Giving patients multiple antibiotics is a popular strategy for addressing the issue of treating infections that are resistant to certain antibiotics, but a new study shows that this strategy may actually be strengthening resistance, according to The Scientific American.
The study, published in the journal Science, found that developing tolerance to one of the antibiotics in a combination may increase the likelihood of developing resistance to the second drug. Antibiotic tolerance indicates that the drug takes more time to kill the bacteria.
Researchers studied the evolution of methicillin-resistant Staphylococcus aureus, a common healthcare-associated infection that can be lethal in patients who had the infection for more than two weeks despite being treated with antibiotics. One patient first received the antibiotic vancomycin, and after four days another antibiotic rifampicin was added to their regimen. Then, the vancomycin was swapped out for daptomycin.
They found that the microbes in the bacteria taken from the patient that had developed tolerance against vancomycinwere also being eliminated more slowly by daptomycin. The rifampicin-daptomycin combination was not more effective than just using one antibiotic.
The researchers showed similar development of resistance in other bacteria with other different antibiotic combinations.
The study indicates that clinicians may need to laboratory test bacteria infecting their patients to determine whether it is tolerant to an antibiotic that is part of a patient's planned treatment.