Methods for Health Risk Assessment by Clostridium botulinum in Biocompost

Abstract

In recent investigations in 66 out of 143 tested samples of biocompost or substrates containing biocompost Clostridium botulinum was detetcted.

In commercial potting soils, containing 50% biocompost, even at the purchase day, botulinum toxin was found in the plastic bags.

Obviously,

• the number of cases of botulism in animals has been constantly increasing in the past years;

• demands for quality control of human food make it necessary to reduce any contamination of the soil;

• physicians need to become aware of the importance of human botulism.

The pathogen Clostridium botulinum endangers health and life of man and animals by production of a very potent metabolite, the Botulinum Neurotoxin (BoNT). It is an anaerobic bacterium, ie., it multiplies and forms toxin under exclusion of oxygen. Under certain conditions it is even able to create its own anaerobic micro-environment in aerobic atmosphere, supporting multiplication. Clostridia are sporeformers, ie., they may survive adverse conditions very well. By the so-called hygienisation during composting possibly not all spores are destroyed. As a result surviving spores will multiply during subsequent curing and storage in compost. The nutrients, warmer temperatures, humidity, and exclusion from air form ideal growing conditions.

The different influence factors will be discussed. The laboratory proof of bacteria and toxins is complicated due to the fact that internationally only the mouse bio-assay for food and pathological samples is accepted which takes at least 5–10 days for completion. New field and laboratory tests for compost and soils were established. First results are presented.