Characterization of Fungal Biofilms within a Municipal Water Distribution System

Abstract

Biofilms of a municipal water distribution system were characterized to assess the occurrence of fungi within surface matrixes. Densities of filamentous fungi ranged from 4.0 to 25.2 CFU cm ؊2 , whereas yeast densities ranged from 0 to 8.9 CFU cm ؊2 . Observations by scanning electron microscopy further suggested that spores, not hyphae or vegetative cells, comprised the primary source of viable propagules.The presence of fungi in drinking water and within biofilms of distribution systems has received limited attention. This is due, in part, to the fact that causal relationships between fungal occurrence and water quality remain uncertain. Nonetheless, waterborne fungi are likely associated with taste and odor problems, contamination in food and beverage preparation, and a variety of health-related effects (3,5,10,17). Uncertain ramifications of fungi in potable water have led to a limited number of investigations which show that fungi are present in a significant proportion of tap water samples; however, species abundance and diversity are extremely variable (6,11,13,16). This variation is often attributed to factors such as raw water source, water temperature patterns, treatment conditions, and maintenance of distribution systems (5). The nature and extent of fungi within distribution biofilms remain more obscure; only a single report has demonstrated conclusively that fungi are an integral biofilm component (12). Although it is assumed that contamination is attributable to spore deposition within the biofilm matrix, there is limited evidence to support this premise.Pipe surfaces were collected from the Springfield, Mo., water distribution system from March to July 1997. This municipal system serves approximately 100,000 people and consists of over 900 miles of water mains. Physical and chemical characteristics of this distribution system from January to July 1997 are reported in Table 1. Each sample consisted of a single pipe coupon (i.e., a longitudinal section of the inner pipe surface) obtained during routine maintenance and extension of 30-in. mains. During collection, each coupon was carefully rinsed with 2 liters of sterile distilled water and then placed in a sterile plastic bag. Coupons were immediately transported to the laboratory and rinsed again with 1 liter of sterile distilled water. The purpose of each rinse was to minimize the likelihood of contamination by airborne spores. Although each rinse was discarded, preliminary investigations of polyvinyl chloride (PVC) and iron coupons indicated that rinses did not remove biofilm deposition.Small biofilm fragments, each consisting of 0.5 cm 2 of surface matrix, were removed and plated on the following nonselective media: potato dextrose agar (Difco), Czapek solution agar (Difco), cornmeal agar (Difco), Sabouraud dextrose agar (Difco), and YMPG (10 g of dextrose, 5 g of neopeptone, 3 g of yeast extract, 3 g of malt extract, 10 g of agar, 1 liter distilled water). Four replicates of each medium were employed for each coupon to yield a total of 100 frag...

Molecular analysis of long-term biofilm formation on PVC and cast iron surfaces in drinking water distribution system

“…Only few of previous studies have focused fungi in distribution systems (Doggett, 2000;Nagy and Olson, 1982). Most of the fungi identified in this study belonged to the phylum Ascomycota (37.79%-62.52%).…”

“…(5.79%-9.42%). Their occurrences in drinking water or biofilms have been reported (Doggett, 2000;Sammon et al, 2010). Recently, using atomic force microscope, Abe et al (2011) found that biofilm aggregates were embedded in an extensive network of filamentous fungi during the development of drinking-water biofilm, and indicated that the fungal structure may assist in reinforcing biofilm adhesion to a substratum surface.…”

Microbiological monitoring mf mineral water commercialized in Brazil

“…Some of them may survive for longer periods, because of their ability to form biofilms (12). Most of these organisms are not pathogenic to humans.…”

Opportunistic Aspergillus pathogens measured in home and hospital tap water by quantitative PCR (QPCR)

“…Doggett (2000) isolated 39 different species of fungi from a Springfield, MO water distribution system.…”

“…Yet, earlier studies have shown that many fungi can survive in the potable water system, including species of Aspergillus (Rosenzweig et al 1986;Arvanitidou et al 1999;Doggett 2000;Pryor et al 2004). Aspergillus fumigatus from a hospital water system was genotypically linked to a case of aspergillosis (Anaissie et al 2003).…”