Detection of type a botulinal toxin-producing organisms subcultured from cheese using an amplified ELISA system

Mascarpone cheese implicated in a botulism outbreak was examined for prefor med and cultural botulinal toxins using the mouse bioassay. The cheese was also assayed for cultural toxins and for the most probable number (MPN) of toxin producing organisms/g using an amplified ELISA. No preformed botulina l toxins were discovered in the cheese samples (pH range 5.54-5.86) using t he mouse bioassay. However, after cheese subculture ii? tryptone-peptone-gl ucose-yeast extract broth, type A botulinal toxin-producing organisms that formed more than 10,000 MLD (mouse lethal dose)/mL in culture were detected . The ELISA results also revealed that type A toxin was present in the cult ure with a sensitivity of similar to 10 MLD/mL. The MPN of type A toxin-pro ducing organisms/g in 12 cheese samples examined ranged from < 0.3-9.33. No ELISA cross-reactivity was noted between the type A toxic cultures and oth er types (B, E, or F). The ELISA sensitivity was similar to 5 MLD/mL casein buffer using purified type A neurotoxin. The advantages of the ELISA test are that the toxin type and approximate lethal dose can be determined withi n one day compared to the mouse bioassay which takes 3-5 days.