Prevalence of carbapenem-resistant Enterobacteriaceae in in- and out-of-hospital environments

Abstract

Introduction: Healthcare is recognized as a condition of high selective pressure (SP) due to the use of antimicrobials. The emergence of community bacterial species resistant to the antimicrobials most extensively used in hospitals is of concern, as is the case with Gram-negative rods producing extended-spectrum beta-lactamases (ESBL). Hospital colonization by carbapenem-resistant Enterobacteria (CRE) can persist for many months after hospital discharge, and their encoding genes can be transferred among different species. Methododology: Because of the scarcity of options due to resistance to carbapenems, we sought to evaluate the occurrence of CRE in stool samples from outpatients and inpatients of a University Hospital, for whom clinical and epidemiological data were obtained from the analysis of medical records. After parasitological examination, stool samples from outpatients and inpatients were diluted in saline (1:20, 1:1000 and 1:2000) solution and 0.1 mL seeding was performed on MacConkey Agar (MA) containing gentamicin 8 μg/mL and MA containing cephalexin 32 μg/mL. Once isolated, strains were identified by biochemical tests and AST (with imipenem, ertapenem, and meropenem) was performed according to CLSI (2020). Results: We isolated carbapenem-resistant strains of enterobacteria in 13 (43.3%) of the 30 inpatients and in 13 (29%) of the 31 outpatients (p>0.05). In 7 (23.3%) of the 30 inpatients and in 5 (16.1%) of the 31 outpatients, we isolated CRE at 1:1000 or 1:5000 dilutions of stool samples, which correspond to “microbial loads”. Ten bacterial species were isolated in the CRE related to the 13 inpatients and 13 outpatients, among whom we identified two or more species in 9 (69.2%) and 10 (76.9%), respectively. Even taking into account the limitations of the study due to the possibility of bias arising from the absence of data in the medical records, the detection of intestinal colonization with CRE in non-hospitalized individuals is of concern and may jeopardize the implementation of rational empirical therapy in patients of that community. Conclusion: It is possible that, as was the case of ESBL-producing strains decades ago, infections by carbapenem-resistant strains have become endemic in the community. In general, this development is a cause of concern, for plasmid-associated antimicrobial resistance strains, due to the fact that an often-recognized plasmid-associated fitness of bacterial cell favors persistence of the strains, even in the absence of antimicrobial (co-)selective pressures.