Journal
CANADIAN JOURNAL OF MICROBIOLOGY
Volume 62, Issue 1, Pages 16-23Publisher
CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
DOI: 10.1139/cjm-2015-0511
Keywords
Clostridium difficile; wastewater treatment; community-associated infections; sewage; anaerobic digester; thermophilic; endospores
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Funding
- Ontario Ministry of Agriculture, Food and Rural Affairs
- Chinese Scholarship Council
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There has been an increase in community-associated Clostridium difficile infections with biosolids derived from wastewater treatment being identified as one potential source. The current study evaluated the efficacy of thermophilic digestion in decreasing levels of C. difficile ribotype 078 associated with sewage sludge. Five isolates of C. difficile 078 were introduced (final density of 5 log CFU/ g) into digested sludge and subjected to anaerobic digestion at mesophilic (36 or 42 degrees C) or thermophilic (55 degrees C) temperatures for up to 60 days. It was found that mesophilic digestion at 36 degrees C did not result in a significant reduction in C. difficile spore levels. In contrast, thermophilic sludge digestion reduced endospore levels at a rate of 0.19-2.68 log CFU/ day, depending on the strain tested. The mechanism of lethality was indirect -by stimulating germination then inactivating the resultant vegetative cells. Acidification of sludge by adding acetic acid (6 g/L) inhibited the germination of spores regardless of the sludge digestion temperature. In conclusion, thermophilic digestion can be applied to reduce C. difficile in biosolids, thereby reducing the environmental burden of the enteric pathogen.
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