Features of community-acquired pneumonia in immunocompetent hospitalized adults according to the causal agent

Abstract

Background: Molecular biological techniques allow the identification of more pathogens associated with community-acquired pneumonia (CAP). Aim: To compare clinical and laboratory parameters of patients with CAP caused by different groups of pathogens. Material and Methods: In a prospective study, immunocompetent adult patients hospitalized with CAP were tested for the presence of a broad range of possible respiratory pathogens using bacterial cultures, polymerase chain reaction, urinary antigen testing and serology. Results: Pathogens were detected in 367 of 935 patients with CAP (39.2%). Streptococcus pneumoniae (10.7%) and influenza virus (6%) were the most frequently identified bacterial and viral pathogens, respectively. Pneumococcal pneumonia predominated in older adults, with multiple comorbidities, with elevation of inflammatory parameters and hypoxemia, like other bacterial pneumonias. Viral pneumonia predominated in elderly patients with multiple comorbidities, with a shorter hospital length of stay and lower mortality. Pneumonia associated with atypical microorganisms predominated in young adults, smokers, with subacute clinical evolution. Their hospital stays and lethality was similar to other bacterial pneumonias. Viral and classical bacterial pneumonias predominated in high risk pneumonia severity index categories. Although several variables were associated with the detection of a pathogen group, substantial overlap avoided the identification of reliable clinical predictors to distinguish etiologies. Conclusions: The clinical and radiographic characteristics were similar in pulmonary infections caused by classical bacteria, respiratory viruses and atypical microorganisms. Therefore, microbial testing for common respiratory pathogens is still necessary to optimize treatment.