access to alcohol, reducing their voluntary ethanol intake by 70%, an inhibition that remained after the antibiotic administration was discontinued. Oral administration of Lactobacillus rhamnosus Gorbach-Goldin (GG) induced the synthesis of FGF21, a vagal β-Klotho receptor agonist, and partially re-invoked a mechanism that reduces alcohol intake. The vagus nerve constitutes the main axis transferring gut microbiota information to the brain ("microbiota-gut-brain" axis). Bilateral vagotomy inhibited rat alcohol intake by 75%. Neither antibiotic treatment nor vagotomy affected total fluid intake. A microbiota-mediated marked inflammatory environment was observed in the gut of ethanol-naive high-drinker rats, as gene expression of proinflammatory cytokines (TNF-α; IL-6; IL-1β) was significantly reduced by nonabsorbable antibiotic administration. Gut cytokines are known to activate the vagus nerve, while vagal activation induces pro-rewarding effects in nucleus accumbens. Both alcoholics and alcohol-preferring rats share a marked preference for sweet tastes-likely an evolutionary trait to seek sweet fermented fruits. Saccharin intake by UChB rats was inhibited by 75%-85% by vagotomy or oral antibiotic administration, despite saccharin-induced polydipsia. Overall, data indicate that the mechanisms that normally curtail heavy drinking are inhibited in alcohol-preferring animals and inform a gut microbiota origin. Whether it applies to other mammals and humans merits further investigation.

Background Understanding the characteristics of the Covid-19 pandemic in different geographical regions, ethnic and socioeconomic settings are of emerging importance. This study presents the demographic and clinical features of SARS-CoV-2 infected patients in a large private healthcare center in Santiago, Chile, during the first month of the pandemic. Methods We analyzed the demographics, laboratory and clinical characteristics including severity and outcome of all patients diagnosed with Covid-19 during the first month of the pandemic. SARS-2-CoV infection was confirmed by RT-PCR in nosopharyngeal samples. The primary outcome was a composite of ICU admission or all-cause, in-hospital mortality. Clinical and laboratory parameters of hospitalized patients were analyzed regarding their association with the primary outcome. Results From March 3 to April 4, 2020, 3679 individuals were tested for SARS-CoV-2 in our hospital. Of those, 381 had Covid-19 and were included into this analysis. Most patients (99.2%) were Chileans, 12% returning from recent travel. The median age was 39 years (IQR 31–49) and 52% were female. A total of 88 patients (23.1%) were hospitalized; 18 (3.7%) required ICU and/or died. The overall mortality was 0.7%. Increased body mass index (BMI) and elevated C-reactive protein (CRP) were independently associated with ICU care or death. Conclusion During the first weeks of the pandemic in Chile, most Covid-19 patients were young, with low rates of hospitalization, ICU requirement, and fatality. BMI and CRP on admission were predictors for severity. Our data provide important information on the clinical course and outcome of Covid-19 in a Latin American setting.

The evaluated SARS-CoV-2 antigen rapid fluorescence immunoassays reliably identified patients within the first 5 days of symptom onset, when respiratory secretions carried high viral loads. This high performance suggests that these tests might play an important role for future PCR-independent strategies to detect early or infective cases.

IntroductionUnderstanding the clinical course and outcomes of patients with Covid-19 in underrepresented populations like Latin America is paramount. In this study, we report the clinical characteristics of Covid-19 in Chile, with a focus on subjects requiring hospitalization during the initial phases of the SARS-CoV-2 pandemic.MethodsThis is a single center study including all consecutive patients diagnosed with Covid-19 during the first month of the pandemic. Demographics, clinical characteristics and laboratory data were collected within 24 hours of admission. The primary outcome was a composite of ICU admission or all-cause, in-hospital mortality.ResultsDuring the first month of the pandemic, 381 patients were confirmed as positive for SARS-CoV-2 by molecular testing; 88 (23.1%) of them eventually required hospitalization. Median age of the cohort was 39 years (IQR 31-49). Overall mortality was 0.7% and 18 (3.7%) out of the 88 subjects who required hospitalization either died and/or required ICU. Increased body mass index (BMI), C-reactive protein levels (CRP) and the SaTO2/FiO2 index on admission were independently associated with a higher risk of ICU care or death.DiscussionThe lower mortality observed in our prospective cohort during the first month of SARS-Cov-2 pandemic was lower than previously reported. This finding could be due to a lower threshold for admission, a healthcare system not yet overburdened and a younger population, among other factors. BMI, CRP on admission were strong predictors for ICU care or all-cause, in-hospital mortality. Our data provide important information regarding the clinical course of Covid-19 in Latin America.

A multicenter, retrospective study of patients infected with carbapenem-resistant Pseudomonas aeruginosa who were treated with ceftolozane/tazobactam was performed. Among 35 patients, pneumonia was the most common indication and treatment was successful in 26 (74%). Treatment failure was observed in all cases where isolates demonstrated ceftolozane-tazobactam minimum inhibitory concentrations ≥8 μg/mL.

Made available in DSpace on 2021-06-25T10:55:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Faecal carriage of extended-spectrum cephalosporin-resistant Escherichia coli (ESC-R E. coli) in dogs has been reported worldwide and can reduce the effectiveness of treatments against bacterial infections. However, the drivers that influence faecal carriage of ESC-R E. coli in dogs are poorly understood. The aims of this study were to estimate the prevalence of ESC-R E. coli among dogs prior to their admission to a veterinary teaching hospital and to identify risk factors associated with the faecal carriage of ESC-R E. coli. Rectal swabs (n = 130) were collected from dogs and screened for ESC-R E. coli using MacConkey agar supplemented with cefotaxime (2 μg/mL). E. coli species was confirmed by MALDI-TOF and screening of extended-spectrum beta-lactamase (ESBL) genes was conducted by multiplex PCR. Questionnaires were completed by each dog's owner to test several human and dog characteristics associated with ESC-R E. coli. The prevalence of faecal carriage of ESC-R E. coli was 9.2 % and 67 % of ESC-R E. coli isolates harboured ESBL genes including CTX-M alone or in combination with TEM. All ESC-R E. coli isolates were resistant to ceftriaxone, cefpodoxime, and cefotaxime and were susceptible to cefoxitin and carbapenems. The likelihood of carrying ESC-R E. coli was 15 times higher (OR = 14.41 [95 % CI: 1.80−38.02], p < 0.01) if the dog was treated with antibiotics 3–12 months prior to sampling and 8 times higher (OR = 7.96 [95 % CI: 2.96−92.07], p < 0.01) if the dog had direct contact with livestock, but 15 times lower (OR = 0.07 [95 % CI: 0.01−0.32], p < 0.01) if the dog was dewormed during the previous year. Our findings confirm the faecal carriage of ESC-R E. coli in subclinical dogs and call for further investigation regarding the impact of deworming on antibiotic-resistant bacteria in companion animals. Department of Animal Production and Preventive Veterinary Medicine School of Veterinary Medicine and Animal Science Sao Paulo State University (UNESP) Millennium Initiative for Collaborative Research On Bacterial Resistance (MICROB-R) Departamento de Ecología y Biodiversidad Facultad de Ciencias de la Vida Universidad Andres Bello Centro de Investigación para la Sustentabilidad Universidad Andres Bello, Facultad de Ciencias de la Vida Genomics and Resistant Microbes Group Facultad de Medicina Clínica Alemana Universidad del Desarrollo Escuela de Medicina Facultad de Medicina Pontificia Universidad Católica de Chile Escuela de Medicina Veterinaria Pontificia Universidad Católica de Chile Department of Animal Production and Preventive Veterinary Medicine School of Veterinary Medicine and Animal Science Sao Paulo State University (UNESP)

