Antibiotics resistance has caused much complication in the treatment of diseases, where the pathogen is no longer susceptible to specific antibiotics and the use of such antibiotics are no longer effective for treatment. A recent study that utilizes digital organisms suggests that complete elimination of specific antibiotic resistance is unlikely after the disuse of antibiotics, assuming that there are no fitness costs for maintaining resistance once resistance are established. Fitness cost are referred to as reaction to change in environment, where organism improves its' abilities in one area at the expense of the other. Our goal in this study is to use digital organisms to examine the rate of gain and loss of resistance where fitness costs have incurred in maintaining resistance. Our results showed that GC-content based fitness cost during de-selection by removal of antibiotic-induced selective pressure portrayed similar trends in resistance compared to that of no fitness cost, at all stages of initial selection, repeated de-selection and re-introduction of selective pressure. Paired t-test suggested that prolonged stabilization of resistance after initial loss is not statistically significant for its difference to that of no fitness cost. This suggests that complete elimination of specific antibiotics resistance is unlikely after the disuse of antibiotics despite presence of fitness cost in maintaining antibiotic resistance during the disuse of antibiotics, once a resistant pool of micro-organism has been established.

翻译：抗生素耐药性已导致疾病治疗中的诸多并发症，病原体对特定抗生素不再敏感，使用此类抗生素已无法有效治疗。近期一项利用数字有机体的研究提示，在假定抗性一旦建立后维持抗性无适应性代价的情况下，停用抗生素后完全消除特定抗生素耐药性几乎不可能。适应性代价指生物体为适应环境变化而在某一能力提升时以其他能力为代价的反应。本研究旨在利用数字有机体探究在维持耐药性产生适应性代价时，耐药性的获得与丧失速率。结果表明，在通过移除抗生素诱导选择压力实现去选择的过程中，基于GC含量的适应性代价在初始选择、重复去选择及重新引入选择压力的各个阶段，均呈现出与无适应性代价相似的耐药性趋势。配对t检验显示，初始丧失后耐药性的长期稳定化与无适应性代价情况相比，差异无统计学显著性。这表明，一旦耐药微生物库建立，尽管在停用抗生素期间维持耐药性存在适应性代价，停用抗生素后仍难以完全消除特定抗生素耐药性。