Genetic diversity of Clostridium perfringens type A isolates from animals, food poisoning outbreaks and sludge

Background: Clostridium perfringens, a serious pathogen, causes enteric diseases in domestic animals and food poisoning in humans. The epidemiological relationship between C. perfringens isolates from the same source has previously been investigated chiefly by pulsed-field gel electrophoresis (PFGE). In this study the genetic diversity of C. perfringens isolated from various animals, from food poisoning outbreaks and from sludge was investigated. Results: We used PFGE to examine the genetic diversity of 95 C. perfringens type A isolates from eight different sources. The isolates were also examined for the presence of the beta2 toxin gene (cpb2) and the enterotoxin gene (cpe). The cpb2 gene from the 28 cpb2-positive isolates was also partially sequenced ( 519 bp, corresponding to positions 188 to 706 in the consensus cpb2 sequence). The results of PFGE revealed a wide genetic diversity among the C. perfringens type A isolates. The genetic relatedness of the isolates ranged from 58 to 100% and 56 distinct PFGE types were identified. Almost all clusters with similar patterns comprised isolates with a known epidemiological correlation. Most of the isolates from pig, horse and sheep carried the cpb2 gene. All isolates originating from food poisoning outbreaks carried the cpe gene and three of these also carried cpb2. Two evolutionary different populations were identified by sequence analysis of the partially sequenced cpb2 genes from our study and cpb2 sequences previously deposited in GenBank. Conclusion: As revealed by PFGE, there was a wide genetic diversity among C. perfringens isolates from different sources. Epidemiologically related isolates showed a high genetic similarity, as expected, while isolates with no obvious epidemiological relationship expressed a lesser degree of genetic similarity. The wide diversity revealed by PFGE was not reflected in the 16S rRNA sequences, which had a considerable degree of sequence similarity. Sequence comparison of the partially sequenced cpb2 gene revealed two genetically different populations. This is to our knowledge the first study in which the genetic diversity of C. perfringens isolates both from different animals species, from food poisoning outbreaks and from sludge has been investigated.