Introduction: Antimicrobial drug resistance (AMR) is considered a serious threat to public health worldwide. The relation between AMR and human mobility, particularly international migration, has drawn attention from the scientific community in recent years. However, several aspects about this relation remain unclear. Therefore, we aimed at expanding and updating previous systematic review studies, with a novel focus on the AMR prevalence in migrants compared to the local population of the host country, to examine external validity of previous findings.Methods: We searched in Ovid MEDLINE all types of observational studies, without language or year of publication restrictions. We aimed at exploring differences in countries´ bacterial drug resistance rates based on immigration rates. All types of AMR were included, except for those related to HIV/AIDS and Tuberculosis. The comparator group of interest was the local population of the host country. The study protocol is registered with PROSPERO, number CRD42018114436. Results: After screening of 322 articles, 15 papers were selected for data extraction, including 1930 migrants. Compared to the local population, higher rates of methicillin-resistant Staphylococcus aureus, Panton-Valentine leucocidin positive strains, multidrug-resistant Gram-negative bacteria, vancomycin-resistant Enterococcus, and having at least one multidrug-resistant organism were found in migrants in 12 of the 15 papers. Rates of AMR did not differ significantly in two studies and only one of them reported a lower burden of AMR in migrants.Conclusions: Higher prevalence of AMR in migrants were presented in the majority of the included articles, addressing the emerge of the circulation of resistant strains within this group. More detailed descriptions, including time span and route taken by migrants to arrive to country of destination and length of stay by the time of inclusion are essential to gain a deeper understanding of the relation in between AMR and migration. Countries with high migration rates outside Europe should be encouraged to implement strategies for screening of both local population and migrants in countries.

In the context of the Covid-19 pandemic, the development and validation of rapid and easy-to-perform diagnostic methods are of high priority. We compared the performance of four rapid antigen detection tests for SARS-CoV-2 in respiratory samples. Immunochromatographic SARS-CoV-2 assays from RapiGEN, Liming bio, Savant, and Bioeasy were evaluated using universal transport medium containing naso-oropharyngeal swabs from suspected Covid-19 cases. The diagnostic accuracy was determined in comparison to SARS-CoV-2 RT-PCR. A total of 111 samples were included; 80 were RT-PCR positive. Median patients’ age was 40 years, 55% were female, and 88% presented within the first week after symptom onset. The evaluation of the Liming bio assay was discontinued due to insufficient performance. The overall sensitivity values of RapiGEN, Liming bio, and Bioeasy tests were 62.0% (CI95% 51.0–71.9), 16.7% (CI95% 10.0–26.5), and 85.0% (CI95% 75.6–91.2), respectively, with specificities of 100%. Sensitivity was significantly higher in samples with high viral loads (RapiGEN, 84.9%; Bioeasy, 100%). The study highlighted the significant heterogeneity of test performance among evaluated assays, which might have been influenced by the use of a non-validated sample material. The high sensitivity of some tests demonstrated that rapid antigen detection has the potential to serve as an alternative diagnostic method, especially in patients presenting with high viral loads in early phases of infection. This is particularly important in situations with limited access to RT-PCR or prolonged turnaround time. Further comparative evaluations are necessary to select products with high performance among the growing market of diagnostic tests for SARS-CoV-2.

Background: In the context of the COVID-19 pandemic, the development and validation of rapid and easy-to-perform diagnostic methods are of high priority to enable the required testing scale up in most countries. We evaluated a novel rapid antigen detection test (RDT) for SARS-CoV-2 in respiratory samples. Method: sA new fluorescence immunochromatographic SARS-CoV-2 antigen detection test (Bioeasy Biotechnology Co., Shenzhen, China) was evaluated in nasophayngeal (NP) and oropharyngeal (OP) swabs from patients with suspected COVID-19 in Santiago, Chile. Diagnostic accuracy was determined in comparison to SARS-CoV-2 real time (RT)-PCR, using the same material (universal transport medium with NP and OP swab). Findings: A total of 127 samples were included. The median patients’ age was 38 years (IQR 29·5–44), 53·5% were male, and 93·7% were in the first week after symptom onset. Among 82 RT-PCR positive specimens, 77 were correctly detected by RDT. All 45 RT-PCR negative samples were correctly identified. The overall sensitivity and specificity of the RDT were 93·9% (CI95% 86·5–97·4) and 100% (CI95% 92·1–100), respectively, with a diagnostic accuracy of 96·1% and Kappa coefficient of 0·9. Sensitivity was significantly higher in samples with increased viral loads. Interpretation: The antigen-based immunofluorescence RDT showed a high sensitivity and specificity in respiratory samples obtained from patients who mainly presented during the first week of COVID-19, despite the use of a non-validated sample. The assay was easy to use and provided results in a timely manner. It has the potential to become an important tool for early diagnosis of SARS-CoV-2, particularly in situations with limited access to molecular methods. Funding Statement: This work did not receive funding. Declaration of Interests: All authors declare no competing interests. Ethics Approval Statement: The study was approved by the local Institutional Review Board (Comite Etico Cientifico, Facultad de Medicina Clinica Alemana, Universidad del Desarrollo, Santiago, Chile) and need for informed consent was waived.

Background There is marked interest in using DNA-based methods to detect antimicrobial resistance (AMR), with targeted polymerase chain reaction (PCR) approaches increasingly being incorporated into clinical care. Whole-genome sequencing (WGS) could offer significant advantages over targeted PCR for AMR detection, particularly for species where mutations are major drivers of AMR. Methods Illumina MiSeq WGS and broth microdilution (BMD) assays were performed on 90 bloodstream isolates of the 4 most common gram-negative bacteria causing bloodstream infections in neutropenic patients. The WGS data, including both gene presence/absence and detection of mutations in an array of AMR-relevant genes, were used to predict resistance to 4 β-lactams commonly used in the empiric treatment of neutropenic fever. The genotypic predictions were then compared to phenotypic resistance as determined by BMD and by commercial methods during routine patient care. Results Of 133 putative instances of resistance to the β-lactams of interest identified by WGS, only 87 (65%) would have been detected by a typical PCR-based approach. The sensitivity, specificity, and positive and negative predictive values for WGS in predicting AMR were 0.87, 0.98, 0.97, and 0.91, respectively. Using BMD as the gold standard, our genotypic resistance prediction approach had a significantly higher positive predictive value compared to minimum inhibitory concentrations generated by commercial methods (0.97 vs 0.92; P = .025). Conclusions These data demonstrate the potential feasibility of using WGS to guide antibiotic treatment decisions for patients with life-threatening infections for an array of medically important pathogens.

