Antibiotics in Animal Feeds Can Be Harmful

A hotly contested debate has been brewing over the past 2 decades. Animal feed has been supplemented with antimicrobial agents (medications that kill bacteria) to get the animals to grow bigger and faster. This practice saves the meat industry an enormous amount of money. Pharmaceutical companies also make a large amount of money selling these growth enhancing antimicrobial agents to beef, chicken, and pork producers.

No one knows for sure how adding antimicrobials to animal feed makes the animals grow faster and bigger but it works. The effect on growth may be due to the fact that the antimicrobial agents reduce the numbers of bacteria in the intestines of the animals and allow more nutrients to get to the animal rather than to the bacteria growing in the gut. It may also be due to the antimicrobial agents ability to kill organisms that would make the animals sick. When the animal is ill then their growth slows. If they are healthy they will continue to grow.

Unfortunately, when you routinely feed animals antimicrobials certain bacteria become resistant to these antimicrobials. The antimicrobials in certain cases are not the same ones used in humans however, they share similar ways of killing organisms. So if the bacterium is resistant to an antimicrobial in animal feed it is much more likely that it will also be resistant to antimicrobials used in humans.

This is the case for an antimicrobial agent called avoparcin. Avoparcin was given to animals in Europe for a number of years. Soon after this practice began strains of a bacterium called Enterococcus faecium became resistant to avoparcin. This was not a major problem the animals still grew faster and bigger. The problems began when people started getting the avoparcin resistant strains of Enterococcus faecium through contact with the meat. No humans receive avoparcin. Instead vancomycin is given to many people with hard to treat bacterial infections. Unfortunately, avoparcin resistant Enterococcus faecium are also resistant to vancomycin. That is because avoparcin and vancomycin are structurally similar and kill bacteria via the same means. As a result vancomycin resistant Enterococcus faecium were more commonly isolated from the intestines of people in these countries.

Now Enterococcus faecium rarely causes problems for healthy people. In fact Enterococcus faecium is very good for our intestines. Unfortunately, people that are immunosuppressed or have various tubes inserted in their bodies are more likely to get Enterococcus faecium infections. This now becomes a problem. Vancomycin/avopircin resistant Enterococcus faecium are almost impossible to treat. They are resistant to nearly all the commonly used antimicrobial agents known to man.

It has also been shown that Enterococcus faecium

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