Incidence and Origin of Clostridium botulinum Spores in Honey

Eighty honey samples, including some from foreign countries, were obtained from a local processor or from apiaries in Pennsylvania, Illinois and New Jersey. They were analyzed for Clostridium botulinum spores by a dilution-centrifugation (DC) procedure and by direct addition (DA) of honey to two different enrichment media. All were negative by the DC method; five were positive by DA in fluid thioglycollate media and six by DA in cooked meat media. Some samples positive in fluid thioglycollate media were negative in cooked meat media and vice versa. Bees ( Apis mellifera , 25,000 per hive) were experimentally inoculated with spores of C. botulinum by feeding a 50% sugar-water solution containing 1.6 × 10⁵ spores of 20 strains (equal numbers of 11 type A and 9 type B). Honey collected from the hive 2 weeks later contained 1100 spores per g; that collected after 5 weeks contained 50 spores per g. Quantitative estimates of honey yield and spore contents indicated that all the spores originally ingested by the bees had been incorporated into the honey. No botulinal spores were found in the intestinal or rectal contents of the bees 2 weeks or more after spore ingestion.