Multidrug Resistance and the Predominance of blaCTX-M in 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: Escherichia coli (n = 17), Hafnia spp. (n = 13), Citrobacter spp. (n = 1), Enterobacter cloacae (n = 1), Klebsiella pneumoniae (n = 1), and K. oxytoca (n = 1). Animal isolates were identified as: E. coli (n = 11), E. cloacae (n = 1), Hafnia spp. (n = 1), and K. pneumoniae (n = 1). PCR investigation of blaCTX-M, blaTEM, and blaSHV genes showed that amongst the 48 isolates with a positive DDST, 41 (87.5%) carried the blaCTX-M gene, 1 isolate harbored the blaSHV gene, and 1 isolate coharbored blaCTX-M with blaSHV 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 blaCTX-M genes.