Re: Fwd:New York Times - Red Meat Irradiation Rules

["Gregg Claycamp" <hgc2+@pitt.edu>]

The notion that one could equate acquisition of antibiotic resistance and a
future radiation resistant bacterium is scientifically flawed for many
reasons:

1.    The mechanisms of action are not the same.  Most antibiotics interfere
with fission (bacterial division, not nuclear!).  The cells are more
vulnerable to attack during this stage giving the body time to catch up with
the infection in addition to simply wearing down the bacteria population.
Selection of bacterial resistance genes occurs with repeated under-dosing
(patients don't comply with prescriptions) much like natural selection.
Once that a resistant cell grows, the infected patient provides a medium for
expansion of the population.  From there, hospitals are usually great places
to expand the population from host-to-host  (ie, there are lots of sick
people at hospitals, and hygiene among care-giving staff is not perfect).

This is not the same as giving lethal --not just division-inhibiting-- doses
of radiation to small populations of bacteria contaminating meat.  Here, a
rare surviving bacteria cell is likely to die during cooking or consumption.
The idea is to lower the population number (if it's there in the first
place) low enough or "zero" that a significant regrowth and human infection
is unlikely, given proper food handling.   (We consume microbes every
day--normal biology and proper food handling keeps things in check.)

2.  By analogy, we should already have "superbugs"  that survive heat
pasteurization of milk.  In fact, we know that a radiation resistant
bacterium, M. radiodurans, was discovered  as a survivor of an autoclave:
steam heat and high pressure.  Much less harsh heating for pasteurization
should have by now selected for the superbug that makes the pasteurization
process useless, should it not?  After all, we've relied on pasteurization
of milk for about 7 decades now!

3.  The author's notion that selection of a radioresistant bacterium might
occur is mixing lab science with food science:  In the lab, repeated
experiments using "survivable" high doses of radiation could be used on
large cultures of bacteria cells (i.e., 10E12 cells at a time) in search of
the superbug.  For about 100 years of such experiments,  there has been
remarkably little in terms of isolating significant radioresistance.  Again,
M. radiodurans was HEAT resistant, and then discovered to be radioresistant,
also.

A simple reason that the analogous "experiment" won't work in the food
irradiation scenario is that, like pasteurization, irradiation cannot hide
tainted or spoiled meat.  In other words, if there is a large population of
baceria infecting the meat, the product will be useless before or after
irradiation. (Heat pasteurization also cannot improve spoiled milk).  THe
process is only intended to significantly reduce the chances for low-level
counts of cells to survive and grow into an active population.

H. Gregg Claycamp, Ph.D., C.H.P.
Assoc. Professor and Assoc. Chair
Univ. of Pittsburgh
Environmental and Occupational Health
hgc2+@pitt.edu



-----Original Message-----
From: elizabeth_algutifan@wssrap-host.wssrap.com
<elizabeth_algutifan@wssrap-host.wssrap.com>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Date: Friday, February 12, 1999 8:54 AM
Subject: Fwd:New York Times - Red Meat Irradiation Rules


>Would anyone care to comment on this statement?
>
>Elizabeth Algutifan
>Elizabeth_Algutifan@wssrap-host.wssrap.com
>
>____________________Forward Header_____________________
>Subject:    New York Times - Red Meat Irradiation Rules
>Author: <radsafe@romulus.ehs.uiuc.edu>
>Date:       2/12/99 7:08 AM
>
>>But its lasting efficacy is being debated. Ms. Foreman, who says there
>>is a place for irradiated foods in nursing homes and hospitals, warns
>>that "in the long run, years out, bacteria are likely to develop
>>resistance to irradiation," just as they have to one antibiotic after
>>another.
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