Detection of shigatoxin-producing Escherichia coli (STEC) in foods and characterization of isolates

We detected STEC in foods of animal origin like raw milk including certifie d milk, raw or undercooked minced beef and beef containing raw sausage. Fur thermore we isolated and characterized the STEC. The number of STEC in the total bacterial count is low. A multistep procedure was to be performed inc luding two-step enrichment, sensitive screening tests, methods for specific STEC isolation and characterization. The STEC isolates were checked for th e existence of genes encoding 10 virulence factors (stx1, stx2, eae, hlyA, katP, espP, etpD, astA, colD157 and ileX) by using PCR. All genes of these virulence factors could be detected in isolates from raw milk and with exce ption of katP in raw minced beef, too. The genes katP, etPD, colD157 and il eX could not be detected in isolates from raw sausage. One isolate from thi s matrix belonged to serogroup 022:Hs and had the gene combination eae, hly A and espP. 15,2 % of the investigated STEC isolates from raw milk had the stx-genes and besides the factors hlyA, katP, espP and etpD. In addition, 9 ,1% of these isolates showed the genes eae and colD157. One isolate from mi nced beef had the combination stx2, hlyA; espF, etPD and eae. All these iso lates belonged to serogroup O157. Furthermore, we investigated 28 EHEC stra ins belonging to serogroup O157. These isolates were obtained from patients suffering from HUS. The combination eae, hlyA, etpD, katP and espP was fou nd in 18 cases (64 %).EHEC strains belonging to other serogroups isolated f rom stool samples of HUS patients showed different combinations of virulenc e factor genes. In the serogroups O26, O103 and O111 the combination eae hl yA and etpD was frequent. The genes for the virulence factors were distribu ted sporadically in 10 EHEC isolates of different serogroups from patients suffering from diarrhoea and in 17 isolates from carriers showing no sympto ms.