March 23, 2009

Researchers at the Johns Hopkins Bloomberg School of Public Health in Baltimore, US, found evidence that houseflies collected near broiler poultry operations may contribute to the dispersion of drug-resistant bacteria.

The findings demonstrate another potential link between industrial food animal production and exposures to antibiotic resistant pathogens.

Previous studies have linked antibiotic use in poultry production to antibiotic resistant bacteria in farm workers, consumer poultry products and the environment surrounding confined poultry operations, as well as releases from poultry transport.

Researchers said flies are well-known vectors of disease and have been implicated in the spread of various viral and bacterial infections affecting humans, which are found to be similar in the antibiotic-resistant bacteria in both the flies and poultry litter that they sampled.

They said that the evidence is an example of the risks associated with the inadequate treatment of animal wastes.

Researcher Ellen Silbergeld said that results suggest that flies in intensive production areas could efficiently spread resistant organisms over large distances.

The analysis by the research team isolated antibiotic-resistant enterococci and staphylococci bacteria from both flies and litter. The bacteria isolated from flies had very similar resistance characteristics and resistance genes to bacteria found in the poultry litter.

Flies have ready access to both stored poultry waste and to poultry houses and a study by researchers in Denmark estimated that as many as 30,000 flies could enter a poultry house over the course of six week period.

According to the Centre for a Livable Future managing director Robert Lawrence, confined animal feeding operations – where thousands of animals are crowded together and are fed antibiotics for growth promotion - create the perfect environment for selection of bacteria that are resistant to antibiotics.