Farm level survey of spore forming bacteria on four dairy farms in the Waikato region of New Zealand

Aim To determine the occurrence and diversity of New Zealand dairy associated spore forming bacteria at farm level. Methods and Results The methods described in this study resulted in improved differential isolation of Bacillus and Clostridium species. A modified Perfringens Agar under anaerobic conditions aided the isolation of sulphite reducing Clostridium spp.. The use of molecular methods such as ERIC genotyping, 16S rDNA sequence analysis and C. sporogenes signature PCR gave further information on the phylogenetic relationship of the Clostridium isolates. In total 19 Bacillus spp., 5 Paenibacillus spp. and 17 Clostridium spp. were isolated. Conclusions Despite regional, seasonal, and methodological differences, the diversity of Bacillus species was very similar to that seen internationally with an increase in occurrence in summer. Conversely, Clostridium species were more diverse in winter. Potential toxin producing strains, B. cereus, C. perfringens, C. butyricum and C. botulinum were found on at least three of the farms, whereas, economically important spoilage associated bacteria, C. butyricum, C. sporogenes and members of the Paenibacillus Genus were isolated from all four farms. Significance and Impact of Study The results of this study highlight the importance of implementing hygienic farm practices in controlling anaerobic spore numbers in raw milk.