Detection of the Legionnaires’ Disease Agent in Patients With Respiratory Symptoms by Culture, Detection of Urinary Antigen and Polymerase Chain Reaction of the 16S rRNA Gene in Ahvaz, Iran

Background: Legionnaires’ disease (LD) is a common form of severe pneumonia, caused by Legionella spp. Legionella pneumophila is an important agent of severe pneumonia including 15 serogroups, which are all human pathogens. However, L. pneumophila serogroup 1 is the most prevalent agent of LD. Fatality rates among elderly and immunocompromised patients are high and may occur as a result of infection with this pathogen. Objectives: The aim of this study was to detect the LD agent in clinical samples of patients with respiratory symptoms by culture, urinary antigen and polymerase chain reaction (PCR) of the 16SrRNA gene. Methods: In this study, a total of 200 specimens (including 100 urine and 100 respiratory samples), which were collected from hospitalized patients with respiratory symptoms were examined. The respiratory specimens were inoculated to the buffered charcoal-yeast extract and modified Wodowsky and Yee agar media for isolation of the Legionella spp. The 16S rRNA gene in the respiratory specimens was amplified by the PCR method and the urinary antigen of L. pneumophila serogroup 1 was detected by EIA (enzyme immunoassay) test using the Coris Legionella V-test kit. Results: From a total of 200 specimens from patients with respiratory symptoms, 5% of urine specimens and 3% of respiratory specimens were positive for L. pneumophila using the EIA test and PCR of the 16SrRNA gene, respectively. The results of the culture of the respiratory samples showed that 1% of them were positive for Legionella spp. Conclusions: In this study, the LD agent was detected by the rapid EIA test. In addition, the sensitivity of the urinary antigen test using the Coris Legionella V-test kit for detection of L. pneumophila in respiratory specimens was more than those of the PCR and culture methods.