The prevalence of respiratory pathogens in adults with community-acquired pneumonia in an outpatient cohort

Purpose: Community-acquired pneumonia is a common illness worldwide. In adults, community-acquired bacterial pneumonia has been well studied, but viral pneumonia is less well understood. We designed this study to identify respiratory pathogens, including common pneumonia-causing bacteria, viruses and atypical pneumonia pathogens, using reverse transcription-polymerase chain reaction. Patients and methods: We conducted a retrospective study of outpatients with community-acquired pneumonia at the Fever Clinic of Peking University Third Hospital. We collected sputum or throat swabs from patients diagnosed with community-acquired pneumonia. Multiplex real-time reverse transcription-polymerase chain reaction was performed for 20 pathogens, including 9 viruses, 3 atypical pathogens and 8 bacteria. Results: There were 232 outpatients enrolled in our study, and 153 patients (65.9%) had positive test results, of which 26.7% were viruses, 19.4% were atypical pathogens and 19.8% were bacteria. Mycoplasma pneumoniae infection was detected at the highest frequency (19.0%), exceeding Streptococcus pneumoniae infection. The most commonly identified viral pathogens were IFVs (15.1%), PIVs (3.4%) and RhV (2.6%). The most commonly identified bacteria were Streptococcus pneumoniae (9.1%), Haemophilus influenza (6.5%) and Klebsiella pneumoniae (2.6%). Conclusion: Our study suggests that viruses were commonly detected in outpatients with CAP, and IFVs were the most common viruses, especially during flu season. Patients with viral infection were prone to viral-bacterial coinfection. Mycoplasma pneumoniae was the leading pathogen in the outpatients with CAP. Viral infection occurs in a large number of outpatients with CAP, and it should receive greater attention in clinical work.