Legionella pneumophila are intracellular pathogens, associated with human disease,
attributed to the presence and absence of certain virulent genes. In this study, virulent gene loci
(lvh and rtxA regions) associated with human disease were determined. Thirty-three cooling
tower water isolates, isolated between 2004 to 2006, were analyzed for the presence of these
genes by PCR method. Results showed that 19 of 33 (57.5%) of the L. pneumophila serogroup 1
isolates have both the genes. Six (18.2%) of the isolates have only the lvh gene and 2 (6.1%) of the isolates have only the rtxA gene. However, both genes were absent in 6 (18.2%) of the L.
pneumophila isolates. The result of our study provides some insight into the presence of the
disease causing L. pneumophila serogroup 1 in the environment. Molecular epidemiological studies
will provide better understanding of the prevalence of the disease in Malaysia.