Background: Estimating the burden of intestinal colonization with antibiotic-resistant gram-negative bacteria (AR-GNB) is critical to understanding their global epidemiology and spread. We aimed to determine the prevalence of, and risk factors for, intestinal colonization due to AR-GNB in population-based hospital and community settings in Chile. Methods: Between December 2018 and May 2019, we enrolled randomly selected hospitalized adults in 4 tertiary-care public hospitals (Antofagasta, Santiago, Curico and Puerto Montt), and adults residing in a community-based cohort in the rural town of Molina. Following informed consent, we collected rectal swabs and epidemiological information through a standardized questionnaire. Swabs were plated onto MacConkey agar with 2 µg/mL ciprofloxacin or ceftazidime. All recovered morphotypes were identified, and antibiotic susceptibility testing was performed via disk diffusion. The primary outcome was the prevalence of colonization with fluoroquinolone (FQ)- or third-generation cephalosporin (3GC)–resistant GNB. The secondary outcome was the prevalence of colonization with multidrug-resistant (MDR) GNB, defined as GNB resistant to ≥3 antibiotic classes. Categories were not mutually exclusive. Bivariate and multivariate analyses were performed to describe risk factors for colonization with these categories. Results: In total, 775 hospitalized adults and 357 community participants were enrolled, with a median age of 60 years (IQR, 42–72) and 55 years (IQR, 48–62) years, respectively. Among hospitalized participants, the prevalence of colonization with FQ- or 3GC-resistant GNB was 47% (95% CI, 43%–50%) and 41% (95% CI, 38%–45%), respectively, whereas the prevalence of MDR-GNB colonization was 27% (95% CI, 24%–31%). In the community setting, the prevalence of colonization with either FQ-, 3GC-resistant GNB, or MDR-GNB was 40% (95% CI, 34%–45%), 29% (95% CI, 24%– 34%), and 5% (95% CI, 3%–8%), respectively. Independent risk factors for hospital MDR-GNB colonization included the hospital of admission, unit of hospitalization (intensive care units carried the highest risk), in-hospital antimicrobial exposure, comorbidities (Charlson index), and length of stay. In the community setting, recent antibiotic exposure (Conclusions: A high burden of colonization with AR-GNB was observed in this sample of hospitalized and community-dwelling adults in Chile. The high burden of colonization with GNB resistant to commonly used antibiotics such as FQ and 3GC found in community dwellers, suggests that the community may be a relevant source of antibiotic resistance. Efforts to understand relatedness between resistant strains circulating in the community and the hospital are needed.Funding: NoneDisclosures: None

Background E. faecalis (Efc) isolates are usually susceptible to ampicillin (AMP). AMP-based regimens are the standard of care for enterococcal infections, although other antibiotics are often used as definitive treatment. We thus compared outcomes of patients with cancer and Efc bacteremia treated with AMP-containing (ACR) and non-AMP-containing antibiotic regimens (NACR). Methods A multicenter, prospective, observational cohort study conducted at MD Anderson Cancer Center, Henry Ford Hospital, and Memorial Hermann Health System. Eligible patients were ≥ 18 years old, diagnosed with cancer, and had at least one Efc bloodstream isolate collected from 12/2015 to 12/2018. Patients with polymicrobial infections were excluded. Patients were divided into two groups: i) ACR and ii) NACR. ACR included patients who received AMP at any time during treatment; other antimicrobials were permitted. NACR patients did not receive AMP at any time. The primary outcome compared desirability of outcome ranking (DOOR) between ACR and NACR at day 14. The DOOR consisted of six hierarchical levels: 1 - death; 2 - inpatient without microbiological cure (MC) and with acute kidney injury (AKI); 3 - inpatient without MC and without AKI; 4 - inpatient admitted with MC and with AKI; 5 - inpatient with MC and without AKI; 6 - alive and discharged. Comparison of DOORs between ACR and NACR was performed using inverse probability of treatment weighted (IPTW) ordered logistic regression. Results Seventy-one patients were included (ACR, n = 35; NACR, n = 36). No difference was seen in DOORs at day 14 between ACR and NACR (odds ratio [OR] 1.14, 95% Confidence Interval [CI] 0.45 – 2.92, p=0.78). No difference was observed for all-cause mortality at day 14 (OR 0.6, 95% CI 0.09 – 3.77, p=0.58) or day 30 (OR 0.42, 95% CI 0.09 – 1.94, p=0.27). Patients treated with ACR received a lower median duration of other antibiotics at any point during treatment compared to NACR: daptomycin (2 v 4 days) vancomycin (2 v 4 days), and linezolid (1 v 2 days). Conclusion Patients with cancer and Efc bloodstream infections had similar outcomes when treated with ACR and NACR. ACR were associated with less use of broad-spectrum antimicrobials. Future research should focus on the ecologic impact of use of NACR. Disclosures Marcus Zervos, MD, Melinta Therapeutics (Grant/Research Support) Cesar A. Arias, MD, MSc, PhD, FIDSA, Entasis Therapeutics (Scientific Research Study Investigator)MeMed (Scientific Research Study Investigator)Merck (Grant/Research Support)

The recent development of new antimicrobials active against carbapenemase-producing Enterobacteriales (CPE) has brought new hope for the treatment of infections due to these organisms. However, the evolving epidemiology of bacteria with carbapenemases may complicate management, as providers are faced with treating patients colonized by bacteria producing multiple carbapenemases. Here, we present the clinical course and treatment of Raoultella planticola bacteremia in a cirrhotic patient known to be colonized with both bla(KPC)- and bla(OXA-48)-carrying organisms.

Purpose of review: Vancomycin-resistant enterococci (VRE) are important nosocomial pathogens that commonly affect critically ill patients. VRE have a remarkable genetic plasticity allowing them to acquire genes associated with antimicrobial resistance. Therefore, the treatment of deep-seated infections due to VRE has become a challenge for the clinician. The purpose of this review is to assess the current and future strategies for the management of recalcitrant deep-seated VRE infections and efforts for infection control in the hospital setting. Recent findings: Preventing colonization and decolonization of multidrug-resistant bacteria are becoming the most promising novel strategies to control and eradicate VRE from the hospital environment. Fecal microbiota transplantation (FMT) has shown remarkable results on treating colonization and infection due to Clostridiodes difficille and VRE, as well as to recover the integrity of the gut microbiota under antibiotic pressure. Initial reports have shown the efficacy of FMT on reestablishing patient microbiota diversity in the gut and reducing the dominance of VRE in the gastrointestinal tract. In addition, the use of bacteriophages may be a promising strategy in eradicating VRE from the gut of patients. Until these strategies become widely available in the hospital setting, the implementation of infection control measures and stewardship programs are paramount for the control of this pathogen and each program should provide recommendations for the proper use of antibiotics and develop strategies that help to detect populations at risk of VRE colonization, prevent and control nosocomial transmission of VRE, and develop educational programs for all healthcare workers addressing the epidemiology of VRE and the potential impact of these pathogens on the cost and outcomes of patients. In terms of antibiotic strategies, daptomycin has become the standard of care for the management of deep-seated infections due to VRE. However, recent evidence indicates that the efficacy of this antibiotic is limited, and higher (10-12 mg/kg) doses and/or combination with β-lactams is needed for therapeutic success. Clinical data to support the best use of daptomycin against VRE are urgently needed. This review provides an overview of recent developments regarding the prevention, treatment, control, and eradication of VRE in the hospital setting. We aim to provide an update of the most recent therapeutic strategies to treat deep-seated infections due to VRE.

Ceftaroline (CPT) is a broad-spectrum agent with potent activity against methicillin-resistant Staphylococcus aureus (MRSA). The sequence type 5 (ST5) Chilean-Cordobés clone, associated with CPT nonsusceptibility, is dominant in Chile, a region with high rates of MRSA infections., Ceftaroline (CPT) is a broad-spectrum agent with potent activity against methicillin-resistant Staphylococcus aureus (MRSA). The sequence type 5 (ST5) Chilean-Cordobés clone, associated with CPT nonsusceptibility, is dominant in Chile, a region with high rates of MRSA infections. Here, we assessed the in vitro activity of CPT against a collection of MRSA isolates collected between 1999 and 2018 from nine hospitals (n = 320) and community settings (n = 41) in Santiago, Chile, and evaluated performance across testing methodologies. We found that our hospital-associated isolates exhibited higher CPT MIC distributions (MIC50 and MIC90 of 2 mg/liter) than the community isolates (MIC50 and MIC90 of 0.5 mg/liter), a finding that was consistent across time and independent of the culture source. High proportions (64%) of isolates were CPT nonsusceptible despite the absence of CPT use in Chile. Across methodologies, the Etest underestimated the MIC relative to the gold standard broth microdilution (BMD) test (MIC50 and MIC90 of 1 and 1.5 mg/liter, respectively). There was low (∼51%) categorical agreement (CA) between Etest and BMD results across CLSI and EUCAST breakpoints. The recent revision of CLSI guidelines abolished “very major error” (VME) from the previous guidelines (81%), which perform similarly to the EUCAST guidelines. The level of concordance between CLSI and EUCAST for BMD testing and Etest was >95%. Disk diffusion performed poorly relative to BMD under CLSI (CA, 55%) and EUCAST (CA, 36%) guidelines. Comparison of EUCAST to CLSI for disk diffusion (with EUCAST used as the reference) showed low agreement (CA, 25%; VME, 70%). In summary, CPT-nonsusceptible MRSA are dominant in clinical settings in Chile. Our results provide data to support the reevaluation of CPT breakpoints and to improve agreement across methodologies and agencies.

