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Prevalence of Atypical Pathogens in Patients With Cough and Community-Acquired Pneumonia: A Meta-Analysis
Christian Marchello1, Ariella Perry Dale1, Thuy Nhu Thai1
1Department of Epidemiology and Biostatistics, College of Public Health, University of Georgia, Athens, Georgia.
Purpose:
Community-acquired pneumonia (CAP), acute cough, bronchitis, and lower respiratory tract infections (LRTI) are often caused by infections with viruses or Streptococcus pneumoniae. The prevalence of atypical pathogens Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Bordetella pertussis among patients with these illnesses in the ambulatory setting has not been previously summarized. We set out to derive prevalence information from the existing literature.
Methods:
We performed a systematic review of MEDLINE for prospective, consecutive-series studies reporting the prevalence of M pneumoniae, C pneumoniae, L pneumophila and/or B pertussis in outpatients with cough, acute bronchitis, LRTI, or CAP. Articles were independently reviewed by 2 authors for inclusion and abstraction of data; discrepancies were resolved by consensus discussion. A meta-analysis was performed on each pathogen to calculate the pooled prevalence estimates using a random effects model of raw proportions.
Results:
Fifty studies met our inclusion criteria. While calculated heterogeneity was high, most studies reported prevalence for each pathogen within a fairly narrow range. In patients with CAP, the overall prevalences of M pneumoniae and C pneumoniae were 10.1% (95% CI, 7.1%-13.1%) and 3.5% (95% CI, 2.2%-4.9%), respectively. Consistent with previous reports, M pneumoniae prevalence peaked in roughly 6-year intervals. Overall prevalence of L pneumophila was 2.7% (95% CI, 2.0%-3.4%), but the organism was rare in children, with only 1 case in 1,765. In patients with prolonged cough in primary care, the prevalence of B pertussis was 12.4% (95% CI, 4.9%-19.8%), although it was higher in studies that included only children (17.6%; 95% CI, 3.4%-31.8%).
Conclusions:
Atypical bacterial pathogens are relatively common causes of lower respiratory diseases, including cough, bronchitis, and CAP. Where surveillance data were available, we found higher prevalences in studies where all patients are tested for these pathogens. It is likely that these conditions are underreported, underdiagnosed, and undertreated in current clinical practice.
Insights
Atypical pathogens like Mycoplasma pneumoniae and Bordetella pertussis are common causes of community-acquired pneumonia and prolonged cough. These infections may be underdiagnosed and undertreated in clinical practice.
Area of Science:
- Infectious Diseases
- Microbiology
- Public Health
Background:
- Community-acquired pneumonia (CAP), acute cough, bronchitis, and lower respiratory tract infections (LRTI) are frequently caused by viruses or Streptococcus pneumoniae.
- The prevalence of specific atypical pathogens in ambulatory settings for these conditions has not been comprehensively summarized.
Purpose of the Study:
- To systematically review and summarize the prevalence of atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, and Bordetella pertussis) in outpatients with respiratory illnesses.
Main Methods:
- A systematic review of MEDLINE was conducted for prospective studies on outpatients with cough, acute bronchitis, LRTI, or CAP.
- Prevalence data for the specified atypical pathogens were extracted and analyzed using a random effects meta-analysis model.
Main Results:
- Fifty studies were included. Mycoplasma pneumoniae prevalence was 10.1% in CAP, and Chlamydophila pneumoniae was 3.5%.
- Legionella pneumophila prevalence was 2.7% overall, rare in children. Bordetella pertussis prevalence was 12.4% in prolonged cough, higher in children (17.6%).
Conclusions:
- Atypical bacterial pathogens are significant contributors to lower respiratory diseases like cough, bronchitis, and CAP.
- Higher prevalences were observed in studies testing all patients for these pathogens, suggesting potential underreporting, underdiagnosis, and undertreatment in clinical practice.