Incidence and Distribution of Microfungi in a Treated Municipal Water Supply System in Sub-Tropical Australia

Noel B Sammon,Larelle D Fabbro,Keith M Harrower,Rob H Reed

doi:10.3390/ijerph7041597

Abstract

Drinking water quality is usually determined by its pathogenic bacterial content. However, the potential of water-borne spores as a source of nosocomial fungal infection is increasingly being recognised. This study into the incidence of microfungal contaminants in a typical Australian municipal water supply was carried out over an 18 month period. Microfungal abundance was estimated by the membrane filtration method with filters incubated on malt extract agar at 25 °C for seven days. Colony forming units were recovered from all parts of the system and these were enumerated and identified to genus level. The most commonly recovered genera were Cladosporium, Penicillium, Aspergillus and Fusarium. Nonparametric multivariate statistical analyses of the data using MDS, PCA, BEST and bubble plots were carried out with PRIMER v6 software. Positive and significant correlations were found between filamentous fungi, yeasts and bacteria. This study has demonstrated that numerous microfungal genera, including those that contain species which are opportunistic human pathogens, populate a typical treated municipal water supply in sub-tropical Australia.

Highlights

The quality of drinking water is usually determined by the level of pathogenic bacteria it contains, and the standard indicator is the number of Escherichia coli CFU per 100 mL of water as stated, for example, in the Australian Drinking Water Guidelines (2004)
Microfungi and bacteria were recovered from all parts of the water treatment and distribution systems but there was considerable variation in frequencies between sites
62 genera of filamentous microfungi were recovered and identified during the course of this study, only 11 of them accounted for ≥1% of the total from any one site group, and there was a fairly high percentage of unidentified, asporogenous colonies (Table 1)

Summary

Introduction

The quality of drinking water is usually determined by the level of pathogenic bacteria it contains, and the standard indicator is the number of Escherichia coli CFU per 100 mL of water as stated, for example, in the Australian Drinking Water Guidelines (2004) (http://www.nhmrc.gov.au/publications/synopses/_files/adwg_11_06.pdf). Many studies have been conducted into the contamination of drinking water by bacterial pathogens including enteric and aquatic bacteria. Few studies have been carried out on microfungal contamination of municipal drinking water systems [5,6,7,8,9,10,11,12,13,14,15,16,17]. This may be because the only primary human pathogens are the genera Histoplasma, Coccidioides, Blastomyces and Paracoccidioides and these are not known to be waterborne. There are a number of opportunistic human fungal pathogens which are known to be waterborne [5,6,7,8,9,10,11,12,13,14,15,16,17]

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