Enumeration of virulent Yersinia enterocolitica colonies by DNA colony hybridization using alkaline treatment and paper filters.

The efficiency of enumerating virulent Yersinia enterocolitica colonies was determined for 10 artificially contaminated foods by autoradiography after DNA colony hybridization using a 32P-labelled genetic probe and paper filters. Enumeration efficiency, which ranged from 0-98% (average 25 +/- 31% standard deviation), improved (42-138%, average 83 +/- 27% standard deviation) after enrichment with 0.5% KOH-0.5% NaCl. These efficiencies are equivalent to those obtained with nitrocellulose filters.