The genus Vibrio comprises pathogens ubiquitous to marine environments. This study evaluated the cultivable Vibrio community in the Guanabara Bay (GB), a recreational, yet heavily polluted estuary in Rio de Janeiro, Brazil. Over one year, 66 water samples from three locations along a pollution gradient were investigated. Isolates were identified by MALDI-TOF mass spectrometry, revealing 20 Vibrio species, including several potential pathogens. Antimicrobial susceptibility testing confirmed resistance to aminoglycosides, beta-lactams (including carbapenems and third-generation cephalosporins), fluoroquinolones, sulfonamides, and tetracyclines. Four strains were producers of extended-spectrum beta-lactamases (ESBL), all of which carried beta-lactam and heavy metal resistance genes. The toxR gene was detected in all V. parahaemolyticus strains, although none carried the tdh or trh genes. Higher bacterial isolation rates occurred in months marked by higher water temperatures, lower salinities, and lower phosphorus and nitrogen concentrations. The presence of non-susceptible Vibrio spp. was related to indicators of eutrophication and sewage inflow. DNA fingerprinting analyses revealed that V. harveyi and V. parahaemolyticus strains non-susceptible to antimicrobials might persist in these waters throughout the year. Our findings indicate the presence of antimicrobial-resistant and potentially pathogenic Vibrio spp. in a recreational environment, raising concerns about the possible risks of human exposure to these waters.

Bacterial resistance to antimicrobials is a global public health problem that surpasses the human context and can be increased by pollution. However, the lack of systematic monitoring of resistance in some aquatic matrices, such as tropical estuaries, makes it unknown whether its occurrence is associated with anthropogenic pollution in these environments. Therefore, we investigated the occurrence of extended‐spectrum beta‐lactamases (ESBLs) producing Escherichia coli as a resistance indicator for 12 consecutive months at three representative points of a pollution gradient in Guanabara Bay (GB), Brazil. Sixty‐six E. coli strains were selected from 72 samples of GB waters in the presence of ceftriaxone (8 μg mL−1) and identified by MALDI‐TOF MS. Of the 66, 55 (83.3%) strains were ESBL producers. They carried beta‐lactamase/ESBL genes, with the predominance of blaCTX‐M (54, 98.2%), especially the blaCTX‐M‐1,2 allele (49.1%). These strains were detected frequently (81.8%) from the point with the highest pollution levels. Furthermore, the marker for Class 1 integron, intI1 gene, was detected in 54.5% of ESBL producers. These data suggest an association between antimicrobial‐resistant E. coli and sewage pollution in aquatic environments raising concerns about the possible risks of human exposure to these waters and fish consumption.

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