Detection of virulence factors in culturable escherichia coli isolates from water samples by dna probes and recovery of toxin-bearing strains in minimal ortho-nitrophenol-beta-d-galactopyranoside-4-methylumbelliferyl-beta-d-g lucuronide media - Martins, Maria Therezinha; Gutierrez Rivera, Irma Nelly; Clark, D L; Olson, B H (Applied and Environmental Microbiology, 1992)