生物被膜形成相关基因对鼠伤寒沙门菌耐药性的影响

The effect of biofilm formation-related genes on the antibiotic resistance of Salmonella typhimurium

目的检测鼠伤寒沙门菌S025△rpoN、△rpoS、△csgA和△bcsA缺失株生物被膜形成能力和对药物敏感性的差异,研究生物被膜及其成分对细菌耐药性的影响。方法运用试管法检测生物被膜,药敏试验、最小抑菌浓度(MIC)法和最小杀菌浓度(MBC)法检测细菌对药物的敏感性。结果与野生株相比,△rpoN缺失株生物被膜形成能力增强,但对抗生素的敏感性没有发生改变,△rpoS和△csgA缺失株丧失生物被膜形成能力,△bcsA缺失株生物被膜形成能力下降,△rpoS、△csgA和△bcsA缺失株对头孢噻肟、美福仙、四环素、强力霉素和庆大霉素的敏感性提高,且△csgA缺失株抑菌圈直径大于△bcsA缺失株,表明生物被膜形成提高了细菌的耐药性。庆大霉素MBC结果显示,野生株和△rpoN为6.25μg/ml,而△rpoS、△csgA和△bcsA分别为1.56μg/ml、1.56μg/ml和3.125μg/ml,表明生物被膜形成提高抗生素的杀菌浓度。结论沙门菌形成生物被膜能提高细菌的耐药性,且卷曲菌毛的作用更为重要。

Objective In order to evaluate the effect of biofilm formation-related genes on the antibiotic resistance of Salmonella typhimurium,the biofilm-forming ability and antibiotic sensitivity of△rpoN,△rpoS,△csgA,and△bcsA of the S.typhimurium S025 strain were examined.Methods Biofilm-forming ability was examined using a glass tube assay,and antibiotic sensitivity was determined using a drug susceptibility test,the minimum inhibitory concentration(MIC),and the minimal bactericidal concentration(MBC).Results The biofilm-forming ability of the△rpoN strain(A550=0.59±0.02)was significantly enhanced while the pattern of antibiotic sensitivity was similar to that of the wild-type(WT)strain(A550=0033±0.01).The△rpoS(A550=0.07±0.02)and△csgA(A550=0.09±0.02)strains did not form biofilm,while the△bcsA strain(A550=0.26±0.01)had reduced biofilm-forming ability.Importantly,the△rpoS,△csgA,and△bcsA strains displayed increased sensitivity to cefotaxime,cefoxitin,tetracycline,doxycycline,and gentamicin in comparison to the WT strain.The inhibition zone for the△csgA strain was larger than that for the△bcsA strain,indicating that biofilms contributed to the increase in antibiotic resistance.The MBC of gentamicin to the△rpoS strain was 1.56μg/mL,the MBC of gentamicin to the AcsgA strain was 1.56μg/mL,and the MBC of gentami-cin to the△bcsA strain was 3.125μg/mL.The MBC of gentamicin to the WT-strain was 6.25μg/mL,and the MBC of gentamicin to the△rpoN strain was 6.25μg/mL,indicating that biofilm formation by S.typhimurium required an increased bactericidal concentration of gentamicin.Conclusion Biofilm formation by S.typhimurium increased its drug resistance,and curli fimbriae played a more important role than cellulose in biofilm formation.