Distribution of Virulence Genes in Environmental and Clinical Isolates of Legionella Pneumophila in Busan, South Korea

Legionella pneumophila is the major causative agent of Legionnaires’ disease. The distribution of L. pneumophila in environmental water systems of public facilities in Busan, South Korea was previously reported; however, the distribution of virulence genes in environmental and clinical isolates in Busan is unknown. Here, we investigated using PCR the distribution of three virulence loci (dot/icm, lvh, and rtxA) in isolates from Busan. A high prevalence of environmental (127/254) and clinical (3/4) isolates were observed for the simultaneous presence of all three genes, while environmental harboring dot/icm + rtxA, dot/icm + lvh, rtxA + lvh, and only one gene were 21%, 11%, 9% and <1-4%, respectively, The remaining clinical isolate carried dot/icm + rtxA. In addition, 68% of isolates from serogroup 1, the main cause of legionellosis, possessed all three virulence genes compared with 40% of isolates from serogroups 2 to 15. Prevalence of isolates with two genes was 5-14% and 6-29% in serogroup 1 and serogroups 2 to 15, respectively, whereas that of isolates with one gene was 1-2% and 0-6%, respectively. These results provide valuable information for epidemiological investigations of the relationship between environmental and clinical isolates in legionellosis outbreaks in Busan.