Multidrug Resistance and the Predominance of <b><i>bla</i></b><sub>CTX-M</sub> in<sub></sub> Extended Spectrum Beta-Lactamase-Producing Enterobacteriaceae of Animal and Water Origin

The aim of this work was the genetic characterization of cefotaxime-resistant enterobacteria from animals (53 samples), the surface water of rivers (17 samples), and wastewater treatment plants (43 samples) in Tunisia. A total of 48 (42.4%) cefotaxime-resistant isolates were recovered. An extended spectrum beta-lactamase (ESBL) phenotype with a positive double-disk synergy test (DDST) was exhibited by 34 (70.8%) and 14 (29.1%) isolates from water and animal origins, respectively. Isolates from water were identified as: <i>Escherichia coli</i> (<i>n</i> = 17), <i>Hafnia</i> spp<i>.</i> (<i>n</i> = 13), <i>Citrobacter</i> spp<i>.</i> (<i>n</i> = 1), <i>Enterobacter cloacae</i> (<i>n</i> = 1), <i>Klebsiella pneumoniae</i> (<i>n</i> = 1), and <i>K. oxytoca</i> (<i>n</i> = 1). Animal isolates were identified as: <i>E. coli</i> (<i>n</i> = 11), <i>E. cloacae</i> (<i>n</i> = 1), <i>Hafnia</i> spp<i>.</i> (<i>n</i> = 1), and <i>K. pneumoniae</i> (<i>n</i> = 1). PCR investigation of <i>bla</i>_CTX-M, <i>bla</i>_TEM, and <i>bla</i>_SHV genes showed that amongst the 48 isolates with a positive DDST, 41 (87.5%) carried the <i>bla</i>_CTX-M gene, 1 isolate harbored the <i>bla</i>_SHV gene, and 1 isolate coharbored <i>bla</i>_CTX-M with <i>bla</i>_SHV genes. The class 1 and 2 integrons were detected in 27 (56.2%) and 1 (2%) isolates, respectively. Our study showed a significant occurrence of ESBL-producing enterobacteria in animals and aquatic environments with a predominance of <i>bla</i>_CTX-M genes.