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Background Infections due to Gram-negative pathogens that cause gastrointestinal illnesses are a significant cause of morbidity in children. The contemporary clinical and epidemiological features of pediatric Shigella spp. infections in urban cities in the United States are not well described. Methods We used a retrospective cohort of patients (0-18 years of age) from a network of hospitals in Houston, TX. Only patients with Shigella spp. isolated from clinical samples dated from 2016 to 2021 were included in the study. Demographic, clinical, and microbiological data and susceptibility profile were extracted from the medical record. Results We identified a total of 73 pediatric patients with Shigella spp. Infections. The median age at presentation was 5 years. Hospital admission occurred in 32 % of infections with a median length of stay of 1 day (Table 1). Of cases with available clinical data, 80% of patients with Shigella spp. infections reported fever (Table 2). Of note, 62% of patients developed bloody diarrhea (Table 2). The majority of patients infected with Shigella flexneri (4/7) reported a history of international travel. Seizures were observed in 5 patients. No episodes of bacteremia were identified. Among patients with an identified exposure, daycare attendance and contact with individuals experiencing similar symptoms were the most common (Table 2). The majority of Shigella species were S. sonnei (90.4%) (Table 3). Resistance to trimethoprim-sulfamethoxazole (TMP-SMX) was common (45/68, 66%) among Shigella spp. isolates tested. No resistance to third generation cephalosporins was observed. (Table 3). Although azithromycin was the most common antibiotic used for treatment, susceptibility testing for this antibiotic was not performed in any of the cases. Conclusion Infections due to Shigella spp. are a significant burden among pediatric patients in a major metropolitan health care system (Houston, TX). Bloody diarrhea was the most common presentation, although the presence of Shiga-toxin-positive isolates was unknown. The observed high frequency of resistance to TMP-SMX and emergence of multi-drug resistant Shigella spp. in other countries warrants continued surveillance. Disclosures Cesar A. Arias, MD, PhD, Entasis Phramceuticals: Grant/Research Support|MeMed Diagnostics: Grant/Research Support|Merck: Grant/Research Support.

Background Staphylococcus argenteus (SAR) is a novel species within the S. aureus (SAU) complex. SAR has been misidentified as SAU but has been increasingly reported worldwide as a pathogen. This study evaluated the prevalence of SAR causing bloodstream infection (BSI) in US centers, and the phenotypic, genotypic, and clinical outcomes associated with SAR BSI. Methods 785 SAU (326/459 MRSA/MSSA) from blood cultures (BC) of patients in 31 sites located in all 9 US Census Divisions during the SENTRY Antimicrobial Surveillance Program for 2019 were included. Isolates were screened for SAR by multiplex PCR. Isolates were subjected to MALDI-TOF and susceptibility (S) testing using the CLSI method. Isolates were subjected to genome sequencing, followed by DNA analysis. Results 0.4% (3/785) SAR were detected and originated from Milwaukee (12 yo female; patient 1), Houston (64 yo male; patient 2), and Seattle (21 yo male; patient 3). Patient 1 had a SAR recovered from BC 10 days after admission, but additional clinical information was not available. Patient 2 had end-stage renal disease and was admitted due to MRSA bacteremia/endocarditis, along with septic embolism in the lungs and brain. SAR grew from BC on day 4 and vancomycin was prescribed; the patient died on day 24. Patient 3 presented fever and chills in the 24 hours pre-admission, with a medical history significant for catheter-associated BSI. SAR was cultured from BC upon admission, and the patient received linezolid (5 days), but BCs remained positive. The central line was removed, and BCs cleared thereafter. MALDI-TOF generated highest scores for SAR for all 3 strains, but scores ≥2.0 were also obtained for SAU and S. schweitzeri. SAR (ST2198) from patient 1 was S to all agents tested, as were the other 2 strains (ST2250 and ST1223), except for oxacillin. The latter 2 strains carried SCCmec type IV(2B) and a dfrG was also detected in the ST2250 lineage strain. All 3 strains carried multiple virulence genes. Conclusion Low prevalence of SAR causing BSI was observed in US hospitals in 2019; however, SAR can clearly cause invasive infections. ST2250 has predominantly been detected in the USA and Canada, but this study showed distinct lineages causing BSI, including strains carrying mecA and various virulence genes. Disclosures Rafael Mendes, BS, JMI Laboratory: Grant/Research Support Lalitagauri M. Deshpande, PhD, Melinta: Grant/Research Support|Pfizer: Grant/Research Support Cecilia G. Carvalhaes, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support.

