Large piles of aging to be used chicken manure as fertilizer on farm crops can house bacteria that are resistant to antibiotics, finds a study from Johns Hopkins University.
The results raise concern that typical storage conditions may fail to keep the microbes from reaching people through contaminated food or drinking water. Poultry manure is not required to be treated before it is applied to farm fields.
Poultry producers commonly use antibiotics to promote growth of the chickens. This can lead to bacteria in the chickens' digestive system becoming resistant to antibiotics. The antibiotic-resistant bacteria are excreted in the manure and wind up - or poultry litter.
The poultry industry in the U.S. produces an estimated 13-26 million mt of manure each year. Much of the litter is used as a fertilizer. 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 study's researchers Examined the survival and the antibiotic-resistance pattern of 2 different types of bacteria, staphylococci and enterococci in chicken litter. These bacteria are found in the digestive systems of both chickens and people.
Although the bacteria numbers initially declined in the manure piles, some survived and increased in numbers again over the course of the 4-month survey.
Antibiotic-resistant bacteria were found throughout the entire 4 months of monitoring. The resistant bacteria ranged from 0-69% of the total bacteria, depending on the strain and the type of antibiotic against the bacteria which were tested for resistance.
Composting may be a better choice than mere storage, the authors suggest *. Composting kills bacteria more effectively by controlling the storage environment so that high temperatures occur throughout - not just in the middle - or the entire pile.
Further studies will be needed to determining if the resistant bacteria in manure used as fertilizer can wind up in people or if improved storage / treatment methods are necessary.
* Jay P. Graham, Sean L. Evans, Lance B. Price and Ellen K. Silbergeld
Source: Environmental Health News
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