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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.

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.

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).

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.

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.

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.

Background Diagnostic tests are a crucial part of clinical care. However, they can often result in unnecessary testing with no patient impact. Diagnostic stewardship seeks to modify the process of ordering, performing and reporting diagnostic tests to improve resource utilization and patient outcomes. We have identified infectious diseases viral molecular tests that are meant for outpatient management that are often ordered during a hospital stay. Our objective was to quantify how often these tests were ordered and acted upon, as well as the cost associated with them. Methods HIV quantitative PCR, HIV genotype and HCV genotype were selected as the target tests to be evaluated in this study. We measured the number of times these tests performed at Memorial Hermann Hospital TMC from January to December 2017. The individual and total cost of these tests were calculated. We sampled charts to determine whether the test had been acted on during or after the hospitalization. Results During the study period, a total of 512 HIV viral loads, 29 HIV genotypes, and 58 Hepatitis C genotypes were ordered. The total expense on the HIV viral load tests was $43,228, total expense on HIV genotypes was $8,669, and for Hepatitis C genotype was $43,055. Our chart sampling showed that HIV viral load was not acted on 65% of the time, HIV genotype test was not acted on 62% of the time and HCV genotype was not acted on 50% of the time. Conclusion Three molecular viral tests that were acted upon less than 50% of the time they were ordered, collectively added an expense of $94,952 over the course of a year at MHH TMC. A diagnostic stewardship program based on education and selective restriction of diagnostic testing may result in avoidance of unnecessary testing and substantial savings. Disclosures All authors: No reported disclosures.

Background The identification of yeast traditionally entails macroscopic/microscopic findings and biochemical testing. Recently, MALDI TOF MS has replaced traditional methods for identification as a proposed new standard. We performed identification of previously unidentifiable yeasts from a collection in the United States. Methods The Mycoses Study Group (MSG) collected 2,947 Candida isolates from 1,911 patients as part of two U.S. studies between 1995 and 1999. The identification of the isolates was done in 2002 using API 20 c aux with supplemented standard mycological and biochemical test (corn meal agar, germ tube and the Murex ID system). Ninety-four isolates could not be identified at that time. For this study, the isolates were defrosted, plated on Sabureau Dextrose agar, and incubated at 30°C for 48 hours. We then sub-cultured again in Blood Agar. Isolates when then tested by MALDI TOF MS following the methodology for the Bruker MALDI biotyper. Results In the first attempt, 65/94 (69%) isolates were identified. The remaining 29 samples were re-tested with a yield of 21/29 (72.4%) identified isolates. The remaining isolates had to be identified with another round of MALDI TOF and further biochemical testing. The table below shows the final identification of the isolates. Conclusion MALDI TOF MS is rapidly becoming a reference method for yeast identification. However, in a historical collection of yeast that could not be identified by conventional biochemical methods, it took up to three rounds of MALDI TOF MS with a yield of ~70% per round, and additional biochemical testing, for identification of all isolates. Continuing validation of MALDI TOF MS for identification of difficult yeast isolates is warranted. Species Number Percentage C. albicans 20 21 C. glabrata 22 23.40 C. parapsilosis 34 36.10 C. tropicalis 8 8.50 C. krusei 2 2.10 C. orthopsilosis 3 3.10 C. nivariensis 1 1.06 C. Kefyr 1 1.06 Pichia norvegensis 1 1.06 C. lusitane 1 1.06 Trichosporum spp. 1 1.06 Total 94 100 Disclosures All authors: No reported disclosures.

