Vol. 11, Special Issue 2 (2022)

Method: A total of 100 fecal samples were collected from calves of cattle and buffalo of below 3 months of age. Sterile fecal swabs (Hi-media, India) were used for sample collection. All the samples were transported immediately to the laboratory under cold chain and were processed for isolation of Salmonella spp. using standard microbiological techniques. For isolation and identification of Salmonella spp. a loopful of fecal sample was enriched in Selenite broth and incubated at 42 °C for 12-14 hours. After that a loopful of selenite broth was inoculated and streaked separately onto selective agar plates as xylose Lysine Deoxycholate (XLD) agar, Brilliant Green agar (BGA), MacConkeyꞌs agar and incubated at 37 ℃ for 24hours. Partially identified cultures were suspended in normal saline and smeared over a slide. The smears were allowed to air dry followed by heat fixing and Gram’s staining. All Gram negative culture was subjected to biochemical characterization by using various biochemical tests such as catalase, oxidation, oxidation-fermentation, Indole, methyl –red, Voges-Poskauer, citrate test, TSI and urease test. Molecular characterization by Genomic DNA isolation using heat treatment method All the biochemically confirmed isolates for Salmonella spp. Where subjected to PCR for the presence of invA gene (284bp) genus specific primer (F-GTGAAATTATCGCCACGTTCGGGCAA) (R-TCATCGCACCGTCAAAGGAACC) (Borges et al., 2017) ^[4] were used to amplify Salmonella strain.

Results: Only 3% (3/100) of them were found positive for invA (universal stress protein) gene. The nucleotide sequences flanking the gene encoding the invA and was found to be highly specific for Salmonella. The antibiogram of Salmonella isolates by Kirby Bauer disc diffusion method revealed highest resistance against azithromycin, streptomycin and tetracycline and lowest against ciprofloxacin and gentamicin. All three isolates were MDR. Hence, surveillance based study and search for an alternative to antibiotics is needed to address the global issue of the antimicrobial resistance.