Se aislaron dos pares de P. aeruginosa sensible/resistente a ceftolozano/tazobactam de 2 pacientes después de la exposición a β-lactámicos. Se evaluó la base genética de la resistencia a ceftolozano/tazobactam y se evaluaron los mecanismos de resistencia a los β-lactámicos mediante ensayos fenotípicos. La secuenciación del genoma completo identificó mutaciones en AmpC, incluida la mutación (V213A) y una eliminación de 7 aminoácidos (P210–G216) en el bucle Ω. Los ensayos fenotípicos mostraron que la resistencia a ceftolozano/tazobactam en la cepa con la variante AmpCV213A se asoció con una mayor actividad de hidrólisis de β-lactamasa. Por otro lado, la eliminación de 7 aminoácidos en el bucle Ω de AmpC no mostró una actividad de β-lactamasa mejorada. La resistencia a ceftolozano/tazobactam en P. aeruginosa se asocia con cambios en AmpC; sin embargo, la aparente pérdida de actividad de β-lactamasa en AmpC∆7 sugiere que los mecanismos distintos de AmpC podrían desempeñar un papel importante en la resistencia a las combinaciones de β-lactámicos/inhibidores de β-lactamasas. Two pairs of ceftolozane/tazobactam susceptible/resistant P. aeruginosa were isolated from 2 patients after exposure to β-lactams. The genetic basis of ceftolozane/tazobactam resistance was evaluated, and β-lactam-resistant mechanisms were assessed by phenotypic assays. Whole genome sequencing identified mutations in AmpC including the mutation (V213A) and a deletion of 7 amino acids (P210–G216) in the Ω-loop. Phenotypic assays showed that ceftolozane/tazobactam resistance in the strain with AmpCV213A variant was associated with increased β-lactamase hydrolysis activity. On the other hand, the deletion of 7 amino acids in the Ω-loop of AmpC did not display enhanced β-lactamase activity. Resistance to ceftolozane/tazobactam in P. aeruginosa is associated with changes in AmpC; however, the apparent loss of β-lactamase activity in AmpC∆7 suggests that non-AmpC mechanisms could play an important role in resistance to β-lactam/β-lactamase inhibitor combinations.

Background Real-Time Reverse-Transcription Polymerase Chain Reaction (RT-PCR) is currently the only recommended diagnostic method for SARS-CoV-2. However, rapid immunoassays for SARS-CoV-2 antigen could significantly reduce the COVID-19 burden currently weighing on laboratories around the world. Methods We evaluated the performance of two rapid fluorescence immunoassays (FIAs), SOFIA SARS Antigen FIA (Quidel Corporation, San Diego, CA, USA) and STANDARD F COVID-19 Ag FIA (SD Biosensor Inc., Gyeonggi-do, Republic of Korea), which use an automated reader. The study used 64 RT-PCR characterized clinical samples (32 positive; 32 negative), which consisted of nasopharyngeal swabs in universal transport medium. Results Of the 32 positive specimens, all from patients within 5 days of symptom onset, the Quidel and SD Biosensor assays detected 30 (93.8%) and 29 (90.6%) samples, respectively. Among the 27 samples with high viral loads (Ct ≤ 25), the two tests had a sensitivity of 100%. Specificity was 96.9% for both kits. Conclusion The high performance of the evaluated FIAs indicates a potential use as rapid and PCR-independent tools for COVID-19 diagnosis in early stages of infection. The excellent sensitivity to detect cases with viral loads above ~106 copies/mL (Ct values ≤ 25), the estimated threshold of contagiousness, suggests that the assays might serve to rapidly identify infective individuals.

Background CPT is a last-generation cephalosporin active against MRSA due to its affinity for PBP2a. CPT-resistance (CPT-R) is well-described, with mutations in the active transpeptidase domain of PBP2a associated to high-level resistance. The accumulation of changes in the non-penicillin-binding domain of PBP2a has been linked to elevations of the minimal inhibitory concentration (MIC) to CPT to levels around 2-4ug/mL. PBP4 and PBP2 have also been implicated as potentially relevant mecA-independent mechanisms of CPT-R. We recently reported high rates of CPT-non-susceptibility in clinical MRSA strains from Chile. However, the mutational landscape of PBPs in clinical MRSA isolates from Chile and its relation to CPT susceptibility has not been assessed. Methods We analyzed 180 MRSA isolates collected from 2000-2018 in Santiago, Chile. Identification was confirmed by MALDI-TOF and methicillin resistance with cefoxitin disk-diffusion. CPT susceptibility was performed by BMD following CLSI-2019 guidance. Whole-genome sequencing was performed for all isolates; the mutational profile of PBPs was determined using reference sequences for PBP2 (AGY89563.1), PBP2a (NG_047938.1) and PBP4 (X91786.1). Results All isolates were phenotypically-confirmed MRSA and harbored mecA. The MIC50/MIC90 by BMD was 2/2μg/dL; only 71 (39%) isolates were CPT-susceptible (MIC Table 1. PBPs mutations compared to CPT MICs by MLST and SCCmec Conclusion Changes in the studied PBPs were frequent among MRSA circulating in Chile and were conserved among different genetic backgrounds. However, these changes were not associated with the level of CPT MIC among these isolates. Disclosures Cesar A. Arias, MD, MSc, PhD, FIDSA, Entasis Therapeutics (Scientific Research Study Investigator)MeMed (Scientific Research Study Investigator)Merck (Grant/Research Support)

Background: Antimicrobial stewardship programs (ASPs) are useful in improving clinical outcomes in a cost-effective way and in reducing antimicrobial resistance. Objective: We sought to determine the impact of ASP in adult medical-surgical intensive care units (MS-ICUs). Methods: A multicenter study, in 77 MS-ICUs of 9 Latin-American countries, was conducted along 12 months (July 2018–June 2019). A self-assessment survey using a tool based on CDC recommendations (0–100 scale) was performed at the beginning, after 6 months, and at the end of the study. The impact of ASP was evaluated monthly using the following indicators: antimicrobial consumption (defined daily doses [DDD] per 100 patient days), appropriateness of antimicrobial prescriptions (percentage of total prescriptions), crude mortality rate (events per 100 discharges), and hospital-acquired multidrug-resistant microorganisms (MDRs) and Clostridioides difficile infections (CDI events per 1,000 patient days). These indicators were compared between MS-ICUs that reached the 75th percentile and those that maintained the 25th percentile at the final self-assessment. Results: Of all indicators evaluated, only surgical prophylaxis ≤24 hours, vancomycin therapeutic monitoring, and aminoglycosides (1 dose per day) did not show significant differences between MS-ICUs at the 75th percentile and the 25th percentile. CDI events were significantly higher at the 75th percentile MS-ICUs, probably related to better detection of C. difficile (Table 1). Conclusions: This study confirmed that MS-ICUs with more comprehensive ASPs had significantly better indicators.Funding: Proprietary Organization: MERCKDisclosures: None

