Identical Gene Enables Transfer of Antibiotic Resistance, Say Hong Kong Scientists
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According to a recent study conducted by scientists from the University of Hong Kong’s Carol Yu Centre for Infection, genes that cause antibiotic-resistance in bacteria can be transferred between animals and humans – for example, when a human eats an animal that has developed resistance. The findings are expected to help researchers determine what the effects of using antibiotics on livestock are on the treatment of human disease.
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The scientists looked at Escherichia coli bacteria (E. coli), that was responsible for causing human urinary tract infections, as well as bacteria from human and livestock fecal samples. They identified a gene that causes antibiotic resistance and was identical in both samples. The gene was found in about the same proportion and location in all the samples, which seems to imply that the gene is transferred from bacteria to bacteria, even across different hosts.
The gene is called aacC2, and was found in about 80 per cent of the samples, both human and animal. The gene encodes antibiotic resistance, specifically to a widely-used antibiotic called gentamicin. Furthermore, it was found in DNA segments that have the ability to exchange material with different types of bacterial, indicating that the gene can be carried by bacteria that live in different species. That indication is also supported by the identical gene sequences found in the samples.
This ability for aacC2 to transfer between different host species makes the problem of bacterial infections – in this case, E. coli infections – unfortunately more difficult to control, say University scientists. According to study leader, Dr. Pak-Leung Ho, “These resistance genes may possibly spread to the human gut via the food chain, through direct contact with animals or by exposure to contaminated water sources. When the resistance genes end up in bacteria that cause infections in humans, the diseases will be more difficult to treat.”
Dr. Ho points to a dearth of quantitative data on human risk from antibiotic-resistant bacteria and feels it deserves further study. ”Health authorities need to closely monitor the transmission of resistance between food-producing animals and humans and assess how such transfers are affecting the effectiveness of human use of antibiotics,” he said. “With the international trading of meats and food animals, antibiotic resistance in one geographic area can easily become global.”
