Detection of virulent and ESBL-resistant Salmonella species from cattle and associated farm environment

Abstract

The aim of this study was to explore the virulence characteristics and antibiotic resistance in Salmonella species isolated from cattle farms. During the study, 10 cattle farms were selected and from each farm, 35 samples consisting of faeces, milk, udder swabs, hand swabs, floor swabs, animal drinking water, pit water, composite fodder sample, and dairy utensil swabs were collected. Accordingly, 350 samples were collected from 10 farms and processed for the detection of Salmonella spp. Presumptive Salmonella isolates were confirmed by PCR and characterized for virulence and antibiotic resistance genes. From 350 samples, 19 (5.40%) Salmonellae were recovered, and out of 19 Salmonellae, 12 were ESBL producers. Similarly, out of 19 isolates, spvC was the predominant gene detected (42.10%), followed by stn (31.5%), and spvR (26.31%), whereas, invA, and iroB genes were detected in all 19 Salmonella isolates. Most of the Salmonella isolates were multi-drug resistant strains exhibiting resistance to nalidixic acid (94.73%), tetracycline (36.84%), and ceftazidime (42.10%). Out of 12 ESBL-positive Salmonellae, 9 (75%) isolates harboured ESBL genes, viz. blaSHV and blaTEM (25% each) and blaCTX-M and blaOXA (16.66% each). Six Salmonella isolates showed the presence of tetA gene. The current study indicated healthy cattle and the associated farm environments could be a source of virulent and drug-resistant Salmonellae. The current study also advocates phenotypic and genotypic antibiotic resistance monitoring at farm animal premises and agricultural ecosystems.

Keywords

• Antibiotic resistance, Cattle, ESBL, Salmonella, Virulence