Limited information existed about the distributions of microbial etiology and drug-resistance with severe community-acquired pneumonia (CAP) in China, partly attributing to the antibiotics abuse in rearing livestock for Chinese farmers in recent decades. Moreover, the relevant guidelines have not been updated for at least a decade. Methods: A prospective observational study was carried out in Zhongshan Hospital (Shanghai, China). All consecutive cases of severe CAP diagnosed in Respiratory

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... sive care unit (ICU) and Emergency ICU were included. We assessed the microbial etiology features and multidrug-resistance (MDR) status. The risk factors were used by multivariate analyses for outcomes. Results: One hundred and twelve adults with severe CAP in ICUs, mean age of 65.7±15.1 years were studied. Etiological diagnoses were established in 76 (67.9%) cases; Klebsiella pneumoniae was the most frequent pathogen in 27 (35.5%) cases followed by Acinetobacter baumannii (n=15, 19.7%) and Methicillin-resistant Staphylococcus aureus (MRSA) (n=9, 11.8%); While Streptococcus pneumoniae (n=3, 3.9%) was ranked the 6 th in the study. The majority of pathogens were the MDR and the 30-days mortality rate was 43.8% in severe CAP patients. Klebsiella pneumoniae (OR, 6.88; 95%CI, 1.13-41.83), Sequential organ failure assessment (SOFA)≥5 (OR, 12.30; 95%CI,) was associated to death. Conclusions: The study indicates a change in the usual pattern of microbiol etiology of severe CAP and the MDR emerged in the majority of pathogens over a decade in eastern China. Enhanced control of using antibiotics to reduce the acquired resistance is urgent.