GLOBAL - A human and livestock antibiotic widely used in animal health in developing countries could be rendered ineffective by resistant bacteria shed by cattle.
Laboratory screening of cow dung has found bacteria resistant to chloramphenicol, an antibiotic used for eye infections in humans and respiratory infections in livestock.
This is according to a Yale University study summary which found a ‘surprising’ amount of antibiotic resistant (AR) bacteria in the manure of dairy cows.
Although less important in developed countries, chloramphenicol products are popular in developing nations due to affordability and availability.
The investigation identified thousands of antibiotic resistant genes, 80 of which were unique and functional, according to senior study author Professor Jo Handelsman.
She reassured that the majority of resistant genes did not pose a threat as they were found in harmless bacteria but could adapt to reach humans between the barn and the table.
"The diversity of genes we found is remarkable in itself considering the small set of five manure samples," she said.
"But also, these are evolutionarily distant from the genes we already have in the genetic databases, which largely represent AR genes we see in the clinic."
The team’s remit was to bolster understanding around environmental bacteria and the potential for cross-over in human health.
Further studies are scheduled to ascertain the likelihood and dangers of AR bacteria crossing into the food chain.
Threats are posed if the bacteria containing the genes colonize humans or if genes offer resistance to bacteria that can colonize humans – a process known as ‘horizontal transfer’.
Transfer from benign to pathogenic bacteria could occur at numerous points along supply chains, according to the Yale team who added that soil amendment via muck spreading could be a possible route.
Professor Handelsman said: "This is just the first in a sequence of studies—starting in the barn, moving to the soil and food on the table and then ending up in the clinic—to find out whether these genes have the potential to move in that direction."
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