Whether a viral or bacterial pathogen is detected has little effect on cough symptoms or duration

Reference

Ordonez-Mena J, Fanshawe TR, Butler CC, et al. Relationship between microbiology of throat swab and clinical course among primary care patients with acute cough: a prospective cohort study. Fam Pract 2020;37(3):332-339.

Synopsis

In this UK study, researchers identified aduts presenting to their primary care physician with an acute cough for less than 28 days. They performed a pharyngeal swab for 10 viral and 11 bacterial pathogens; in their primary analysis they considered Coagulase negative staphylococcus, Fusobacterium necrophorum, Moraxella catarrhalis, Neisseria meningitidis, Staphylococcus aureus, and Streptococcus pyogenes to be commensal, leaving Haemophilus influenzae, Bordetella pertussis, Chlamydia pneumonia, Mycoplasma pneumoniae, and Streptococcus pneumoniae as potential bacterial pathogens.The authors recruited 645 adults who all had pharngeal swabs; 354 of whom also completed a 7-day symptom diary. No pathogen was detected in 46.4%. Swab results were not available to the clinician to affect their decision-making. The most common viral pathogens were enterovirus or rhinovirus (25.6%), human parainfluenza virus (3.3%), respiratory syncytial virus (3.1%), and influenza A (1.5%). Bacterial pathogens detected included H. influenzae (25.7%), S. pneumoniae (3.7%), B. pertussis (0.5%), C. pneumoniae (0.5%), and M. pneumoniae (0.3%). Approximately 12% of patients had both viral and bacterial pathogens detected. At baseline the duration of illness was a bit longer in those with a bacterial pathogen (11.5 vs 8.1 days; P < .001), but those patients were actually less likely to have been prescribed an antibiotic (59.2% vs 67.5%; P = .009). Symptoms of nasal congestion or coryza, myalgias, lung crackles, and wheeze were more common with viral pathogens, but these differences were largely small and unhelpful for clinical decision-making. Symptoms like productive cough, shortness of breath, bronchial breathing, and fever did not differ between patients with a viral or bacterial pathogen. Based on the symptom diaries, symptom severity was greater for those with a viral or mixed infection than for those with a bacterial infection or no pathogen detected. Duration of moderate or severe symptoms after initial presentation did not differ between groups. Adjusting for antibiotic use had no effect on this outcome.