Background Staphylococcus lugdunensis (SL) is a coagulase negative staphylococci (CoNS) demonstrating more virulent pathogenicity compared to other CoNS. With implementation of rapid diagnostics such as multiplex PCR on blood culture and use of MALDI-TOF (MALDI), CoNS can now be routinely specifically identified as SL. We sought to describe the antibiotic susceptibility of SL over time, and to utilize whole genome sequencing (WGS) to identify the characteristics of oxacillin (OXA) resistant SL. Methods Retrospective review of all culture isolates positive for SL from two major hospital systems, Memorial Hermann Hospital System (MHHS) and Baylor St. Lukes Medical Center (BSLMC) in Houston, TX. MALDI was implemented in 2016 at BSLMC and 2019 at MHHS. MHHS utilizes Microscan®, and BSLMC utilizes Vitek2® for susceptibility testing. For this study, all duplicated isolates within a 2-week period were excluded. Six patient isolates, three OXA resistant and three susceptible, were sent for WGS and analysis. Results Between 2014 and 2021, 744 culture isolates were identified as SL, 325 from MHHS and 419 from BSLMC (Fig 1). An increasing trend was observed at MHHS over time, however this trend was not observed at BSLMC. 83.6% (622/744) of isolates were susceptible to OXA. An overall trend towards increasing resistance was observed over time (Fig 2). Six isolates, three OXA susceptible (S) and three resistant (R), were sent for WGS. The R isolates were found to share the same sequence type (ST3), and while they were not clonal, were closely related and all harbored an SCCmec cassette most closely related to SCCmec type IVg. Conclusion In our study, an increasing number of isolates were identified at MHHS over time. This finding may be related to implementation of MALDI. Overall OXA susceptibility was lower than expected at 83.6%, when compared to a prior large-scale United States based study in 2017 demonstrating 95.3% susceptibility. This finding of developing resistance is concerning. While WGS analysis of R isolates did not demonstrate clonality, it did show close relation. This data may suggest expansion of an emerging lineage, however more isolates will need to be studied for conclusion given limited sample size. Disclosures All Authors: No reported disclosures.

Soon after commencement of the SARS-CoV-2 disease outbreak of 2019 (COVID-19), it became evident that the receptor-binding domain of the viral spike protein is the target of neutralizing antibodies that comprise a critical element of protective immunity to the virus. This study addresses the relative lack of information regarding actual antibody concentrations in convalescent plasma samples from COVID-19 patients and extends these analyses to post-vaccination samples to estimate protective IgG antibody (Ab) levels. Both sample populations were similar and a protective Ab level of 7.5 µg/ml was determined, based on 95% of the normal distribution of the post-vaccination population. The results of this study have implications for future vaccine development, projection of protective efficacy duration, and understanding of the immune response to SARS-CoV-2 infection.One-Sentence SummaryUsing two quantitative immunoassays, we have found similar IgG antibody responses to the SARS-CoV-2 spike protein in populations of COVID-19 survivors and vaccine recipients that indicate a protective antibody concentration.

Historically, children evaluated for vomiting and diarrhea secondary to viral enteritis have symptoms lasting 2–4 days and respond to supportive care, including oral rehydration and anti-emetics if required. Recently, within a 14-day timespan, we encountered three children with severe diarrhea who rapidly became dehydrated and went into hypotensive shock. Although SARS-CoV-2 molecular tests were negative by nasopharyngeal swab, all were later found to have MIS-C. This small case series underscores features reported in previous larger studies and emphasizes the rapid clinical evolution of this condition. We highlight the importance of early recognition of cardinal laboratory findings characteristic of MIS-C (i.e., lymphopenia, markedly elevated acute phase reactants, and hypoalbuminemia). We also show serologic evidence that the pathophysiological mechanism of SARS-CoV-2 related diarrhea may differ from other causes of dehydrating vomiting and diarrhea, with no serologic evidence of villus cell injury.

