Molecular Studies on Antibiotic Resistance and Virulence Among Salmonella Serovars Isolated from Blood Cultures

Abstract

Introduction: Salmonellosis is a major public health challenge. Enteric fever caused by Typhoidal Salmonella, (S. enterica serovar Typhi and Paratyphi A, B and C) is one of the most common causes of systemic infections in India. Despite the availability of antibiotics and vaccines, enteric fever remains a significant cause of morbidity and mortality among pediatric population in developing countries including India. Fluoroquinolone resistance exhibited by the typhoidal salmonellae complicates the therapeutic management of enteric fever. Hence, Cephalosporins are currently recommended for the treatment of typhoid fever. However, the emergence of beta lactamase producing strains of Salmonella further complicates clinical management. Non-typhoidal Salmonella is a leading cause of food borne illness. Bacteremia caused by NTS especially remain a major health problem among susceptible children in developing countries. The case fatality rate is 21%-24%, even when appropriate antibiotics are available. There is paucity of data on the incidence of NTS infections and the accompanying emergence of multidrug-resistant (MDR) strains of NTS serovars in India. Materials and methods: 88 clinical isolates of Salmonella serovars were collected from hospitals in Chennai, Coimbatore, Erode and Salem districts of Tamil Nadu. Serovar confirmation was done using specific antisera at the National Escherichia and Salmonella Reference Centre, Kasauli. Molecular detection of Genes encoding beta-lactamase mediated resistance TEM, SHV, CTX-M, OXA Genes encoding fluoroquinolone resistance Plasmid Mediated: qnr A, qnr B, qnr S Salmonella Pathogenicity islands were determined using PCR. A total of 34 isolates (15 S. Typhi, 17 S. Paratyphi A, 1 S.Lindenberg, and 1 S. Weltevreden) were tested for the presence of CRISPR 1 and CRISPR 2. As an herbal alternative AntiSalmonella activity of the methanol extract of Mango kernel seed was assessed against S. Typhi isolates Results: Of 88 Salmonella isolates S. Typhi (64), S. Paratyphi A (17), S. Lindenberg