Occurrence of multidrug-resistant ESBL-producing Enterobacteriaceae in livestock and in silico identification of probable catalytic domains in circulating ESBL variants.

This study was conducted to detect the occurrence and phenotypic resistance pattern of extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in livestock using docking-based analysis to reveal the classes of antibiotics against which ESBL-producers are active. Rectal swabs from healthy cattle (n = 100), goats (n = 88), and pigs (n = 66) were collected from backyard farms in Andaman and Nicobar Island (India). In total, 304 isolates comprising Escherichia coli (131), Salmonella (75), and Klebsiella pneumoniae (98) were recovered. The phenotypic resistance pattern showed that the highest resistance was found against erythromycin, followed by ampicillin/cloxacillin, ciprofloxacin, amoxicillin/clavulanic acid, and oxytetracycline. Screening of the isolates demonstrated maximum presence of blaTEM-Type, followed by blaCTX-M-Type, and blaSHV-Type. Sequence homology revealed the presence of CTX-M-15, SHV-228, SHV-40, and TEM-82. The possible interactions of CTX-M-15 with cephalosporins and SHV with carbapenems have been identified by docking analysis. The study revealed the occurrence of ESBL-producers with circulating emerging ESBL variants like SHV-40, along with the common variants with clinical relevance (CTX-M-15, TEM-82), highlighting the potential role of livestock as reservoirs for antimicrobial resistance genes. Identifying these ESBLs in livestock is crucial for understanding their contribution to the dissemination of antimicrobial resistant bacteria into the human food chain.