2.院内获得性肺炎（hospitalacquiredpneumonia，HAP）指住院48小时后发生的肺炎，HAP病原除了CAP的常见病原外，还应考虑：①原寄生在患儿口腔或肠道的细菌，多为革兰阴性杆菌，常见肠科杆菌，如肺炎克雷伯杆菌、大肠埃希菌、肠杆菌、沙雷菌、变形杆菌和枸橼酸杆菌等。
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