August 11, 2009

Large piles of aging chicken manure to be used as fertiliser on farm crops can house antibiotic-resistant bacteria, according to a study from Johns Hopkins University in the US.

 

The results raise concern that typical storage conditions may fail to keep the microbes from reaching the public through contaminated food or drinking water, as poultry manure is not required to be treated before their application to farm fields.

 

Poultry producers commonly use antibiotics to promote chicken growth, which can lead to bacteria in the chickens' digestive system to develop resistance. The antibiotic-resistant bacteria are then excreted in the manure or poultry litter.

 

The US poultry industry produces about 13 to 26 million tonnes of manure each year, most of which are used as fertiliser. It is stored in huge piles until it is ready to be spread onto farm fields. Rich in nitrogen, it is also fed to beef cattle and farmed fish.

 

The researchers studied Staphylococci and enterococci in chicken litter, and found that while they initially declined in the manure piles, some survived and increased in numbers again over the course of the four-month survey.

 

Antibiotic-resistant bacteria were found throughout the four-month monitoring. The resistant bacteria ranged from 0-69 percent of the total bacteria, depending on the strain and the type of antibiotic against which the bacteria were tested for resistance.

 

The study suggested that composting may be a better choice than mere storage, as it could kill bacteria more effectively by controlling the storage environment so that high temperatures occur throughout the entire pile instead of just in the middle.