Serostatus and Epidemiological Characteristics for Atypical Pneumonia Causative Bacteria among Healthy Individuals in Medina, Saudi Arabia, a Retrospective Study.

Background: Community-acquired atypical pneumonia is generally a mild and self-limiting infection. Still, it may lead to hospitalization and progressive clinical complications in some cases, particularly among the elderly and individuals with chronic diseases. Chlamydia pneumoniae, Legionella pneumophila, and Mycoplasma pneumoniae are the community’s main causative agents of atypical pneumonia. However, most published studies evaluated their incidence in the hospital setting, and little is known about their prevalence among healthy individuals. This work aims to assess the seroprevalence of these bacteria among healthy people to determine the status of immunity against these bacteria in the community. Methodology: Two hundred and eighty-three serum samples from a multicenter in Medina, Saudi Arabia, were collected in this study. Serum samples were subjected to indirect enzyme-linked immunosorbent assays (ELISAs) to detect IgG antibodies against C. pneumoniae, L. pneumophila, and M. pneumoniae to investigate the seroprevalence of these bacteria and their distribution among different genders and age groups of healthy people. Results: IgG seropositivity for at least one of the three atypical pneumonia-causative bacteria occurred in 85.8% (n= 243/283) of the sample population. IgG seropositivity for C. pneumoniae occurred in 80.6% (228/283) of the population, followed by 37.5% for L. pneumophila and 23% for M. pneumoniae (66/283). In addition, the IgG seropositivity rates for the three bacteria were observed predominantly among male participants. Furthermore, no significant difference in IgG seropositivity distribution occurred between different age groups of healthy people for C. pneumoniae, L. pneumophila and M. pneumoniae. Conclusions: The current study found that C. pneumoniae, L. pneumophila, and M. pneumoniae tended to be highly prevalent among healthy people and more common among males than females. Additionally, their pattern of distribution among healthy individuals seemed to be predominant among young adults (aged 20−40 years), which differs from their predominant distribution among elderly patients in hospital settings (>50 years).