Mechanisms of mepA Overexpression and Membrane Potential Reduction Leading to Ciprofloxacin Heteroresistance in a Staphylococcus aureus Isolate

作者：Mengyuan Li, Qianting Jian, Xinyi Ye, Mou Jing, Jia-en Wu, Zhihong Wu, Yali Ruan, Xinxian Long, Rongmin Zhang, Hao Ren, Jian Sun, Yahong Liu, Xiaoping Liao, Xin-Lei Lian · 发表于：International Journal of Molecular Sciences · 年份：2025 · DOI：10.3390/ijms26052372 · 被引用次数：6 · 研究领域：Antimicrobial Resistance in Staphylococcus、Bacterial biofilms and quorum sensing、Antibiotic Resistance in Bacteria

Heteroresistance has seriously affected the evaluation of antibiotic efficacy against pathogenic bacteria, causing misjudgment of antibiotics’ sensitivity in clinical therapy, leading to treatment failure, and posing a serious threat to current medical health. However, the mechanism of Staphylococcus aureus heteroresistance to ciprofloxacin remains unclear. In this study, heteroresistance to ciprofloxacin in S. aureus strain 529 was confirmed by antimicrobial susceptibility testing and population analysis profiling (PAP), with the resistance of subclonal 529_HR based on MIC being 8-fold that of the original bacteria. A 7-day serial MIC evaluation and growth curves demonstrate that their phenotype was stable, with 529_HR growing more slowly than 529, but reaching a plateau in a similar proportion. WGS analysis showed that there were 11 nonsynonymous mutations and one deletion gene between the two bacteria, but none of these SNPs were directly associated with ciprofloxacin resistance. Transcriptome data analysis showed that the expression of membrane potential related genes (qoxA, qoxB, qoxC, qoxD, mprF) was downregulated, and the expression of multidrug resistance efflux pump gene mepA was upregulated. The combination of ciprofloxacin and limonene restored the 529_HR MIC from 1 mg/L to 0.125 mg/L. Measurement of the membrane potential found that 529_HR had a lower potential, which may enable it to withstand the ciprofloxacin-induced decrease in membrane potential. In summary, ...