Examination of Keratinolytic and Associated Non-Keratinolytic Fungi in Sewage Sludge

Sewage sludge is frequently applied to land. It has been shown, however, that sludges contain many toxic components and pathogenic organisms. Keratinolytic and associated non-keratinolytic fungi are considered potentially pathogenic. Our knowledge on the incidence of the fungi in the sludge environment is still insufficient. Sludge from the Bytom-Miechowice wastewater treatment plant in Upper Silesia, Poland, was examined. The objective of the study was to compare fungal compositions in the sludge using three methods: (1) dilution pour plating method (2) hair-baiting method, and (3) most probable number method. The MPN method combined sludge dilution in sterile clay or sand and hair-baiting techniques. Actidioneresistant fungi were examined in the sludge. The dilution pour plating method provided poor data on the incidence of keratinolytic fungi, while using the method more information was obtained on non-keratinolytic fungi in the sludge. Subsequently, the conventional hair-baiting method provided extensive data on the growth of fungi in the hair spread over the sludge, but the method did not allow determining fungal quantities. Such quantities were obtained by means of the MPN method. The method complemented results obtained with two other methods. The ecological and epidemiological significance of MPN values was discussed.