Background Individuals living with HIV infection and/or Hep C infection and unaware of their infected status are at risk of significant morbidity and a risk to public health. It has been recommended that all conscious adults presenting to Emergency Departments (EDs) be tested for HIV and increasingly testing for Hep C. Testing of all arrivals is important because a majority of both infections may not present signature signs or symptoms associated with the reason for the ED visit. For these reasons, the implementation of a bundled HIV/HepC testing protocol is reported here. Methods Data from 4 years of HIV/Hep C screening of patients 18 to 64 years old made in 9 EDs in the Houston Metropolitan Area are reviewed. Screening for HIV was using HIV fourth-generation ADVIA Centaur™ Ag/Ab COMBO (Siemens) and Hep C was tested for using Gilead Hep C Ab testing. Results During January 2013 until October 2016, 3,976 HIV/Hep C test bundles were performed. There were 40 (1.0%) HIV+ and 407 (10.2%) Hep C positive detected. Nine (0.2%) of these individuals were positive for both HIV and Hep C. A 22.5% of HIV-positive patients were co-infected with Hep C. The population had a median age of 53 years, comprising an equal number of males and females. Conclusion A significant prevalence of Hep C (10%) and HIV (1%) was found in patients presenting for any cause of major EDs in the Houston region. Bundled HIV/Hep C testing of all arrivals to EDs is an effective way to identify individuals that need to be directed to antiviral and linkage to care. Disclosures All authors: No reported disclosures.

Background Rapid identification of antimicrobial resistance markers has the potential to help targeting antimicrobial therapy and enhance efforts for antibiotic stewardship. However, limited data are available to correlate phenotypic and genotypic results for some of these platforms in positive blood cultures (BC). Here, we aimed to evaluate the ability of the Verigene® (VG) Blood Culture System to predict phenotypic susceptibility patterns with the detection of the genes encoding the CTX-M in Enterobacteriaceae and MecA in S. aureus (SA) in a large dataset. Methods Phenotypic susceptibility and VG results were retrospectively collected between August 2017 and December 2018 from 12 hospitals in Houston, TX. VG testing was performed on only the first isolate was considered in persistent positive BCs. The VG report of the presence of blaCTX-M or mecA was correlated with phenotypic susceptibility to ceftriaxone (CTO) (E. coli [EC] and Klebsiella spp.[KL]) or oxacillin (SA), respectively. Results We identified a total of 5,937 VG results. The final analysis was performed on 2,356 cases where EC, KL or SA was identified. Isolates detected KPC and NDM by VG were excluded. 30 EC/KL were missed by VG in polymicrobial bacteremia. 7 polymicrobial positive BCs with coagulase-negative staphyloccocci were mislabeled as MecA positive MSSA. Among isolated detected by VG, there were the high sensitivity and specificity of CTX-M to identify CTO resistance (97.2% and 99.7% in EC and 91.4% and 99.2% in KL). For SA, the sensitivity and specificity of mecA were 100% and 99.6% to identify oxacillin resistance. 2 isolates with mecA positive by VG were reported as oxacillin-suscpetible. Conclusion Our results revealed that there is a high correlation between VG and phenotype. For SA, discrepancies between genotype and phenotype seem to be influenced by the presence of other organisms in the sample. Genotypic information seems reliable and should guide targeted therapy in bloodstream infections. Disclosures All authors: No reported disclosures.

Trehalose 6,6'dimycolate (TDM) is a glycolipid found in nearly pure form on the surface of virulent Mycobacterium tuberculosis (MTB). This manuscript investigated the production of TDM, growth rate and colony morphology of multiple strains of MTB, each of which had been isolated from both pulmonary (sputum) and extrapulmonary sites of multiple patients. Since sputum contains MTB primarily from cavities and extrapulmonary biopsies are typically granulomas, this provided an opportunity to compare the behavior of single strains of MTB that had been isolated from cavities and granulomas. The results demonstrated that MTB isolated from pulmonary sites produced more TDM (3.23 ± 1.75 μg TDM/mg MTB), grew more rapidly as thin spreading pellicles, demonstrated early cording, and climbed culture well walls. In contrast, extrapulmonary isolates produced less TDM (1.42 ± 0.58 μg TDM/mg MTB) (p

