ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF ESCHERICHIA COLI AND ENTEROBACTER SPP. CAUSING COMMUNITY-ACQUIRED INFECTIONS IN MÉRIDA, VENEZUELA.

Abstract

Enterobacterales are among the leading causes of community-acquired infections and represent an increasing public health concern due to the emergence of antimicrobial resistance. This study aimed to characterize the antimicrobial susceptibility profiles and resistance phenotypes of Escherichia coli and Enterobacter spp. isolates recovered from clinical specimens processed in a microbiology laboratory in Mérida, Venezuela, between January 2017 and May 2021. A descriptive, retrospective, cross-sectional study was conducted, including 39 clinically relevant isolates corresponding to E. coli (n=17) and Enterobacter spp. (n=22). Bacterial identification was performed using conventional biochemical methods, and antimicrobial susceptibility testing was carried out by disk diffusion according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Phenotypic detection of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases was also performed. Escherichia coli was the predominant pathogen isolated from urine samples (58.8%), whereas Enterobacter spp. predominated in skin and wound secretion specimens. Ten antimicrobial susceptibility profiles were identified among E. coli isolates and eight among Enterobacter spp., revealing substantial phenotypic diversity. E. coli isolates exhibited high susceptibility to cefepime, aztreonam, imipenem, and meropenem, but showed high resistance rates to ampicillin, cefuroxime, and trimethoprim-sulfamethoxazole. In addition, susceptibility patterns compatible with ESBL production and multidrug-resistant phenotypes were identified. Enterobacter spp. isolates retained susceptibility to third- and fourth-generation cephalosporins, monobactams, and carbapenems, while displaying frequent resistance to β-lactam/β-lactamase inhibitor combinations, a pattern consistent with inducible chromosomal AmpC production. No isolate exhibited a phenotype compatible with carbapenemase production. These findings demonstrate the circulation of Enterobacterales with diverse resistance profiles in community-acquired infections and highlight the importance of continuous microbiological surveillance to support empirical antimicrobial therapy and prevent the dissemination of emerging resistance mechanisms.