Serotyping, Antimicrobial Resistance Profile and Virulence Genes of Salmonella Serovars Isolated from Human, Animals and Birds

Abstract The study was undertaken to investigate the prevalence, antimicrobial susceptibility, antimicrobial resistance and virulence genes of Salmonella isolates recovered from human and different species of animals and birds. Out of 88 (7.15%), 21 (23.86%) belonged to Salmonella enterica subsp. enterica serovar Weltevreden, 22 (25%) to serovar Enteritidis, 16 (18.2%) to serovar Typhi and 14 (15.9%) to serovar Newport, while 7 (7.95%) isolates were found to be untypable. Among the 88 isolates, 45.45% showed resistance to ampicillin, 61.36% to tetracycline, 61.18% to cefotaxime, 65.90% to gentamicin, 48.86% to trimethoprim, 11.36% to ceftriaxone, 10.22% to chloramphenicol, and 7.95% each to ciprofloxacin and cefepime. Most of the isolates were susceptible to a low MIC (≤ 0.25 µg/ml) of Cefepime, Cefotaxime, Ciprofloxacin, Ceftriaxone and Co-trimoxazole and a moderate MIC (0.5µg/ml − 4µg/ml) of Ampicillin, Tetracycline, Gentamicin and Chloramphenicol. The resistance genes, blaTEM, tetA and dfrA12 were most prevalent, irrespective of the host of origin of the isolates. While invA was used for molecular detection of Salmonella, other virulence genes, viz. sipA, sipB, sipC, stn and T2544 were also detected in all (100%) the Salmonella isolates. Total 69.32 % of tested samples were found to be contaminated with multi-drug resistant (MDR) Salmonella and various virulence genes were present among the isolated serovars. Another virulence-associated gene, T2544 (pagN) could also be found in all the isolates, irrespective of serovar or host of origin suggesting the possibility of using this gene as a marker for identification of pathogenic Salmonella isolates. This study highlights the importance of continuous monitoring and surveillance for pathogenic salmonellae and their potential risks to both human and animal.