Recovery and Behaviour of Stressed Escherichia coli O157:H7 Cells on Rocket Leaf Surfaces Inoculated by Different Methods

Abstract

E. coli O157:H7 is an emerging public health concern worldwide because of its low infectious dose and ability to survive under adverse conditions. Tests were conducted to determine the abilityof unstressed E. coli O157:H7 cells or those stressed by acid, cold, salt exposure or starvation to survive on the surfaces of rocket leaves after contamination by three methods (dip, spray or spot inoculation) and following storage at 10 or 25ºC. E. coli O157:H7 numbers recovered from rocket leaves contaminated by the different techniques were in the order of dip > spot > spray inoculation.Numbers of stressed E. coli O157:H7 recovered after inoculation by all three methods increased significantly over 7d storage at 10 or 25ºC, while unstressed E. coli O157:H7 only grew following dip inoculation. Exposure to adverse environmental conditions may increase the risk of E. coli O157:H7 survival and spread on leafy green vegetables.

Keywords

• E. coli O157:H7, environmental stress, leafy green vegetables, rocket leaves, inoculation method