Virulence potentials of Bacillus strains recovered from edible snails and survival during culinary preparation

Abstract

Some Bacillus species are underestimated pathogens which commonly occur as irregular cases, rather than in major outbreaks. There are reports confirming the consistent presence of Bacillus species in edible snails. This study aimed to assess, by molecular studies, the virulent nature of some Bacillus strains in live edible snails (Achatina achatina) sold in Nigerian markets and to ascertain the survival of bacilli during culinary preparation. Results showed that isolates with high virulence potentials were B. thuringiensis and two strains of B. cereus (GenBank accession numbers: MK530172, MK530171 and MK530202). The nheb gene was detected in all three isolates, while B. thuringiensis strain was found to possess hbla, nhea, nheb and cytk genes for enterotoxins often implicated in diarrhoea cases. Most isolates were resistant to chloramphenicol and norfloxacin. The stages of culinary preparation of snail meat could not reduce bacilli counts below allowable limits. Therefore, A. achatina may be a neglected source of virulent strains of Bacillus in the food chain. We envisage that cross contamination during handling and preparation of edible snails along the food chain will put the health of handlers and consumers at risk, especially in the rural population. Proper hygiene during handling and culinary preparation is recommended.