Re: food irradiation related questions

[js_dukelow@ccmail.pnl.gov (James S Jr Dukelow)]

Regarding Drew Thatcher's initial questions and the several responses 
(including his reporting of his conversation with David Doyle):

Drew's "adversary" in the Seattle PI's letter columns has it just about 
right.  Much of the recent flap about food irradiation was just the meat 
processing industry's attempt to change the subject from their poor 
performance in the area of product contamination to the government's 
unreasonable delay in approving the irradiation of red meat.  Although 
poultry is badly contaminated with Salmonella and Campylobacter and 
although irradiation of poultry has been permitted for several years, 
there are only one or two local grocery chains where you can buy 
irradiated chicken.  It will be instructive to see how the red meat 
processing industry responds to the recent approval of irradiation for 
red meat.  As noted by Drew's adversary, irradiation of red meat will 
not solve the whole problem because a lot of other foods are subject to 
contamination by cattle (and other livestock) manure, as are swimming 
lakes.

Thorough cooking doesn't completely solve the problem either, because 
improper handling of contaminated foods in home, commercial, or 
institutional kitchens can cross-contaminate other foods.  It is 
actually pretty easy to do, because one of the striking features of E. 
coli O157:H7 is its high infectivity (most estimates of the infectuous 
dose run around 10 organisms, which is an extraordinarily small number). 
A recent posting to the FOODSAFE mailing list noted that the CDC 
recommends that research laboratories treat Salmonella and Campylobacter 
(almost ubiquitous contaminants of the chicken and turkey we buy at the 
grocery store) as Biosafety Level 2 biohazards.  This implies a series 
of safety requirements that are not met by ANY of the millions of 
kitchens that routinely handle contaminated poultry.

On to Drew's adversary's second point, that a possible approach to the 
virulent E. coli strains was to provide competitors.  This is a 
perfectly legitimate and a logical idea and one that is being pursued.  
E. coli O157:H7, along with every other species, has to compete for food 
and living space with other species.  There are indications from 
research studies, which experimentally inoculated cows and calves with 
E. coli O157:H7, that it causes a transient disease in cattle, 
particularly calves.  It would make the cattle sick for a while, but 
after 9-10 weeks O157 organisms could not be recovered from the manure 
of most of the subjects.  Generic or "wild" strains of E. coli could be 
recovered at all times.  This suggests that eventually the "wild" (and 
benign) strains out-compete and suppress O157.  Part of the folklore of 
yogurt is that it is healthful precisely because it inoculates the human 
gut with benign lacto-bacteria.  In addition, microbes that invest part 
of their genome in antibiotic resistance or virulence genes frequently 
do not compete well with "wild" strains whose genome is fully invested 
in the normal environment (that is, they don't compete well in the 
absence of the antibiotics or the hosts against whom the virulence 
factors are directed).

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory 
Richland, WA
js_dukelow@pnl.gov

These thoughts are mine and have not been reviewed and/or approved by my 
management or by the U.S. Department of Energy.