As a class, β-lactamase inhibitors have proved successful in extending the clinical utility of β-lactam antibiotics by circumventing β-lactamase-mediated resistance. However, the rapid evolution of these β-lactamases calls for a critical reevaluation of the relationships between susceptibility, drug exposures, and bacterial response. The existing paradigm for in vitro susceptibility testing and development of β-lactam/β-lactamase inhibitor combinations may not optimally facilitate clinical use. Thus, alternative approaches for pairing these combinations and evaluating in vitro susceptibility are needed to provide better guidance to clinicians.

Background Salmonella spp. Infections are a significant cause of morbidity in children in the United States. Contemporary clinical and microbiological characteristics of pediatric Salmonella infections in urban cities are not well described. Methods We used a retrospective chart review of records (0-18 years of age) from a network of hospitals (n=11) in Houston, TX. Only patients with Salmonella spp. isolated from clinical samples in 2019 and 2020 were included. Demographic, clinical, and microbiological data were extracted from the medical record. Results A total of 35 pediatric cases of Salmonella spp infection were identified over the two-year period. Median age was 1.6 years with over one-third (13/35, 37.1%) under one year (Table 1). Nearly half (15/35, 42.9%) of patients required hospitalization with a median length of stay of 2 days. From cases with available clinical data (n=31), most common symptoms were fever (22/31, 71%) and bloody diarrhea (21/31, 67.7%) (Table 2). Bacteremia was detected in 17.1% (6/35) of cases (Table 3). Exposure history was elicited in 29% (9/31) of cases with foreign travel being most common risk factor (Table 2). All speciated isolates were Salmonella enterica with the majority (24/29, 82.8%) subspecies enterica. Of 24 samples with serotype information, the most common was infantis (Table 3). A single isolate was resistant to all antibiotics tested except meropenem (Table 3) and was recovered from a patient after travel to Pakistan. Nearly half of patients (15/31, 48.4%) received definitive therapy with a third generation cephalosporin antibiotic. Complications were rare and included septic arthritis/osteomyelitis (n=1), UTI (n=3), coagulopathy (n=1), and hepatitis (n=1). Conclusion Salmonella spp. Infections were common in the Houston metropolitan area over the 2-year period and occurred primarily in young children. Foreign travel seems to be a major risk factor for acquisition of this infection in children. For the first time, the identification of a multi-drug resistant Salmonella isolate suggests that this phenotype is likely to increase and highlights the importance of ongoing surveillance. Disclosures Anthony R. Flores, MD, MPH, PhD, Nothing to disclose Cesar A. Arias, M.D., MSc, Ph.D., FIDSA, Entasis Therapeutics (Grant/Research Support)MeMed Diagnostics (Grant/Research Support)Merk (Grant/Research Support)

Background S. lugdunensis is a coagulase negative staphylococci (CoNS) demonstrating high level pathogenicity. In contrast to other CoNS, S. lugdunensis (SL) remains susceptible to most antibiotics. Prior to the implementation of Verigene®, SL was identified by provider request only. We sought to describe the susceptibility data of SL isolated from blood culture after the implementation of multiplex PCR, as well as to determine the correlation of the mecA gene provided by Verigene® and oxacillin resistance. Methods Retrospective review of all blood culture isolates positive for SL from two major hospital systems, Memorial Hermann Hospital System (14 hospitals) and HarrisHealth System (two acute care hospitals) identified on Verigene® PCR. Multiple isolates detected from the same patients were excluded from this analysis. Memorial Hermann utilized Microscan®, and HarrisHealth utilized BD Phoenix® for susceptibility testing. Results Between 2017 – 2021, 157 patients were identified with SL positive blood cultures. Of them, 141 isolates had susceptibility data collected, which is summarized in table 1. Resistance rates were highest amongst clindamycin 97/141 (68.8 %) susceptible, erythromycin 98/141 (69.5%) susceptible, and oxacillin 120/141 (85.1%) susceptible. 127/141 (90.1%) of isolates were tested for mecA on Verigene®. 13 of 21 oxacillin resistant isolates were from pure culture, of these isolates, none had mecA detected. Conclusion In our study, clindamycin and erythromycin demonstrated similar susceptibility compared to prior studies in the literature, however oxacillin susceptibility rate was lower than expected at 85.1%, compared to 95.3% in a prior large-scale United States based study in 2017. Absence of mecA gene detection on multiplex PCR did not correlate with oxacillin susceptibility suggesting that oxacillin susceptibility cannot be accurately predicted by the use of multiplex PCR systems, such as Verigene®, as demonstrated in Table 2. Our study also suggested that increased prevalence of oxacillin resistant SL isolates may be emerging. Disclosures All Authors: No reported disclosures

