Detection and Correlation of Virulence Determinants of Ampicillin Resistant Isolates of Salmonella Typhimurium

Salmonella Typhimurium is an important serovar causing non-typhoidal salmonellosis in humans. Poultry products are a common source of infection. In the present study, we used 46 isolates of S. Typhimurium, which were isolated from poultry eggs. Isolates were screened for their virulence, virulence factors (genes and plasmids), presence of ampicillin-resistant bla PSE-1 gene and Minimum Inhibitory Concentration (MIC) for ampicillin. Out of 46 isolates, bla PSE-1 gene was present in all 46 isolates and MIC ranged from 2.0 to 64 µg/ml. In mice inoculation test, out of 46 isolates, three isolates were found to be avirulent. Among virulence genes, stn, inv A, pef and spv C genes were detected in 45 (97.82%), 44(95.65%),13(28.26%), 4 (8.6%) isolates, respectively. Plasmids were detected in 37 isolates (80.43%). Plasmids, stn and inv A gene were more closely associated with virulence as compared to pef and spv C genes. As these isolates were virulent and exhibited resistance to ampicillin, the spread of such isolates may result in a serious threat to human and animal health.