GES-5 among the β-lactamases detected in ubiquitous bacteria isolated from aquatic environment samples

In this study, we investigated the -lactamase-encoding genes responsible for -lactam resistance phenotypes detected among 56 Gram-negative isolates (Gamma- and Alpha-proteobacteria) recovered from wastewater, urban streams, and drinking water. The -lactam resistance mechanisms detected in 36 isolates comprised the presence of class A (bla(TEM-1), bla(SHV-1), bla(SHV-11), bla(GES-5)), class B (ImiS, L1), class C (bla(CMY-2), bla(CMY-34), bla(CMY-65), bla(CMY-89), bla(CMY-90), bla(ACC-5), bla(ACT-13)), and class D (blaOXA-309)-lactamase-encoding genes, some variants described for the first time here. Notably, the results showed antimicrobial resistance genes related not only to commonly used antibiotics, but also to carbapenems, providing the first description of a GES-5-producing Enterobacteriaceae. The importance of ubiquitous bacteria thriving in aquatic environments as reservoirs or carriers of clinically relevant resistance determinants was confirmed, and the need to monitor water habitats as potential sources for the emergence and/or spread of antibiotic resistance in the environment was highlighted.