Between 19, 350 outbreaks caused by EcO157 were reported 52% and 9% were caused by foodborne and waterborne sources, respectively.
It has been estimated that EcO157 causes approximately 73,000 illnesses in the United States each year. Intensive studies of the sources, incidence, fate and transport of EcO157 near produce production are required to determine the mechanisms of pre-harvest contamination and potential risks for human illness.Įscherichia coli O157:H7 (EcO157) is an enteric pathogen that can cause life threatening hemorrhagic colitis and, in very severe cases, hemolytic uremic syndrome. These results indicate that contamination of the environment is a dynamic process involving multiple sources and methods of transport. During the 2006 baby spinach outbreak investigation, transport was also detected where water was unlikely to be involved. However, possible transport up to 32 km was detected during periods of higher water flow associated with flooding. In a preliminary study, EcO157 was detected in water at multiple locations in a low-flow creek only within 135 meters of a point source. Recurrence of identical and closely related EcO157 strains from specific locations in the Salinas and San Juan valleys suggests that transport of the pathogen is usually restricted. A subset of these environmental isolates were typed by Pulse Field Gel Electrophoresis (PFGE) in order to make comparisons with human clinical isolates associated with outbreak and sporadic illness. Approximately 1000 EcO157 isolates obtained from cultures of>100 individual samples were typed using Multi- Locus Variable-number-tandem-repeat Analysis (MLVA) to assist in identifying potential fate and transport of EcO157 in this region. The incidence of EcO157 increased significantly when heavy rain caused an increased flow rate in the rivers. EcO157 was isolated at least once from 15 of 22 different watershed sites over a 19 month period. Outbreaks between 20 induced investigations of possible sources of pre-harvest contamination on implicated farms in the Salinas and San Juan valleys of California, and a survey of the Salinas watershed.
Between 1995–2006, 22 produce outbreaks were documented in the United States, with nearly half traced to lettuce or spinach grown in California. Fresh vegetables have become associated with outbreaks caused by Escherichia coli O157:H7 (EcO157).
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