About

Gerard Gawrys, Pharm.D., is an adjunct assistant professor and inpatient coordinator for the San Antonio region at the University of Texas at Austin College of Pharmacy. After graduating from the St. Louis College of Pharmacy, he completed a PGY1 pharmacy practice residency at the VA Hudson Valley HealthCare System in Castle Point, NY, followed by a PGY2 residency in infectious diseases at the Milwaukee VA Medical Center. Since August 2013, he has served as an infectious disease clinical pharmacy specialist, coordinating antimicrobial stewardship efforts within the Methodist Healthcare System in San Antonio. He is also the residency program director for the PGY1 pharmacy residency program at Methodist Hospital and Methodist Children’s Hospital. His professional focus includes infectious diseases and antimicrobial stewardship, contributing to the advancement of patient care and professional development in the pharmaceutical sciences.

Research topics

• Medicine
• Genetics
• Microbiology
• Biology
• Environmental health

Selected publications

• P-1678. Gram-Negative Rod Bacteremia due to Organisms not Detected on the BioFire® Blood Culture Identification 2 (BCID2) Panel: Time to Effective Antimicrobial Therapy

  Open Forum Infectious Diseases · 2026-01-01

  articleOpen access

  Abstract Background The BioFire® BCID2 panel has revolutionized rapid diagnostics, reducing time to organism identification and targeted therapy. Despite detectability of 16 additional organisms and resistance genes compared to the original panel, limited data exists regarding the clinical impact of BCID-2 negative Gram-Negative Rod (GNR) bacteremia cases. Methods We evaluated the effect of BCID2-negative GNR bacteremia on time to effective therapy (TTET). Overall, 135 patients had BCID2-negative GNR bacteremia from July 2020 to August 2024. Further analysis examined the distribution of BCID-2 negative GNR pathogens and compared clinical outcomes between aerobic and anaerobic cases. Descriptive statistics were used to summarize patient characteristics. Chi-square and Wilcoxon Rank Sum tests were used to compare health outcomes. P-values were statistically significant if they were less than a pre-specified alpha level of 0.05. Results At 12 hours post-BCID2 result, 24% (32/135) of patients lacked effective therapy. This group consisted of 15 aerobes and 17 anaerobes, with a median (interquartile range) TTET of 41 (20-51) hours. A 20-hour increase in median TTET was observed in the aerobic group vs. the anaerobic group: 47 (39-59) vs. 27 (18-42), p=0.02. Aerobes not on effective therapy were led by Pseudomonas putida (13%), Achromobacter spp. (13%), Brucella anthropi (13%), and Myroides spp. (13%). Despite these findings, a 7-day increase in median hospital length of stay (LOS) was observed among anaerobes: (17 (10-34) vs. 10 (7-19) days, p=0.01), with Bacteroides thetaiotaomicron (n=23) and Fusobacterium spp. (n=27) accounting for 60% (50/83) of the anaerobic pathogens. Conclusion These findings indicate that nearly 1 in 4 patients lacked effective therapy 12 hours after a negative BCID2 result. Over half of these cases involved anaerobic pathogens, particularly Bacteroides thetaiotaomicron and Fusobacterium spp., which were associated with a prolonged hospital LOS. Disclosures Christopher R. Frei, PharmD, FCCP, BCPS, Amgen: Grant/Research Support|AstraZeneca: Grant/Research Support

  PublisherOA PDFDOI

• P-1925. Comparison of Outcomes in Obese Versus Non-Obese Patients Receiving Fluconazole and/or Micafungin for the Treatment of Candidemia