Background Scrub typhus is a neglected vector-borne zoonosis causing life-threatening illnesses, endemic in the Asian-Pacific region and, as recently discovered, in southern Chile. Scrub typhus is rarely reported in travelers, most probably due to the lack of clinical experience and diagnostic tests in non-endemic countries. We report the first case of imported scrub typhus in South America. Case presentation A 62-year-old tourist from South Korea presented severely ill with fever, rash, and eschar in Santiago, Chile. Laboratory exams showed thrombocytopenia and elevated inflammation parameters, hepatic enzymes, and LDH. With the clinical suspicion of scrub typhus, empirical treatment with doxycycline was initiated and the patient recovered rapidly and without complications. The diagnosis was confirmed by IgM serology and by real-time PCR, which demonstrated infection with Orientia tsutsugamushi (Kawasaki clade). Conclusions Only due to the emerging clinical experience with endemic South American scrub typhus and the recent implementation of appropriate diagnostic techniques in Chile, were we able to firstly identify and adequately manage a severe case of imported scrub typhus in South America. Physicians attending febrile travelers need to be aware of this rickettsiosis, since it requires prompt treatment with doxycycline to avoid complications.

Background. Recent studies have favored the use of cefazolin over nafcillin for the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia. The clinical influence of the cefazolin inoculum effect (CzIE) in the effectiveness of cephalosporins for severe MSSA infections has not been evaluated. Methods. We prospectively included patients from 3 Argentinian hospitals with S. aureus bacteremia. Cefazolin minimum inhibitory concentrations (MICs) were determined at standard (105 colony-forming units [CFU]/mL) and high (107 CFU/mL) inoculum. The CzIE was defined as an increase of MIC to ≥16 µg/mL when tested at high inoculum. Whole-genome sequencing was performed in all isolates. Results. A total of 77 patients, contributing 89 MSSA isolates, were included in the study; 42 patients (54.5%) had isolates with the CzIE. In univariate analysis, patients with MSSA exhibiting the CzIE had increased 30-day mortality (P = .034) and were more likely to have catheter-associated or unknown source of bacteremia (P = .033) compared with patients infected with MSSA isolates without the CzIE. No statistically significant difference between the groups was observed in age, clinical illness severity, place of acquisition (community vs hospital), or presence of endocarditis. The CzIE remained associated with increased 30-day mortality in multivariate analysis (risk ratio, 2.65; 95% confidence interval, 1.10-6.42; P = .03). MSSA genomes displayed a high degree of heterogeneity, and the CzIE was not associated with a specific lineage. Conclusions. In patients with MSSA bacteremia where cephalosporins are used as firstline therapy, the CzIE was associated with increased 30-day mortality. Clinicians should be cautious when using cefazolin as firstline therapy for these infections. Fil: Goss, William Miller. University of Texas; Estados Unidos Fil: Seas, Carlos. Universidad Peruana Cayetano Heredia; Perú Fil: Carvajal, Lina P.. Universidad El Bosque; Colombia Fil: Diaz, Lorena. Universidad El Bosque; Colombia. UTHealth McGovern Medical School; Estados Unidos Fil: Echeverri, Aura M.. Universidad El Bosque; Colombia Fil: Ferro, Carolina. Universidad El Bosque; Colombia Fil: Rios, Rafael. Universidad El Bosque; Colombia Fil: Porras, Paola. Universidad El Bosque; Colombia Fil: Luna, Carlos. Universidad de Buenos Aires. Facultad de Medicina. Hospital de Clínicas General San Martín; Argentina Fil: Gotuzzo, Eduardo. Universidad Peruana Cayetano Heredia; Perú Fil: Munita, Jose M.. Universidad del Desarrollo. Facultad de Medicina Clínica Alemana; Chile Fil: Nannini, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Inmunología Clinica y Experimental de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Instituto de Inmunología Clinica y Experimental de Rosario; Argentina Fil: Carcamo, Cesar. Universidad Peruana Cayetano Heredia; Perú Fil: Reyes, Jinnethe. Universidad El Bosque; Colombia Fil: Arias, Cesar A.. University of Texas; Estados Unidos

Staphylococcus aureus is an important pathogen causing a spectrum of diseases ranging from mild skin and soft tissue infections to life-threatening conditions. Bloodstream infections are particularly important, and the treatment approach is complicated by the presence of methicillin-resistant S. aureus (MRSA) isolates. The emergence of new genetic lineages of MRSA has occurred in Latin America (LA) with the rise and dissemination of the community-associated USA300 Latin American variant (USA300-LV). Here, we prospectively characterized bloodstream MRSA recovered from selected hospitals in 9 Latin American countries. All isolates were typed by pulsed-field gel electrophoresis (PFGE) and subjected to antibiotic susceptibility testing. Whole-genome sequencing was performed on 96 MRSA representatives. MRSA represented 45% of all (1,185 S. aureus) isolates. The majority of MRSA isolates belonged to clonal cluster (CC) 5. In Colombia and Ecuador, most isolates (≥72%) belonged to the USA300-LV lineage (CC8). Phylogenetic reconstructions indicated that MRSA isolates from participating hospitals belonged to three major clades. Clade A grouped isolates with sequence type 5 (ST5), ST105, and ST1011 (mostly staphylococcal chromosomal cassette mec [SCCmec] I and II). Clade B included ST8, ST88, ST97, and ST72 strains (SCCmec IV, subtypes a, b, and c/E), and clade C grouped mostly Argentinian MRSA belonging to ST30. In summary, CC5 MRSA was prevalent in bloodstream infections in LA with the exception of Colombia and Ecuador, where USA300-LV is now the dominant lineage. Clonal replacement appears to be a common phenomenon, and continuous surveillance is crucial to identify changes in the molecular epidemiology of MRSA.

Background Ceftolozane/tazobactam (C/T) is a novel cephalosporin/β-lactamase inhibitor combination for treating Gram-negative infections, particularly Pseudomonas aeruginosa (PA). C/T has been FDA-approved for complicated intra-abdominal and urinary tract infections and has just completed a trial in ventilator nosocomial pneumonia, but real-world outcome data are still emerging. Methods Demographic, microbiologic, treatment and outcome data of patients who received C/T for ≥48 hours from January 2016 to August 2018 at multiple centers within a single hospital system were retrospectively collected. Available isolates were analyzed for C/T susceptibility (by Etest) and whole-genome sequencing (WGS). Spades v.3.11.1 was used for assembly, multi-locus sequence typing v2.10 performed for in silico MLST with the PubMLST database and Abricate v0.7 was used for resistance gene screening with the CARD database. Results Among 45 patients, 58% were non-white, 53% were female and 13% were immunocompromised. The median age was 64 years (IQR, 50 to 69). At the time of the index event, a high proportion of patients required ICU care (42%) and pressor support (13%) as well as had invasive devices in place (64%). A minority (2.4%) had prior exposure to C/T. Respiratory infections were most common (38%) followed by urinary tract (20%). Concomitant Gram-negative agents were used in 18%. 69% achieved clinical success (i.e., recovery from infection-related signs and symptoms). The in-hospital mortality rate was 16% of which 5 out of 7 were attributed to infection. Microbiology was available for 91% of patients; 84% had PA isolates resistant to at least 3 antipseudomonal classes (Figures 1 and 2). Ten PA isolates were analyzed with WGS (Table 1). C/T resistance arose during therapy in one patient (MIC increase from 1 to 128 µg/mL). WGS showed a substitution in AmpC β-lactamase (A46D) and presence of blaCARB-2. Conclusion Although C/T was used in a critically ill population with highly resistant organisms, cure rates were high and mortality was low. Acquired β-lactamases were not frequently seen among the PA isolates. C/T is a vital therapeutic option, particularly on MDR isolates for which options are limited. Disclosures Samuel L. Aitken, PharmD, Melinta Therapeutoics: Grant/Research Support, Research Grant; Merck, Sharpe, and Dohme: Advisory Board; Shionogi: Advisory Board.

