Molecular typing of isolates of Clostridium perfringens from healthy and diseased poultry.

The bacterium Clostridium perfringens can cause both clinical and subclinical disease in poultry. To study the pathogenesis and epidemiology of disease caused by C. perfringens, methods for typing its various strains need to be evaluated. C. perfringens isolates from healthy and diseased poultry from different parts of Sweden were analysed by polymerase chain reaction (PCR) in order to establish the presence of alpha-, beta-, beta2-, epsilon -, iota- and enterotoxin genes. In order to subtype C. perfringens isolates, the two methods amplified fragment length polymorphism (AFLP) and pulsed field gel electrophoresis (PFGE) were compared on 21 C. perfringens isolates from 10 different farms. In a second study, 32 isolates of C. perfringens type A from three broilers from a healthy flock reared without ionophorous anticoccidials were subtyped by PFGE. All 53 isolates analysed with PCR belonged to the toxin type A of C. perfringens, with the gene coding for alpha-toxin production. Two isolates possessed the beta2-gene as well, but none had the other toxin genes. Both AFLP and PFGE differentiated 21 strains into 10 different subtypes. This differentiation correlated closely with the origins of the isolates. Unique subtypes were isolated from seven farms. Only isolates from birds of one farm demonstrated more than one subtype of C. perfringens. The subtyping of the isolates from a healthy flock showed that each bird carried two to three different subtypes and two different subtypes were found in the same kind of tissue sample in four cases. Three of the four different subtypes found in this study were new, compared with the first study. AFLP and PFGE were found to be equally suitable for subtyping of C. perfringens isolates. The wide variation in subtypes in the healthy broilers could be the result of the antibiotic-free rearing of these birds.