Contribution of Different Mechanisms to Ciprofloxacin Resistance in Salmonella spp.

Development of fluoroquinolone resistance can involve several mechanisms that include chromosomal mutations in genes ( gyrAB and parCE ) encoding the target bacterial topoisomerase enzymes, increased expression AcrAB-TolC efflux system, acquisition transmissible quinolone-resistance genes. In this study, 176 Salmonella isolates from animals with a broad range ciprofloxacin MICs were collected to analyze contribution these different phenotypes. All classified according their susceptibility pattern into five groups as follows: highly resistant (HR), (R), intermediate (I), reduced (RS), susceptible (S). We found ParC T57S substitution was common strains exhibiting lowest while depended on type GyrA mutation. The appeared incur little cost fitness its own. presence PMQR represented an route for development absence target-site mutations. Switching plasmid-mediated quinolone (PMQR) gene location plasmid chromosome observed resulted decreased susceptibility; also correlated stable phenotype. overexpression played important role small decreases upregulated by MarA more often than RamA. This study increases our understanding relative importance food chain.