Fowl play

Usage of antibiotics in farm animals could be making human microbes drug-resistant

Published: Tuesday 15 January 2002

a chicken a day would not keep bugs at bay. Yes, this mantra has been resounding in the scientific circle for long, but now scientists have found conclusive evidence that meat laced with antibiotics promotes the growth of super strains of drug-resistant microbes. Recently conducted studies show that regularly feeding a so-called 'sub therapeutic' dose of antibiotics to farm animals could make their microbes resistant to the drugs. These microbes can cause among human beings diseases that are difficult to contain.

Farm animals are regularly given antibiotics, primarily for promoting their growth. This helps to cut down the cost of rearing. Alarming statistics complied by the Union of Concerned Scientists, a us-based non-profit organisation, show that farm animals are given 11.2 million kilogrammes of antibiotics per year, whereas human beings have just 1.3 million kilogrammes.

The studies showing the possible adverse affects of the practice were done by a number of premier organisations such as the us Food and Drug Administration (fda), Atlanta-based Centres of Disease Control and Prevention (cdc) and Statens Serum Institut, Denmark. During the fda study, 200 samples of ground meat collected from the markets of Washington dc were tested. It was found that every fifth sample was contaminated with salmonella bacteria that are responsible for around 1.4 million food poisoning cases in the us. The bacteria were then tested against a number of antibiotics to determine their resistance. The researchers found that eight-four per cent bacteria were resistant to at least one of the antibiotic. For example, 16 per cent were resistant to the antibiotic ceftriaxone, which is commonly used to treat food poisoning among children.

In another study done by researchers from cdc and other organisations, 407 chickens samples from 26 stores in four us states were cultured along with 334 stool samples from outpatients. It was found that 58 per cent of the chicken had drug resistant strains of Enterococcus faecium, another pathogenic intestinal bacterium. Compared to this only one per cent of the outpatients had the bacteria. The researchers ascribed this comparison to the widespread use of virginiamycin antibiotic in chicken feed. A third study done by the Statens Serum Institut showed that the resistant bacteria from poultry or pigs could colonise human intestinal tract for up to 14 days.

In the wake of such studies, researchers advocate that antibiotics should be used only to treat infected animals. "Though abstinence from antibiotics would raise the cost of animal care, the increase is justified, as the resistant organisms can intensify the severity of infection among humans, thereby, hiking the cost of treatment," says Sherwood Gorbach of Tufts University School of Medicine, Boston, usa.

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