  Open Forum Infectious Diseases · 2026-01-01

  articleOpen access

  Abstract Background Clinical practice guidelines recommend initial echinocandin therapy followed by oral azole step-down therapy for the treatment of candidemia. However, the pharmacokinetics of these medications can be altered by patient characteristics, such as obesity. The purpose of this study was to compare outcomes in obese versus non-obese patients with candidemia treated with fluconazole and/or micafungin. Methods This single-center, retrospective cohort study included adults with candidemia admitted from 1/1/20 - 12/1/24. Patients receiving < 48 hours of fluconazole and/or micafungin, those with resistance to both agents, or those not receiving antifungals within 24 hours of positive culture were excluded. Treatment failure, the primary composite outcome comprised of 14-day mortality, 14-day microbiologic failure, and 30-day candidemia recurrence, was compared between obese (BMI > 30 kg/m2) and non-obese patients. Secondary outcomes included hospital length of stay (LOS). Results Ninety-six patients were included, 34 (35%) obese and 62 (65%) non-obese. Eleven (32%) obese and 7 (11%) non-obese patients received micafungin doses > 100 mg/day (P = 0.01). Among patients receiving fluconazole (n = 48), the median (interquartile range, IQR) weight-normalized dose to minimum inhibitory concentration (MIC) ratio was 6.6 (3.9-10.8) and 9.7 (3.3-21.2) in obese versus non-obese patients, respectively (P = 0.62). Treatment failure occurred in 13 (38%) obese and 20 (32%) non-obese patients (P=0.56). The median (IQR) LOS was 23 days in obese patients and 22 days in non-obese patients (P = 0.96). Conclusion Obesity was not associated with treatment failure in this cohort of hospitalized patients with candidemia. Nearly one-third of obese patients received micafungin doses > 100 mg/day, and the weight-normalized fluconazole dose to MIC ratios did not significantly differ in obese versus non-obese patients. Depending on local epidemiologic factors, it may be prudent to consider higher doses of fluconazole and/or micafungin in obese patients with candidemia. Disclosures Travis J. Carlson, PharmD, BCIDP, Aimmune Therapeutics, Inc.: Speaker bureau

  PublisherDOI

• A Case of Recurrent Candida Glabrata Fungemia and Successful Treatment with Rezafungin

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• A case of recurrent Candida glabrata fungemia and successful treatment with rezafungin

  IDCases · 2025-01-01 · 3 citations

  articleOpen access

  Antifungal resistance in Candida glabrata can develop to different classes of drugs, including the azoles and echinocandins. This organism is known to cause infective endocarditis with a particular predilection for prosthetic valves. Herein we present a case of recurrent fungemia with C. glabrata in a middle-aged woman with Tetralogy of Fallot who had a right ventricle to pulmonary artery conduit, and a transcatheter pulmonary valve replacement in the past. Her isolate showed increasing minimum inhibitory concentrations (MIC) to various antifungals with higher MICs to azoles, including resistance to fluconazole, resulting in limited treatment options. She had affliction of her prosthetic pulmonic valve with C. glabrata and was treated with the second-generation echinocandin, rezafungin, for six months. This case illustrates the tolerability profile of long-term treatment with rezafungin.

  PublisherDOI

• 469 Diverse Role of blaCTX-M and Porins in Mediating Ertapenem Resistance Among Carbapenem Resistant Enterobacterales

  Journal of Clinical and Translational Science · 2024-04-01

  articleOpen access

  OBJECTIVES/GOALS: In this study, we aim to report the role of porins and bla CTX-M β-lactamases among Escherichia coli and Klebsiella pneumoniae, focusing on emerging carbapenem resistant Enterobacterales (CRE) subtypes, including non-carbapenemase producing Enterobacterales (NCPE) and ertapenem-resistant but meropenem-susceptible (ErMs) strains. METHODS/STUDY POPULATION: Whole genome sequencing was conducted on 76 carbapenem-resistant isolates across 5 hospitals in San Antonio, U.S. Among these, NCP isolates accounted for the majority of CRE (41/76). Identification and antimicrobial susceptibility testing (AST) results were collected from the clinical charts. Repeat speciation was determined through whole genome sequencing (WGS) analysis and repeat AST, performed with microdilution or ETEST®. Minimum inhibitory concentrations (MIC) were consistent with Clinical and Laboratory Standards Institute (CLSI M100, ED33). WGS and qPCR were used to characterize the resistome of all clinical CRE subtypes, while western blotting and liquid chromatography with tandem mass spectrometry (LC-MS-MS) were used to determine porin expression and carbapenem hydrolysis, respectively. RESULTS/ANTICIPATED RESULTS: bla CTX-M was found to be most prevalent among NCP isolates (p = 0.02). LC-MS/MS analysis of carbapenem hydrolysis revealed that bla CTX-M -mediated carbapenem hydrolysis, indicating the need to reappraise the term, “non-carbapenemase (NCP)®” for quantitatively uncharacterized CRE strains harboring bla CTX-M . Susceptibility results showed that 56% of all NCPE isolates had an ErMs phenotype (NCPE vs. CPE, p < 0.001), with E. coli driving the phenotype (E. coli vs. K. pneumoniae, p < 0.001). ErMs strains carrying bla CTX-M , had 4-fold more copies of bla CTX-M than ceftriaxone-resistant but ertapenem-susceptible isolates (3.7 v. 0.9, p < 0.001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage ofompC. DISCUSSION/SIGNIFICANCE: Overall, this work provides evidence of a collaborative effort between bla CTX-M and OmpC in NCP strains that confer resistance to ertapenem but not meropenem. Clinically, CRE subtypes are not readily appreciated, potentially leading to mismanagement of CRE infected patients. A greater focus on optimal treatments for CRE subtypes is needed.

