Detection and genetic characterisation of ESBL, carbapenemase, and mcr-1 genes in Gram-negative bacterial isolates from companion animals in Batna, Algeria

The escalating prevalence of drug-resistant Gram-negative bacteria represents a widespread threat to global public health. This study aimed to investigate the occurrence and genetic determinants of extended-spectrum β-lactamases (ESBLs), carbapenemases, and mcr-encoding genes in GNB isolates from companion animals in the city of Batna, Algeria. In total, 50 faecal samples were collected from various veterinary clinics and pet shops, including direct collection of faecal droppings (n = 22) and rectal swabs (n = 28). After selective isolation, Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry was used to identify representative colonies. Susceptibility testing was carried out using the disk diffusion method. ESBLs, carbapenemases, and colistin resistance determinants were searched for by real-time PCR. Thirty-seven strains were isolated and were mostly identified as Escherichia coli (n = 21). Molecular analysis revealed that 23 isolates carried only the bla_ESBL genes. The genes which were most detected were bla_CTX-M-A (n = 14) and bla_CTX-M-A associated with bla_TEM (n = 8). Two Enterobacter cloacae isolates were positive for the bla_OXA-48 gene while one of them additionally carried the bla_CTX-M-A gene. The mcr-1 gene was detected in one Enterobacter kobei isolate. To the best of our knowledge, this is the first report of E. kobei carrying the mcr-1 gene from rectal swabs of cats.