Background The use of rapid diagnostic tests (RDT) in microbiology decreases time to pathogen identification (ID). When coupled with an Antimicrobial Stewardship Program (ASP), time to optimal antibiotics can be significantly reduced. The purpose of this study was to evaluate the impact of Verigene® Gram-Positive Blood Culture Test (BC-GP) and Gram-Negative Blood Culture Test (BC-GN) implementation with an ASP at three community hospitals within a health system with centralized microbiology services. Methods A retrospective analysis was conducted to compare time to targeted antibiotics for treatment of bloodstream infections (BSI) before and after implementation of Verigene®. Patients were included with a positive blood culture for organisms detectable by Verigene BC-GP and BC-GN during September 2016 (pre-implementation group) and September 2017 (post-implementation group). Patients were excluded if positive blood culture had more than one organism, patient was actively being treated for an infection unrelated to blood culture or blood culture results were available after patient expired, was discharged or transferred. Targeted antibiotic therapy was defined as antibiotic therapy tailored toward pathogen based on ID and sensitivities. Each ASP pharmacist received Verigene® notifications in real-time. Secondary endpoints were in-hospital mortality, hospital length of stay (LOS), and days of vancomycin therapy. Results A total of 93 patients were included in the final analysis with 42 patients in pre- group and 51 in post-group. Patients achieving targeted therapy during their hospital stay was 38 of 42 (90%) in the pre-group and 47 of 51 (92%) in the post-group. Of those who achieved targeted therapy, time to targeted therapy was 78.4 hours vs. 43.1 hours in pre-group vs. post-group, respectively (P < 0.001). No significant difference was detected for in-hospital mortality or hospital LOS. Length of vancomycin therapy was decreased from 85.8 hours to 48.6 hours in post-group (P < 0.001). Conclusion Implementation of RDT in three community hospitals with a centralized microbiology laboratory resulted in a significantly improved time to targeted antibiotics in patients with BSI when combined with ASP pharmacist real-time notification. Disclosures All authors: No reported disclosures.

Background The spread of carbapenem resistance in Enterobacteriacae (CRE) and PA is an urgent public health concern. Candida auris (CA) is also an emerging threat, with the epicenter of US cases on the East Coast. Transcontinental spread of multi-drug-resistant (MDR) organisms has the potential to change local susceptibility patterns via dissemination of resistance determinants or high-risk clones. Here, we report and characterize MDR-isolates of EC, KP, PA and CA, all isolated from a single patient admitted to an ICU in Houston, Texas after complications from plastic surgery in India. Methods CRE were isolated from the urine, PA from respiratory cultures and CA from wound cultures. Antimicrobial susceptibility testing was performed on Vitek 2 or by Etest. Synergy testing was done by Aztreonam (ATM) E-test on Mueller-Hinton agar supplemented with 2.2 µg/mL avibactam. Bacterial isolates underwent whole genome sequencing on an Illumina MiSeq, and resistance determinants (Abricate using CARD), plasmid replicon types (PlasmidFinder 1.3) and sequence type (Tseemann MLSTtool) were identified. Genes were verified by PCR. Results The CRE were resistant to all β-lactams, including ceftazidime/avibactam (CZA) and ceftolozane/tazobactam. Synergy testing with CZA+ATM reduced the ATM MICs of the EC from >256 to 0.5 µg/mL and the KP from >256 to .094 µg/mL, while the PA ATM MIC was 4 µg/mL irrespective of the presence of avibactam. WGS indicated that the EC and KP shared the blaNDM-5, blaTEM-4, and blaCTX-M-15 β-lactamase genes, as well as IncFII and IncX3 plasmid replicon types. In addition, the EC harbored blaCMY-59, blaOXA-181, qnrS1 and two additional IncB and IncY plasmid replicon types. The PA isolate harbored blaNDM-1, qnrVC1, several aminoglycoside resistance genes and a type 1 integrase. The CA isolate had a fluconazole MIC of >256 µg/mL and a micafungin MIC of 0.125 µg/mL. Conclusion Here we report the identification of 4 MDR organisms, including the first reported isolate of CA in Houston, in one patient. The pattern of resistance determinants suggests horizontal transmission of blaNDM-5 between the CRE isolates. Prompt recognition of MDR organisms is imperative to prevent healthcare-associated spread. Disclosures W. Miller, Merck: Investigator, Research support. C. Arias, Merck & Co., Inc.: Grant Investigator, Research support. MeMed: Grant Investigator, Research support. Allergan: Grant Investigator, Research support.

