Report No DWI0780

Dec 1996

Objective 1

To develop, validate and carry out limited performance testing of isolation and culture media and techniques for the detection and quantification of filamentous fungi in water distribution systems.

Propagule suspensions of thirteen fungal strains were incubated in stirred phosphate buffer for 24 hours, the fungi were then recovered by plating out serial dilutions using up to six different media for each fungus. viable propagules were recovered for all the fungi. The proportion of propagules recovered varied widely between the fungi. There was no single optimum combination of medium and incubation conditions for recovery of all the fungi. Of the incubation conditions, the longest and warmest conditions produced the highest recovery rates in most of the fungi. irrespective of incubation conditions, no one medium was responsible for high or low recoveries across the entire range of fungi. Ten of the fungi showed recovery levels which suggest that growth may have occurred in the buffer or that propagules were clumped initially but became more evenly dispersed after 24 hours in the stirred buffer. Recommendations for routine enumeration of fungi in water systems include limiting the incubation conditions to 6 days at 22ºC but using an additional close range of low dilutions in conjunction with a tenfold dilution series. Any growth of fungi within a system will be incorporated in the count but the potential for fungal growth in water systems would require further study.

Objective 2

To carry out limited performance testing of trial media and to investigate the possibility of using enrichment and baiting techniques for the detection and quantification of fungi. To compare results from direct plating and filter methods.

Two samplings were conducted. Some 141 fungal taxa have been identified. Differences between media, plating techniques and temperature of incubation are apparent. The selected range of conditions used was essential to isolate the many diverse fungal str ains. A number of isolates have been found in treated waters only. Scanning Electron Micrographic examination of filters indicates that fungi are equally present as both spores and hyphal fragments.

Objective 3

To prepare a database of fungi isolated from water distribution systems to include any known health implications.

A database bas been prepared which is ready for transferral.

Objective 4

To provide results from the above in a format suitable for publication in the Standing Committee of Analysts "Blue Book" series.

This present report is provided in the appropriate Blue Book format and is available in electronic format.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.