  PublisherOA PDFDOI

• Diverse Role of blaCTX-M and Porins in Mediating Ertapenem Resistance among Carbapenem-Resistant Enterobacterales

  Antibiotics · 2024-02-13 · 9 citations

  articleOpen access

  Among carbapenem-resistant Enterobacterales (CRE) are diverse mechanisms, including those that are resistant to meropenem but susceptible to ertapenem, adding further complexity to the clinical landscape. This study investigates the emergence of ertapenem-resistant, meropenem-susceptible (ErMs) Escherichia coli and Klebsiella pneumoniae CRE across five hospitals in San Antonio, Texas, USA, from 2012 to 2018. The majority of the CRE isolates were non-carbapenemase producers (NCP; 54%; 41/76); 56% of all NCP isolates had an ErMs phenotype. Among ErMs strains, E. coli comprised the majority (72%). ErMs strains carrying blaCTX-M had, on average, 9-fold higher copies of blaCTX-M than CP-ErMs strains as well as approximately 4-fold more copies than blaCTX-M-positive but ertapenem- and meropenem-susceptible (EsMs) strains (3.7 vs. 0.9, p < 0.001). Notably, carbapenem hydrolysis was observed to be mediated by strains harboring blaCTX-M with and without a carbapenemase(s). ErMs also carried more mobile genetic elements, particularly IS26 composite transposons, than EsMs (37 vs. 0.2, p < 0.0001). MGE- ISVsa5 was uniquely more abundant in ErMs than either EsMs or ErMr strains, with over 30 more average ISVsa5 counts than both phenotype groups (p < 0.0001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage of ompC. Overall, our findings characterize both collaborative and independent efforts between blaCTX-M and OmpC in ErMs strains, indicating the need to reappraise the term “non-carbapenemase (NCP)”, particularly for strains highly expressing blaCTX-M. To improve outcomes for CRE-infected patients, future efforts should focus on mechanisms underlying the emerging ErMs subphenotype of CRE strains to develop technologies for its rapid detection and provide targeted therapeutic strategies.

  PublisherOA PDFDOI

• Diverse Role of blaCTX-M and Porins in Mediating Ertapenem Resistance Among Carbapenem Resistant Enterobacterales

