Department of Emergency Medicine, National Taiwan University Hospital, Taipei, Taiwan.
Clin Infect Dis. 2012 Nov 15;55(10):1329-37. doi: 10.1093/cid/cis717. Epub 2012 Aug 20.
Recent evidence has shown that community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is less virulent than traditional hospital-associated MRSA. We explored whether the antimicrobial susceptibilities of the different strains account for their disparity in clinical virulence.
This 10-year retrospective cohort study enrolled 291 patients with community-onset, healthcare-associated MRSA bacteremia. The vancomycin minimum inhibitory concentration (MIC) and staphylococcal cassette chromosome mec (SCCmec) type were determined for all isolates. CA-MRSA was defined as an isolate possessing the SCCmec type IV or V genes, and hospital-associated MRSA (HA-MRSA) was defined as an isolate possessing SCCmec type I, II, or III genes. Low and high vancomycin MICs were defined as MICs of ≤1 and ≥2 μg/mL, respectively. Patients with bacteremia due to CA-MRSA with a low vancomycin MIC (n = 111), due to HA-MRSA with a low vancomycin MIC (n = 127), or due to HA-MRSA with a high vancomycin MIC (n = 47) entered the outcome analysis. The outcomes of the 2 HA-MRSA bacteremia groups were compared to those of the CA-MRSA bacteremia group.
Treatment failure was observed in 35 (31.5%), 59 (46.5%), and 27 (57.4%) of patients with low-vancomycin-MIC CA-MRSA, low-vancomycin-MIC HA-MRSA, and high-vancomycin-MIC HA-MRSA bacteremia, respectively. After adjustment for potential confounding factors, the risk of treatment failure was significantly higher among patients with low-vancomycin-MIC HA-MRSA (adjusted odds ratio [aOR], 1.853; 95% confidence interval [CI], 1.006-3.413) and high-vancomycin-MIC HA-MRSA (aOR, 2.393; 95% CI, 1.079-5.309), compared with patients with low-vancomycin-MIC CA-MRSA.
The higher risk for treatment failure among patients with traditional hospital-associated MRSA infections, compared with patients with CA-MRSA infections, is independent of the vancomycin MIC, suggesting a potential intrinsic strain-specific virulence effect.
最近的证据表明，社区相关性耐甲氧西林金黄色葡萄球菌（CA-MRSA）的毒力低于传统医院相关性 MRSA。我们探讨了不同菌株的抗菌药敏是否与其临床毒力的差异有关。
这项回顾性队列研究纳入了 291 例社区获得性、与医疗保健相关的耐甲氧西林金黄色葡萄球菌菌血症患者。对所有分离株进行万古霉素最小抑菌浓度（MIC）和葡萄球菌盒染色体 mec（SCCmec）型检测。CA-MRSA 定义为携带 SCCmec 型 IV 或 V 基因的分离株，医院相关性 MRSA（HA-MRSA）定义为携带 SCCmec 型 I、II 或 III 基因的分离株。低和高万古霉素 MIC 定义为 MIC 值分别为≤1 和≥2μg/mL。由于 CA-MRSA 低万古霉素 MIC（n=111）、由于 HA-MRSA 低万古霉素 MIC（n=127）或由于 HA-MRSA 高万古霉素 MIC（n=47）而发生菌血症的患者进入结局分析。比较了 2 组 HA-MRSA 菌血症患者的结局与 CA-MRSA 菌血症患者的结局。
低万古霉素 MIC CA-MRSA、低万古霉素 MIC HA-MRSA 和高万古霉素 MIC HA-MRSA 血症患者的治疗失败率分别为 35（31.5%）、59（46.5%）和 27（57.4%）。在调整了潜在混杂因素后，低万古霉素 MIC HA-MRSA（调整优势比[OR]，1.853；95%置信区间[CI]，1.006-3.413）和高万古霉素 MIC HA-MRSA（调整 OR，2.393；95%CI，1.079-5.309）患者的治疗失败风险显著高于低万古霉素 MIC CA-MRSA 患者。
与 CA-MRSA 感染患者相比，传统医院相关性 MRSA 感染患者治疗失败的风险更高，这与万古霉素 MIC 无关，提示存在潜在的固有菌株特异性毒力效应。
