Contamination status and genetic characteristics of Legionella pneumophila in shower water in public bathing places in Maanshan, Anhui, 2020−2021

Objective To understand the contamination of Legionella pneumophila in shower water of public bathing places in Maanshan, Anhui province, analyze the whole genome information of isolated strains, predict the virulence and drug resistance genes and provide data support for Legionellosis prevention and control.

Methods From 2020 to 2021, a total of 216 samples of shower water were collected from 49 public bathing places in 3 districts of Maanshan, and the isolation, culture, serotyping and PCR-identification of L. pneumophila were conducted. The sequencing and assembling of whole genome of the isolated strains were carried out to predict the virulence genes and drug resistance genes. Meanwhile, the phylogenetic tree was constructed based on serotype 1 Legionella pneumophila strain and the representative strains both at home and abroad.

Results In the 49 public bathing places, L. pneumophila was detected in 27 public bathing places (55.10%, 27/49). There were significant differences in the positive rate of L. pneumophila among three public bathing places in different districts (χ²=13.070, P<0.05). A total of 216 samples of shower water were collected, in which 66 were L. pneumophila positive (30.56%, 66/216). A total of 91 strains of L. pneumophila were isolated, and the strains belonged to 6 serotypes, with serotype 1 and serotype 3 as the predominant serotypes. The whole genome sequencing showed that the genome size of the 91 strains ranged from 3.10 Mb to 3.80 Mb, and the G+C content ranged from 38.08% to 41.02%. The virulence gene prediction showed 294–432 virulence factors, and 175 virulence factors were detected in the 91 strains, including secretion system related genes, flagellar synthesis related genes, flagellar movement related genes. The drug resistance gene prediction showed 20 drug resistance genes, mainly producing resistance to sulfonamides and fluoroquinolones. Phylogenetic tree showed that the two strains of L. pneumophila type 1 shared high homology with Danish isolate.

Conclusion Contamiantion of L. pneumophila exists in the shower water of public bathing places in Maanshan. The whole genome sequencing predicted a variety of virulence genes and drug resistance genes, suggesting that the disinfection of shower water in public bathing places should be strengthened, and strict supervision should be carried out to prevent the incidence of Legionellosis.