DETECTION OF SALMONELLA SPP IN EGGS - DNA ANALYSES, CULTURE TECHNIQUES, AND SEROLOGY

A polymerase chain reaction (PCR) method for direct detection of Salmo nella spp, in whole-shell eggs is described, The method does not requi re isolating strains, Preenrichment, rapid DNA isolation, and a nested PCR system targeting the invA gene enabled detection of the genus Sal monella, The specific nested PCR product of 283 base pairs was formed from all 21 serovars, including 43 Salmonella strains tested. No PCR p roduct was formed from 56 non-Salmonella enterobacteriacea and other b acterial strains tested, Experiments with artificially contaminated eg gs showed a detection limit of about 10(3)-10(4) colony-forming units (cfu)/egg before and about 1-10 cfu/egg after preenrichment, In analys is of 180 single eggs from 4 flocks and 36 pools of 5 eggs each from a nother 4 flocks from the same producer, Salmonella spp, were detected in 5 of 90 eggs from 2 different flocks. Determination of anti-Salmone lla antibodies in eggs yielded positive results for 2 additional and t he 2 PCR-positive flocks, In contrast, classical selective culture det ected Salmonella spp. in only 1 of 100 eggs in one flock when Inn eggs from each flock were analyzed.