SEQUENCE-ANALYSIS AND DISTRIBUTION OF AN IS3-LIKE INSERTION ELEMENT ISOLATED FROM SALMONELLA-ENTERITIDIS

The nucleotide sequence of a 3 kb region immediately upstream of the s ef operon operon of Salmonella enteritidis was determined. A 1230 base pair insertion sequence which shared sequence identity (> 75%) with m embers of the IS3 family was revealed. This element, designated IS1230 , had almost identical (90% identity) terminal inverted repeats to Esc herichia coli IS3 but unlike other IS3-like sequences lacked the two c haracteristic open reading frames which encode the putative transposas e. S. enteritidis possessed only one copy of this insertion sequence a lthough Southern hybridisation analysis of restriction digests of geno mic DNA revealed another fragment located in a region different from t he sef operon which hybridised weakly which suggested the presence of an IS1230 homologue. The distribution of IS1230 and IS1230-like elemen ts was shown to be widespread amongst salmonellas and the patterns of restriction fragments which hybridised differed significantly between Salmonella serotypes and it is suggested that IS1230 has potential for development as a differential diagnostic tool.