Epidemiology, microbiology and treatment implications in adult patients hospitalized with pneumonia in different regions of China: a retrospective study

Pneumonia is the most common and serious lower respiratory tract infectious disease worldwide, and is a leading cause of mortality, accounting for approximately 3.1 million deaths globally in 2012 (1). The aetiology of bacterial pneumonia varies depending on its origin. Approximately 10 bacterial species have been identified as significant pathogens in community-acquired pneumonia (CAP) in Europe, North America and Australia (2-4). In a 2002 review of 41 European studies, Streptococcus pneumoniae was the most frequent bacterial pathogen in hospitalized CAP patients, followed by Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella species and Haemophilus influenzae (2). Data regarding the bacterial aetiology of hospital-acquired pneumonia (HAP) are limited, and establishing the aetiological agent(s) of HAP can be problematic as it is often not possible to distinguish between colonisation and infection. Gram-negative bacteria are implicated in the majority of HAP cases in Europe and the USA (55–85%), while Gram-positive pathogens (predominantly Staphylococcus aureus) account for 20–30% of cases (3)