Genotyping of thermotolerant Campylobacter from poultry slaughterhouse by amplified fragment length polymorphism G. Johnsen, H. Kruse and M. Hofshagen National Veterinary Institute, Oslo, Norway Introduction Campylobacteriosis is currently the most frequently reported bacterial enteric infection in humans in Norway, as well as in many other developed countries (Blaser et al. 1983; Altekruse et al. 1999; Friedman et al. 2000). During the last decade, there has been a signifi- cant increase in campylobacteriosis in Norway, with a doubling of the incidence rate from 1995 to 2004 (Nyga ˚rd and Kapperud 2005). Similar tendencies have been reported from other developed countries (Friedman et al. 2000). Two case–control studies conducted in Nor- way during 1989–1990 and 1999–2000 (Kapperud et al. 1992, 2003), as well as another Scandinavian study (Wingstrand et al. 2006), identified consumption of poultry meat purchased raw as a significant risk factor for campylobacteriosis. Minimizing the prevalence of positive carcasses at slaughterhouse level and reducing cross-contamination at the slaughterhouse are considered as effective means to reduce the prevalence of contamin- ated poultry meat at retail (Park et al. 1991; Corry and Atabay 2001). In Norway, an action plan against Campylobacter in broilers was implemented in 2001 to reduce the Keywords amplified fragment length polymorphism, Campylobacter, genotyping, poultry, slaughterhouse. Correspondence Gro Johnsen, National Veterinary Institute, P.O. Box 8156 Dep, N-0033 Oslo, Norway. E-mail: sarogde@online.no 2006/0666: received 10 May 2006, revised 28 August 2006 and accepted 17 October 2006 doi:10.1111/j.1365-2672.2006.03238.x Abstract Aim: To examine the occurrence, diversity and transmission of Campylobacter in a poultry slaughterhouse. Methods and Results: During a 4-week period, a slaughterhouse was sampled alternately during slaughtering and the following mornings post-disinfection. Samples were taken from poultry at six stages in the slaughter process and from 25 environmental sites. For positive broiler flocks slaughtered on one occasion, 92% and 48% of the environmental sites were positive during slaugh- ter and post-disinfection, respectively. For positive laying hen flocks slaugh- tered on three occasions, 8–56% and 12–20% of the environmental sites were positive during slaughter and post-disinfection, respectively. Genetic finger- printing by amplified fragment length polymorphism (AFLP) of the 109 iso- lates obtained resulted in 28 different AFLP clones. Five AFLP clones were present for more than 1 week. Conclusions: Slaughtering of Campylobacter-positive broilers resulted in exten- sive contamination of the slaughterhouse, including the air. A high proportion of the laying hen flocks were Campylobacter positive, but these caused less envi- ronmental contamination than the broilers. This, together with the freezing of all layer carcasses, results in a lower public health risk from laying hens, when compared with broilers. Significance and Impact of the Study: When slaughtering Campylobacter-posit- ive broilers, the implementation of preventive measures is important to reduce contamination of negative carcasses and to protect the workers against infec- tion.