Identification of antibiotic resistance and virulence genes in Legionella found in hospital water using next generation sequencing
Project Period:
2017
Project Investigator(s):
W. Hottel, Department of Epidemiology, The University of Iowa
N. Hall, V. Reeb, L Desjardin, State Hygienic Laboratory at The University of Iowa
Abstract:
Legionella bacteria, a cause of pneumonia, are ubiquitous in the freshwater environment and man-made water systems. The majority of human disease is caused by L. pneumophila serogroup 1, although other strains and Legionella species can cause disease. Legionella species have a relatively high genetic diversity and the mobile transfer of genetic material is a mechanism for environmental Legionella to acquire virulence and antibiotic resistance genes, potentially increasing their pathogenicity. SHL has an extensive Legionella isolate collection from Midwest hospital water supplies providing a unique opportunity to look for antibiotic susceptibility and virulence genes in these isolates by whole genome sequencing using Next Generation Sequencing. The presence of virulence and antibiotic resistance genetic markers in environmental Legionella isolates cultured from hospital water could provide important information on the potential risks resulting from infection with these bacteria and whether water control measures are indicated to prevent hospital-acquired Legionnaires’ disease.
Project Results:
Legionellosis caused by Legionella bacteria has been increasingly reported in the United States and is a serious public health threat. Legionella are ubiquitous in the freshwater environment and in man-made water systems (e.g. hot water heaters, cooling towers, hot tubs) where they can infect humans through aerosolization and cause disease. Since its addition to the Centers for Disease Control's (CDC) Waterborne Disease and Outbreak Surveillance System in 2001, Legionella bacteria have been the single most commonly reported pathogen identified in drinking water-associated outbreaks.
The greatest proportion of illness is attributed to L. pneumophila serogroup 1. A better understanding of the presence of virulence and antibiotic resistance genetic markers in L. pneumophila serogroup 1, other Legionella species and L. pneumophila serogroups cultured from hospital water could provide important information on the potential risks resulting from exposure and infection with these bacteria. This information will add knowledge to help answer the controversial question if the presence of these non-pneumophila environmental isolates in hospital water supplies requires eradication.
There were four key findings of the study.
- Whole genome sequencing (WGS) identified antibiotic resistance and virulence genes in Legionella pneumophila and Legionella anisa isolates.
- Only a subset (Sequence Type 1) of L. pneumophila isolates contained a resistance gene for a current antibiotic treatment (macrolides) for Legionnaires’ disease.
- All L. anisa isolates had a beta-lactamase associated gene, which was not found in any of the L. pneumophila isolates
- L. pneumophila isolates had significantly higher prevalence rates of virulence genes than L. anisa isolates as determined by WGS.