We report a case of infective endocarditis (IE) caused by ceftaroline-resistant, daptomycin-tolerant, and heterogeneous vancomycin-intermediate methicillin-resistant S. aureus (MRSA). Resistance to ceftaroline emerged in the absence of drug exposure, and the E447K substitution in the active site of PBP2a previously associated with ceftaroline resistance was identified. Additionally, we present evidence of patient-to-patient transmission of the strain within the same unit. This case illustrates the difficulties in treating MRSA IE in the setting of a multidrug-resistant phenotype.

Staphylococcus aureus is an important pathogen causing a spectrum of diseases ranging from mild skin and soft tissue infections to life-threatening conditions. Bloodstream infections are particularly important, and the treatment approach is complicated by the presence of methicillin-resistant S. aureus (MRSA) isolates. The emergence of new genetic lineages of MRSA has occurred in Latin America (LA) with the rise and dissemination of the community-associated USA300 Latin American variant (USA300-LV). Here, we prospectively characterized bloodstream MRSA recovered from selected hospitals in 9 Latin American countries. All isolates were typed by pulsed-field gel electrophoresis (PFGE) and subjected to antibiotic susceptibility testing. Whole-genome sequencing was performed on 96 MRSA representatives. MRSA represented 45% of all (1,185 S. aureus ) isolates. The majority of MRSA isolates belonged to clonal cluster (CC) 5. In Colombia and Ecuador, most isolates (≥72%) belonged to the USA300-LV lineage (CC8). Phylogenetic reconstructions indicated that MRSA isolates from participating hospitals belonged to three major clades. Clade A grouped isolates with sequence type 5 (ST5), ST105, and ST1011 (mostly staphylococcal chromosomal cassette mec [SCC mec ] I and II). Clade B included ST8, ST88, ST97, and ST72 strains (SCC mec IV, subtypes a, b, and c/E), and clade C grouped mostly Argentinian MRSA belonging to ST30. In summary, CC5 MRSA was prevalent in bloodstream infections in LA with the exception of Colombia and Ecuador, where USA300-LV is now the dominant lineage. Clonal replacement appears to be a common phenomenon, and continuous surveillance is crucial to identify changes in the molecular epidemiology of MRSA.

Treatment of severe infections caused by vancomycin-resistant enterococci (VRE) is challenging due to the scarcity of reliable therapeutic alternatives. In this context, daptomycin (DAP), a lipopeptide antibiotic, has emerged as an interesting alternative as it is one of the few compounds that retain in vitro bactericidal activity against VRE isolates, although it has not been approved for this purpose by regulatory agencies. In this review, we will summarise the clinical, animal and in vitro evidence evaluating the efficacy of DAP for the management of deep-seated VRE infections. In addition, we will address important clinical concerns such as the emergence of DAP resistance during therapy and reports of therapeutic failure with DAP monotherapy. Finally, we will discuss possible future strategies (such as the use of higher doses and/or combination therapies) to optimise the use of this antibiotic against VRE.

High-dose daptomycin (DAP) therapy failed in a neutropenic patient with bloodstream infection caused by a DAP-susceptible Enterococcus faecium (minimum inhibitory concentration, 3 µg/mL) harboring genetic changes associated with DAP resistance, with persistent bacteremia and selection of additional resistances. Daptomycin monotherapy should be used cautiously against DAP-susceptible E. faecium strains with minimum inhibitory concentrations >2 µg/mL.

En los últimos años se han desarrollado nuevas alternativas para el tratamiento de infecciones por patógenos Gram positivos multirresistentes, entre los cuales Staphylococcus aureus resistente a la meticilina (SARM) y los enterococos resistentes a la vancomicina (ERV) se consideran un verdadero reto terapéutico, y aunque el uso de la vancomicina en infecciones graves causadas por SARM ha generado serias dudas en los últimos años, continúa siendo escasa la información clínica de respaldo al uso de agentes terapéuticos que la superen en eficacia. El linezolid, la daptomicina y la tigeciclina son agentes que tienen actividad contra los cocos Gram positivos y que fueron aprobados e introducidos en la terapia clínica en la década pasada. Además, se han probado o están en las fases finales de desarrollo otros agentes como las cefalosporinas de última generación (ceftarolina y ceftobiprol). El propósito de esta revisión fue describir las nuevas alternativas terapéuticas, particularmente en la era posterior a la vancomicina, y repasar las características químicas más relevantes de los compuestos y su espectro de actividad, haciendo énfasis en sus mecanismos de acción y resistencia.

Background Carbapenem-resistant Enterobacteriaceae (CRE) are a critical global health problem. We detected a surge of CRE cases in a pediatric hospital in Chile, a country with a low endemicity of KPC-producing organisms. Herein, we describe the molecular epidemiology of this outbreak. Methods CRE isolates from clinical specimens and surveillance rectal swabs (obtained using chromID CARBA SMART agar, BioMerieux) of pediatric patients were collected from July 2015 to January 2017. Species identity was confirmed by MALDI-TOF. Carbapenemase genes (blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA-48-like) were detected by multiplex PCR, followed by amplification and sequencing of the blaKPC allele. Conjugation experiments were conducted with representative species as donors and sodium azide-resistant E. coli J53 as recipient. PCR-based plasmid typing (PBRT Diatheva kit) was then performed on donors and recipients. For K. pneumoniae, genetic relatedness was investigated by PFGE, multilocus sequence typing and wzi typing. Results Sixty-one CRE clinical and surveillance isolates were obtained from 49 patients aged 17 days to 16 years. blaKPC-2 was present in 57/62 isolates; no other carbapenemases were found. For 11 patients, multiple cultures were obtained; 4/11 had more than one KPC-harboring species. KPC-harboring isolates displayed ertapenem MICs ranging from 1 to >8 mg/L. Preliminary analyses suggest that blaKPC-2 is contained within a nonclassical Tn4401 structure (lacking the upstream promoter). Mating experiments indicate that blaKPC-2 is carried by a conjugative IncN backbone plasmid. Interestingly, K. pneumoniae isolates were nonclonal by PFGE and belonged to multiple STs unrelated to CG258 (ST34, ST36, among others) and different wzi types (37, 154, among others). Conclusion We report a multispecies outbreak of KPC-2 producing CRE in children mainly driven by horizontal dissemination of a promiscuous IncN plasmid. The nonclonal, multispecies nature of this outbreak provides insights into the complex dynamics of KPC dissemination in countries like Chile, where the clonal spread of highly successful clones like CG258 is not the predominant dissemination vehicle, and instead HGT-related spread could be playing a more important role. Disclosures All authors: No reported disclosures.

