Clostridium botulinum is a gram-positive anaerobic bacillus, widely distributed in nature, its buds are found in silt, dust and animal feces. The buds in water and soil are the main sources of food contamination. The bacterium secretes strong botulinum toxin in anaerobic environment, which can cause special neurotoxic symptoms and is highly lethal to humans and animals. Therefore, the toxin can also be used in the manufacture of biological weapons.
The pathogenicity of Clostridium botulinum is due to the botulinum neurotoxin (BoNT) it produces. According to the antigenicity of BoNT, there are 7 types of Clostridium botulinum: A, B, C, D, E, F and G. Among them, types A, B, E and F can cause human poisoning, while types C and D are mainly pathogenic agents of animal and poultry poisoning, and do not cause disease to humans. There are four main ways of botulinum neurotoxin poisoning: foodborne poisoning, inhalation poisoning, traumatic poisoning and iatrogenic poisoning. The most common symptoms of BoNT poisoning are dysphagia, blurred vision, slurred speech, difficulty speaking, hoarseness and other articulatory abnormalities, gastrointestinal symptoms, dry mouth, shortness of breath, and double vision. The most common signs are descending paralysis, ptosis and eye muscle paralysis.
Fig.1 Genetic organization of the botulinum toxin gene locus (Connan C 2015)
Because the pathogenicity of Clostridium botulinum is mainly due to the exotoxin produced by Clostridium botulinum, the detection focus is mainly on the detection of botulinum neurotoxin. At present, the commonly used methods in the laboratory are based on antigen-antibody reaction, detection of toxin proteins, mouse bioassay, colloidal gold immunochromatography and so on.
Table 1 Methods for detection of botulism neurotoxin (Hatheway, CL 1996)