Cutaneous tuberculosis secondary to skin inoculation of Mycobacterium tuberculosis is uncommon but it can occur in the health care settings. Herein, we report an unusual case of primary cutaneous tuberculosis of the thumb following a needlestick injury. The infection progressed with a necrotic granuloma, lymphatic dysfunction as visualized by near-infrared fluorescence lymphatic imaging, and the development of an axillary web syndrome.

Background Convalescent plasma is used as a treatment for COVID-19. Only limited data describe the efforts to recruit COVID-19 convalescent plasma (CCP) donors. We describe our experience engaging persons recovered from COVID-19 to donate CCP. Study design and methods We performed a retrospective analysis of the CCP recruitment for an 11-hospital health system in Houston, Texas. We sought CCP donations from: a) "volunteers" responding to advertisements in social media, press releases, and websites and b) "referred" individuals directed to the program or identified from hospitalization records. We determined the proportions of donor candidates who passed initial telephone health screening, who qualified after diagnostic testing, who presented to the regional CCP donation center, and who completed CCP donation. Results There were 900 CCP donor candidates, including 363 volunteers and 537 referred donors. Of 360 contacted volunteers, 186 (5.7%) were excluded by interview; 133 were referred for additional diagnostic screening, 97 completed donor antibody and antigen testing, and 87 were qualified for CCP donation, resulting in 35 CCP donations (9.7% of initial telephone contacts). Among 533 referred donors, 448 (84.1%) were excluded by interview, 71 were referred for additional screening, 48 completed donor antibody and antigen testing, and 40 were qualified for CCP donation, resulting in one CCP donation (0.2% of initial telephone contacts). Conclusion In this community, screening of a high number of candidates yielded a limited number of CCP donations. These observations have important implications for CCP donor recruitment and community pandemic planning.

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.

Candida auris presents a unique challenge to practitioners and infection control teams worldwide because of its virulence, alarming resistance profile, environmental fitness, and risk of nosocomial transmission. We describe 2 cases of Candida auris infection managed with the CDC recommendations with no evidence of in-hospital transmission.

We report our clinical experience treating a critically ill patient with polymicrobial infections due to multidrug-resistant Escherichia coli , Klebsiella pneumoniae , and Pseudomonas aeruginosa in a 56-year-old woman who received health care in India and was also colonized by Candida auris . A precision medicine approach using whole-genome sequencing revealed a multiplicity of mobile elements associated with NDM-1, NDM-5, and OXA-181 and, supplemented with susceptibility testing, guided the selection of rational antimicrobial therapy.

We report a 15 year-old Nigerian adolescent male with chronic osteomyelitis caused by an extensively drug-resistant (XDR) Pseudomonas aeruginosa strain of sequence type 773 (ST773) carrying bla NDM-1 and an extended spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae strain. The patient developed neurological side effects in the form of circumoral paresthesia with polymyxin B and asymptomatic elevation of transaminases with aztreonam (used in combination with ceftazidime-avibactam).

Whole-genome sequencing (WGS) using MinION was used to characterize high-risk clones of Escherichia coli and Klebsiella pneumoniae harboring bla(NDM-5), bla(OXA-181), and bla(CTX-M-15), as well as Pseudomonas aeruginosa harboring bla(NDM), in a patient who received health care in India. Synergy testing demonstrated the activity of aztreonam and ceftazime-avibactam in combination. This case illustrates a “precision medicine” approach where deeper understanding of the genotype through WGS and of the phenotype through synergy testing formed the basis for rational combination therapy.

