Antimicrobial resistance in non-typhi Salmonella enterica isolated from humans and poultry in Palestine

Abstract

Introduction: The efficacy of chemotherapy can be compromised by drug resistance.  This study was undertaken to describe the resistance profiles and fluoroquinolone resistance mechanism of non-typhoidal Salmonella (NTS) isolated from humans and poultry in West Bank, Palestine.

Methodology: One hundred and fifty-one isolates of NTS, obtained from humans (71) and poultry (80), collected between September 2005 and January 2007, were tested for susceptibility to ampicillin, gentamicin, tetracycline ceftriaxone, nalidixic acid and ciprofloxacin. Mutation patterns within gyrA were determined by direct sequencing or by digestion of PCR-amplified DNA fragments with the restriction enzyme HinfI.

Results: Resistance rates among human and poultry isolates were respectively 59% and 51% for ampicillin, 31% and 10% for gentamicin, 59% and 80% for tetracycline, 59% and 45% for nalidixic acid, and 30% and 15% for ciprofloxacin. All the isolates were susceptible to ceftriaxone. Mutations at positions 83 and/or 87 were detected in gyrA of isolates with resistance to nalidixic acid. Isolates which were resistant to nalidixic acid but susceptible to ciprofloxacin had a single gyr A gene mutation at point 87.  This gene mutation was sufficient to induce a new phenotype (6 isolates) with decreased susceptibility to ciprofloxacin.

Conclusion: Mutations in gyrA at positions 83 or 87 were the most prevalent mutation pattern of fluoroquinolone resistant NTS isolates but other unknown mechanisms are also present. Continued surveillance of antimicrobial resistance among NTS isolates is needed to mitigate the increasing prevalence of quinolone resistance.