  Preprints.org · 2024-01-03 · 5 citations

  preprintOpen access

  This study investigates the emergence of ertapenem-resistant, meropenem-susceptible (ErMs) among non-carbapenemase producing (NCP) and carbapenemase producing (CP) Escherichia coli and Klebsiella pneumoniae. As mutations for ertapenem resistance establish the genetic background for non-carbapenemase meropenem resistance, there is a great need for antibiotic stewards and researchers to understand the determinants of a strain’s propensity to become resistant. Whole genome sequencing was conducted on clinical carbapenem-resistant E. coli (CREC) and K. pneumoniae (CRKP) across 5 hospitals in San Antonio, U.S. from 2012-2018. The majority of carbapenem resistant Enterobacterales (CRE) were NCP (54%; 41/76). The blaCTX-M was found to be most prevalent among NCP isolates (p = 0.02). LC-MS/MS analysis of carbapenem hydrolysis revealed that blaCTX-M-mediated carbapenem hydrolysis, indicating the need to reappraise the term, “non-carbapenemase (NCP)” for quantitatively uncharacterized CRE strains harboring blaCTX-M. Antimicrobial susceptibility results showed that 56% of all NCPE isolates had an ErMs phenotype (NCPE vs. CPE, p < 0.001), with E. coli driving the phenotype (E. coli vs. K. pneumoniae, p < 0.001). ErMs strains carrying blaCTX-M, had approximately 4-fold more copies of blaCTX-M than ceftriaxone-resistant but ertapenem and meropenem susceptible (EsMs) isolates (3.7 v. 0.9, p < 0.001). ErMs also carried more mobile genetic elements (MGEs), particularly IS26 composite transposons, than EsMs (37 vs. 0.2, p < 0.0001). Immunoblot analysis demonstrated the absence of OmpC expression in NCP-ErMs E. coli, with 92% of strains lacking full contig coverage of ompC. Overall, this work provides evidence of a collaborative effort between blaCTX-M and OmpC in NCP strains that confer resistance to ertapenem but not meropenem. To thwart potential mismanagement of CRE infected patients, future efforts should focus on understanding the mechanism(s) underlying OmpC loss, developing rapid methods to detect blaCTX-M copy number variants, and targeted antimicrobials for NCPE and ErMs strains.

  PublisherOA PDFDOI

• Molecular Rapid Diagnostics Improve Time to Effective Therapy and Survival in Patients with Vancomycin-Resistant Enterococcus Bloodstream Infections

  Antibiotics · 2023-01-19 · 5 citations

  articleOpen accessCorresponding

  Delays in appropriate antibiotic therapy are a key determinant for deleterious outcomes among patients with vancomycin-resistant Enterococcus (VRE) bloodstream infections (BSIs). This was a multi-center pre/post-implementation study, assessing the impact of a molecular rapid diagnostic test (Verigene® GP-BC, Luminex Corporation, Northbrook, IL, USA) on outcomes of adult patients with VRE BSIs. The primary outcome was time to optimal therapy (TOT). Multivariable logistic and Cox proportional hazard regression models were used to determine the independent associations of post-implementation, TOT, early vs. delayed therapy, and mortality. A total of 104 patients with VRE BSIs were included: 50 and 54 in the pre- and post-implementation periods, respectively. The post- vs. pre-implementation group was associated with a 1.8-fold faster rate to optimized therapy (adjusted risk ratio, 1.841 [95% CI 1.234–2.746]), 6-fold higher likelihood to receive early effective therapy (<24 h, adjusted odds ratio, 6.031 [2.526–14.401]), and a 67% lower hazards for 30-day in-hospital mortality (adjusted hazard ratio, 0.322 [0.124–1.831]), after adjusting for age, sex, and severity scores. Inversely, delayed therapy was associated with a 10-fold higher risk of in-hospital mortality (aOR 10.488, [2.497–44.050]). Reduced TOT and in-hospital mortality were also observed in subgroups of immunosuppressed patients in post-implementation. These findings demonstrate that the addition of molecular rapid diagnostic tests (mRDT) to clinical microbiology and antimicrobial stewardship practices are associated with a clinically significant reduction in TOT, which is associated with lower mortality for patients with VRE BSIs, underscoring the importance of mRDTs in the management of VRE infections.

  PublisherOA PDFDOI

• 118. Machine Learning Approaches to Predicting Treatment Outcomes for Carbapenem-Resistant Enterobacterales in a Region with High Prevalence of Non-Carbapenemase Producers

