An effective, rapid and simple method for isolation of Shiga toxin-producing Escherichia coli O26, O111 and O157 from faeces and food samples.

An effective, rapid and simple method was developed for isolating Shiga toxin-producing Escherichia coli (STEC) O26:H11, O111:H- and O157:H7 from faeces and food in less than 24 h. The procedure involves enrichment of these samples in Trypticase soy broth (TSB) at 42 degrees C for 6 h. The enrichment culture is exposed to 1/8N HCl +0.5% NaCl solution (1 + 1) for 30 sec, then plated onto MacConkey agar containing sorbitol, tellurite and cefixime (CT-SMAC) following culture at 37 degrees C for 18 h. The findings were compared with conventional enrichment methods for efficiency in recovering STEC from bovine faeces. The new method increased the sensitivity for isolation of < 10(2) STEC O26:H11, O111:HUT and O157:H7 CFU/g of bovine faeces and decreased the growth of other gram-negative microorganisms. This procedure is readily implemented for use in laboratories doing routine microbiological testing.