Background Treatment of serious infections due to multidrug-resistant (MDR) Pseudomonas aeruginosa remains a challenge, despite the introduction of novel therapeutics. In this study, we report 2 extensively drug-resistant clinical isolates of sequence type (ST) 309 P aeruginosa resistant to all β-lactams, including the novel combinations ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam. Methods Isolates were sequenced using both short-read (Illumina) and long-read technology to identify resistance determinants, polymorphisms (compared with P aeruginosa PAO1), and reconstruct a phylogenetic tree. A pair of β-lactamases, Guiana extended spectrum β-lactamase (GES)-19 and GES-26, were cloned and expressed in a laboratory strain of Escherichia coli to examine their relative impact on resistance. Using cell lysates from E coli expressing the GES genes individually and in tandem, we determined relative rates of hydrolysis for nitrocefin and ceftazidime. Results Two ST309 P aeruginosa clinical isolates were found to harbor the extended spectrum β-lactamases GES-19 and GES-26 clustered in tandem on a chromosomal class 1 integron. The presence of both enzymes in E coli was associated with significantly elevated minimum inhibitory concentrations to aztreonam, cefepime, meropenem, ceftazidime/avibactam, and ceftolozane/tazobactam, compared with those expressed individually. The combination of ceftazidime/avibactam plus aztreonam was active in vitro and used to achieve cure in one patient. Phylogenetic analysis revealed ST309 P aeruginosa are closely related to MDR strains from Mexico also carrying tandem GES. Conclusions The presence of tandem GES-19 and GES-26 is associated with resistance to all β-lactams, including ceftolozane/tazobactam. Phylogenetic analysis suggests that ST309 P aeruginosa may be an emerging threat in the United States.

Two ST309Pseudomonas aeruginosaclinical isolates resistant to carbapenems and newer β-lactam/β-lactamase inhibitor combinations were found to harbor the extended spectrum beta-lactamases GES 19 and 26 genetically clustered in tandem. The combination of ceftazidime/avibactam plus aztreonam achieved cure in one patient. Phylogenetic analysis suggests that ST309P. aeruginosacarrying tandem GES are an emerging lineage in the United States.

Lactobacillus sp. is a low virulence bacterium, which rarely causes infection in immunocompetent individuals and usually is considered a contaminant. Normally this organism is susceptible to β-lactam antibiotics, yet resistant strains have been reported. Here, we report a case of a 60-year-old renal transplant recipient who developed an intra-abdominal abscess which grew a carbapenem-resistant Lactobacillus casei. This is significant since it is the first report of a clinical isolate of Lactobacillus sp. that demonstrated both microbiological and clinical resistance to carbapenem use. Moreover, the probiotic supplement that the patient had taken also grew a similar organism raising the concern of probiotic associated infection in immunocompromised individual.

Objectives The purpose of this case report is to document the occurrence of granulomatous aortitis complicated by formation of a saccular aneurysm and aortobronchial fistula due to Brucella infection. Methods A 65-year-old man with a history of feral swine hunting presented with hemoptysis and was found to have a saccular thoracic aortic aneurysm and associated aortobronchial fistula. The aneurysm underwent operative repair with closure of the aortobronchial fistula. Results Histopathological examination of the aneurysm wall revealed evidence of granulomatous aortitis. Cultures of the blood and aortic wall tissue were positive for Brucella suis. Conclusions Although rare, Brucella infection should be considered in the differential diagnosis of aortic aneurysm with granulomatous aortitis.

