2017年中国部分省市即食食品来源耐甲氧西林金黄色葡萄球菌耐药性、毒力基因分布及分子分型

Antimicrobial resistance, virulence factors, and molecular characterization of methicillin-resistant Staphylococcus aureus isolates cultured from ready-to-eat foods

目的了解中国部分省市即食食品来源耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus,MRSA)耐药性、毒力基因分布和脉冲场凝胶电泳(pulsed-field gel electrophoresis,PFGE)分型特征。方法收集2017年中国部分省市即食食品中分离到的397株金黄色葡萄球菌,采用聚合酶链式反应方法检测其mecA基因携带情况,对鉴定为MRSA的菌株进行耐药性和毒力基因检测,并进行脉冲场凝胶电泳分型。结果从397株金黄色葡萄球菌中检出32株mecA基因阳性菌株,即为MRSA菌株。32株MRSA对青霉素、苯唑西林和头孢西丁均表现为耐药,对其他抗生素的耐药率分别为红霉素78.1%、克林霉素65.6%、四环素53.1%、氯霉素28.1%和环丙沙星12.5%,对庆大霉素和复方新诺明的耐药率均小于10%;32株MRSA表现为11种耐药谱,其中有29株(90.6%)为多重耐药,最多可同时耐受9种抗生素(2株)。共27株MRSA检出了13种毒力基因,检出前4位的依次为sel-q(56.3%)、sel-k(43.8%)、seb(28.1%)和sec(18.8%),同一菌株可同时携带2种以上毒力基因。32株MRSA共分为26种PFGE带型,优势带型不明显。结论 2017年中国即食食品来源MRSA耐药谱广,多重耐药现象严重,且携带多种毒力基因,PFGE带型呈现多样性。

OBJECTIVE To understand the antimicrobial resistance, virulence factors, and molecular characterization of MRSA isolates cultured from ready-to-eat(RTE) foods from several provinces in China. METHODS Totally, 397 S. aureus isolates were collected from RTE foods from several provinces in China, in 2017. The mecA gene was amplified to detect the MRSA strains among all 397 isolates by a polymerase chain reaction(PCR) method. Furthermore, the antimicrobial susceptibility and virulence factors of the MRSA isolates were detected by broth microdilution method and PCR, respectively, while the molecular characterization of all MRSA isolates were analyzed by pulsed-field gel electrophoresis(PFGE). RESULTS In total, 32 MRSA isolates were identified from 397 isolates. All 32 MRSA isolates were resistant to penicillin, oxacillin and cefoxitin. Meanwhile, 78.1%, 65.6%, 53.1, 28.1% and 12.5% of the 32 MRSA isolates showed resistant to erythromycin, clindamycin, tetracycline, chloramphenicol, and ciprofloxacin, respectively. Resistance rates to gentamicin and trimethoprim-sulfamethoxazole of all MRSA isolates were less than 10%. Eleven drug resistant spectrums were identified and 29 out of 32 MRSA isolates were identified as multi-drug resistant(MDR) isolates and two isolates were found to resistant to 9 antimicrobial agents tested in this study. Of all, 27 MRSA isolates were detected to harboring 13 virulence genes with sel-q(56.3%), sel-k(43.8%), seb(28.1%) and sec(18.8%) genes being the top four frequently detected. Besides, the result also showed that two or more virulence genes could be detected in one MRSA isolate. Finally, all 32 MRSA were identified to have 26 PFGE patterns and no dominant PFGE patterns were found in this study. CONCLUSION An overall high level antimicrobial resistance was found among RTE associated MRSA in China in 2017, so was the MDR condition. Virulence genes could be frequently detected in RTE associated MRSA isolates. The PFGE patterns of RTE associated MRSA showed wide distribution characteristics.