A Study on the Degree of Legionella Contamination Isolated from Apartments in Busan

Apartments are increasingly becoming common in South Korea and have become part of the transmission pathway for Legionnaires' disease.However, research on this topic is scare.This study investigated Legionella contamination in the water supplied to apartments and compared it with that in the water supplied to multiuse facilities, including public bathhouse, a large building, hospital, accommodations, and fountain, to identify infection risk and analyze epidemiological characteristics.From January to November 2023, 298 water samples from apartments and 1,356 samples from multiuse facilities in Busan were tested.Twenty-eight Legionella isolates were identified from apartments, including 3 isolates of L. pneumophila sg 1; 7 of L. pneumophila sg 2-14; as well as the following non-L.pneumophila species: 12 isolates of L. longbeachae, 5 of L. anisa, and 1 of L. erythra.A total of 213 Legionella isolates were identified from multiuse facilities, including 123 of L. pneumophila and 90 of non-L.pneumophila species.The detection rate of Legionella by apartment age was 3.8% for 1-10 years, 6.7% for 11-20 years, and 13.6% for 20 years.Apartments had the highest detection rates in hot water (16.7%),faucets (5.9%), and cool water (5.2%), whereas multiuse facilities had detection rates of 23.3% in cooling tower water, 19.3% in hot water, 8.3% in tank water, 8.3% in fountains, and 8.1% cool water.Legionella counts were in the range of 200-16,000 CFU/L in apartments and 200-80,000 CFU/L in multiuse facilities.Continuous monitoring and appropriate measure should be reinforced to prevent or minimize bacterial contamination in water supply of apartments as well as multiuse facilities.