Quinolone resistance amongSalmonellaKentucky and Typhimurium isolates in Tunisia: first report ofSalmonellaTyphimurium ST34 in Africa andqnrB19in Tunisia

Aims Characterization of quinolone-resistantSalmonellaKentucky and Typhimurium isolates in Tunisia from various sources, detection of some plasmid-mediated quinolone resistance genes and the genetic relatedness. Methods A total of 1404 isolates ofS. Kentucky (n = 1059)/S. Typhimurium (n = 345) from various sources from all over Tunisia were tested for quinolone resistance by disk diffusion method. Minimum inhibitory concentrations of nalidixic acid, ciprofloxacin and ofloxacin were determined. Quinolone-resistant isolates were screened for plasmid-mediated quinolone-resistance genes (qnrA,qnrB,qnrS,aac(6 ')-Ib-crandqepA) by polymerase chain reaction (PCR). Mutations in the quinolone-resistance-determining regions of thegyrAandparCgenes were detected by PCR and DNA sequencing. Pulsed-field gel electrophoresis and multilocus sequence typing were accomplished for isolates harbouring plasmid-mediated quinolone-resistance genes. Results According to our selection criteria (NAL = resistance phenotype; CIP = resistant with diameter 0, or intermediate), only 63S. Kentucky/41S. Typhimurium isolates were investigated: 49% (5/104) were multidrug resistant. TwoS. Typhimurium isolates harbouredqnrB19with different PFGE profiles. A mutation was detected in thegyrAgene for each of these two isolates. MLST revealed the presence of ST313 and ST34, an endemic sequence type. Conclusion Our study highlights the presence of quinolone multidrug-resistantSalmonellain humans and animals in Tunisia. This is the first report ofS. Typhimurium ST34 in Africa andqnrB19in Tunisia. Significance and Impact of the Study This is the first report that describes not only the current epidemiological situation of the quinolone resistance inS. Kentucky and Typhimurium isolated from various sources and regions in Tunisia, but also, the genetic resistance determinants associated with phenotypic antibiotic resistance and the molecular mechanisms of their quinolone-resistance. Also, we provide the first report ofS.Typhimurium ST34 in Africa, and the first report ofqnrB19inSalmonellain Tunisia.

Automated summary

The study revealed the presence of quinolone multidrug-resistant Salmonella in humans and animals in Tunisia, with the first report of S. Typhimurium ST34 in Africa and qnrB19 in Tunisia. The research not only described the epidemiological situation of quinolone resistance in S. Kentucky and Typhimurium in Tunisia, but also analyzed the genetic resistance determinants and molecular mechanisms associated with phenotypic antibiotic resistance.