Aetiological agents of adult community-acquired pneumonia in Japan: systematic review and meta-analysis of published data

Yuji Fujikura; Kohei Somekawa; Toshie Manabe; Nobuyuki Horita; Hiroshi Takahashi; Futoshi Higa; Kazuhiro Yatera; Naoyuki Miyashita; Yoshifumi Imamura; Naoki Iwanaga; Hiroshi Mukae; Akihiko Kawana

doi:10.1136/bmjresp-2023-001800

Aetiological agents of adult community-acquired pneumonia in Japan: systematic review and meta-analysis of published data

BMJ Open Respir Res. 2023 Sep;10(1):e001800. doi: 10.1136/bmjresp-2023-001800.

Authors

Yuji Fujikura^{1

2}, Kohei Somekawa³, Toshie Manabe^{4

5}, Nobuyuki Horita⁶, Hiroshi Takahashi⁷, Futoshi Higa⁸, Kazuhiro Yatera⁹, Naoyuki Miyashita¹⁰, Yoshifumi Imamura¹¹, Naoki Iwanaga¹², Hiroshi Mukae¹³, Akihiko Kawana¹⁴

Affiliations

¹ Division of Infectious Diseases and Respiratory Medicine, Department of Internal Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan fujikura@ndmc.ac.jp.
² Department of Medical Risk Management and Infection Control, National Defense Medical College Hospital, Tokorozawa, Saitama, Japan.
³ Department of Pulmonology, Yokohama City University Graduate School of Medicine, Yokohama, Kanagawa, Japan.
⁴ Graduate School of Medical Science, Nagoya City University, Nagoya, Aichi, Japan.
⁵ West Medical Center, Nagoya City University, Nagoya, Aichi, Japan.
⁶ Chemotherapy Center, Yokohama City University Hospital, Yokohama, Kanagawa, Japan.
⁷ Department of Respiratory Medicine, Saka General Hospital, Shiogama, Miyagi, Japan.
⁸ Division of Respiratory Medicine, National Hospital Organization Okinawa National Hospital, Ginowan, Okinawa, Japan.
⁹ Department of Respiratory Medicine, University of Occupational and Environmental Health, Japan, Kitakyushu, Fukuoka, Japan.
¹⁰ First Department of Internal Medicine, Division of Respiratory Medicine, Infectious Disease and Allergology, Kansai Medical University, Hirakata, Osaka, Japan.
¹¹ Medical Education Development Center, Nagasaki University Hospital, Nagasaki, Nagasaki, Japan.
¹² Department of Respiratory Medicine, Nagasaki University Hospital, Nagasaki, Nagasaki, Japan.
¹³ Department of Respiratory Medicine, Nagasaki University Graduate School of Biomedical Science, Nagasaki, Nagasaki, Japan.
¹⁴ Division of Infectious Diseases and Respiratory Medicine, Department of Internal Medicine, National Defense Medical College, Tokorozawa, Saitama, Japan.

Abstract

Objective: Epidemiological information is essential in providing appropriate empiric antimicrobial therapy for pneumonia. This study aimed to clarify the epidemiology of community-acquired pneumonia (CAP) by conducting a systematic review of published studies in Japan.

Design: Systematic review.

Data source: PubMed and Ichushi web database (January 1970 to October 2022).

Eligibility criteria: Clinical studies describing pathogenic micro-organisms in CAP written in English or Japanese, excluding studies on pneumonia other than adult CAP, investigations limited to specific pathogens and case reports.

Data extraction and synthesis: Patient setting (inpatient vs outpatient), number of patients, concordance with the CAP guidelines, diagnostic criteria and methods for diagnosing pneumonia pathogens as well as the numbers of each isolate. A meta-analysis of various situations was performed to measure the frequency of each aetiological agent.

Results: Fifty-six studies were included and 17 095 cases of CAP were identified. Pathogens were undetectable in 44.1% (95% CI 39.7% to 48.5%). Streptococcus pneumoniae was the most common cause of CAP requiring hospitalisation or outpatient care (20.0% (95% CI 17.2% to 22.8%)), followed by Haemophilus influenzae (10.8% (95% CI 7.3% to 14.3%)) and Mycoplasma pneumoniae (7.5% (95% CI 4.6% to 10.4%)). However, when limited to CAP requiring hospitalisation, Staphylococcus aureus was the third most common at 4.9% (95% CI 3.9% to 5.8%). Pseudomonas aeruginosa was more frequent in hospitalised cases, while atypical pathogens were less common. Methicillin-resistant S. aureus accounted for 40.7% (95% CI 29.0% to 52.4%) of S. aureus cases. In studies that used PCR testing for pan-respiratory viral pathogens, human enterovirus/human rhinovirus (9.4% (95% CI 0% to 20.5%)) and several other respiratory pathogenic viruses were detected. The epidemiology varied depending on the methodology and situation.

Conclusion: The epidemiology of CAP varies depending on the situation, such as in the hospital versus outpatient setting. Viruses are more frequently detected by exhaustive genetic searches, resulting in a significant variation in epidemiology.

Keywords: bacterial infection; pneumonia; respiratory infection; viral infection.