Genetic variability of Campylobacter jejuni isolated from fresh and frozen broiler carcasses.
The aim of this study was to determine the genetic variability of Campylobacter jejuni isolates from poultry before and after freezing treatment in order to identify genotypes that would survive the treatment. C. jejuni was isolated from both fresh and frozen halves of the same carcass after freezing for 2 or more than 20 days at -20 degrees C. From 36 carcasses, representing five unrelated flocks in Norway, a total of 209 isolates were included in the study. Thirty-two of the isolates were recovered with a qualitative method while the remaining 177 were isolated using a quantitative method. Isolates were genotyped with fluorescent amplified fragment length polymorphism using MfeI and BglII restriction enzymes. Nine different genotypes were identified, however, one genotype was shown to be dominant in three different flocks. This genotype and the dominant genotype of another flock were found among isolates from fresh and frozen broiler halves. They were also shown to be identical to genotypes frequently identified among strains isolated from humans, cattle and poultry flocks in previous years. Freezing treatment or isolation method appeared not to select for a particular genotype. The results of the present study indicate that the freezing tolerance of strains is not genotype dependent.