Persistence of Infectious Enterovirus B in Free-Living Amoebae

Abstract

The persistence of human pathogens, such as Legionella bacteria, inside environmental free-living amoebae is emerging as a major waterborne health risk, which could affect pathogen disinfection, removal, and dispersion from engineered water systems. Amoebae are natural predators, which graze on water-based biofilms, where they shape microbial populations. Amoebae are also found in hot water tanks, cooling towers, drinking water outlets, moist surfaces, medical instruments, dental waterline units, and are often linked to nosocomial infections. Amoeba-resistant microorganisms can seek shelter within the disinfection-resistant protozoan cysts and can easily disperse with them through water distribution systems. Despite the co-occurrence of amoebae and human enteric viruses in similar environments, the association between them is currently poorly understood. This is an important knowledge gap of great public health significance, especially for high-risk enteric viruses (e.g. coxsackieviruses, which are associated with Type 1 Diabetes, neonatal neurological impairment, and even miscarriage). Of potential concern to the water industry and public health in general, but not well understood, is virus internalization by amoebae. This could reduce the efficacy of current virus management strategies for contaminated waters. Here I demonstrate that an infectious clinical Enterovirus B isolate (coxsackievirus B5) persisted over time in association with two of the most commonly reported waterborne amoebae (Vermamoeba vermiformis, isolated from a hospital cooling tower, and Acanthamoeba polyphaga, isolated from human corneal scrapings). My findings also demonstrate for the first time that a human enteric virus could be localized in expelled amoebae vesicles. In addition, infectious virions were also associated with mature A. polyphaga cysts for at least 20 months.