耐药猪链球菌膜蛋白图谱分析及能量抑制剂对其敏感性的影响

为证实国内临床分离的动物源链球菌菌株中是否存在与红霉素耐药性相关的主动外排机制,选取含有mefA基因和ermB基因和不含mefA/ermB基因的链球菌耐药菌株和青霉素、红霉素均敏感菌株,在能量抑制剂氰氯苯腙(CCCP)存在时,采用棋盘法分析红霉素、阿齐霉素、替米考星、青霉素对分离菌MIC的影响,并采用SDS-PAGE电泳分析分离株的膜蛋白图谱.结果显示:CCCP可对含有mefA基因的耐药菌株产生影响,可增强其对红霉素、阿齐霉素的敏感性,但不影响其对替米考星和青霉素的敏感性.含有ermB基因、不含mefA/ermB基因的耐药菌,对红霉素、阿齐霉素、替米考星和青霉素的敏感性不受CCCP的影响.菌株膜蛋白的SDS-PAGE电泳图谱显示,含有mefA基因的耐药菌株与其他菌株的膜蛋白图谱差异较大,其膜蛋白条带多而深浓,在45 000处有明显的条带,其他菌株无该条带,推测该蛋白可能是膜主动外排的相关蛋白.本试验结果佐证了在链球菌内存在与红霉素耐药相关的主动外排机制.

Membrane protein profile and the effect of enegic inhibitor on the sensibility against resistant Streptococcus strains

To identify if there was mechanism of active efflux in erythromycin-resistant Streptococcus strains with mefA gene isolated from veterinary clinic,several erythromycin-resistant strains with mefA gene,ermB gene and several susceptive strains were selected in this test.Chess method was used to determine the effect of carbonyl cynide m-chlorophenylhydrazone(CCCP)on the MIC of erythromycin,azithromycin,timilcosin and penicillin against Streptococcus isolates.SDS-PAGE method was used to analyze the membrane protein profile between erythromycin-resistant Streptococcus strains and other strains.The results showed that CCCP obviously reduced the MIC of erythromycin and azithromycin against erythromycin-resistant strains with mefA gene,but could not reduce the MIC of timilcosin and penicillin against the resistant strains as well as the resistant strains with ermB gene and susceptive isolates.Membrane protein profiles were completely different between erythromycin-resistant strains with mefA gene and other strains.The difference was that there was a protein with molecule weight 45 000 in erythromycin-resistant strains with mefA gene.All the results suggest that the active efflux become much stronger in Streptococcus strains showing resistance to erythromycin.