Background Daptomycin (DAP) is one of the mainstay treatments for Enterococcus faecium infections. However, development of resistance threatens its continued viability as a treatment option. Although the mechanisms of DAP resistance in enterococci are not fully comprehended, they are associated with alterations in cell envelope phospholipids assembly which leads to repulsion of the drug from cell exterior and diversion from the cell septum. Previous data suggest that combination of DAP with β-lactams has the potential to improve patient outcomes. In this investigation, we sought to evaluate combinations of DAP with ampicillin (AMP), ceftaroline (CPT), and ertapenem (ERT). Methods E. faecium R497 harboring liaSFR mutations (DAP MIC of 16 mg/L) was evaluated in a simulated endocardial vegetation (SEV) pharmacokinetic and pharmacodynamic model over 336 hours at a starting inoculum of 109 log10 CFU/g of SEV. DAP alone at 10 mg/kg/day or DAP (6, 8, 10 mg/kg/day) in combination with AMP (2 g continuous infusion), CPT 600 mg q12h or ERT 1 g q24h were evaluated. The emergence of DAP resistance was determined daily over the course of the 14-day experiment. Results DAP alone was not bactericidal and high-level DAP resistance was observed (MIC increase from 16 to 256 µg/mL) for all DAP alone regimens. Combination of DAP+AMP offered a significant reduction in log10CFU/g amounts (up to 7 log10 CFU/g and to detection limits) in 24 hours in DAP10+AMP model with no further emergence of DAP resistance. Even in DAP 6 mg/kg/day with AMP (2 g), dramatic killing with no further emergence of resistance was observed. Neither CPT nor ERT in combination with DAP was effective against this strain. At higher doses of DAP (14 mg/kg/day) + CPT or ERT, a temporary (0–48 hours) CFU/g reduction was observed followed by regrowth and the further emergence of DAP resistance. Conclusion Combination of DAP + AMP offered the most encouraging results against E. faecium R497. A DAP dose sparring effect was noted with DAP + AMP but not with CPT or ERT. The reason for the discrepancy is unknown and is under further investigation. Further evaluation of DAP plus β-lactam therapy is warranted to discover the most optimized DAP and β-lactam therapy to improve patient outcome and prevent the emergence of resistance. Disclosures B. Murray, Paratek pharmaceuticals: Consultant and Scientific Advisor, Consulting fee and Speaker honorarium; Forest/Actavis: Grant Investigator, Grant recipient; Cubist/Merck: Grant Investigator, Grant recipient. C. Arias, Merck & Co., Inc.: Grant Investigator, Research support; MeMed: Grant Investigator, Research support; Allergan: Grant Investigator, Research support; M. J. Rybak, Allergan: Consultant, Grant Investigator and Speaker’s Bureau, Research grant and Research support; Achaogen: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Bayer: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Melinta: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Merck: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Theravance: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Sunovian: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; Zavante: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support; NIAID: Consultant, Grant Investigator and Speaker’s Bureau, Consulting fee, Research grant and Research support

Background Vancomycin (VAN) is a first-line therapeutic option for severe MRSA infections, especially in Latin America where other options are limited. However, reduced susceptibility to VAN may lead to therapeutic failures. The molecular mechanisms leading the development of VAN-intermediate S. aureus (VISA) and heterogeneous-VISA (hVISA) phenotypes are still unclear. We explored genetic signatures associated with hVISA phenotype in MRSA isolates recovered from bacteremic patients in 9 Latin American countries (2011–2014) in order to develop a genomic platform to identify these isolates. Methods From 538 VAN-susceptible MRSA (MIC90 = 1 µg/mL) we identified 30 hVISA isolates using GRD and macromethod E-tests; from these, 3 were confirmed by PAP-AUC. Whole-genome sequencing was performed in all 30 isolates using Illumina platform. Based on previous studies, we selected 46 genes involved in hVISA development. Multiple Blast alignments were performed using genomes of ATCC29213 and N315 (VAN-susceptible), Mu3 (hVISA) and Mu50 (VISA) as references. Results A total of 130 changes in 46 predicted proteins belonging to 8 functional categories were determined: 48 changes related to cell wall biogenesis, 22 to DNA/RNA processing, 17 to regulatory systems, 12 to cofactors and enzymes, 11 to membrane biosynthesis, 9 to virulence, 6 to amino acid metabolism, and 5 to transport of nitrogen and putrescine/spermidine. The most common changes identified in all the hVISA were: Y38H in Atl, N16S in PBP4, S160A in RpoB, L14I in WalK and E156G in YvqF, compared with VSSA strains. The proteins with the highest number of changes detected in the isolates confirmed by PAP-AUC were: CapP, DltA, Pbp4, TcaA, LytM (Cell wall biogenesis); MutL, RpoB (DNA/RNA processing); GraS (Regulatory systems); and PgsA (Membrane biosynthesis). Conclusion Changes in genes associated with cell wall biogenesis, DNA/RNA processing, regulatory systems, and membrane biosynthesis were the most prevalent in Latin American hVISA strains. Genetic signatures in genes encoding GraR (N197S), RpoB (H481Y, H481N), VraS (I5N), WalK (L14F, R222K) and MrsR (E146K) are potentially associated with this phenotype. These changes could be used to develop a platform for possible identification of hVISA isolates. Disclosures All Authors: No reported Disclosures.

Background Vancomycin-resistant enterococci (VRE) are a major cause of nosocomial bloodstream infections. Enterococci exhibit remarkable genomic plasticity and can recombine through the acquisition of genetic material via mobile genetic elements (MGEs), including resistance genes. The accessory genome plays a major role in the evolution of enterococci within the human host. Thus, dissecting the entire genome (pan-genome) is of paramount importance to characterize the population structure of enterococci causing disease. Methods VENOUS is an ongoing prospective, observational study of adults with enterococcal bacteremia. From September 2016 to March 2018, E. faecalis (Efs) and E. faecium (Efm) were collected in 14 hospitals of a single hospital system and a major cancer center in Houston, TX, and a general hospital in Detroit, MI. Short- and long-read genomic sequencing were performed with Illumina MiSeq and Oxford Nanopore Technologies GridION X5, respectively. A proprietary bioinformatics pipeline was utilized for genome assembly and further analyses. Results 156 Efs and 98 Efm isolates from single patients were analyzed. The average proportion of core genes in each genome was 64.6% (53.0–74.1) and 49.1% (45.2–51.0) for Efs and Efm, respectively. The vanA gene cluster was identified in 5.1% (8/157) of Efs and 57.1% (56/98) of Efm. The plasmid-encoded aac(6′)-Ie-aph(2″)-Ia gene conferring high-level resistance to aminoglycosides was found in 37.6% (59/157) Efs, seven of which also possessed vanA. Long-read sequencing of vanA-harboring plasmids from a subset of VRE revealed that the vanA cluster was carried in plasmids ranging from 31.7 to 132.3 kb. Although the vanA operon was fairly conserved, insertions of MGE were identified in the intergenic regions of vanS/vanH and vanX/vanY. Furthermore, a variety of MGE insertions mediated integration of the vanA operon, including IS1216 and IS256 (figure). Conclusion Accessory genes, including AMR genes, comprise a significant proportion of the enterococcal pan-genome, indicating major genetic plasticity within these organisms. Acquired resistance genes seem to have a high degree of recombination and play a substantial role in the expansion of the genomic repertoire in clinical isolates. Disclosures Samuel L. Aitken, PharmD, Melinta Therapeutics: Grant/Research Support, Research Grant; Merck, Sharpe, and Dohme: Advisory Board; Shionogi: Advisory Board.