The T2Candida assay is a novel, non-culture-based assay for the diagnosis of candidemia directly from whole blood. The impact of antifungals on the performance of the T2Candida assay and blood culture bottles has not been well described. In this study, the performance of the T2Candida assay was compared to that of blood culture in detecting Candida spp. in spiked blood cultures with or without the presence of antifungals. Clinical bloodstream isolates of Candida spp. were inoculated into human whole blood at low (1 to 5 cells/ml) and high (10 to 50 cells/ml) concentrations with or without the presence of caspofungin and fluconazole. Time to detection (TTD) was assessed for prepared samples using BacT/Alert FA aerobic blood culture bottles or the T2Candida assay. In the absence of antifungals, T2Candida assay sensitivity was comparable to that of blood culture at both the low inoculum and the high inoculum (95% versus 97.5% and 100% versus 100%, respectively) and the assay had an average TTD that was significantly shorter (5.1 h versus 27.2 to 30 h, respectively). Neither caspofungin nor fluconazole was observed to impact the sensitivity or TTD of the T2Candida assay, while fluconazole reduced the overall blood culture sensitivity by 7.5% to 12.5% (at the low inoculum and high inoculum, respectively) and significantly increased the TTD of Candida albicans, C. tropicalis, and C. parapsilosis by 14.8 to 67 h. Neither caspofungin nor fluconazole impacted the performance of the T2Candida assay in vitro, and the assay may be useful for the diagnosis of candidemia in patients receiving antifungal therapy.

Background Carbapenem-resistant Klebsiella pneumoniae (CR-Kpn) are a significant cause of hospital-associated infections. Class A β-lactamases, e.g., Klebsiella pneumoniae carbapenemases (KPCs), are major contributors to carbapenem resistance. Sequence type 258 (ST258) is the most common genetic lineage of CR-Kpn associated with blaKPC carriage. Recently, a newly emergent lineage ST307 has been identified within the Houston metropolitan region. The transmission of blaKPC and other antimicrobial resistance (AMR) genes is driven largely by exchange of mobile genetic elements (MGEs). We sought to describe the dynamics of horizontal gene transfer (HGT) in particular between co-circulating strains of ST307 and ST258. Methods Long-read sequencing technologies allow us to resolve plasmid sequences and their associated AMR genes as well as characterize a comprehensive range of MGEs enabling transmission of these clinically important resistance mechanisms. CR-Kpn isolates were collected as part of a study to describe CRE burden within a Houston metropolitan hospital system. The Oxford Nanopore Technology (ONT) GridION X5 was used for long-read sequencing with Illumina short-read data used to refine and generate high-quality, consensus assemblies. A custom bioinformatic pipeline was used to resolve plasmid structures and identify the genomic context of plasmids carrying blaKPC variants. Results 95 Kpn isolates were collected from May to December 2017. Phylogenetic and in silico MLST analysis revealed 38/95 (40%) and 35/95 (37%) were ST258 and ST307, respectively. 86% of Kpn isolates carried one or more IncF-type conjugative plasmids, which were the prime vectors for blaKPC intercellular transmission. Interestingly, we found similar AMR-harboring plasmids within ST258 and ST307 composed of mosaic, modular IS26 and Tn3-like transposase mediated elements that carried multiple AMR determinants including blaKPC variants (Figure 1). Conclusion We were able to characterize mechanisms by which ST307 and ST258 lineages may transfer AMR determinants. There are clinically relevant implications to these HGT events that occur between these lineages as they may provide insights into how resistance differentially develops. Disclosures All authors: No reported disclosures.

Background Nosocomial infections due to CR-PA are associated with significant morbidity and mortality, and knowledge of epidemiology and underlying mechanisms of antimicrobial resistance is critical to addressing this threat. Recently, we identified a CR-PA of sequence type (ST) 309 resistant to all available β-lactams due to acquired β-lactamases as a potential emerging clone. To assess the evolving landscape of resistance in CR-PA we performed a cross-sectional survey of historical and contemporary isolates utilizing phenotypic testing and whole-genome sequencing (WGS). Methods Historical CR-PA isolates (n = 61, collected from 1999 to 2015) and contemporary isolates (n = 110, collected from 2017 to 2018) from a large urban hospital network in Houston, TX were tested for susceptibility to meropenem, aztreonam (ATM), ceftolozane/tazobactam (C/T), and ceftazidime/avibactam (CZA) using E-test on Mueller–Hinton (MH) agar. WGS for all isolates was performed on a MiSeq platform (Illumina). Data analysis was performed using a custom analysis pipeline, including Tseemann MLST tool, Resfinder, and Abricate using the CARD database. Results The prevalence of resistance across all β-lactams tested increased in contemporary strains as compared with that of historical strains (Figure 1). Among important contemporary antipseudomonal antibiotics C/T, ATM, and CZA, resistance increased from 0%, 22%, and 5% to 15%, 44%, and 16%, respectively (Figure 1). WGS revealed that ST235 was the most common sequence type, followed by ST111 in the historical collection (Figure 2). In contrast, a larger degree of genetic diversity was found in contemporary isolates, with the emergence of multidrug-resistant clones such as ST308 (2%) and ST309 (3%). Resistance to C/T was associated with acquired β-lactamases in 88% (14/16) of isolates, including VIM-2, GES-19/GES-26, VEB-1, NMD-1, and OXA enzymes. Conclusion Resistance to newer agents C/T and CZA markedly increased in contemporary CR-PA strains. While the epidemic clones ST235 and ST111 were the most frequent STs, ST308 and 309 have emerged among contemporary MDR isolates. Most concerning was the association of C/T resistance and the acquisition of β-lactamases, due to the potential for further dissemination. Disclosures All authors: No reported disclosures.

