WORLD-HEALTH-ORGANIZATION - SUPERVISED INTERLABORATORY COMPARISON OF ELISAS FOR THE SEROLOGICAL DETECTION OF SALMONELLA-ENTERICA SEROTYPE ENTERITIDIS IN CHICKENS

A collaborative exercise, supervised by the World Health Organisation, was set up to compare ELISAs used for the serological detection of Sa lmonella enteritica serotype Enteritidis in chickens. The aim was to a scertain how far agreement could be reached on the interpretation of o ptical density readings for high titre, intermediate titre and low tit re sera. Two sets of sera were sent to 14 participants. The first set compared high, medium and low titre sera raised in specified-pathogen- free and commercial broiler breeder chickens. The second set comprised 20 sera of different antibody titres raised in commercial birds reare d under laboratory conditions and sent blind. Both indirect and double -antibody sandwich blocking ELISAs were used with a number of differen t detecting antigens. With a few exceptions good agreement was reached on the interpretation of results obtained from high and low titre ser a from the optical density obtained with a single serum dilution. Diff erences were observed in the interpretation of medium titre sera. The results suggested that most ELISAs produce reasonably comparable resul ts and that practical problems may arise from interpretation of the re sults mainly as a result of the choice of the criteria used for differ entiating sera obtained from infected and uninfected chickens. These p roblems are discussed.