lunes, 8 de marzo de 2010

Pre-harvest food safety revisited

Early applied phages inactivate E. coli O157: H7 efficiently
Recent developments in bacteriophages, vaccines and other technologies have changed my thinking about the importance of pre-harvest interventions in an integrated food safety system.
Pre-harvest interventions by themselves are not going to eliminate E. coli O157:H7 and Salmonella in beef. However, the strategic use of technologies that can eliminate peaks in the incidence of pathogens and generally reduce contamination in and on cattle, make it more likely that the interventions applied at slaughter and post-slaughter will effectively eliminate pathogen contamination on beef carcasses.
Pre-harvest technologies also reduce environmental sources of E. coli O157:H7, which in turn reduces the risk of contamination of fresh cut produce and other foods that are harvested in beef producing areas. A reduction of E. coli in cattle holding pens associated with pre-harvest interventions may also impact the risk of airborne vectors of contamination at beef slaughter plants.
One of the most promising pre-harvest interventions involves a bacteriophage that is specific to E. coli O157:H7. The phage is applied as a spray directly onto the hides of animals without causing discomfort or stress. It then works its way over the hide surface and inactivates E. coli O157:H7 on contact as it binds to specific receptors on the surface of the E. coli cell. The earlier the phage is applied, the more effective it is at reducing E. coli numbers. Currently, most phage applications are done on receipt at packing plants and this approach has been shown to be effective. If the phage were applied upstream, prior to loading cattle onto trucks, it may be even more effective and also have the added benefit of reducing contamination on trucks.
Other pre-harvest food safety technologies are also emerging. The Epitopix and Bioniche E. coli vaccines have received conditional approval in the US and are being tested at several feedlots across the US. Research on competitive exclusion probiotics and Sodium chlorate (produces a cytotoxic effect) is also underway.
Historically, E. coli O157:H7 has been more of a problem over the summer and fall. According to the CDC, 89% of the E. coli outbreaks that occurred from 1982-2002, happened during the months of May - November. If a pre-harvest intervention like the phage can eliminate the spikes in E. coli that occur over this time period, there would be an important corresponding public health benefit.
Ultimately, the beef industry, like the dairy industry, will likely employ some form of pasteurization to eliminate pathogens from consumer products. Pre-harvest interventions will still play an important role in the overall food safety systems of the future by reducing microbiological hazards on cattle prior to slaughter.
Source: Zone

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