Abstract
BackgroundMicroorganisms causing community-acquired pneumonia (CAP) can be categorised into viral, typical and atypical (Legionella species, Coxiella burnetii, Mycoplasma pneumoniae, and Chlamydia species). Extensive microbiological testing to identify the causative microorganism is not standardly recommended, and empiric treatment does not always cover atypical pathogens. In order to optimize epidemiologic knowledge of CAP and to improve empiric antibiotic choice, we investigated whether atypical microorganisms are associated with a particular season or with the patient characteristics age, gender, or chronic obstructive pulmonary disease (COPD).MethodsA data-analysis was performed on databases from four prospective studies, which all included adult patients hospitalised with CAP in the Netherlands (N = 980). All studies performed extensive microbiological testing.ResultsA main causative agent was identified in 565/980 (57.7 %) patients. Of these, 117 (20.7 %) were atypical microorganisms. This percentage was 40.4 % (57/141) during the non-respiratory season (week 20 to week 39, early May to early October), and 67.2 % (41/61) for patients under the age of 60 during this season. Factors that were associated with atypical causative agents were: CAP acquired in the non-respiratory season (odds ratio (OR) 4.3, 95 % CI 2.68–6.84), age <60 year (OR 2.9, 95 % CI 1.83–4.66), male gender (OR 1.7, 95 % CI 1.06–2.71) and absence of COPD (OR 0.2, 95 % CI 0.12–0.52).ConclusionsAtypical causative agents in CAP are associated with respectively non-respiratory season, age <60 years, male gender and absence of COPD. Therefore, to maximise its yield, extensive microbiological testing should be considered in patients <60 years old who are admitted with CAP from early May to early October.Trial registrationNCT00471640, NCT00170196 (numbers of original studies).Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1641-9) contains supplementary material, which is available to authorized users.
Highlights
Microorganisms causing community-acquired pneumonia (CAP) can be categorised into viral, typical and atypical (Legionella species, Coxiella burnetii, Mycoplasma pneumoniae, and Chlamydia species)
We investigated whether atypical causative microorganisms in patients with CAP are more prominent during a particular season or associated with specific patient characteristics
Results from the analysis excluding respectively patients with pneumonia severity index (PSI) class 5 and patients who used antibiotics before hospitalisation can be found in Additional file 1: Table S1. In this analysis of 980 patients hospitalised with CAP in whom extensive microbiological testing was performed, we found non-respiratory season, age < 60, male gender and absence of chronic obstructive pulmonary disease (COPD) to be associated with an atypical microorganism as causative agent
Summary
Microorganisms causing community-acquired pneumonia (CAP) can be categorised into viral, typical and atypical (Legionella species, Coxiella burnetii, Mycoplasma pneumoniae, and Chlamydia species). Extensive microbiological testing to identify the causative microorganism is not standardly recommended, and empiric treatment does not always cover atypical pathogens. Atypical microorganisms are Legionella species, Coxiella (C.) burnetii (Q-fever), Mycoplasma (M.) pneumoniae, and Chlamydia species. Cases of CAP are seen throughout the year, but overall incidence rises during winter months [4] This is due to certain aetiological agents that show seasonal variation: Streptococcus (S.) pneumoniae, Haemophilus influenzae and respiratory viruses occur mainly during winter season [4, 5]. Only Legionella (L.) species and C. burnetii show seasonal variation, increasing during summer and during early spring in the lambing season, respectively [6,7,8]. Numbers of cases of M. pneumoniae increase during wintertime, but the incidence is relatively high during summer as well
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