Current status of fluoroquinolone and cephalosporin resistance in Salmonella enterica serovar Typhi isolates from Faisalabad, Pakistan

Objectives: Currently fluoroquinolones and cephalosporins are at the forefront of typhoid treatment. The objective of this study was to assess the current drug resistance status of S. Typhi isolates from Faisalabad region by conventional and molecular methods. Methodology: Drug resistance pattern of 30 clinical isolates (2011) against 8 drugs (nalidixic acid, ciprofloxacin, ofloxacin, gatifloxacin, cephradine, cefixime, ceftriaxone and cefpodoxime) was determined. MICs were noted by E-test. ESBL production was also tested. Relevant drug resistance genes bla(TEM), bla(OXA), gyrA, gyrB, parC, parE, qnrS and qnrA were targeted and QRDR regions of gyrA, gyrB, parC, and parE were sequenced for mutations. Results: Nalidixic acid and ciprofloxacin resistance were seen in 30.0% and 10.0% of isolates respectively. No resistance was detected towards ofloxacin and gatifloxacin. Resistance to cephradine, cefixime, cefpodoxime and ceftriaxone was found in 46.7%, 13.3%, 16.7%, and 3.3% of isolates respectively. In ciprofloxacin resistant isolates a single mutation at codon Ser83 in gyrA gene was detected. Conclusions: A slow increase in ciprofloxacin resistance was indicated. However, newer fluoroquinolones ofloxacin and gatifloxacin are still very effective. Among cephalosporins, ceftriaxone showed promising results but emerging resistance was evident. Fortunately no ESBL producing isolate was detected. No correlation between two groups Was detected in emergence of drug resistance.