Molecular depiction of lepa, lida, ralf, rtxa and ivhb virulence factors of legionella pneumophila isolated from respiratory tract infections


  • Forouzan Khedri
  • Fatemeh Alaei Faradonbeh
  • Mahvash Eliyasi
  • Anahita Barghi
  • Abbas Doosti
  • Pardis Emad
  • Aida Alaei Faradonbeh



Legionella pneumophila, Prevalence, Broncho Alveolar Lavages, Respiratory infections, Risk factors


Background: Among all bacterial species in the genus Legionella, Legionella pneumophila is responsible for 90% of Legionella infections in humans. Putative virulence genes are the main factors in pathogenesis of L. pneumophila. The aim of this study was to determine the incidence of L. pneumophila in the broncho alveolar lavages of patients hospitalized due to respiratory tract infections as well as study the distribution of lepA, lidA, ralF, rtxA and lvhB virulence factors in bacterial strains.

Methods: One hundred fifty BAL samples were collected from patients who were referred to several Iranian health centers. Samples were cultured and those that were L. pneumophila positive were subjected to PCR method targeting the 16S rRNA gene. Samples positive for Legionella were analyzed for presence of latent virulence factors.

Results: Thirteen out of 90 male BAL samples (14.4%) and 5 out of 60 female BAL samples (8.3%) were positive for L. pneumophila (P =0.046). Patients older than 50 years had the highest incidence of L. pneumophila (20%), while patients younger than 15 years old had the lowest (4.16%) (P =0.017). All patients positive for L. pneumophila had fever, while the distribution of cough, dyspnea, chest pain and headache were 77.7%, 77.7%, 66.6% and 44.4%, respectively. The most commonly detected virulence factors among L. pneumophila isolates were lidA (50%) and ralF (27.77%).

Conclusion: Results indicate that sex and age of patients and climate conditions may constitute risk factors for incidence of L. pneumophila. Due to the high prevalence of L. pneumophila, wide-ranging amendments should be done in the principles of clinical care in some Iranian hospitals.