携带杀白细胞素基因金黄色葡萄球菌临床感染菌株的回顾性研究

Retrospective study of clinical Staphylococcus aureus isolates carrying with panton-valentine leukocidin gene

目的研究临床分离的金黄色葡萄球菌携带杀白细胞素基因在社区与医院菌株分布流行的情况,及其携带mecA基因型的相关性分析。方法收集2010年1月-2014年12月医院临床分离的188株非重复金黄色葡萄球菌,进行菌株鉴定和药敏分析,用头孢西丁药敏纸片法初筛耐甲氧西林金黄色葡萄球菌(MRSA),用PCR法检测金黄色葡萄球菌的杀白细胞素基因(PVL)和耐甲氧西林金黄色葡萄球菌mecA基因,并测序部分阳性基因PCR产物。结果头孢西丁药敏纸片法初筛试验与mecA基因PCR法结果差异有统计学意义;188株金黄色葡萄球菌中,76株为MRSA,阳性率为40.4%,其中64株MRSA为医院获得株,12株MRSA为社区获得株;112株甲氧西林敏感金黄色葡萄球菌(MSSA)中99株为医院获得株,13株为社区获得株;共有14株PVL基因阳性,阳性率7.4%,社区检测到2株PVL(+)CA-MSSA(社区获得性甲氧西林敏感金黄色葡萄球菌),医院共检测到12株、阳性率6.4%,其中7株为PVL(+)HA-MRSA(医院获得性耐甲氧西林金黄色葡萄球菌)、5株为PVL(+)HA-MSSA(医院获得性甲氧西林敏感金黄色葡萄球菌),对该14株PVL基因阳性菌株进行MIC(最低抑菌浓度)分析,喹奴普汀/达福普汀、呋喃妥因、利福平、万古霉素、利奈唑胺、替加环素的耐药率为0,耐药率较低的有四环素(21.4%)、磺胺甲噁唑/甲氧苄啶(14.3%)、左氧沙星(7.1%)、庆大霉素(7.1%),菌株大部分分离自皮肤软组织、脓等标本。结论携带PVL毒力基因的MRSA在医院的检出率比在社区的明显高,提示含PVL高毒力与多重耐药基因的医院获得株-金黄色葡萄球菌PVL(+)MRSA已经从社区转移到医院感染,应引起院感与临床部门的高度重视。

OBJECTIVE To investigate the prevalence of clinical Staphylococcus aureus isolates carrying with pan- ton-valentine leukocidin gene in communities and hospitals and analyze its relationship with mecA genotype. METHODS A total of 188 clinical isolates of non-repetitive S. aureus were collected from Jan 2010 to Dec 2014, then the strains were identified, the drug susceptibility testing was performed, the cefoxitin drug susceptibility disk method was employed for primary screening of methicillin-resistant S. aureus （MRSA）, the panton-valentine leukocidin （PVL） gene in the S. aureus strains and mecA gene in the MRSA strains were detected by using PCR, and the PCR products of some positive genes were sequenced. RESULTS There was significant difference in the test result between the cefoxitin drug susceptibility disk method and the mecA gene PCR. Of the 188 strains of S. aureus, 76 were MRSA, with the positive rate 40. 4%, including 64 strains of hospital-acquired MRSA and 12 strains of community-acquired MRSA. Of 112 strains of methcillin-sensitive S. aureus （MSSA）, 99 were hospital- acquired, and 13 were community-acquired. Totally 14 isolates were positive for PVL gene, with the positive rate 7.4%, the PVL（＋） was detected in 2 strains of community-acquired methcillin-sensitive S. aureus （CA-MSSA） and was detected in 12 hospital-acquired strains, with the positive rate 6.4%, including 7 strains of hospital-acquired methicillin-resistant S. aureus （HA-MRSA） and 5 strains of hospital-acquired methicillin-sensitive S. aureus （HA-MSSA）. The analysis of minimum inhibitory concentrations （MICs） against the 14 PVL-positive isolates showed that the drug resistance rates to quinupristin-dalfopristin, nitrofurantoin, rifampicin, vancomycin, linezolid, and tigecycline were 0; the drug resistance rates to tetracycline, sulfamethoxazole-trimethoprim, levofloxacin, and gentamicin were 21.4 %, 14.3 %, 7.1%, and 7.1%, respectively; most of the strains were isolated from skin soft tissues and pus specimens. CONCLUSION The isolation rate of the MRSA strains carrying with PVL virulence gene was significantly higher in hospitals than in communities, indicating that the PVL-positive HA-MRSA strains carrying with high-virulence PVL and multiple drug resistance genes have transferred from communities to hospi- tals, to which the hospital infection control department and clinical department should attach great importance.