A pilot study of the impact of bacterial and fungal coinfections on mildly ill COVID-19 patients

Background Coinfections and superinfections significantly impair prognosis in severely ill COVID-19 patients who may develop ventilator-associated pneumonia. However, the role of bacterial and fungal infections and/or lung colonization in patients with moderate COVID-19 who are not on mechanical ventilation remains controversial. Additionally, there is limited data on the impact of coinfections on pneumonia development in vaccinated subjects. To clarify this question, we summarize the data for patients treated in the single infectious department for a moderate form of COVID-19-associated pneumonia. Methods We evaluated the association of the medical condition on hospital admission and disease duration with anti- Chlamydophila pneumoniae and anti- Mycoplasma pneumoniae quantitative IgM and sputum culture results in COVID-19 in patients (n=271). Results Non-pneumococcal Streptococci were the most frequent bacteria isolated from sputum (70% of the population; only one case of St.  pneumoniae ), followed by Candida albicans (15.6% of the population) and Neisseria spp. (13% of the population). Airway colonization with C. albicans and anti- M. pneumoniae IgM seropositivity was significantly associated with a higher CT score, especially in vaccinated patients; meanwhile, fungal pathogen C. albicans colonization was associated with prolonged hospital duration. Airway colonization with C. albicans was associated with slightly longer disease duration. Conclusion The results demonstrate that respiratory pathogens, at least M. pneumoniae , can contribute to the risk of COVID-19 onset and/or severity in the vaccinated population. Meanwhile, neither bacterial agents of atypical pneumonia nor lung colonization with opportunistic pathogens are essential for recovery in patients with moderate COVID-19 infection when appropriate treatment is provided.