Out into the Open: Occurrence of Extended-spectrum β-lactamase-producing and Multidrug-resistant Escherichia coli in Mariculture and Recreational Coastal Waters

Abstract The Tricycle Protocol is a One Health initiative that involves monitoring extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec), an opportunistic intestinal and extraintestinal pathogen that is recognized as critically important for the development of new antimicrobial agents and as a key indicator of water, food, and environmental contamination. This study aimed to detect and characterize, phenotypically and genotypically, the presence of ESBL-Ec in coastal waters collected from three urban marine ecosystems and mussels from a mariculture area in the metropolitan region of Rio de Janeiro City, Brazil. Eighteen samples from each beach and from mussels were collected between June 2022 and December 2023. A total of 299 E. coli strains were identified over the study period, of which 33 (11%) were initially identified as potential ESBL producers after selective pressure cultivation. Antimicrobial susceptibility analysis revealed a high frequency of resistance to ampicillin and third-generation cephalosporins, exceeding 80%. Eighteen (54.4%) of the 33 E. coli strains were classified as multidrug resistant (MDR). Genotypic confirmation revealed at least one ESBL gene ( bla CTX-M-1,2 , bla CTX-M-8 , bla CTX-M-14 , bla TEM , or bla SHV ) in 30 of the 33 strains, with bla CTX-M-1,2 being the most prevalent in samples from one estuarine beach and from the mariculture site. Additionally, the genes qnrS , intl1 , and intl2 were detected in 21.5%, 7.6%, and 1.3% of the confirmed ESBL-Ec strains, respectively. Since we could not associate the presence of MDR ESBL-Ec strains with unsuitable water classification, these findings underscore a grave threat to both human and animal health in densely inhabited coastal regions.