Construction of baeSR gene knock-out in Salmonella typhimurium and analysis of its sensitivity to antibiotics

Abstract:

[Background] The multi-drug resistance of Salmonella is becoming more and more serious. It is particularly urgent to study the mechanism of antibiotic resistance in Salmonella. The two-component system (TCS) is closely related to bacterial antibiotic resistance. [Objective] The baeSR gene deletion and complementary strains of Salmonella typhimurium were carried out to study the effect of BaeSR on antibiotic resistance in S. typhimurium. [Methods] S. typhimurium selected in vitro to obtain cipro?oxacin-resistant strain CR, and take it as the study object, deleted mutants CRΔbaeSR were obtained by homologous recombination mediated by suicide plasmid pLP12. And we used chloramphenicol and arabinose-induced vmt toxicity gene for selecting. In addition, the complemental strains of CR C△baeSR were generated through transformation of a recombinant expression plasmid of pBAD-baeSR into CR△baeSR. And minimum inhibitory concentration (MIC) of 11 antibiotics against CR, CR△baeSR and CR C△baeSR strains was determined by broth microdilution method. Growth curve, migration ability and biofilm formation ability of three strains were also measured. [Results] The results showed that the MICs of CIP, ENR, SAR, CEF, GEN, AMK, APR were lower than those of wild strains; The growth rate of CR△baeSR was slightly slower than CR, and the final concentration was relatively low, but there was no significant difference (P>0.05). The migration ability (P<0.05) and biofilm formation ability (P<0.01) of CR△baeSR decreased significantly. [Conclusion] The deletion of baeSR gene in S. typhimurium can affect the ability of migration and biofilm-forming to affect the sensitivity to antibiotics.

Key words:Salmonella typhimurium, Two-component system BaeSR, Gene knock-out, Antibiotic resistance