Objective At our institution, our microbiologist, pharmacist, and infectious disease (ID) team meet to discuss ID patients, and this meeting is referred to as microbiology rounds. We hypothesized that our microbiology rounds reduce antibiotic costs. The study involved a review of 80 patients with an ID consultation order at each of the 3 hospitals: hospital A (HA) (only HA has microbiology rounds), hospital B (HB), and hospital C (HC). Of this population, we included patients with a positive blood culture. Thirty-six patients who met the above criteria were included in the study. The average antibiotic cost/patient/day at HA, HB, and HC were $66.0, $123, and $109, respectively. Also, we found that change in antibiotics was appropriate when compared to the final microbiology results in 90%, 44%, and 40% of the time at HA, HB, and HC, respectively. Herein, we found an association between conducting microbiology rounds and reduction of antibiotic cost.

Aims The utility of bone marrow aspiration and biopsy (BMAB) as a diagnostic tool in patients with HIV/AIDS and fever of unknown origin (FUO) is a subject of debate. Because highly active antiretroviral therapy has reduced incidence of opportunistic infections, it is important to reassess the efficacy of BMAB for this diagnostic purpose. To our knowledge, no such studies have been performed in Harris County which has the highest incidence of HIV in the state of Texas. Methods We reviewed all BMABs from patients with HIV/AIDS and FUO or persistent cytopenia(s) from 2007 to 2011. Results Of 57 evaluable patients, BMAB was positive in 24 samples by acid fast bacilli (AFB) or Gomori methenamine silver (GMS) stains (17.5%), presence of granuloma and/or lymphohistiocytic aggregates (31.6%), culture (21.0%) or a combination. Cultures demonstrated Mycobacterium avium/intracellulare (4), M tuberculosis (2), M gordonae (1), Histoplasma capsulatum (3) and Cryptococcus neoformans (2). There were three cases in which a pathogen was grown in culture but that had a negative of ‘direct examination’ on tissue sections (negative AFB and GMS special stains, no morphological evidence of granuloma/lymphohistiocytic infiltrates). Conclusions This study supports the use of diagnostic BMAB as a rapid decision-making tool in patients with HIV and FUO in the proper clinical setting. BMAB demonstrated infection-related evidence prior to positive bone marrow culture in 75% of cases. Special stains and blood cultures had similar diagnostic yield, but BMAB offers faster results. Thus, this procedure assists in clinical decision making and the refinement of treatment in a more timely manner.

Dirofilariasis is caused by filarial nematodes (roundworms) of the genus Dirofilaria. Dirofilariasis of the oral mucosa is very rare. Herein, we report a case of a 79-year-old man who had a slowly growing infiltrative mass in the right buccal space. Histopathologic examination showed an inflammatory infiltrate with eosinophilia, histiocytes, and small organisms (0.2-0.3 mm). Digital images were sent to the Centers for Disease Control and Prevention, which identified the parasite as a nematode in the genus Dirofilaria. It appeared to be dead and degenerating, but external, fine longitudinal cuticular ridges and the presence of tall muscle cells were diagnostic. Thus, Dirofilaria, despite its rarity, should be considered in the differential diagnosis of tumor-like lesions in the buccal mucosa.

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.

This chapter will deal with medically important protozoa, cestodes, trematodes, nematodes, and arthropods. Special attention will be given to life cycles and diagnostic tools.

