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Legionella - (re-)awakening to the Amoeba-based Pathogens of Distribution System Biofilm
Citation:
ASHBOLT, N. Legionella - (re-)awakening to the Amoeba-based Pathogens of Distribution System Biofilm. Presented at Center for Biofilm Engineering, Bozeman, MT, July 15, 2008.
Impact/Purpose:
EPA Research Goals for Biofilm: 1. Identify the possible significance/occurrence of Legionella and novel pathogens in distribution biofilms; 2. Specific focus on virulence up-regulation in Legionella associated with biofilm/amoeba growth; and 3. Sampling pathogens with a biofilm-like device Role of ABNC Cells in biofilms using macrophage and animal dose-response models; disinfection efficacy studies Add biofilm/pathogen issues to EPA-Net model and provide missing key QMRA data inputs for piped water
Description:
Fecal pathogens have long been the focus of concern in the distribution of drinking waters. Yet today, with distribution system ‘failures’ accounting for the majority of waterborne outbreaks in the USA, there is growing realization that pathogens endemic to aquatic biofilms may also be of concern, particularly to susceptible sub-populations. These concerns have focused on strains of Legionella spp., Mycobacterium avium complex and Helicobacter pylori, as raised in EPA’s contaminant candidate lists (CCL-1, 2 & 3). Such pathogens, however, may only be the tip of the ‘iceberg’. Turning to biofilm ecology, it is clear from studies on Legionella that biofilm amoeba play an important ‘Trojan Horse’ role by introducing, amplifying and possibly up-regulating virulence in Legionella and other pathogens. However, there are very few studies of Legionella spp. pathogenesis aimed at associating the role of biofilm colonization, parasitization of biofilm microbiota and release of virulent bacterial cell/vacuoles into drinking water distribution systems. Moreover, the implications of these environmental niches for drinking and reuse water exposures to pathogenic legionellae are poorly understood. On-going research at EPA’s Cincinnati laboratories into the putative role of biofilms and amoeba in the proliferation, development and dissemination of potentially pathogenic Legionella and other intracellular pathogens will be discussed. The goal of this research is to aid in identifying control strategies and to provide key data to enable quantitative microbial risk assessments of biofilm-associated pathogens.