The evolution of resistance to synergistic multi-drug combinations is more complex than evolving resistance to each individual drug component.

Multidrug antibiotic resistance is an urgent public health concern. Multiple strategies have been suggested to alleviate this problem, including the use of antibiotic combinations and cyclic therapies. We examine how adaptation to (i) combinations of drugs affects resistance to individual drugs, and to (ii) individual drugs alters responses to drug combinations. To evaluate this, we evolved multiple strains of drug resistant Staphylococcus epidermidis in the lab. We show that evolving resistance to four highly synergistic combinations does not result in cross-resistance to all of their components. Likewise, prior resistance to one antibiotic in a combination does not guarantee survival when exposed to the combination. We also identify four three-step and four two-step treatments that inhibit bacterial growth and confer collateral sensitivity with each step, impeding the development of multidrug resistance. This study highlights the importance of considering higher-order drug combinations in sequential therapies and how antibiotic interactions can influence the evolutionary trajectory of bacterial populations.

多重耐药性抗生素问题已成为一项紧迫的公共卫生关切。针对这一问题，已提出多种缓解策略，包括抗生素联合用药及循环治疗等。本研究旨在探讨药物组合适应（i）对单个药物耐药性影响以及（ii）单个药物对药物组合反应的改变。为此，我们在实验室中进化了多种耐药性表皮葡萄球菌菌株。研究发现，对四种高度协同作用的药物组合产生耐药性并不会导致对所有成分的交叉耐药性。同样，对联合用药中某一抗生素的先前耐药性并不能保证在接触该组合时仍能存活。此外，我们还确定了四种三步法和四种两步法治疗，这些方法能够抑制细菌生长，并在每一步中赋予辅助敏感性，从而阻碍多重耐药性的发展。本研究强调了在连续治疗中考虑高阶药物组合的重要性，以及抗生素相互作用如何影响细菌种群演化的轨迹。