Increasing resistance in Pseudomonas aeruginosa to multiple antibiotics has been observed and is posing therapeutic dilemmas. Antibiotic utilization is one factor that has been associated with the emergence of antimicrobial resistance. We examined the overall and specific antimicrobial use in relation to changes in susceptibility patterns in P. aeruginosa. Regression analysis was performed to explore the relationships between annual antibiotic use and the incidence of resistant P. aeruginosa. There were statistically significant relationships between increasing anti-pseudomonal cephalosporin and levofloxacin use and the increasing incidence of ciprofloxacin resistant P. aeruginosa. However, there was not an association between other fluoroquinolone or overall fluoroquinolone use and this change. In addition, there was no association between increasing anti-pseudomonal cephalosporin use and cefepime resistant P. aeruginosa. No statistical relationship was seen with overall antibiotic use and the development of resistance in P. aeruginosa, suggesting that the development of resistance is associated with the use of individual agents, rather than overall antibiotic consumption.

Critically ill patients have altered pharmacokinetics (PK) that need to be considered when choosing and dosing antibiotics. We conducted a prospective, observational study to assess clinical and microbiologic response rates in 19 critically ill patients with nosocomial Gram-negative infections. Antibiotics were dosed based on a mathematical pharmacodynamic (PD) model accounting for these altered kinetic parameters. The average APACHE II score +/- SE on intensive care unit admission and at the time of infection was 13.6 +/- 1.2 and 14.6 +/- 1.1, respectively. With targeted antimicrobial therapy adjusted to achieve an optimal PD profile, 17/19 (89%) patients had a clinical cure or improvement and 16/19 (84%) had either microbiologic eradication or presumed eradication. Modeling PD in these critically ill patients resulted in good clinical and microbiologic outcomes.

Tuberculosis remains the leading cause of death worldwide from a single infectious organism. Approximately 32% of the world's population is infected and an estimated two million people die annually from this treatable disease. Over the past 50 years, with medical treatment and standard public health practices, tuberculosis diminished in developed countries and resulted in a loss of interest and funding for research in improving diagnostic and treatment options. In developing countries, efforts including BCG vaccination have failed to control tuberculosis and the disease continues to spread as the world becomes more globalized. At the same time, multidrug resistant tuberculosis has emerged, challenging even the most advance treatment centers. Better diagnostic techniques, control measures and treatment options are desperately needed but advances require worldwide commitment to battle this age-old disease.

HbhA ofMycobacterium tuberculosisis a multifunctional binding protein, binding to both sulfated sugars such as heparin and to human complement component C3. HbhA may therefore interact with host molecules and/or host cells duringM. tuberculosisinfection and play a role in the pathogenesis of this bacterium. The purpose of this study was to use allelic exchange to create anM. tuberculosisstrain deficient in expression of HbhA to determine whether this protein's C3-binding activity plays a role in the pathogenesis ofM. tuberculosis. An in-frame, 576-bp unmarked deletion in thehbhAgene was created usingsacBas a counterselectable marker. Southern blotting and PCR analyses confirmed deletion ofhbhAin the ΔhbhAmutant. The ΔhbhAmutant strain grew at a rate similar to that of the parent in broth culture and in J774.A1 murine macrophage-like cells but was deficient in growth compared to the parent strain in the lungs, liver, and spleen of infected mice. In addition, the ΔhbhAmutation did not reduce binding ofM. tuberculosisto human C3 or to J774.A1 cells in the presence or absence of serum, suggesting that in the absence of HbhA, other molecules serve as C3-binding molecules on theM. tuberculosissurface. Taken together, these data indicate that HbhA is important in the infectivity ofM. tuberculosis, but its ability to bind C3 is not required for mycobacterial adherence to macrophage-like cells. Using the ΔhbhAmutant strain, a secondM. tuberculosisC3-binding protein similar in size to HbhA was identified as HupB, but the role of HupB as a C3-binding protein in intact organisms remains to be determined.

