Genotypic characterisation by PFGE of Salmonella enterica serotype Enteritidis phage types 1, 4, 6, and 8 isolated from animal and human sources in three European countries

A total of 101 strains of Salmonella Enteritidis phage types (PT) 1, 4, 6, and 8 from Denmark, England and Spain were studied by PFGE to elucidate gen etic relationships among strains isolated from animal, human and environmen tal sources between 1983 and 1997. Analysis with Xba I, Bin I and Spe I enz ymes showed that the power of discrimination of this method was increased b y the combination of the three enzymes (D=0.802), subdividing the strains i nto 28 genomic groups or genotypes. Many of the PT1, PT4, and PT6 strains f rom the three countries shared the same PFGE combination profile A1-A1-A1, confirming the close relationship among these phage types and the protracte d spread of a single clone over a large geographical area. In general, stra ins from Denmark showed more variation in their PFGE profiles than those fr om England and Spain. PT4 strains exhibited genetic homogeneity in the thre e countries independently of their sources and period of isolation. Spe I g ave the highest index of discrimination among PT6 strains as evidenced by a variety of PFGE profiles. The data clearly confirmed that PT8 strains isol ated in the three countries were of a unique clonal origin, and the PFGE co mbination profile A10-A10-A1 was predominant and specific for this phage ty pe. It is concluded that PFGE, in combination with phage typing, represents a suitable tool for the epidemiological typing of Salmonella Enteritidis s trains which could be used for investigations or surveillance of the intern ational spread of these clones. (C) 2000 Elsevier Science B.V. All rights r eserved.