Acanthamoeba as a protective reservoir for Pseudomonas aeruginosa in a clinical environment.

Abstract

Pseudomonas aeruginosa is a growing concern in healthcare associated infections and poses significant risk to those with serious underlying health conditions. The antimicrobial resistance traits of the pathogen and ability to form biofilms make effective mitigation and disinfection strategies difficult. Added to this challenge is the role that free-living amoebae such as Acanthamoeba play in the detection, disinfection, and transmission of P. aeruginosa. P. aeruginosa can survive intracellularly within amoebae, which has the potential to limit detectability and permit transmission into high-risk areas. Herein, we have screened for the presence of Acanthamoeba species and P. aeruginosa within a functioning general hospital in Scotland using a culture and molecular approach, noting their presence at several sites over a 4-month period, particularly within floor drains connecting patient rooms. In addition, microbiome analysis revealed amoebae harbour a unique microbial community comprised primarily of Pseudomonas species that were not readily detected using microbiome sequencing techniques on environmental swabs. Having demonstrated that both organisms were consistently present in hospital settings, we investigated the relationship between Acanthamoeba and P. aeruginosa in the laboratory, showing that i) Acanthamoeba growth rate is increased in the presence of Pseudomonas biofilms and viable Pseudomonas persist within the amoebae and ii) hydrogen peroxide-based disinfectants are significantly less effective against an isolate of P. aeruginosa in the presence of Acanthamoeba than when the bacteria are incubated alone. These findings suggest that amoebae, and other protists, can influence the detection and persistence of P. aeruginosa in high-risk areas and should be considered when implementing mitigation strategies.