Prevalence and Molecular Diversity of Legionella pneumophila in Domestic Hot Water Systems of Private Apartments

Aims: To determine the prevalence of Legionella spp. in domestic hot water systems and evaluate the molecular diversity among these Legionella spp. Isolates.
Place and Duration of Study: Sample collection area was the city of Aqaba, Jordan, between May and December 2012. Sample analysis was done in Ben-Hayyan international laboratories, Aqaba city, and the molecular microbiology laboratories, Taibah University, Saudi Arabia.
Methodology: Two hundred (200) water samples were collected randomly from hot water tanks of private apartments, and were tested for the occurrence of Legionella spp. using direct membrane filtration method followed by species identification using Gram stain, the API 20NE biochemical system and the Legionella species latex agglutination test. Genotype characterizations of the Legionella isolates was carried out using DNA extraction followed by RAPD-PCR amplification with OP-A3 primer and analysis of the resulting patterns.
Results: Of the 200 samples, 17 (8.5%) were positive for the presence of Legionella spp. A total of 15 (88.2%) out the 17 positive samples were confirmed as Legionella pneumophila, 10 of them were of serogroup 1 and 5 isolates were of serogroup 2-14, the remaining two isolate were Legionella species other than L. pneumophila. RAPD-PCR analysis classified all 17 Legionella isolates into three groups. Serogroup 1 isolates were classified into group A, serogroup 2-14 isolates in group B and Legionella spp. isolates in group C. Group A was further sub-clustered into two subgroups, genotype A1 containing isolates collected from hot water tanks of a temperature set at 25-30°C and A2 containing isolates collected from hot water tanks of a temperature set at 55-80°C.
Conclusion: This study showed the colonization of the plumbing systems of private houses by Legionella spp. and demonstrated that the temperature of the water tanks maybe one of the most important factors that affect the genotypic behavior of Legionella pneumophila.