Direct detection of Escherichia coli Shiga-like toxin genes in primary fecal cultures by polymerase chain reaction.

A single pair of oligonucleotide primers was used for polymerase chain reaction amplification of a 212- or 215-bp region of Escherichia coli Shiga-like toxin (SLT) genes from crude fecal culture extracts. Genes were typed by hybridization of the polymerase chain reaction products to SLT-I- or SLT-II-specific oligonucleotide probes. The procedure was capable of detecting fewer than 10 SLT-producing E. coli organisms per ml of culture against a background of more than 10(9) other organisms per ml and provides a rapid and sensitive means of screening primary fecal cultures for the presence of such strains. When this procedure was used to test primary cultures from gut contents or feces from various patient groups, including apparently healthy infants, approximately half of all samples yielded positive results for SLT-I and/or SLT-II sequences.