The mechanism of pathogenesis of Mycobacterium tuberculosis is thought to be multifactorial. Among the putative virulence factors is the antigen 85 (Ag85) complex. This family of exported fibronectin-binding proteins consists of members Ag85A, Ag85B, and Ag85C and is most prominently represented by 85A and 85B. These proteins have recently been shown to possess mycolyl transferase activity and likely play a role in cell wall synthesis. The purpose of this study was to generate strains of M. tuberculosis deficient in expression of the principal members of this complex in order to determine their role in the pathogenesis of M. tuberculosis . Constructs of fbpA and fbpB disrupted with the kanamycin resistance marker ΩKm and containing varying amounts of flanking gene and plasmid vector sequences were then introduced as linear fragments into H37Rv by electroporation. Southern blot and PCR analyses revealed disruption of the homologous gene locus in one fbpA ::ΩKm transformant and one fbpB ::ΩKm transformant. The fbpA ::ΩKm mutant, LAa1, resulted from a double-crossover integration event, whereas the fbpB ::ΩKm variant, LAb1, was the product of a single-crossover type event that resulted in insertion of both ΩKm and plasmid sequences. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis confirmed that expression of the disrupted gene was not detectable in the fbpA and fbpB mutants. Analysis of growth rates demonstrated that the fbpB mutant LAb1 grew at a rate similar to that of the wild-type parent in enriched and nutrient-poor laboratory media as well as in human (THP-1) and mouse (J774.1A) macrophage-like cell lines. The fbpA mutant LAa1 grew similarly to the parent H37Rv in enriched laboratory media but exhibited little or no growth in nutrient-poor media and macrophage-like cell lines. The targeted disruption of two genes encoding mycolyl transferase and fibronectin-binding activities in M. tuberculosis will permit the systematic determination of their roles in the physiology and pathogenesis of this organism.

To the Editor: Routine vaccination of children with the 7-valent pneumococcal conjugate vaccine (PCV-7; Wyeth Pharmaceuticals, Collegeville, PA, USA), initiated in the United States in 2000, was followed within 2 years by an extensive and rapid decline in invasive pneumococcal disease (IPD) (1). During the past few years, increasing frequency of invasive disease including necrotizing pneumonia caused by serotypes not included in the vaccine has been reported (2). We show an expanded pattern of the changing spectrum of the disease associated with nonvaccine serotypes through this report of 4 cases of necrotizing pneumonia in children, caused by Streptococcus pneumoniae serotype 19A. Over a 6-month period ending in March 2008, 4 children (median age 3.6 years, 1 with asthma) (Table) were brought to our hospital with signs of respiratory distress and a 4- to 7-day history of fever and cough. All had decreased breath sounds or crackles, and radiologic studies showed evidence of complicated pneumonia, which led to hospital admission (3 to an intensive care unit [ICU]). S. pneumoniae 19A was isolated from normally sterile sites with each child. All received intravenous antimicrobial drugs followed by an oral antimicrobial drug regimen and were discharged in good health. By reviewing immunization records, we confirmed that all had completed the PCV-7 series before becoming ill. Table Characteristics of patients in study of severe necrotizing pneumonia in children, Houston, Texas, USA, 2007–2008* During the same period, complicated pneumonia was identified in 7 other inpatients by using the International Classification of Diseases, 9th revision, codes for necrotizing pneumonia and empyema and Current Procedural Terminology codes for thoracoscopic surgery (median age 4.3 years); 2 had asthma, 1 had congenital diaphragmatic hernia with resultant left lung hypoplasia. No causative organism was identified for any of these cases. As illustrated by our 4 cases, serotype 19A is emerging as an increasing cause of severe disease such as complicated pneumonia. Although the incidence of IPD in general has decreased since the introduction of PCV-7, the emergence of nonvaccine serotypes as a cause of severe disease is becoming more prevalent. Among 8 geographic areas in the United States, the incidence of IPD caused by nonvaccine serotypes in children

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections increased from 2000 to 2003 in hospitalized pediatric patients in Houston. CA-MRSA was associated with greater illness than was infection with methicillin-susceptible strains. Children with CA-MRSA were younger and mostly African American. Of MRSA isolates, 4.5% had the inducible macrolide-lincosamide-streptogramin B phenotype.

