Int. J. Environ. Res. Public Health 2010, 7 3232 was not rechlorinated during that study, produced an average of 147 yeast cells per litre of water. The water utility involved in this study has already taken appropriate action, and is constructing a rechlorination facility at reservoir R3 to manage the risk of recontamination. The yeast genera Candida, Rhodotorula and Trichosporon which were recovered from excrement of L. caerulea collected from reservoir R3 contain species which can be opportunistic human pathogens [11]. Three of the ten representative yeast isolates from frog excrement were Candida species. It is known that metabolites of Candida are the aetiological agents of candidids, an allergic skin reaction [12]. The recovery of Candida glabrata is of some concern since it is a major cause of candidiasis in humans. This yeast, like C. albicans, is a commensal organism and is also an opportunistic pathogen causing superficial and systemic infections such as endocarditis, cystitis, osteomylitis, vaginitis and fungemia [13]. C. albicans was not found in this study but has been recovered from overseas water systems [14]. Thuraisingam and Denning [15] reported increasing frequency of systemic and vaginal infections with C. glabrata and stated that such infections are difficult to treat. Vaginitis is caused by both C. albicans and C. glabrata. However, increased prevalence of C. glabrata in diabetic women was reported by Ray et al. [16] who isolated C. glabrata from 61.3% and C. albicans from only 28.8% of 111 consecutive diabetic patients suffering from vulvovaginal candidiasis during their study into the prevalence of C. glabrata and its response to certain treatments. According to Gugic et al. [17], C. glabrata is the second most common species of Candida found in hospital patients in the U.S.A. The other yeasts recovered from frog excrement and skin, Rhodotorula spp. and Trichosporon spp., are commonly occurring genera and while they have, on rare occasions, been associated with opportunistic human infections their involvement is of little importance [12]. It is not known if infections and allergies caused by C. glabrata or other yeasts can be acquired through contact with water containing them, but it is reasonable to expect that this may be so. In recent years it has been increasingly recognised that opportunistic, pathogenic microfungi, particularly filamentous genera such as Aspergillus, may be the waterborne aetiological agents of nosocomial mycoses but only a limited number of studies have been undertaken into this potential mode of infection. 5. Conclusions The evidence presented in this study suggests that the Australian green tree frog L. caerulea, a diurnal resident of covered water reservoirs, is a source of yeast/yeast-like and filamentous microfungi found in water supply systems in northern Australia. The excrement of this species introduces fungal spores directly into the water body of water storage reservoirs and, when deposited on internal reservoir architecture, it also acts as a substrate on which microfungi grow and sporulate thus increasing the spore load within the reservoir air and consequently in the water body. The results presented here suggest that the frog species L. caerulea is an important source of yeasts in water storage reservoirs in areas where the animal is endemic. While this study was focused on a municipal water supply system where the water is treated and water quality is monitored closely, the findings would also be applicable to household water supply derived from rainwater tanks. In fact, if L. caerulea can gain access to domestic rainwater tanks to