NATURALLY-OCCURRING DELETIONS IN THE CENTISOME-63 PATHOGENICITY ISLAND OF ENVIRONMENTAL ISOLATES OF SALMONELLA SPP

We have identified several environmental isolates of Salmonella senfte nberg and S. litchfield which carry a deletion encompassing a vast seg ment of the centisome 63 region of the Salmonella chromosome, The dele tion includes the entire inv, spa, and hil loci, which are required fo r entry of Salmonella spp, into mammalian cells, Consequently, these i solates were found to be markedly deficient in the ability to enter cu ltured epithelial cells, In contrast, no deletions were found in the c orresponding regions of the chromosomes of clinical isolates of these serovars; consequently, these isolates were found to be highly invasiv e for cultured epithelial cells, These data confirm the importance of the centisome 63 region of the Salmonella chromosome in mediating the entry of these organisms into cultured mammalian cells and indicate th at additional entry pathways are presumably not utilized by these envi ronmental isolates, These results are also consistent with the notion that this region constitutes a pathogenicity island which remains unst able in certain Salmonella serotypes.