阿奇霉素对儿科临床常见细菌的体外抗菌活性及耐阿奇霉素菌株的erm、mef、mph基因的监测与分析

Surveillance and analysis of azithromycin resistance and erm/mef/mph genes in common bacteria isolated from pediatric patients

目的调查分析阿奇霉素对儿科临床常见细菌的体外抗菌活性和阿奇霉素耐药株的ermA、ermB、ermC、mefA/E、mphC等基因分布情况,为临床合理应用抗生素提供一定的实验依据。方法应用VITEK 60全自动微生物分析仪和/或API手工鉴定药敏系统对临床菌株进行细菌鉴定、药敏试验;应用PCR方法检测耐药基因。结果 2009年7月至2010年10月期间,儿科临床分离的149株苯唑西林敏感的金黄色葡萄球菌(MSSA)、58株苯唑西林耐药的金黄色葡萄球菌(MRSA)、65株苯唑西林敏感的凝固酶阴性葡萄球菌(MSCNS)、421株笨唑西林耐药的凝固酶阴性葡萄球(MRCNS)、10株侵袭性肺炎链球茵、148株非侵袭性肺炎链球茵、11株β溶血性A和B群链球菌、32株流感嗜血杆菌)对阿奇霉素的平均耐药率分别为62.4%、74.1%、44.6%、87.6%、100%、96.0%、90.9%和12.5%。耐阿奇霉素的葡萄球菌以ermC检出为主,而耐阿奇霉素的链球菌中以ermB多见。结论儿科临床分离的葡萄球菌、肺炎链球菌、β溶血性链球菌对阿奇霉素的耐药率高,流感嗜血杆菌对阿奇霉素仍较敏感。ermB和ermC编码23S rRNA甲基化酶致靶位改变是肺炎链球菌和葡萄球菌对大环内酯药物耐药的主要机制,其次是mefA/E基因表达主动外排系统导致对大环内酯药物耐药。菌株携带erm基因可能比mef基因预示更强的阿奇霉素耐药性。阿奇霉素可能并不适合作为儿科抗常见细菌感染的首选药物。

Objective To investigate azithromycin resistance of common bacteria isolated from pediatric patients and macrolide-resistance -related genes(ermA,ermB,ermC,mefA/E,mphC) in azithromycin-resistant strains during July 2009 to October 2010,which will contribute to apply antibiotics appropriately in hospital settings.Methods VITEK 60 microbiology analyzer and/or API manual system were used for identifying clinical strains and VITEK 60 microbiology analyzer and/or K-B method were used for detecting antibiotic resistance.Macrolide-resistance-related genes in azithromycin resistant strains were amplified by PCRs.Results The average azithromycin resistance rates among 149 strains of Methicillin-susceptible Staphylococcus aureus(MSSA),58 stains of Methicillin-resistant Staphylococcus aureus(MRSA),65 strains of methicillin-susceptible coagulase negative staphylococci(MSCNS),421 strains of methicillin-resistant coagulase negative staphylococci(MRCNS),10 stains of invasive Streptococcus pneumoniae,148 stains of non-invasive Sreptococcus pneumoniae,11β-hemolytic-streptococci and 32 strains of Haemophilus influenzae were 62.4%,74.1%, 44.6%,87.6%,100%,96.0%,90.9%and 12.5%,respectively.Conclusion Most of Streptococcus pneumoniae strains,hemolytic-streptococci isolated from children show high-level resistance to azithromycin except Haemophilus influenzae.ermC is predominant macrolide-resistant genes for staphylococci and ermB for Streptococcus pneumoniae andβ-hemolytic-streptococci and erm genes could inspire stronger azithromycin resistance than mef genes.Azithromycin is not an appropriate antibiotic to treat the infectious diseases caused by streptococci and staphylococci.