Isolation and characterisation of multi-drug resistant non-typhoidal Salmonella spp. from cloacal samples of broilers in the Wayanad district

The purpose of this study was to investigate the occurrence of multi-drug resistant non-typhoidal Salmonella spp. (MDR-NTS) in Wayanad district, Kerala. Initially, the cloacal swabs (n = 31) collected from different broiler farms in the Wayanad district were subjected to isolation and identification of Salmonella spp. and confirmation by polymerase chain reaction (PCR). A total of 24 (77.42 %) Salmonella spp. isolates were recovered by isolation and identification in selective media and confirmed by PCR assay. Out of the 24 confirmed isolates, 20 (83.33 %) were confirmed to be NTS strains, of which 2 (8.33 %) belonged to S. Typhimurium and 18 (75 %) were S. Enteritidis. Later, the antibiotic susceptibility testing was carried out by a disc diffusion assay using 8 different classes of antibiotics. Of the 24 isolates tested, 16 (66.67 %) were resistant to more than 4 classes of antibiotics, 10 (41.67 %) were resistant to more than or equal to 6 classes of antibiotics, and 2 (8.33 %) were found to produce extended-spectrum beta-lactamase. Out of the 24 Salmonella spp. isolated, 21 (87.5 %) were confirmed to be MDR in nature, while 18 NTS strains exhibited MDR pattern. The occurrence of MDR-NTS strains in broilers necessitates strict biosecurity measures to be adopted to reduce disease incidence and avoid indiscriminate use of antibiotics in broiler farms to safeguard public health. Keywords: Antibiotic, broiler chicken, multi-drug resistance, non-typhoidal Salmonella