Behavior of enteroaggregative Escherichia coli, non-O157-shiga toxin-producing E. coli, enteroinvasive E. coli, enteropathogenic E. coli and enterotoxigenic E. coli strains on mung bean seeds and sprout

Abstract

The behavior of enteroaggregative Escherichia coli (EAEC), non-O157 shiga toxin-producing E. coli (non-O157-STEC), enteroinvasive E. coli (EIEC), enterotoxigenic E. coli (ETEC) and enteropathogenic E. coli (EPEC) on mung bean seeds at 25±2°C and during germination and sprouting of mung bean seeds at 20±2° and 30±2°C and on mung bean sprouts at 3±2°C was determined. When mung bean seeds were inoculated with EAEC, non-O157 STEC, EIEC, EPEC or ETEC strains, all these diarrheagenic E. coli pathotypes (DEPs) survived at least 90days on mung bean seeds at 25±2°C. All DEPs grew during germination and sprouting of seeds, reaching counts of approximately 5 Log and 7 Log CFU/g after 2days at 20±2° and 30±2°C, respectively. However, when the sprouts were inoculated after 1day of seeds germination and stored at 20±2° or 30±2°C, no growth was observed for any DEPs during sprouting at 20±2°C per 9 d; however, a significant increase in the concentration of DEPs of approximately 0.7 log CFU/g was observed during sprouting at 30±2°C after 1day of sprout contamination. Refrigeration reduced the number of viable DEPs strains on sprouts after 10days in storage; nevertheless, these decreases have no practical significance in the safety of the sprouts.