THE USE OF SELECTIVE AND DIFFERENTIAL AGARS IN THE ISOLATION OF ESCHERICHIA-COLI O157 FROM DAIRY HERDS

The use of selective and differential agars for the isolation of Esche richia coli O157 from the faeces of dairy herds was in investigated. O ut of the 614 isolates which were positive for one or more of the sele ctive criteria employed in the media only four proved to be E. roll O1 57, Ninety-nine per cent of the isolates were false positives, The pro cedure which resulted in the Isolation off. roll O157 from faecal samp les was enrichment in modified Tryptone Soya Broth supplemented with n ovobiocin and subsequent growth on Chromagar(R) O157.