Antimicrobial Sensitivity Profile and Resistance Gene Research in Escherichia coli Isolated From Water and Fish From Lagoa da Conceição, Florianópolis, SC, Brazil

This study investigated the occurrence and the phenotypic and genotypic profile of antimicrobial resistance (AMR) in Escherichia coli isolated from water and fish samples from Lagoa da Conceição (Florianópolis, SC, Brazil). Analysis of 97 isolates revealed that 70.10% ( n = 68) of isolates exhibited resistance to at least one of the 17 antimicrobials tested, with a higher frequency during summer. Carbapenem (97.94%) and monobactam (89.70%) antimicrobials showed the highest sensitivity rates, whereas tetracycline demonstrated the highest resistance rates, with 51.02% in water isolates and 33.33% in fish isolates. Of the total analyzed, 29.90% of the isolates were susceptible to all antimicrobials tested, whereas 38.14% exhibited resistance to at least two antimicrobials, and the extended‐spectrum beta‐lactamase (ESBL) expression phenotype was detected in 15 water isolates and 2 fish isolates. In the genotypic analysis using polymerase chain reaction (PCR), the identified resistance genes included bla CTX‐M‐1 , bla CTX‐M‐2 , bla CTX‐M‐8 , bla CMY‐2 , bla TEM , and bla SHV , as well as qnrB , qnrS , tetA, and tetB . The bla CTX‐M , bla TEM and tetA genes were more frequently detected in water samples, whereas the tetB and qnrS genes appeared more frequently in fish isolates. The findings highlight a concerning scenario of environmental contamination by multidrug‐resistant bacteria.