Recovery and survival of Escherichia coli O157 : H7 in reconditioned pork-processing wastewater

The pathogen Escherichia coli O157:H7 has been recovered from various water sources and food samples. The growth potential of this bacterium in nutrie nt-limited, reconditioned wastewater from a pork-processing plant was deter mined over a temperature range of 4 to 46 degrees C. Even though the biolog ical oxygen demand of the wastewater was <2 mg/liter, results of bioassays for assimilable organic carbon and the coliform growth response of the wate r suggested that sufficient nutrients were present to support limited bacte rial growth. A three-strain mixture of E. coli O157:H7 grew over the temper ature range of 10.2 to 29.4 degrees C. Bioassays appear to be a good indica tor of the ability of this wastewater to support growth of this pathogen. S tatistically higher levels of bacterial growth (P < 0.05) were detected on a nonselective medium (tryptic soy agar) than on a selective medium (sorbit ol-MacConkey agar), suggesting that stress or injury of the bacterium occur s when the organism is exposed to the nutrient-limited conditions of the wa stewater. These results indicate that E. coli O157:H7 can survive and grow in this particular nutrient-limited wastewater suggesting a potential hazar d if this water becomes contaminated with this pathogen.