Legionella and its carriage of virulence genes detected in air condition cooling towers at public places in Quanzhou, Fujian, 2008–2019

  Objective  To understand the contamination of Legionella in air condition cooling towers at public places in Quanzhou, Fujian province, from 2008 to 2019, and identify its carriage of virulence genes and pathogenicity and provide evidence for the prevention and control of Legionellosis.

  Methods  The isolation, identification, genotyping and nucleic acid testing of Legionella from water samples collected from the air condition cooling towers at 31 public places in 12 counties of Quanzhou from 2008 to 2019 were conducted. PCR assay was used to detect 7 virulence genes of the isolated strains, including iraA, cpxR, cpxA, dotA, rpoB, icmC, icmD.

  Results  A total of 569 water samples were collected from the air condition cooling towers during 2008–2019, in which 159 Legionella strains were isolated (27.94%). The majority of the Legionella strains were L. pneumophila (136, 23.90%), and the remaining included L. longbeachae, L. philliflora and L. dumoffii. The serotypes of L. pneumophila were 1, 3, 5, 6, 8 and 10, and serotype 1 was the predominant one (49, 30.82%). The consistent rate of the two methods was 88.40%, but the positive rate of quantitative real-time PCR was significantly higher than that of isolation. The difference was significant ( χ²=313.532, P<0.05). All the 136 L. pneumophila strains carried 7 virulence genes, while the virulence genes detection results of 82.61% of the non-L. pneumophila strains were negative.

  Conclusion  Serious contamination of Legionella was found in the air condition cooling towers at public places in Quanzhou, and L. pneumophila was predominant and carried virulence genes. Timely cleaning and disinfection of air condition cooling towers are necessary to prevent the infection of Legionella.