This chapter will discuss all common stains (e.g., acid fast stain, rhodamine auramine stain, flagellar stain, etc.) and common biochemical tests (e.g., catalase, pyrolidonyl arylamidase, etc.). Specific examples used for differentiation of microorganisms will be reviewed.

Tests for detection of antibodies, antigens, and immunologic evidence of microbial infections will be reviewed. Appropriate use of these tests for diagnosis of infectious diseases will also be discussed.

This chapter will discuss proper sample collection, transportation, and storage of various specimens including blood culture, sputum, stool, urine, and various body fluids. How to preserve specimen integrity as well as avoiding pre-analytical errors will also be discussed.

This chapter will provide the fundamental knowledge of molecular diagnostics needed for a trainee during board preparation and the general practicing pathologist and will briefly discuss the basic principles of molecular biology and outline the basic techniques used in molecular diagnostics. This chapter will also touch on the available molecular diagnostic instruments and the design of a clinical molecular laboratory.

This chapter will discuss common antibiotics in treating infection including susceptibility testing which is conducted prior to selecting a proper antibiotic. In this chapter, pharmacology of life saving antibiotics such as vancomycin and aminoglycosides will also be discussed.

This chapter will deal with all common Gram-positive and Gram-negative bacteria, as well as Enterobacteriaceae, anaerobes, and mycobacteria and their role in infective patients. Drugs which are used in treating such infections will also be addressed.

This chapter will discuss issues with quality control, biosafety, requirements of College of American Pathologists, and Clinical Laboratory Improvement Amendments essential for laboratory accreditation. Moreover, various management and budget issues regarding smooth operation of clinical microbiology laboratory will also be discussed.

Fungi infections due to pathogenic fungi will be reviewed. Morphologic features used for identification of yeast, including dimorphic and other filamentous fungi, will be discussed. Medications used in treating various fungal infections will also be addressed.

The chapter will examine the applications of molecular diagnostics and will include applications in inherited genetic diseases, infectious diseases, and human neoplasms. An introduction to pharmacogenomics will also be provided.

Viral infections including hepatitis and human immunodeficiency virus will be reviewed and the best methods for diagnosis of each will be discussed. Key features of ribonucleic acid and deoxyribonucleic acid viruses including cytopathic effect in cell culture and tissue will be discussed.

This chapter will discuss all practical aspects of various media use in clinical microbiology laboratory. Appropriate use of primary as well as secondary selective and nonselective media for identification of microorganisms will also be reviewed.

This chapter will discuss various microbiological aspects of urinary tract infection, gastrointestinal tract infections, respiratory tract infections, endocarditis, infection of the nervous system, joint infection, hepatitis, bacteremia, and septicemias.

Background Prevention of infection associated with uncemented orthopaedic implants could lead to improved implant stability and better patient outcomes. We hypothesized that coating porous metal implants with antibiotic-containing microspheres would prevent infections in grossly contaminated wounds. Methods Bioresorbable polymer microspheres containing tobramycin were manufactured and pressed into porous metal cylinders that were then implanted into radial defects in rabbits. Control implants that did not contain antibiotic microspheres were also implanted into the contralateral limbs. Each implant was then contaminated with Staphylococcus aureus prior to closure of the wound. The animal was euthanized after clinical signs of infection appeared, or at two weeks after surgery. Periprosthetic tissue was cultured for the presence of S. aureus, and integration of the implant with the surrounding bone was measured. Results The antibiotic microspheres successfully prevented infection in 100% of the eleven limbs with treated implants, which represented a significant improvement (p = 0.004) compared with the infection rate of 64% (seven of eleven) for the limbs with control implants. Implant integration averaged 38.87% ± 12.69% in the fifteen uninfected limbs, which was significantly better (p = 0.012) than the average of 19.46% ± 14.49% in the seven infected limbs. Conclusions The antibiotic delivery system successfully prevented infection in 100% of the cases studied, resulting in an increase in implant integration. Clinical relevance Antibiotic delivery utilizing the system described here may be effective in preventing implant-associated infections after orthopaedic surgery and increasing the longevity of orthopaedic implants.