Antibiotyping and Genotyping of Extensively Drug Resistant (XDR) Salmonella Spp. Isolated from Clinical Samples of Lahore, Pakistan

Aims
Antibiotic resistance is a major problem in Salmonella enterica serovar Typhi. Objective of this study was to evaluate the prevalence of XDR Salmonella among local population of Lahore and genotyping of isolates for antibiotic resistant genes.

Methods and results
A total of 200 blood samples from suspected typhoid fever patients were collected. One hundred and fifty-seven bacterial samples were confirmed as Salmonella Typhi and twenty-three samples were confirmed as Salmonella Paratyphi after biochemical, serological and PCR based molecular characterization. Antibiogram analysis classified 121 (67.2%) Salmonella isolates as MDR and 62 isolates (34.4%) as XDR. The predominant resistance gene was ampC with 47.7% prevalence, followed by gyrA, catA1, tet(A), aac (3)-la, qnrS, bla_NDM-1 and bla_CTX-M-15 genes in 45.5%, 40%, 21.6%, 18.3%, 11.6%, 2.2% and 0.5% isolates, respectively. Sequence analysis showed the presence of sul1 and dfrA7 gene cassette arrays in twelve class 1 integron integrase positive isolates.

Conclusion
Large number of clinical XDR S. Typhi resistant against third generation cephalosporins have been reported.

Significance and impact of study
Current study highlights the possible emergence of clinical XDR S. Typhi cases in Lahore, Pakistan. Potential attribution of phenotypic and genotypic XDR cases may help to contribute targeted therapy.