Isolation of Shiga-toxin producing E. coli (STEC) from fresh food and their natural environment

Abstract

Shiga-toxin producing E. coli (STEC) is a pathogen that causes diseases in humans, ranging from non-bloody diarrhea to severe illnesses as haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). Ruminants are regarded as the natural reservoir for Shiga toxin-producing Escherichia coli (STEC). Monitoring of ruminants and environmental samples (such as irrigation water and soil) is essential to evaluate the risk factor associated with STEC infection in humans. This study highlights the occurrence of different types of O157 STEC and non-O157 STEC in animals such as cattle, sheep, goat and calves; environmental samples as irrigation water, soil and food samples of plant and animal origins. A total of 642 samples were investigated directly for Shiga-toxin encoded genes by Real Time PCR method using stx and eae specific probes. After enrichment of the samples isolation of STEC on selective media was carried out. Suspected colonies were tested for shiga-toxin by Real Time PCR. Results indicated that out of the642 samples only 36 isolates were positive to one or more of the previously mentioned genes. Out of 120 fecal samples from different ruminants, 16.7% were positive for Shiga toxin. The highest percent of positive STEC samples was recorded in buffalos (30%) were positive, while cows (15%); sheep (20%); goats (10%) and calves (20%).