Characterization of Clostridium botulinum spores and its toxin in honey

Botulism is a serious paralytic disease caused by Clostridium botulinum toxin in foods. There are seven recognized serotypes of botulinum neurotoxins among which the principal prevalent types in humans include A, B and E. Infant botulism results from intestinal colonization and toxin production by C. botulinum spores in babies less than 1 year old. Honey is the most important food discriminated as the cause of infant botulism. In this study, a total of 100 honey samples were collected from retail markets in Shiraz,Iran and analysed for the presence of C. botulinum using a multiplex PCR assay. Three pairs of primers were designed and optimized to identify A, B and E strains in the specimens. Positive samples were further examined to find out whether they carried the toxin gene; toxin products were also checked by mouse bioassay. The results showed that out of 100 honey samples tested, 2% were found positive for type B which carried the neurotoxin B gene confirmed by sequencing. All the injected mice died, whereas no symptoms were observed in the control groups. The honey collected from Shiraz retail markets was contaminated with the spore of the bacteria and can thus potentially cause infant botulism. Bioassay is described as a standard method; however, molecular based techniques also easily, quickly and reliably detect C. botulinum, its toxins and spores in food stuffs and is strongly advised for use in the food microbial lab.