OBJECTIVE: To describe a nosocomial outbreak caused by multiresistant Acinetobacter baumannii. DESIGN: Descriptive and case-control study. Antibiotic susceptibilities and pulsed-field gel electrophoresis (PFGE) of genomic DNA digested with SfiI and also with ApaI were used as markers of strain identity. SETTING: A large medical school-affiliated hospital in the city of Houston, Texas. RESULTS: During a 10-week period, A baumannii was isolated from 25 patients admitted to the intensive care unit (ICU). The attack rate was 14.3 per 100 ICU admissions. Case patients were intubated more frequently and for longer periods, and had longer ICU and hospital stays (P < 0.05 for each of these characteristics). Multivariate logistic regression analysis identified the length of ICU stay and the use of third-generation cephalosporins as associated with the acquisition of A baumannii. Patients infected with A baumannii had a higher mortality rate than colonized patients and control patients (P < 0.01). Sixteen isolates recovered from these 25 patients were susceptible only to imipenem/cilastatin, and PFGE confirmed that a single clone was the cause of this outbreak. Nine isolates of A baumannii from patients infected or colonized in two other hospitals in Houston during the same period, differed from the outbreak isolates by their susceptibility to ciprofloxacin. However, PFGE results were identical, indicating unsuscepted genetic relatedness among isolates from three different hospitals. CONCLUSIONS: A baumannii is an important nosocomial opportunistic pathogen and can adversely affect the outcome of ICU patients who acquire this organism. This outbreak was caused by a single clone that was isolated concurrently from three hospitals.

Histoplasma capsulatum is a dimorphic endemic fungus which infects both immunocompetent and immunocompromised hosts. Isolated CNS histoplasmosis is a rare presentation with increased risk in individuals with impaired cellular immunity, however not all patients with this condition are immunocompromised. We report a case of isolated CNS histoplasmosis in an otherwise healthy immunocompetent patient who was initially treated with Liposomal Amphotericin B followed by oral Voriconazole and later Itraconazole with significant improvement in clinical status.

Mutations in liaFSR , a three-component regulatory system controlling cell-envelope stress response, were recently linked with the emergence of daptomycin (DAP) resistance in enterococci. Our previous work showed that a liaF mutation increased the DAP MIC of a vancomycin-resistant Enterococcus faecalis strain from 1 to 3 μg/ml (the DAP breakpoint is 4 μg/ml), suggesting that mutations in the liaFSR system could be a pivotal initial event in the development of DAP resistance. With the hypothesis that clinical enterococcal isolates with DAP MICs between 3 and 4 μg/ml might harbor mutations in liaFSR , we studied 38 Enterococcus faecium bloodstream isolates, of which 8 had DAP MICs between 3 and 4 μg/ml by Etest in Mueller-Hinton agar. Interestingly, 6 of these 8 isolates had predicted amino acid changes in the LiaFSR system. Moreover, we previously showed that among 6 DAP-resistant E. faecium isolates (MICs of >4 μg/ml), 5 had mutations in liaFSR . In contrast, none of 16 E. faecium isolates with a DAP MIC of ≤2 μg/ml harbored mutations in this system ( P < 0.0001). All but one isolate with liaFSR changes exhibited DAP MICs of ≥16 μg/ml by Etest using brain heart infusion agar (BHIA), a medium that better supports enterococcal growth. Our findings provide a strong association between DAP MICs within the upper susceptibility range and mutations in the liaFSR system. Concomitant susceptibility testing on BHIA may be useful for identifying these E. faecium first-step mutants. Our results also suggest that the current DAP breakpoint for E. faecium may need to be reevaluated.

We describe a patient who developed Corynebacterium striatum native valve endocarditis after receiving two 6-week courses of daptomycin for the treatment of methicillin-resistant Staphylococcus aureus bacteremia and osteomyelitis. The organism exhibited in vitro heteroresistance to daptomycin, with two subpopulations showing daptomycin susceptibility (MIC of ≤0.094 μg/ml) and high-level resistance to daptomycin (MIC of ≥256 μg/ml). The selection of daptomycin-resistant Gram-positive skin flora with the potential of causing invasive disease may be a concern during prolonged courses of daptomycin.

