Reduced Efficiency of Chlorine Disinfection of Naegleria fowleri in a Drinking Water Distribution Biofilm

Abstract

Naegleria fowleri associated with biofilm and biological demand water (organic matter suspended in water that consumes disinfectants) sourced from operational drinking water distribution systems (DWDSs) had significantly increased resistance to chlorine disinfection. N. fowleri survived intermittent chlorine dosing of 0.6 mg/L for 7 days in a mixed biofilm from field and laboratory-cultured Escherichia coli strains. However, N. fowleri associated with an attached drinking water distribution biofilm survived more than 30 times (20 mg/L for 3 h) the recommended concentration of chlorine for drinking water. N. fowleri showed considerably more resistance to chlorine when associated with a real field biofilm compared to the mixed laboratory biofilm. This increased resistance is likely due to not only the consumption of disinfectants by the biofilm and the reduced disinfectant penetration into the biofilm but also the composition and microbial community of the biofilm itself. The increased diversity of the field biofilm community likely increased N. fowleri's resistance to chlorine disinfection compared to that of the laboratory-cultured biofilm. Previous research has been conducted in only laboratory scale models of DWDSs and laboratory-cultured biofilms. To the best of our knowledge, this is the first study demonstrating how N. fowleri can persist in a field drinking water distribution biofilm despite chlorination.

Molecular Detection of Legionella spp. and their associations with Mycobacterium spp., Pseudomonas aeruginosa and amoeba hosts in a drinking water distribution system

“…; Miller et al . ). In general, the efficacy of disinfectants for OPs are only transient, due to their regrowth within biofilm (Wéry et al .…”

“…It is well understood that planktonic cells are well controlled by residual disinfectants (e.g. chlorine dioxide, 0Á5 mg l À1 ; chlorine, 2Á5 mg l À1 ; monochloramine, 0Á5 mg l À1 ; and copper-silver ionization, 0Á8/0Á02 mg l À1 ), but biofilm and amoeba-bound cells are much more resistant to such treatments (Buse et al 2012;Miller et al 2015). In general, the efficacy of disinfectants for OPs are only transient, due to their regrowth within biofilm (W ery et al 2008a) and following loss of any biocide residual (Kilvington and Price 1990;Thomas et al 2004).…”

A human exposome framework for guiding risk management and holistic assessment of recycled water quality

“…Recycled waters have complex microbial communities and high availability of nutrients and other organic matter, creating optimal conditions for biofilm establishment. 170 Recent studies have also shown increased chlorine resistance of FLA in the presence of naturally established biofilm 171,172 and even non-biofilm Vermamoeba spp. have been observed to resist chlorination.…”

Effectiveness of Devices to Monitor Biofouling and Metals Deposition on Plumbing Materials Exposed to a Full-Scale Drinking Water Distribution System

“…rate and extend of formation) in drinking water distribution systems. Additionally, use of this device has been further extended to investigate occurrences of discoloured water [7] and pathogenic organisms [33] in drinking water distribution systems. Unlike the MRD, this offline monitor is cost effective and is easy to install to facilitate routine biological and chemical assessment of drinking water distribution systems.…”