High prevalence of Clostridium botulinum types A and B in honey samples detected by polymerase chain reaction.
A test protocol for reliable detection of Clostridium botulinum types A and B spores in honey by polymerase chain reaction (PCR) was developed and used for a prevalence survey of C. botulinum spores in 190 honey samples. The inhibiting effects of honey on microbial growth and PCR analysis were overcome by using a method of supernatant filtration (SF) in the preparation of the samples before enrichment and PCR. By using this method, an inoculum of 0.1 spore of C. botulinum/g honey could be detected. In the prevalence survey, spores of C. botulinum were detected in 8 (7%) of the 114 Finnish and in 12 (16%) of the 76 imported honey samples. The quantity of spores in PCR-positive samples varied from less than 18 to 140 spores/kg. Neurotoxin gene sequences corresponding to C. botulinum type A were detected in 17 samples and proteolytic type B in 12 samples by PCR analysis. Both types A and B were detected in nine samples. Strains of C. botulinum type A were isolated from 14 and type B from 2 of the 20 PCR-positive samples. This is the first report of type A spores of C. botulinum being detected and isolated in Fennoscandia.
Nevas
Mari
M
Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Finland. mari.nevas@helsinki.fi
Hielm
Sebastian
S
Lindström
Miia
M
Horn
Helmut
H
Koivulehto
Kari
K
Korkeala
Hannu
H
D003014:Clostridium botulinum / Q000235:genetics / Q000302:isolation & purification*; D005516:Food Microbiology; D006722:Honey / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D015995:Prevalence; D013171:Spores, Bacterial / Q000302:isolation & purification