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New Research Points to Better Method to Weigh Risk of Antibiotic Resistance in Bacteria

Jan. 14, 2013
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Pharmaceuticals and other personal care products such as antibiotics may be a problem in the aquatic environment.

A recent study demonstrates a new approach that may allow scientists to better approximate the risks for bacteria to develop resistance to different families of antibiotics.

In the study, conducted by NOAA’s National Centers for Coastal Ocean Science and the Arnold School of Public Health at the University of South Carolina, resistance genes from E. coli bacteria were found to be nearly a thousand times higher in sediments downstream of a sewage treatment plant than in the effluent at the source of the plant. This indicates that antibiotic resistance genes may be transferred to marine pathogens such as Vibrio bacteria. Vibrio bacteria are common to estuarine and marine waters and include the pathogens that cause minor gastrointestinal disorders, serious wound infections, and cholera.

Pharmaceuticals and other personal care products such as antibiotics may enter coastal waters in sewage discharges as well as non-point source runoff from agricultural operations. Some of these products have been known to bioaccumulate and others may be hazardous to marine life at very low concentrations. Typically, they are most hazardous in large doses. However, with antibiotics, resistance actually occurs with more frequent exposure to lower doses. This continual exposure may result in the formation of resistance genes that enable bacteria to survive higher antibiotic doses.

A measurement known as Minimum Inhibitory Concentrations (MICs) is typically used by scientists to measure the amount of antibiotic resistance within bacteria. However, the study revealed that the ratio of maximum to minimum inhibitory concentrations may provide an estimate of the potential for an antibiotic to cause antibiotic resistance. Using this approach, scientists approximated the risk of bacteria developing resistance to different families of antibiotics.

The findings may help researchers better understand how specific antibiotics released into the environment affect bacteria and other marine life, which has important implications for human health.