基因受限的甲氧西林敏感菌株对社区获得性金黄色葡萄球菌感染持续流行的作用。
contribution of genetically restricted, methicillin-susceptible strains to the ongoing epidemic of community-acquired Staphylococcus aureus infections.
作者信息
Orscheln Rachel C, Hunstad David A, Fritz Stephanie A, Loughman Jennifer A, Mitchell Kimberly, Storch Emily K, Gaudreault Monique, Sellenriek Patricia L, Armstrong Jon R, Mardis Elaine R, Storch Gregory A
机构信息
Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
出版信息
Clin Infect Dis. 2009 Aug 15;49(4):536-42. doi: 10.1086/600881.
BACKGROUND
Within the current worldwide epidemic of community-acquired Staphylococcus aureus infections, attention has focused on the role of methicillin-resistant strains. We characterize methicillin-susceptible strains that also contribute to this epidemic.
METHODS
We tracked cultures from abscess specimens submitted to the microbiology laboratory at St. Louis Children's Hospital and examined Panton-Valentine leukocidin (PVL) genes in methicillin-susceptible S. aureus (MSSA) isolates. We further characterized some isolates by multilocus sequence typing, pulsed-field gel electrophoresis, antibiotic susceptibility, accessory gene regulator (agr) allele, and presence of the arcA gene of the arginine catabolic mobile element.
RESULTS
From 1999 to 2007, we detected a 250-fold increase in cultures of abscesses yielding methicillin-resistant S. aureus (MRSA) and a 5-fold increase in abscess cultures yielding MSSA. MSSA isolates from abscesses and wounds were more likely to encode PVL than isolates from other sources. In contrast to PVL-negative isolates of MSSA, which were genetically diverse, PVL-positive isolates were predominantly multilocus sequence typing type 8 and agr type 1. More than half of PVL-positive MSSA isolates were resistant to erythromycin and susceptible to clindamycin with the absence of inducible resistance, a pattern uncommon in PVL-negative MSSA but frequent in the USA300 clone of MRSA. In addition, pulsed-field gel electrophoresis of PVL-positive MSSA strains revealed the USA300 pattern.
CONCLUSIONS
In addition to methicillin-resistant strains, the current epidemic of S. aureus infections includes infections caused by methicillin-susceptible strains that are closely related genetically and share phenotypic characteristics other than susceptibility to methicillin. These findings suggest that factors other than methicillin resistance are driving the epidemic.
背景
在当前全球社区获得性金黄色葡萄球菌感染的流行中，注意力主要集中在耐甲氧西林菌株的作用上。我们对同样导致此次流行的甲氧西林敏感菌株进行了特征分析。
方法
我们追踪了提交至圣路易斯儿童医院微生物实验室的脓肿标本培养物，并检测了甲氧西林敏感金黄色葡萄球菌（MSSA）分离株中的杀白细胞素（PVL）基因。我们通过多位点序列分型、脉冲场凝胶电泳、抗生素敏感性、辅助基因调节子（agr）等位基因以及精氨酸分解代谢移动元件的arcA基因存在情况，进一步对部分分离株进行了特征分析。
结果
1999年至2007年期间，我们发现脓肿培养物中耐甲氧西林金黄色葡萄球菌（MRSA）的检出量增加了250倍，而脓肿培养物中MSSA的检出量增加了5倍。来自脓肿和伤口的MSSA分离株比来自其他来源的分离株更有可能编码PVL。与基因多样的PVL阴性MSSA分离株不同，PVL阳性分离株主要为多位点序列分型8型和agr 1型。超过一半的PVL阳性MSSA分离株对红霉素耐药，对克林霉素敏感且无诱导性耐药，这种模式在PVL阴性MSSA中不常见，但在美国MRSA的USA300克隆中很常见。此外，PVL阳性MSSA菌株的脉冲场凝胶电泳显示出USA300模式。
结论
除了耐甲氧西林菌株外，当前金黄色葡萄球菌感染的流行还包括由甲氧西林敏感菌株引起的感染，这些菌株在基因上密切相关，并且除了对甲氧西林敏感外还具有其他共同的表型特征。这些发现表明，除了甲氧西林耐药性之外，还有其他因素在推动此次流行。
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