BACKGROUND: USA300 community-associated (CA) methicillin-resistant Staphylococcus aureus (MRSA) strains causing necrotizing pneumonia have been reported in association with antecedent viral upper respiratory tract infections (URI).METHODS: A case series of necrotizing pneumonia presenting as a primary or coprimary infection, secondary to CA-MRSA without evidence of antecedent viral URI, is presented. Cases were identified through the infectious diseases consultation service records. Clinical and radiographic data were collected by chart review and electronic records. MRSA strains were isolated from sputum, bronchoalveolar lavage, pleural fluid or blood cultures and confirmed using standard laboratory procedures. MRSA strains were characterized by susceptibility testing, pulsed-field gel electrophoresis, spa typing, agr typing and multilocus sequence typing. Testing for respiratory viruses was performed by appropriate serological testing of banked sera, or nucleic acid testing of nasopharyngeal or bronchoalveloar lavage specimens.RESULTS: Ten patients who presented or copresented with CA necrotizing pneumonia secondary to CA-MRSA from April 2004 to October 2011 were identified. The median length of stay was 22.5 days. Mortality was 20.0%. Classical risk factors for CA-MRSA were identified in seven of 10 (70.0%) cases. Chest tube placement occurred in seven of 10 patients with empyema. None of the patients had historical evidence of antecedent URI. In eight of 10 patients, serological or nucleic acid testing testing revealed no evidence of acute viral coinfection. Eight strains were CMRSA-10 (USA300). The remaining two strains were a USA300 genetically related strain and a USA1100 strain.CONCLUSION: Pneumonia secondary to CA-MRSA can occur in the absence of an antecedent URI. Infections due to CA-MRSA are associated with significant morbidity and mortality. Clinicians need to have an awareness of this clinical entity, particularly in patients who are in risk groups that predispose to exposure to this bacterium.

中文翻译：

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社区相关的耐甲氧西林金黄色葡萄球菌坏死性肺炎，没有先前病毒性上呼吸道感染的证据。

背景：据报道，USA300 社区相关 (CA) 耐甲氧西林金黄色葡萄球菌(MRSA) 菌株与先前的病毒性上呼吸道感染 (URI) 相关。继发于 CA-MRSA 的共原发感染，没有先行病毒 URI 的证据。病例通过传染病咨询服务记录确定。通过图表审查和电子记录收集临床和放射学数据。MRSA 菌株是从痰液、支气管肺泡灌洗液、胸水或血培养物中分离出来的，并使用标准实验室程序进行确认。MRSA 菌株通过药敏试验、脉冲场凝胶电泳、水疗打字，agr分型和多位点序列分型。呼吸道病毒检测通过对储存血清进行适当的血清学检测，或对鼻咽或支气管肺泡灌洗标本进行核酸检测。 结果：确定了 2004 年 4 月至 2011 年 10 月间出现或同时出现继发于 CA-MRSA 的 CA 坏死性肺炎的 10 名患者. 中位逗留时间为 22.5 天。死亡率为 20.0%。在 10 例 (70.0%) 病例中的 7 例中确定了 CA-MRSA 的经典危险因素。10 名脓胸患者中有 7 名进行了胸管放置。没有患者有先行 URI 的历史证据。在 10 名患者中的 8 名中，血清学或核酸检测未显示急性病毒合并感染的证据。八个菌株是 CMRSA-10 (USA300)。剩下的两个菌株是USA300 基因相关菌株和USA1100 菌株。结论：继发于CA-MRSA 的肺炎可以在没有先行URI 的情况下发生。CA-MRSA 引起的感染与显着的发病率和死亡率相关。临床医生需要了解这种临床实体，尤其是那些属于易暴露于这种细菌的风险人群中的患者。