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Aims: To use amplified fragment length polymorphism (AFLP) analysis to evaluate the genetic relatedness among 254 Campylobacter jejuni reference and field strains of diverse origin representing all defined ÔPennerÕ serotypes for this species. Methods and Results: Field strains (n ¼ 207) from human diarrhoea and diverse animal and environmental sources were collected mainly through a National surveillance programme in Denmark and serotyped by use of the established ÔPennerÕ scheme. Genetic relationships among these isolates, and the archetypal serotype reference strains, were assessed by numerical analysis of AFLP profiles derived from genomic DNA. Extensive genetic diversity was seen among the strains examined; however, 43 groups of isolates were identified at the 92% similarity (S-) level. Thirteen groups contained isolates from a single host, possibly representing genotypes of Ôlow riskÕ to human health. The remaining 30 groups contained isolates from humans, chickens and associated food products, cattle, sheep, turkeys, ostriches and/or dogs. Strains assigned to serotypes 2, 6/7, 11 and 12 formed major clusters at the 77AE6% S-level. Most other serotypes did not form homogeneous clusters. Conclusions: High-resolution genotyping applied to strains from a comprehensive range of sources provides evidence for multiple sources of sporadic C. jejuni infection. The results suggest that public health protection measures should be directed at all foods of animal origin. Significance and Impact of the Study: The genetic relatedness among all ÔPennerÕ serotypes of C. jejuni is assessed by AFLP analysis. In addition, further evidence of epidemic and host-specific clones of C. jejuni is provided.

Thermotolerant Campylobacter spp. have been the most common bacterial cause of human gastrointestinal disease in Denmark since 1999. In 2003, the Danish voluntary strategy to control Campylobacter was intensified. The focus was on biosecurity, allocation of meat from Campylobacter-negative broilers to the production of chilled products, and consumer information campaigns. From 2002 to 2007, the percentage of Campylobacter-positive broiler flocks at slaughter decreased from 43% to 27%. After processing, Campylobacter-positive samples of chilled broiler meat fell from 18% in 2004 to 8% in 2007. Furthermore, the number of registered human Campylobacter cases decreased by 12%; from 4379 cases in 2002 to 3865 cases in 2007. We believe that the observed decrease in the occurrence of Campylobacter in broilers and broiler meat and the coincidental fall in the number of registered human cases is, in part, a result of the implemented control strategy.

A total of 117 Campylobacter jejuni isolates from Danish turkeys were tested for the presence of seven virulence and toxin genes by PCR. One hundred seventeen (100%) isolates were positive for flaA, cadF, and ceuE gene primers. One hundred three (88%) isolates were positive for cdt gene cluster PCR detection (cdt gene cluster-PCR), whereas 101 (86.3%), 102 (87.2%), and 110 (94%) isolates were positive for cdtA-, cdtB-, and cdtC-PCR, respectively. Only 39 (33.3%) isolates were positive for virB11. Of 117 isolates, 114 (97.4%) produced cytolethal distending toxin (CDT) in Vero cell assays, 105 (89.7%) in Colon 205 assays, and 109 (93.2%) in chicken embryo cell assays. The CDT titers were determined in Vero cell assays. Of 117 isolates, 50 (42.7%) produced a CDT titer of 1:100, 29 (24.8%) of 1:50, and 27 (23%) of 1:5 to 1:10; 8 (6.8%) produced a CDT titer at undiluted supernatants and 3 (2.6%) produced no toxin. Twenty-nine C. jejuni isolates that were PCR negative for one or more individual cdt toxin genes also produced low or no CDT toxin. The high prevalence of the seven virulence and toxin genes demonstrates that these putative pathogenic determinants are widespread among Campylobacter isolates from turkeys and calls for further investigation for the elimination of Campylobacter infection in industrial turkey production and in industrial food chains.