Development and structure of drinking water biofilms and techniques for their study

The failure to reduce the Campylobacter contamination of intensively reared poultry may be partially due to Campylobacter resisting disinfection in water after their internalization by waterborne protozoa. Campylobacter jejuni and a variety of waterborne protozoa, including ciliates, flagellates, and alveolates, were detected in the drinking water of intensively reared poultry by a combination of culture and molecular techniques. An in vitro assay showed that C. jejuni remained viable when internalized by Tetrahymena pyriformis and Acanthamoeba castellanii for significantly longer (up to 36 h) than when they were in purely a planktonic state. The internalized Campylobacter were also significantly more resistant to disinfection than planktonic organisms. Collectively, our results strongly suggest that protozoa in broiler drinking water systems can delay the decline of Campylobacter viability and increase Campylobacter disinfection resistance, thus increasing the potential of Campylobacter to colonize broilers.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Survival of Campylobacter jejuni in Waterborne Protozoa

Snelling¹,

McKenna²,

Lecky³

et al. 2005

“…Among these are the recovery of total coliforms from distribution systems in which water leaving the treatment plant tested negative for coliforms (20,21); the observation that environmentally derived strains of total coliforms and E. coli can grow in unsupplemented distribution system water (7); and the recovery of increased numbers of E. coli organisms from drinking water distribution pilot plants after the calculated inoculum should have theoretically washed out (12). Other studies have shown that E. coli can attach and become incorporated into biofilms within model distribution systems (8,11), as well as into biofilms derived from groundwater populations (2). In recent years, the advent of molecular detection techniques has greatly facilitated our understanding of bacteria indigenous to the environment.…”

mentioning

confidence: 99%

Growth of Escherichia coli in Model Distribution System Biofilms Exposed to Hypochlorous Acid or Monochloramine

Williams

Braun-Howland

2003

Bacteria indigenous to water distribution systems were used to grow multispecies biofilms within continuous-flow slide chambers. Six flow chambers were also inoculated with an Escherichia coli isolate obtained from potable water. The effect of disinfectants on bacterial populations was determined after exposure of established biofilms to 1 ppm of hypochlorous acid (ClOH) for 67 min or 4 ppm of monochloramine (NH 2 Cl) for 155 min. To test the ability of bacterial populations to initiate biofilm formation in the presence of disinfectants, we assessed the biofilms after 2 weeks of exposure to residual concentrations of 0.2 ppm of ClOH or 4 ppm of NH 2 Cl. Lastly, to determine the effect of recommended residual concentrations on newly established biofilms, we treated systems with 0.2 ppm of ClOH after 5 days of growth in the absence of disinfectant. Whole-cell in situ hybridizations using fluorescently tagged, 16S rRNA-targeted oligonucleotide probes performed on cryosectioned biofilms permitted the direct observation of metabolically active bacterial populations, including certain phylogenetic groups and species. The results of these studies confirmed the resistance of established bacterial biofilms to treatment with recommended levels of disinfectants. Specifically, Legionella pneumophila, E. coli, and ␤ and ␦ proteobacteria were identified within biofilms both before and after treatment. Furthermore, although it was undetected using routine monitoring techniques, the observation of rRNA-containing E. coli within biofilms demonstrated not only survival but also metabolic activity of this organism within the model distribution systems. The persistence of diverse bacterial species within disinfectant-treated biofilms suggests that current testing practices underestimate the risk to immunocompromised individuals of contracting waterborne disease.Assessment of the microbiological safety of drinking water is based largely on the routine monitoring of water supplies for the presence of total coliforms and Escherichia coli. Detection of E. coli is considered indicative of recent fecal contamination and of the potential presence of enteric pathogens, while the presence of total coliforms is indicative of poor water quality.Whereas routine water quality measurements assess the presence of planktonic bacteria, the vast majority of bacteria indigenous to aquatic environments exist attached to solid particles or surfaces. Within water distribution systems, significant bacterial populations exist as complex, structurally heterogeneous biofilms attached to pipe surfaces. Residence within these complex matrices provides organisms with higher localized nutrient concentrations than are commonly found in drinking waters (10,14,18,22), and recent studies have shown that attached bacteria are more metabolically active than are their free-living counterparts (26, 29). Furthermore, biofilms afford bacteria significant protection from disinfecting agents (3, 31, 35), including hypochlorous acid and monochloramine. Biofilms are dynamic ...

“…In the kitchen, a variety of normal domestic wastes will pass through the drain conduit, especially where waste disposal units are fitted, along with residues from high-risk infectious materials, such as uncooked meat (12) and vegetable waste (15). Additionally, potential pathogens, including pseudomonads and Legionella pneumophila, may also enter the drain through tap water (6,20,27). Domestic sink drain biofilms therefore represent a largely unstudied nidus for potentially pathogenic bacteria, situated close to food preparation areas.…”

mentioning

confidence: 99%

Microbial Characterization of Biofilms in Domestic Drains and the Establishment of Stable Biofilm Microcosms

McBain

Bartolo

Catrenich

et al. 2003

137

111

We have used heterotrophic plate counts, together with live-dead direct staining and denaturing gradient gel electrophoresis (DGGE), to characterize the eubacterial communities that had formed as biofilms within domestic sink drain outlets. Laboratory microcosms of these environments were established using excised biofilms from two separate drain biofilm samples to inoculate constant-depth film fermentors (CDFFs). Drain biofilms harbored 9.8 to 11.3 log 10 cells of viable enteric species and pseudomonads/g, while CDFF-grown biofilms harbored 10.6 to 11.4 log 10 cells/g. Since live-dead direct staining revealed various efficiencies of recovery by culture, samples were analyzed by DGGE, utilizing primers specific for the V2-V3 region of eubacterial 16S rDNA. These analyses showed that the major PCR amplicons from in situ material were represented in the microcosms and maintained there over extended periods. Sequencing of amplicons resolved by DGGE revealed that the biofilms were dominated by a small number of genera, which were also isolated by culture. One drain sample harbored the protozoan Colpoda maupasi, together with rhabtidid nematodes and bdelloid rotifers. The microcosm enables the maintenance of stable drain-type bacterial communities and represents a useful tool for the modeling of this ecosystem.Clinical epidemiologists have long recognized the potential of sink drains in hospital wards to harbor pathogens. Several studies have identified sink drains within medical-surgical intensive-care wards (19,22,30,35) and cystic fibrosis units (24) as possible sources of infection. Despite the increased information relating to the occurrence of bacterial biofilms and their reported involvement in the biofouling of domestic drains (7), there are few reports in the literature concerning the ecology and microbiology of this environment. The persistence (1) and significance (10) of biofilms in virtually all environments is widely acknowledged. Studies in the home (14, 34) have identified the potential health risks of microbial contamination. Scott et al. (34) identified possible pathogens in the kitchen, toilet, and bathrooms in Ͼ200 homes in the United Kingdom. More recent studies (3,8,9) have demonstrated that homes represent an environment into which bacterial, viral, and fungal pathogens are continuously introduced in association with food, people, and pets. Studies by Cogan et al. (8,9) showed that detergent-based cleaning was relatively ineffective in controlling the spread of salmonella and campylobacter to kitchen surfaces during the preparation of contaminated poultry. Despite such concerns, there have been few investigations into the bacterial composition of biofilms within domestic sink drains. As with hospital drains, the pipe work presents a variety of solid surfaces that are suitable substrates for biofilm formation (7, 26). Biofilm has been implicated in a high proportion of slow-running drains in the United States (7). Domestic drains are subject to intermittent wetting, periodic feeding with a plet...