Prevalence of Legionella pneumophila serogroups 1-15 and non-pneumophila Legionella species in hospitalized patients with community and hospital-acquired pneumonia

Since the initial description of Legionnaires? disease (LD) in 1976, Legionella pneumophila has been increasingly recognized as a pathogen causing both community-acquired and nosocomial pneumonia. Legionella pneumonia is an often severe and potentially fatal form of bacterial pneumonia caused by an extensive list of Legionella species. Legionellae account for 2 to 9% of all pneumonias. Moreover, Legionella pneumonia is associated with greater severity and a higher case-fatality rate (up to 30%) than pneumonia from other atypical pathogens. The genus Legionella comprises 50 species; among these around 30 species can infect humans. Among these Legionella species, L. pneumophila alone has 15 serogroups of which L. pneumophila serogroup 1 is responsible for 70 to 92% of laboratory-detected legionellosis cases in the United States and Europe and 50% of the cases in Australia. The exact burden of legionella causing human infections in Oman is currently unknown. Similarly, the published literature on the subject from the region including GCC countries is scarce. Interestingly, a large outbreak of Legionnaires? disease associated with travel to Dubai, UAE among travelers from the United Kingdom, Sweden and the Netherlands was reported in 2017 suggesting that the legionella is likely to be prevalent in this region. This is further supported by the findings of several epidemiological and environmental surveys from the region. Currently, diagnosis of Legionella pneumonia relies almost solely on the urinary antigen test, which captures only Legionella pneumophila serogroup 1. This test has been in use at SQUH for many years but has not been very useful in our practice due to the fact that it almost always produces a negative result even when the clinical suspicion is extremely high for LD. This has created a diagnostic ?blind spot? for Legionella pneumonia caused by non-Legionella pneumophila serogroup 1 strains. sole reliance on urinary antigen tests that only detect Legionella pneumophila serogroup 1 means there is likely to be a substantial hidden burden of undiagnosed disease. This hidden burden results in a misleading understanding of Legionnaires? disease epidemiology and undue reliance on empirical treatment. Detailing the epidemiology of various legionella species [aim of our research] will inform SQUH (and other health systems in the country) on selection of the most suitable diagnostic test and will minimize unnecessary use of empirical anti legionella antibiotics. Outcome of this research shall positively impact the diagnostic and therapeutic targets with better use of resources including antimicrobial stewardship. The finding of this research will have national impact on this relatively common cause yet unrecognized of pneumonia. We postulate that this particularly low detection rate is likely to be explained by the prevalence of non-serogroup 1 L. pneumophila in our setting. Because these urinary assays only detect a limited number of serogroups of L. pneumophila, some authors suggest that total dependence on this diagnostic assay may miss up to 40% of cases of Legionella pneumonia. Currently, real?time PCR is considered as the molecular method of choice for detecting Legionella infections providing sensitivity, specificity, and rapid results. The aim of this study is to use Legionella-specific PCR test to examine the prevalence of Legionella pneumophila serogroups 1-15 and non-pneumophila Legionella species in hospitalized patients with community or hospital-acquired pneumonia in SQUH.