Inactivation of β-lactam antibiotics by resistant bacteria is a 'cooperative' behavior that may allow sensitive bacteria to survive antibiotic treatment. However, the factors that determine the fraction of resistant cells in the bacterial population remain unclear, indicating a fundamental gap in our understanding of how antibiotic resistance evolves. Here, we experimentally track the spread of a plasmid that encodes a β-lactamase enzyme through the bacterial population. We find that independent of the initial fraction of resistant cells, the population settles to an equilibrium fraction proportional to the antibiotic concentration divided by the cell density. A simple model explains this behavior, successfully predicting a data collapse over two orders of magnitude in antibiotic concentration. This model also successfully predicts that adding a commonly used β-lactamase inhibitor will lead to the spread of resistance, highlighting the need to incorporate social dynamics into the study of antibiotic resistance.

中文翻译：

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细菌作弊驱动协同抗生素抗性质粒的种群动态。

抗性细菌对 β-内酰胺类抗生素的灭活是一种“合作”行为，可以使敏感细菌在抗生素治疗中存活下来。然而，决定细菌种群中耐药细胞比例的因素仍不清楚，这表明我们对抗生素耐药性如何演变的理解存在根本差距。在这里，我们通过实验跟踪编码 β-内酰胺酶的质粒在细菌群体中的传播。我们发现，独立于耐药细胞的初始分数，种群稳定到与抗生素浓度除以细胞密度成正比的平衡分数。一个简单的模型解释了这种行为，成功地预测了抗生素浓度超过两个数量级的数据崩溃。