Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, USA.
Clin Infect Dis. 2012 Sep;55(6):781-8. doi: 10.1093/cid/cis527. Epub 2012 Jun 5.
Since its emergence in 2000, epidemic spread of the methicillin-resistant Staphylococcus aureus (MRSA) clone USA300 has led to a high burden of skin and soft tissue infections (SSTIs) in the United States, yet its impact on MRSA bloodstream infections (BSIs) is poorly characterized.
To assess clonality of the MRSA isolates causing SSTI and BSI during the epidemic period, a stratified, random sample of 1350 unique infection isolates (from a total of 7252) recovered at the Community Health Network of San Francisco from 2000 to 2008 were selected for genotyping. Risk factors and outcomes for 549 BSI cases caused by the USA300 epidemic clone and non-USA300 MRSA clones were assessed by retrospective review of patient medical records.
From 2000 to 2008, secular trends of USA300 SSTI and USA300 BSI were strongly correlated (Pearson r = 0.953). USA300 accounted for 55% (304/549) of BSIs as it was the predominant MRSA clone that caused community-associated (115/160), healthcare-associated community-onset (125/207), and hospital-onset (64/182) BSIs. Length of hospitalization after BSI diagnosis and mortality rates for USA300 and non-USA300 were similar. Two independent risk factors for USA300 BSI were identified: concurrent SSTI (adjusted relative risk, 1.4 [95% confidence interval {CI}, 1.2-1.6]) and anti-MRSA antimicrobial use in the preceding 30 days (0.7 [95% CI, .6-.8]). Isolates from concurrent SSTI were indistinguishable genotypically from the USA300 isolates that caused BSI.
USA300 SSTIs serve as a source for BSI. Strategies to control the USA300 SSTI epidemic may lessen the severity of the concurrent USA300 BSI epidemic.
自 2000 年出现以来，耐甲氧西林金黄色葡萄球菌（MRSA）克隆 USA300 的流行传播导致了美国皮肤和软组织感染（SSTIs）的高负担，但它对 MRSA 血流感染（BSIs）的影响尚未得到很好的描述。
为了评估流行期间导致 SSTI 和 BSI 的 MRSA 分离株的克隆性，对 2000 年至 2008 年期间旧金山社区卫生网络从 7252 例总感染分离株中随机抽取的 1350 个独特感染分离株进行了分层随机抽样进行基因分型。通过回顾性审查患者病历，评估了 549 例由 USA300 流行克隆和非 USA300 MRSA 克隆引起的 BSI 的危险因素和结局。
2000 年至 2008 年，USA300 SSTI 和 USA300 BSI 的季节性趋势呈强相关性（Pearson r = 0.953）。USA300 占 BSIs 的 55%（304/549），因为它是导致社区相关性（115/160）、卫生保健相关性社区发病（125/207）和医院发病（64/182）BSIs 的主要 MRSA 克隆。BSI 诊断后住院时间和 USA300 和非 USA300 的死亡率相似。确定了 USA300 BSI 的两个独立危险因素：并发 SSTI（调整后的相对风险，1.4[95%置信区间{CI}，1.2-1.6]）和在过去 30 天内使用抗-MRSA 抗菌药物（0.7[95%CI，.6-.8]）。来自并发 SSTI 的分离株在基因型上与引起 BSI 的 USA300 分离株无法区分。
USA300 SSTIs 是 BSI 的来源。控制 USA300 SSTI 流行的策略可能会减轻并发 USA300 BSI 流行的严重程度。
