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Abstract：
The emergence of multidrug-resistant bacteria poses a significant threat to human health, necessitating a comprehensive understanding of their underlying mechanisms. Uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections, is frequently associated with multidrug resistance and recurrent infections. To elucidate the mechanism of resistance of UPEC to beta-lactam antibiotics, we generated ampicillin-resistant UPEC strains through continuous exposure to low and high levels of ampicillin in the laboratory, referred to as Low AmpR and High AmpR, respectively. Whole-genome sequencing revealed that both Low and High AmpR strains contained mutations in the marR, acrR, and envZ genes. The High AmpR strain exhibited a single additional mutation in the nlpD gene. Using protein modeling and qRT-PCR analyses, we validated the contributions of each mutation in the identified genes to antibiotic resistance in the AmpR strains, including a decrease in membrane permeability, increased expression of multidrug efflux pump, and inhibition of cell lysis. Furthermore, the AmpR strain does not decrease the bacterial burden in the mouse bladder even after continuous antibiotic treatment in vivo, implicating the increasing difficulty in treating host infections caused by the AmpR strain. Interestingly, ampicillin-induced mutations also result in multidrug resistance in UPEC, suggesting a common mechanism by which bacteria acquire cross-resistance to other classes of antibiotics.
摘要：
多重耐药菌的出现对人类健康构成重大威胁,需要全面了解其基本机制。尿路致病性大肠杆菌（UPEC），尿路感染的主要病原体，经常与多药耐药和反复感染有关。阐明UPEC对β-内酰胺类抗生素的耐药机制,我们通过在实验室中连续暴露于低和高水平的氨苄青霉素产生了耐氨苄青霉素的UPEC菌株，被称为低AmpR和高AmpR，分别。全基因组测序显示，低和高AmpR菌株在marR中都含有突变，acrR,和envZ基因。高AmpR菌株在nlpD基因中表现出单个额外的突变。使用蛋白质建模和qRT-PCR分析，我们验证了鉴定基因中每个突变对AmpR菌株抗生素抗性的贡献，包括膜渗透性的降低，多药外排泵的表达增加，和抑制细胞裂解。此外，即使在体内连续抗生素治疗后，AmpR菌株也不会降低小鼠膀胱中的细菌负担，暗示治疗由AmpR菌株引起的宿主感染的难度越来越大。有趣的是,氨苄青霉素诱导的突变也会导致UPEC的多药耐药性，提示细菌获得对其他类抗生素的交叉耐药性的共同机制。
