GENTECH archive 8.96-97


re: ampicillin resistance

>As I wrote in my message of 27/5, the antibiotics question has not been a
>major issue of interest for me so I must admit I have not a complete
>knowledge of all details. Rick misquoted me about ampicillin usage - In the
>message to the Gentech E-maillist I wrote that it was the most common "as
>far as I know" indicating thereby some uncertainty.

Jaan:  I apologise if I misquoted you but even looking back over our
messages, I am not sure how.  I agreed with you that ampicillin is widely
used in medicine.

>Considering that corn is an important and widely used animal feed, the
>presence of the ampicillin resistance gene in the presently most prevalent
>product may be important in contributing to an increased frequency of
>resistant strains if these genes can be transferred to pathogenic bacteria.

Colleagues working in the antibiotic resistance area tell me that they
don't see a problem even with ampicillin in maize, but I continue to think
it was a poor choice on Ciba's part.  I have prevously sent to this server
a copy of my letter to the US EPA opposing the registration of Ciba's Bt
maize in the US for reasons of insect resistance management.

>I have read the article  by Jim Pittard on the resistance transfer from
>genes to bacteria that Rick Roush refers to. An important cornerstone for
>Pittard's conclusion that such transfer is very improbable is the assumption
>that enough large pieces of DNA to contain a whole gene will not survive

        Without getting into a long-winded argument on the studies of the
Cologne group, I must point out that the key cornerstone on Pittard's paper
is the fact that Kanamycin resistance is already widespread in nature.  It
is Kanamycin resistance that is mostly used in plants; it is Kanamycin
about which Pittard was most specific.   As noted in my earlier message,
the Australian Genetic Manipulation Advisory Committee (GMAC)  "has
consistently stated that the present of Kanamycin resistance genes in
transgenic plants offers no threat to anyone or anything" (starting page
173, first page of Pittard's paper).

        Jaan, can you agree for the benefit of our readers that Kanamycin
is mentioned prominently throughout the first four of the six pages of the
paper, including that Kanamycin resistance is already very common in
bacteria (page 175)?

        The point made by Pittard (and many others) is that "it is highly
likely that most people have now, or at least have had some time in the
last year, a significant number of bacteria in their intestinal tract which
express resistance to Kanamycin and carry the Kanamycin resistance gene
probably on a transmissable plasmid" (page 175).  Wouldn't this be a much
more readily available source of Kanamycin resistance than anything coming
from a plant?

        So far as I am aware, there are NO continuing medical uses of
Kanamycin.  The article by by Wan-Ho and Tappeser, as provided by Jaan,
indicates only that Kanamycin is used for tuberculosis.  I looked for and
found an article on TB in the New Scientist issue they mentioned (May 4,
1996) but there was no mention of kanamycin use.  I have checked with an
antibiotic resistance expert medical doctor here, and he tells me that
streptomycin NOT Kanamycin is still occasionally used for TB.

        Can we agree that at least Kanamycin resistance markers have no
implications for human health?