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

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.

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

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.

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

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/mm3 . 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.

The impact of rapid diagnostic testing, surveillance software, and clinical pharmacist staffing at a large community hospital in the management of Gram-negative bloodstream infections.

Rapid diagnostic testing (RDT) combined with an antimicrobial stewardship program (ASP) has shown improved outcomes in bloodstream infections (BSIs). We assessed the impact of RDT, surveillance software, and ASP pharmacist staffing on time to optimal therapy (TOT) in Gram-negative BSIs. Adults with Gram-negative BSIs were included in this retrospective evaluation across 2 study periods. The preimplementation group (n = 121) had longer TOT than the postimplementation group (n = 120) (59.6 ±â€¯36.2 h versus 29.0 ±â€¯24.2 h, P < 0.001). Escalation (51.1 ±â€¯26.4 h versus 16.9 ±â€¯15.7 h, P < 0.001) and de-escalation (63.1 ±â€¯39.5 h versus 39.2 ±â€¯25.6 h, P < 0.01) of therapy were shorter in the postimplementation group. TOT for patients with multidrug-resistant organisms (MDROs) was shorter in the postimplementation group (61.8 ±â€¯37.2 h versus 21.9 ±â€¯18.8 h, P < 0.001). TOT was shorter during fully staffed clinical pharmacist hours (30.6 ±â€¯58.9 h versus 19.7 ±â€¯31.7 h, p = 0.014). Implementation of RDT and surveillance software with an ASP decreased TOT for Gram-negative BSIs, including MDROs.

Predominance of Non-carbapenemase Producing Carbapenem-Resistant Enterobacterales in South Texas.

BACKGROUND: Carbapenem-resistant Enterobacterales (CRE) pose a significant global public health threat. Resistance among CRE is particularly complex, owing to numerous possible resistance mechanisms and broad definitions. We aimed to characterize the clinical and molecular profiles of CRE in the South Texas region. MATERIALS AND METHODS: We compared the clinical, genotypic, and phenotypic profiles of carbapenemase producing Enterobacterales (CPE) with those of non-carbapenemase producers (NCPE) isolated from South Texas, United States between 2011 and 2019. Molecular characteristics and resistance mechanisms were analyzed using whole-genome sequences. RESULTS: The majority (59%) of the CRE isolates were NCPE while 41% of isolates harbored carbapenemases, predmonantly bla KPC-type. The most common CPE was Klebsiella pneumoniae while majority of Enterobacter cloacae and Escherichia coli were NCPE Among K. pneumoniae, the clonal group 307 has emerged as a predmoninant group and was associated with as many CRE infections as the previous common clonal group 258. Patients with NCPE compared to CPE infections were associated with higher antimicrobial exposure prior to culture collection (days of therapy, 795 vs. 242; p < 0.001) and emergency department visits within past 90 days (22% vs. 4%; p = 0.011). The all cause 30-day mortality was 21%. CONCLUSIONS: This study highlights the diversity of resistance mechanisms underlying CRE in South Texas, with 59% not harboring a carbapenemase. Individuals with NCPE infections were more likely to have had prior antimicrobial therapy and emergency department visits compared to those with CPE. Identification and distinction of these mechanisms by rapid identification of species and carbapenemase would allow for optimal treatment and infection control efforts.