Escherichia coli produtoras de AmpC plasmidiais em águas de diferentes contextos ambientais no Rio de Janeiro: ocorrência e fenótipos de resistência associados

Abstract

Escherichia coli is an important microorganism in the context of antimicrobial resistance, as it is a commensal bacterium that can act as an opportunistic pathogen and has a remarkable ability to acquire and accumulate resistance genes through plasmids. Among the acquired genes found in E. coli, plasmid-mediated AmpC betalactamases (pAmpC) are more frequently associated with animal production and less commonly reported in human clinical infections. These enzymes are capable of hydrolyzing penicillins, third-generation cephalosporins, cephamycins, and monobactams, while remaining resistant to currently available clinical inhibitors. In parallel, carbapenemases such as NDM have been increasingly detected in E. coli, particularly in hospital environments, thereby compromising therapeutic options. This study aimed to investigate the presence of pAmpC-producing E. coli in different aquatic matrices in the municipality of Rio de Janeiro, including hospital effluents (HE), urban rivers impacted by domestic sewage (UR), rural rivers located near livestock farms (RR), and recreational beaches (RB). Sampling was conducted between August and December 2023. Samples were analyzed using the Colilert-Quanti-Tray method, with and without supplementation with cefoxitin (8 μg/mL), followed by isolation on MacConkey agar and replica plating on Chromagar Orientation supplemented with cefoxitin (32 μg/mL). Colonies were identified by MALDI-TOF, subjected to antimicrobial susceptibility testing, and analyzed by PCR for the detection of pAmpC genes. Isolates negative for pAmpC or resistant to imipenem were further evaluated for carbapenemase production using the Carba-NP test and PCR. A total of 69 E. coli isolates were obtained from 21 sampling sites (22 HE, 16 RB, 15 UR, and 16 RR). Results indicated that Colilert-Quanti-Tray with cefoxitin does not reliably reflect the actual abundance of cefoxitin-resistant E. coli in the sampled water, possibly due to the presence of other bacteria with intrinsic AmpC production in the same environment; however, it proved effective for the selective recovery of E. coli harboring pAmpC genes for further analyses. Additional resistance phenotypes ranged from AmpC- restricted profiles to resistance against up to seven additional antimicrobial classes. Hospital isolates were more resistant than those obtained from other environments, although environmental isolates also exhibited resistance to different combinations of antimicrobials, including azithromycin, tetracycline, gentamicin, ciprofloxacin, and sulfamethoxazole-trimethoprim. PCR screening revealed blaDHA in 37% (n=24) of isolates and blaCIT in 21% (n=16), while 42% (n=29) did not amplify any pAmpC genes. In addition, 30 isolates carried NDM-type carbapenemases, detected in rural rivers (n=1), and predominantly in recreational beaches (n=16) and hospital effluents (n=13), the latter including cases of co-occurrence with blaCIT (n=7). Only one isolate carried blaKPC. Strains harboring blaDHA genes displayed narrower betalactam resistance profiles than those classically associated with class C betalactamases, a phenomenon possibly linked to the underestimated frequency of this gene in both clinical and environmental samples. Furthermore, the findings highlight recreational beaches as hotspots for the dissemination of bla_NDM-positive E. coli in the metropolitan region of Rio de Janeiro.