Tuesday, July 12, 2005

Antibiotics and farm animals

Over at the Pandas thumb, Professor Steve Steve is off on more crazy adventures telling scientists how it is, when I noticed the following quote that I thought pertinent to expand upon:
I don’t think Dr. Cassell was very amused when I suggested they should simply keep the population on antibiotics from birth to death, and we wouldn’t have to worry about this silly infection stuff.
First of all, I find it somewhat interesting that it is widely acknowledged by both the scientific and medical communities that wanton use of antibiotics is a bad thing. We've seen the emergence of virtually every kind of antibiotic resistant and disturbingly usual multi-antibiotic resistant bacteria since antibiotics were first used. It is ironic then, with these problems with human antibiotic resistance so widely reported, that the farming industry appears to completely ignore what we've learnt. Many places around the world feed animals antibiotics prophylactically as 'growth promotants'.

This does have some benefit that is not well understood and animals do seem to grow faster under such treatments. Unfortunately, it has been demonstrated the breed the resistance to the antibiotics used in certain hardy gut commensals like Enterococcus faecium. It has also been demonstrated that E. faecium can transfer the antiobiotic resistance it has picked up to other microorganisms it meets, including E. coli. While the antibiotics used in animal feed aren't always medically significant ones in humans, they sometimes still have potentially negative ramifications.

1) Some of these antibiotics are analogs, that is they have a similar structure and function to human antibiotics used in medicine. One such example is avoparcin, which is similar to vanctomycin (important in treating the superbug MRSA) and due to evidence of resistance to avoparcin conferring protection against vanctomycin, its use has been generally banned in many places.

2) One form of resistance often confers at least some protection against other forms of antibiotics, even if it doesn't directly affect the targeted structure or enzyme. This most commonly occurs with cell wall active antibiotics, where resistance mechanisms such as reduced surface charge can affect a wide range of antibiotics: not just one or two.

It just seems almost silly to me that its widely accepted to be bad practice to use antibiotics unnesessarily in humans, yet many places even now are just throwing them into farm animal feed. It's utterly irresponsible.