[Detection and occurrence of verotoxin-forming and/or shigatoxin producing Escherichia coli (VTEC and/or STEC) in...

Raw milk contaminated with VTEC was described as a source of human EHEC infection. Diagnosis of VTEC from milk is complicated by the low number of VT-positive cells in the total bacterial count, the great variety of serovars with different combinations of virulence markers and the lack of characteristic biochemical properties for the cultural detection of all VTEC. The graduated procedure presented and used for the examination of milk samples is based on VT detection in suitable enrichment cultures and the selective isolation of VTEC by means of VT-specific monoclonal antibodies using the VT-colony immunoblot. This method was used to examine 127 samples of raw milk and 146 samples of certified raw milk (Vorzugsmilch) from 5 different regions in Germany. 3.9% of the raw milk samples and 2.1% of the certified raw milk samples were VTEC-positive. Except for one O157:H- isolate from a raw milk sample, the VTEC found belonged to the group of non-O157 VTEC. They were assigned to 5 different serovars with different combinations of virulence markers. Therefore, raw milk and certified raw milk will continue to present a potential source of EHEC infection. It is recommended to use the procedure presented for the elucidation of the route of infection and for the improvement of detection of VTEC and EHEC-strains in milk in order to obtain comparable data for diagnosis in the official food control laboratories of the federal lands.