Toxin production by Clostridium botulinum in grass

Area of Science:

• Food Microbiology
• Veterinary Science
• Toxicology

Background:

• Botulism in cattle has been linked to Clostridium botulinum type B in grass silages.
• Understanding the conditions for C. botulinum growth and toxin production in silage is crucial for animal health.

Purpose of the Study:

• To investigate the potential for proteolytic Clostridium botulinum to grow and produce toxins in grass silage.
• To determine the effects of water activity and pH on C. botulinum toxin production in a grass substrate.

Main Methods:

• In vitro experiments using grass as a substrate to culture proteolytic C. botulinum strains (types A and B).
• Assessing toxin production under varying water activity (aw) and pH conditions.
• Characterizing the forms of toxin produced by proteolytic type B strains.

Main Results:

• Only proteolytic strains of C. botulinum types A and B produced toxin when grass was the substrate.
• Proteolytic type B strains produced both medium (12S) and large (16S) toxin forms.
• Minimal water activity for toxin production was 0.94 at pH 6.5 and 5.8, and 0.985 at pH 5.3.

Conclusions:

• Proteolytic strains of Clostridium botulinum, if present, can multiply and produce toxins in wilted grass silages.
• Water activity and pH are critical factors influencing C. botulinum toxinogenesis in silage.
• Findings highlight a potential risk for botulism in cattle consuming contaminated silage.