Background The widespread dissemination of carbapenem-resistant (CR) P. aeruginosa and Enterobacteriaceae has created a major global public health crisis. C/T is a recently approved therapeutic which consists of the combination of a novel cephalosporin (ceftolozane) and tazobactam (a β-lactamase inhibitor). C/T has shown good activity against a wide range of multidrug-resistant (MDR) Gram negatives, being particularly interesting as an alternative for MDR P. aeruginosa. We aimed to determine the activity of C/T against clinical strains of Enterobacteriaceae and P. aeruginosa recovered in 4 large clinical centers from Chile. Methods We analyzed 434 isolates of Enterobacteriaceae (347 E. coli, 66 K. pneumoniae, 21 Enterobacter cloacae complex) and 57 P. aeruginosa collected during 2017 from 4 tertiary care institutions in Santiago, Chile. Identification was performed as per each local clinical microbiology lab. Susceptibility testing was performed by broth microdilution using customized Sensititre plates (Trek). Carba-NP was performed to screen for carbapenemase production. Susceptibilities were analyzed as per 2019 CLSI breakpoints. Results The MIC50/90 for C/T against Enterobacteriaceae and P. aeruginosa were 1/4 μg/mL and 2/16 μg/mL, respectively. In Enterobacteriaceae, susceptibility to C/T reached 92% in E. coli (Figure 1A), 91% in E. cloacae complex (Figure 1B) and 70% in K. pneumoniae (Figure 1C). Remarkably, C/T remained active against 58% (33/57) of CR Enterobacteriaceae (Figure 2A). Among Carba-NP-negative CR isolates (46%, 26/57), susceptibility to C/T was 54% (Figure 3 A–C). In P. aeruginosa, the overall susceptibility to C/T was 81% (Figure 1D), maintaining activity against 69% (25/36) of CR strains (Figure 2B). Importantly, susceptibility to C/T in CR P. aeruginosa isolates with a negative Carba-NP (67%, 24/36) was 83% (20/24) (Figure 3D). Conclusion In this multicenter study, we observed that C/T was highly active against clinical isolates of Enterobacteriaceae and P. aeruginosa. Of note, C/T remained active against a large proportion of CR clinical strains. Moreover, the activity of C/T was particularly high against CR P. aeruginosa isolates with a negative Carba-NP. Disclosures All authors: No reported disclosures.

We sought to determine the association between previous daptomycin exposure and daptomycin non-susceptible Enterococcus faecium (DNSEf) bloodstream infections (BSI) in adult leukemia patients.We retrospectively identified adult (≥18 years old) leukemia patients with Enterococcus spp. bacteremia at The University of Texas MD Anderson Cancer Center (MDACC) from 6/1/2013 to 7/22/2015. Antimicrobial susceptibility and previous antibiotic exposure within the 90 days prior to bacteremia were collected. Classification and Regression Tree (CART) analysis was used to identify the most significant breakpoint between daptomycin exposure and DNSEf.Any amount of daptomycin received within the 90 days preceding BSI was significantly associated with isolation of DNSEf compared to daptomycin susceptible E. faecium (DSEf) (88% vs. 44%, respectively, p 0.01). CART analysis identified receiving ≥13 days of daptomycin in the preceding 90 days as most significantly correlated with DNSEf (60% vs. 11%, relative risk [RR] 5.31, 95% Confidence interval [CI] 2.36-11.96, p 0.01).Prior daptomycin exposure for ≥13 days within 90 days preceding BSI was significantly associated with isolation of DNSEf BSI in adult leukemia patients at our institution. Antimicrobial stewardship initiatives aimed at minimizing daptomycin exposure in high-risk patients may be of significant benefit in limiting the emergence of DNSEf.

Background Ceftolozane-tazobactam (CT) is a newly approved cephalosporin/β-lactamase inhibitor combination with excellent in vitro activity against multidrug-resistant (MDR) P. aeruginosa. Unfortunately, CT-resistance (CT-R) has already been reported. In this work, we evaluate mutational pathways associated with high level of CT-R and assess the role of AmpC in a clinical strain-pair of MDR P. aeruginosa. Methods A CT susceptible isolate of P. aeruginosa (2365) and its CT-R derivatives (2366 and 2367) were recovered from the infected device of a patient before and after treatment with CT. Minimum inhibitory concentrations (MICs) to CT were determined by Etest. Resistance mediated by AmpC hyperproduction was evaluated using ceftazidime (CAZ) and meropenem (MER) with and without cloxacillin (CLOX) at concentration of 1 mg/ml. In addition, the β-lactamase hydrolysis activity was determined for crude cell lysate of the isolates using a spectrophotometric assay for nitrocefin degradation. Furthermore, whole genome sequencing of the three strains was performed and compared (2365 vs. 2366 and 2367). Reads from each isolate were mapped against the genome of the reference strain PAO1. Variants identified by GATK, SamTools and CLC Genomics Workbench 8.5 were selected and annotated with SnpEff. Results Strain 2365 had a CT MIC of 0.75 mg/ml while 2366 and 2367 have MICs > 256 mg/ml. AmpC hyperproduction test was positive only for the susceptible isolate (2365). In concordance, the hydrolysis assay showed a lack of nitrocefin degradation by CT-R 2366 compared with its CT-susceptible isolate 2365. Notably, the three strains (S and R) exhibited a truncated AmpD. Comparison of the resistant derivatives vs. 2365 and 2367 showed a 7 amino acid deletion in the Ω-loop of the β-lactamase AmpC in both resistant derivatives and mutations in genes predicted to encode a hypothetical protein, an ABC transporter ATP-binding protein and a multidrug resistance operon repressor MexR. Conclusion Our results suggest that the deletion in the Ω-loop of AmpC in 2366 and 2367 does not contribute to CT-R in these P. aeruginosa strains. Further characterization of AmpC and other predicted proteins identified by WGS are needed to determine the mechanism of CT-R. Disclosures All authors: No reported disclosures.

Background MRSA-USA300 is a community-associated clone that has spread worldwide, becoming the most successful clone in the USA. Since 2005, the MRSA-USA300 Latin-American Variant (USA300-LV) has disseminated in community and hospitals in Northern South America. Phylogenetic analysis revealed that USA300-LV is not derived from the USA300 (NA-USA300) but rather, the two clones diverged from a common ancestor. During their evolution, NA-USA300 strains incorporated the ACME element and USA300-LV acquired a copper and mercury resistance mobile element designated COMER. Interestingly, contamination by heavy metals in South American has been recently highlighted and could be driving the selection of resistant genetic lineages. We investigated the frequency of merA, merB, and copB in genomes of clinical isolates of S. aureus from Latin America (LA). Methods The presence of merA/merB and copB encoding mercury and copper resistance, respectively, were investigated in 515 S. aureus sequenced genomes recovered from bacteremic patients in hospitals from nine Latin American hospitals trough BLAST searches. Results The prevalence of merAB in S. aureus was 35% (181 out of 515 genomes). Interestingly, among 181 merAB-positive S. aureus, 174 were MRSA (96%). Moreover, 71%, 60%, 59%, and 51% of MRSA genomes from Peru, Ecuador, Colombia, and Venezuela, respectively, harbored mercury resistance genes. Similarly, 65%, 60%, and 22% of MRSA genomes from Ecuador, Colombia, and Venezuela, contained the copB gene. Among 174 MRSA harboring merAB, ST8 and ST5 were the most predominant lineages in (43% and 45% of genomes, respectively). In contrast, among 95 MRSA carrying copB, ST8 was the most frequent lineage (96% of isolates). MRSA from countries with high prevalence of mercury genes showed association with ST5 and ST8. 88% of Colombian and 87% of Ecuadorian MRSA harboring merAB belonged to ST8 lineage, whereas ST5 was predominant in 88% of Peruvian MRSA. In Venezuela, ST5 and ST8 were found in 44% and 33%, respectively, of MRSA positive for merAB. Conclusion High levels of mercury in rivers of Colombia, Ecuador and Peru has been reported. Thus, the prevalence of heavy metal resistance genes in MRSA clinical isolates suggest an adaptation of endemic genotypes to heavy metal contamination caused by activities like metal mining. Disclosures J. M. Munita, Pfizer: Grant Investigator, Research grant. C. Arias, Merck & Co., Inc.: Grant Investigator, Research support. MeMed: Grant Investigator, Research support. Allergan: Grant Investigator, Research support.