  Open Forum Infectious Diseases · 2021-11-01

  articleOpen access

  Abstract Background Carbapenem-resistant Enterobacterales are a growing threat globally. Early detection of CRE is necessary for appropriate treatment and infection control measures. Many hospital labs can test for carbapenemase production; however, in some regions, including South Texas, the majority of CRE are non-carbapenemase producing (NCPE). This study had two interrelated aims to develop decision rules tailored to a region with high prevalence of NCPE to predict 1) antimicrobial resistance (AMR) from whole genome sequencing (WGS) data and 2) CRE treatment outcomes. Methods To better understand links between resistome, phenotypic AMR, and prediction of outcomes for CRE, we developed decision rules to build machine learning prediction models. We conducted WGS and antibiotic susceptibility testing (21 antibiotics) on CRE isolates from unique patients across 5 hospitals in the South Texas region between 2013 and 2020. Day 30 outcomes were based on desirability of outcome ranking (DOOR). The overall classification accuracies of the models are reported. Results Overall 146 CRE isolates were included, 97 were used to train each model, and 49 were used for validation. Among the K. pneumoniae and E. coli CRE isolates that were available with susceptibility data, the majority (62%) were NCPE. For the clinical recovery model (DOOR), the combination of admission ICU status, piperacillin-tazobactam (PT) MIC > 16, presence of sul gene, and polymyxin-sparring regimens associated with an overall accuracy of 95% for having a worse DOOR. Majority (60%) of patients were empirically treated with piperacillin-tazobactam; notably, less than 33% isolates had PT MIC ≤ 16. Interestingly, combined effects of isolates that did not harbor carbapenemases, blaOXA-1, blaCTX-M-15, blaCMY, or aac(6’)ib-cr genes resulted in a decision rule with a 95.7% overall accuracy for susceptibility to PT (MIC < 16 ug/mL). Conclusion Herein, we used machine learning approaches to predict AMR and treatment-based outcomes linked with WGS data in a region with predominantly NCPE infections. Machine learning can obtain a model that can make repeatable predictions, further data can improve the accuracy and guide tailored clinical decision-making. Disclosures Grace Lee, PharmD, PhD, BCPS, Merck Co. (Grant/Research Support)NIA/NIH (Research Grant or Support)

  PublisherOA PDFDOI

• Early antimicrobial prophylaxis in autologous stem cell transplant recipients: Conventional versus an absolute neutrophil count‐driven approach

  Transplant Infectious Disease · 2021-07-13 · 9 citations

  articleOpen access

  Abstract Background Autologous hematopoietic stem cell transplantation (HSCT) recipients are at increased risk of developing life‐threatening infections. There is discordance in published recommendations for timing of pre‐ and post‐transplant antimicrobial prophylaxis in this patient population, and these recommendations are unsubstantiated by any published comparative analyses. Methods An observational, pre‐ and post‐intervention study of consecutive autologous HSCT recipients was conducted over a 2‐year period. In the pre‐intervention cohort, antimicrobial prophylaxis was initiated on the day prior to transplant. In the post‐intervention cohort, antimicrobials were initiated once absolute neutrophil count (ANC) reached ≤500 cells/mm 3 . The primary outcome assessed was frequency of febrile occurrences. Secondary outcomes included total days of prophylaxis, positive blood cultures, all‐cause mortality, Clostridioides difficile infection rates, and length of stay. Results A total of 208 patients were included in the final analysis, with 105 and 103 patients in the pre‐ and post‐intervention cohorts, respectively. The majority of patients included were male. Lower rates of fever occurrences were observed in the post‐intervention cohort (83% pre‐ vs. 69% post‐intervention; p = 0.019). A significant reduction in the mean antibacterial days per patient was identified (9.7 vs. 4.6 days; p < 0.001). Other than lower rates of febrile neutropenia in the post‐intervention cohort, no differences were identified in secondary outcomes. In multivariable analyses, ANC‐driven prophylaxis was independently associated with decreased febrile events. Conclusions Delaying prophylaxis until severe neutropenia was not associated with increased febrile events or other secondary clinical outcomes evaluated. This approach is associated with a significant reduction in antimicrobial exposure.

  PublisherOA PDFDOI

Frequent coauthors

• Grace C. Lee

  South Texas Veterans Health Care System

  134 shared

• Cody A. Black

  The University of Texas at Austin

  115 shared

• Samantha Aguilar

  University Health System

  77 shared

• Sarah M. Bandy

  Austin College

  73 shared

• Raymond Benavides

  The University of Texas at Austin

  61 shared

• Kelly R. Reveles

  The University of Texas at Austin

  52 shared

• Jim M. Koeller

  Austin College

  48 shared

• Christopher B. Jackson

  University of Helsinki

  46 shared

Labs

• Gerard Gawrys LabPI