Introduction Determining the etiology of community-acquired pneumonia (CAP) is essential for targeted treatment and optimal care. Reliable results require selection of the appropriate sampling site. Methods Paired nasopharyngeal (NP) and oropharyngeal (OP) swabs were collected from 484 patients with CAP between September 2016 and September 2018. The samples were analyzed by PCRs for Streptococcus pneumoniae , Haemophilus influenzae , 6 atypical bacterial species, and 14 viral agents. Results The most common pathogen was S. pneumoniae (24%), followed by H. influenzae (23%). Both were more frequently detected in the oropharynx, with 29% and 40% respectively, identified only in OP swabs. Respiratory viruses were found in 32% of the patients; of these, 65% were present in both NP and OP samples. Notably, 21% were detected only in NP samples, and 15% only in OP samples. Mycoplasma pneumoniae was identified in 6% of all patients, predominantly in OP samples (89%) compared with NP samples (70%). Cq-values were lower in NP swabs for all pathogens except M. pneumoniae , suggesting a higher microbial load in the nasopharynx. Discussion This study highlights the importance of sampling site selection in the diagnosis and management of CAP. Nasopharyngeal sampling was more effective for detecting respiratory viruses, whereas OP samples yielded more cases of S. pneumoniae , H. influenzae and M. pneumoniae . To maximize the diagnostic yield, a combined NP/OP-sampling strategy can thus be recommended.
Hansen et al. (Wed,) studied this question.