Researchers conducted a study to determine possible associations between atypical microorganisms that cause community-acquired pneumonia (CAP) and particular seasons, patient characteristics such as age and gender, and the presence of chronic obstructive pulmonary disease (COPD).
The findings suggest that the microorganisms are associated with non-respiratory season from early May to early October, males, the absence of COPD and in people less than 60 years old.
The research paper, “Atypical aetiology in patients hospitalised with community-acquired pneumonia is associated with age, gender and season; a data-analysis on four Dutch cohorts”, was published in BMC Infectious Diseases.
Microorganisms that cause community-acquired pneumonia (CAP) are often divided into three groups, viral, typical and atypical.
Atypical microorganisms include Legionella species, Coxiella (C.) burnetii (Q-fever), Mycoplasma (M.) pneumoniae, and Chlamydia species. Microbiological testing is not standard in clinical practice so causal microorganisms remain unidentified. The first choice of treatment for patients with low to moderately severe CAP does not always concern atypical microorganisms.
Microorganisms that cause CAP show seasonal variation, with incidence usually rising during wintertime. Among atypical microorganisms, Legionella (L.) species and C. burnetii, for example, increase during summertime and early spring.
Because microbiological testing is not recommended for patients with low to moderately severe CAP, antibiotic treatment for CAP is usually based on observation. But, identification of specific circumstances associated with increased risk of CAP, could be useful to determine optimal treatment.
In the present study, researchers investigated the behavior of the microorganisms, seasonal variability and patients’ characteristics, including diagnosis of COPD. The scientists analyzed databases from four prospective studies, which included 980 patients hospitalized with CAP in the Netherlands.
The findings reveal that in 565 of the cases (57.7%) a main cause was able to be identified. Out of those, 117 (20.7%) were caused by atypical microorganisms. CAP caused by atypical bacteria was 40.4 % during from May to early October (non-respiratory season), and 67.2 % among patients under age 60 during the season.
Researchers concluded that extensive microbiological testing should be considered in patients less than 60 years old who are admitted with CAP from early May to early October.