Antimicrobial resistance may lead to more resistance

July 28, 2021

In a paper published in The Lancet Microbe, researchers from the University of Pittsburgh School of Medicine found that when bacteria become resistant to one antimicrobial drug, they are likely to become resistant to most others. That is, resistance begets more resistance, suggesting that the popular approach of switching between different antimicrobials to avoid resistance may be a losing battle.

But there is good news: In rare cases, certain antibiotics can make bacteria sensitive to other antibiotics, and the scientists found that switching between these drugs might be useful to circumvent antimicrobial resistance in clinical trials.

Overcoming antimicrobial resistance is no small feat. It’s difficult to come up with more powerful antimicrobials, and history shows most attempts to overcome resistance are destined to fail.

In their quest for antibiotic pairs that could be considered for treatment strategies, the researchers scanned hundreds of thousands of health records containing results of antimicrobial susceptibility tests of patients at UPMC hospitals.

Remarkably, researchers found that more than half of tested antibiotic combinations were ineffective at avoiding bacteria’s resistance mechanisms. Conversely, less than 1% of the antibiotic pairs displayed the property of mutually exclusive resistance, which would, in principle, allow for alternating between two drugs without fanning the flames of antimicrobial resistance.

With careful planning, researchers say, certain drug pairs hold potential for treating specific pathogens and these strategies deserve to be explored in clinical trials. But as a whole, the researchers discourage clinicians from relying on antibiotic cycling as a cure for antibiotic resistance. 

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