生牛乳中耐甲氧西林金黄色葡萄球菌全基因组序列分析

Whole genome sequence analysis of methicillin-resistant Staphylococcus aureus in raw milk

中文关键词:  耐甲氧西林金黄色葡萄球菌  全基因组序列  抗生素耐药基因  毒力基因

英文关键词:methicillin-resistant Staphylococcus aureus  Whole genome sequence  Antibiotic resistance gene  Virulence gene

中文摘要:

      目的 了解生牛乳中耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus，MRSA)的全基因组序列特征，分析其耐药基因和毒力基因的分子特征差异，为奶牛场合理用药和控制金黄色葡萄球菌（Staphylococcus aureus，SA）的流行和传播提供参考依据。方法 采用全自动微生物鉴定药敏分析仪进行细菌鉴定；通过肉汤微量稀释法进行药物敏感性检测；利用生物信息学工具对全基因组测序结果进行分子特征分析。结果 SJ23319菌株和SJ23506菌株经鉴定均为MRSA；SJ23319菌株耐药谱为OXA-PEN-FOX，SJ23506菌株耐药谱为OXA-PEN-FOX-CC，耐药基因分析结果显示两个菌株均携带耐药基因mecA和blaZ，这与耐药表型结果基本一致；2个菌株染色体基因组大小、结构和功能蛋白相似，SJ23319菌株为ST59-SCCmecIVa(2B)-t437型，SJ23506菌株为ST398-SCCmec V(5C)-t034型；2个菌株功能蛋白均分布于21个COG条目中，携带13种相同的耐药基因，SJ23319菌株还携带有四环素类耐药基因tetK；2个菌株携带毒力基因多达67种，SJ23319菌株携带更多的细菌黏附相关基因(fnbA/B、sdrD/E)和外毒素基因(Seb、Selk、Selq、set16-26)。结论 SJ23319(ST59)菌株比SJ23506(ST398)菌株携带更多的耐药基因和毒力基因，致病性更强，进一步证明在牲畜相关的MRSA (livestock-associated MRSA，LA-MRSA)菌株中，ST59型比ST398型更容易导致社区流行和感染，应当在MRSA流行监测中更加重视。

英文摘要:

      Objective To investigate the whole genome sequence characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in raw cow milk, and analyze the molecular characteristics differences of its drug resistance gene and virulence gene. To provide reference for rational drug use and control of the prevalence and spread of Staphylococcus aureus in dairy farms. Methods Bacterial identification was performed by automatic microbial identification drug sensitivity analyzer. The drug sensitivity was detected by broth microdilution method. Bioinformatics tools were used to analyze the molecular characteristics of whole genome sequencing results. Results Strains SJ23319 and SJ23506 were identified as MRSA. The drug resistance spectrum of SJ23319 strain was OXA-PEN-FOX, and that of SJ23506 strain was OXA-PEN-FOX-CC. The results of drug resistance gene analysis showed that both strains carried drug resistance genes mecA and blaZ, which was basically consistent with the results of drug resistance phenotype. The two strains were similar in chromosome size, structure and functional protein, SJ23319 strain was ST59-SCCmecIVa(2B)-t437, and SJ23506 strain was ST398-SCCmec V(5C)-t034. The functional proteins of the two strains were distributed in 21 COG articles, carrying 13 identical drug resistance genes. SJ23319 strain also carried tetK, a tetracycline drug resistance gene. The two strains carried 67 kinds of virulence genes, and SJ23319 strain carried more bacterial adhesion related genes (fnbA/B, sdrD/E) and exotoxin genes (Seb, Selk, Selq, set16-26). Conclusion SJ23319(ST59) carries more drug resistance genes and virulence genes than SJ23506(ST398), and is more pathogenic, which further proves that in livestock associated MRSA (LA-MRSA) strains, ST59 is more likely to cause community epidemic and infection than ST398, and more attention should be paid to MRSA epidemic surveillance.