Legionella can cause human respiratory disease which includes the severe, pneumonia-like form called Legionnaires’ disease (LD). Originating from natural environments such as freshwater and soil, Legionella can inhabit infrastructure including engineered water systems or cooling towers, from where contaminated aerosols can transmit to susceptible human populations, e.g. the vulnerable elderly and immunocompromised patients in healthcare facilities. Nosocomial infections can result in high mortality rates of up to 50%.
This is a major concern to Queensland and Australian healthcare facilities, where multiple outbreaks of the disease caused by L. pneumophila have occurred. In these outbreaks, the infectious source has been traced to persistent biofilms present in drinking water distribution systems (DWDS), such as the plumbing systems of hospital buildings. Despite low nutrient conditions and residual disinfectants, biofilms develop and persist in these plumbing systems. These biofilms are likely to favourably support the complex ecology, persistence and increased pathogenicity of waterborne opportunistic pathogens like Legionella.
This project aims to improve understanding of the biofilm ecology of Legionella in DWDS, as well as to determine alternative antimicrobial strategies to remove Legionella from persistent biofilms. One strategy is to use bacteriophages (phages) to selectively target and remove Legionella from biofilms. This approach has been successful in medical and industrial applications on various bacterial species. Although currently there is limited research on phages specific for Legionella, isolating and using synthetic biology approaches to engineer Legionella-specific phages with superior properties has great potential for their control.
To isolate Legionella-specific phages, we are targeting various water samples that contain Legionella as detected by PCR. Sources positive for Legionella spp. include water samples from buildings, cooling towers, riverbanks, creek water and wastewater. These samples have been screened for phages against various Legionella strains using standard phage isolation techniques. Phages specific for Legionella have been isolated, and these are currently undergoing characterisation with regard to host range, host infectivity, and genome sequencing.