The genetic biodiversity of Clostridium botulinum type E strains was studie
d by pulsed-field gel electrophoresis (PFGE) with two macrorestriction enzy
mes (SmaI-XSnaI and XhoI) and by randomly amplified polymorphic DNA (RAPD)
analysis with two primers (OPJ 6 and OPJ 13) to characterize 67 Finnish iso
lates from fresh fish and fishery products, 15 German isolates from farmed
fish, and D isolates of North American or North Atlantic origin derived mai
nly from different types of seafood. The effects of fish species, processin
g, and geographical origin on the epidemiology of the isolates were evaluat
ed. Cluster analysis based on macrorestriction profiles was performed to st
udy the genetic relationships of the isolates. PFGE and RAPD analyses were
combined and resulted in the identification of 62 different subtypes among
the 92 type E isolates analyzed. High genetic biodiversity among the isolat
es was observed regardless of their source. Finnish and North American or N
orth Atlantic isolates did not form distinctly discernible clusters, in con
trast with the genetically homogeneous group of German isolates. On the oth
er hand, indistinguishable or closely related genetic profiles among epidem
iologically unrelated samples were detected. It was concluded that the high
genetic variation was probably a result of a lack of strong selection fact
ors that would influence the evolution of type E. The wide genetic biodiver
sity observed among type E isolates indicates the value of DNA-based typing
methods as a tool in contamination studies in the food industry and in inv
estigations of botulism outbreaks.