A commercial assay (AmplifiedMycobacterium tuberculosis Direct Test, Gen Probe) which combines transcription-mediated amplification of target rRNA with amplicon detection by a chemiluminescent DNA probe for the rapid detection ofMycobacterium tuberculosis in sputum was evaluated. The test was applied to consecutively collected, NALC/NaOH processed sputum sediments from two laboratories (H and L), each serving a different population of patients with pulmonary tuberculosis. Results were compared to those of fluorochrome staining and culture. A total of 760 specimens obtained from 246 patients were used for the study. The test was positive in 141 of 144 (98 %) specimens that were fluorochrome-positive and culture-positive forMycobacterium tuberculosis. Fifteen of 31 specimens that were fluorochromenegative, culture-positive were also assay-positive. A total of 312 specimens (100 patients) from laboratory H (prevalence = 10 %) and 448 specimens (146 patients) from laboratory L (prevalence = 34 %) were analyzed. Compared to culture, test sensitivity, specificity, positive predictive and negative predictive values were 65 %, 99 %, 94 % and 97 %, respectively, for laboratory H and 93 %, 99 %, 99 % and 97 %, respectively, for laboratory L. If the results were analyzed on the basis of at least one concordant result between the amplification assay and culture in three sputum samples per patient, then the sensitivity, specificity, positive and negative predictive values for identifying infected patients was 70 %, 99 %, 87 % and 97 %, respectively, for laboratory H, and 100 %, 98 %, 96 % and 100 %, respectively, for laboratory L.

Among 20 children admitted with laboratory-confirmed influenza, viral RNA was detected in respiratory secretion, stool and blood in 19, 5 and 1 children, respectively. Gastrointestinal symptoms were common but were not associated with viral RNA in stool. nH1N1 viremia was detected, for the first time, in an immunocompetent child.

The accuracy of combining latex agglutination with selective media for the identification of methicillin-resistant Staphylococcus aureus (MRSA) was determined. Test strains were identified by latex agglutination on blood agar, the heat-stable thermonuclease test and broth microdilution MICs of oxacillin and included 97 MRSA, 56 methicillin-susceptible Staphylococcus aureus, 52 methicillin resistant, and 49 methicillin-susceptible Staphylococcus species. Isolates were grown on trypticase-soy agar with 5% sheep red blood cells (TSAB), Mueller-Hinton agar (MHA), mannitol-salt agar (MSA), and four media designed for the selective growth of MRSA:TSAB with clindamycin and gentamicin, MHA with oxacillin, MSA with oxacillin, and lipovitellin-salt-mannitol agar (LVSM) with 1 microgram oxacillin disks applied. The mean sensitivity, specificity, and positive predictive value for the combination of latex agglutination with selective media for the identification of MRSA was 96%, 99% and 98% respectively.

A patient with native valve endocarditis caused by a vancomycin "heteroresistant" strain of Enterococcus faecium experienced failure of daptomycin monotherapy without evidence of daptomycin resistance. The infecting organism exhibited in vivo emergence of a vancomycin-susceptible subpopulation lacking vanA. Treatment with a combination of high-dose daptomycin, gentamicin, and high-dose ampicillin cleared the infection.

The purpose of this study was to determine the carriage rate, susceptibility pattern, and serotype distribution of Streptococcus pneumoniae in the nasopharynx of children younger than 2 years old in Lima, Peru. A total of 666 children were evaluated during 3 periods, 1997, 2001, and 2003. The overall pneumococcal carrier rate was 41%. Reduced susceptibility to penicillin was found in 5% (4/75) of isolates in 1997, 20% (15/75) in 2001, and 37% (40/109) in 2003. Reduced susceptibility to ceftriaxone was found in 12% of isolates in 2003. Serogroups 6, 19, 23, 15, and 14 accounted for 68% of all the isolates and for 81% of the penicillin-nonsusceptible strains. Only 65% of the isolated strains had serogroups found in the 7-valent conjugate pneumococcal vaccine. This highlights the importance of regional surveillance studies for effective vaccine strategies and treatment protocols.