Salmonella isolation was conducted according to Global Foodborne Infections Network, laboratory protocol [17 (link)]. Briefly, 1 g of stool sample was suspended in 9 ml of buffered peptone water (Himedia, India) and incubated for 24 hours at 37°C. Then, 100 μl of the suspension was transferred to 10 ml of Rappaport Vassiliadis enrichment broth (RVB), (Oxoid, UK) and incubated for 24 h at 42°C. Suspension of 1 ml of each sample was also transferred to 9 ml of Muller-Kauffmann-Tetrathionate broth (Himedia, India) and Selanite-F broth (Becton-Dickinson, USA) and incubated for 24 h at 37°C. Samples from these three enrichment broths were streaked on to Xylose-Lysine Deoxycholate Agar (Himedia, India), and the plates were incubated at 37°C for 24-48 hours.
Biochemical tests were conducted for presumptive Salmonella colonies using Urea, Triple Sugar Iron Agar, Lysine Iron Agar, and Citrate as described elsewhere. Typical Salmonella colonies were confirmed using genus specific PCR as described previously [18 (link)]. Serotyping of Salmonella isolates was conducted at the National Microbiology Laboratory, Office International des Epizooties (OIE) Salmonella Reference Laboratory, Public Health Agency of Canada. Somatic (O) antigens were determined using slide agglutination tests whereas flagellar antigens using microplate agglutination technique [19 , 20 (link)].
Biochemical tests were conducted for presumptive Salmonella colonies using Urea, Triple Sugar Iron Agar, Lysine Iron Agar, and Citrate as described elsewhere. Typical Salmonella colonies were confirmed using genus specific PCR as described previously [18 (link)]. Serotyping of Salmonella isolates was conducted at the National Microbiology Laboratory, Office International des Epizooties (OIE) Salmonella Reference Laboratory, Public Health Agency of Canada. Somatic (O) antigens were determined using slide agglutination tests whereas flagellar antigens using microplate agglutination technique [19 , 20 (link)].