Han Jing, Sahin Orhan, Barton Yi-Wen, Zhang Qijing
Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America.
PLoS Pathog. 2008 Jun 6;4(6):e1000083. doi: 10.1371/journal.ppat.1000083.
Campylobacter jejuni is a major food-borne pathogen and a common causative agent of human enterocolitis. Fluoroquinolones are a key class of antibiotics prescribed for clinical treatment of enteric infections including campylobacteriosis, but fluoroquinolone-resistant Campylobacter readily emerges under the antibiotic selection pressure. To understand the mechanisms involved in the development of fluoroquinolone-resistant Campylobacter, we compared the gene expression profiles of C. jejuni in the presence and absence of ciprofloxacin using DNA microarray. Our analysis revealed that multiple genes showed significant changes in expression in the presence of a suprainhibitory concentration of ciprofloxacin. Most importantly, ciprofloxacin induced the expression of mfd, which encodes a transcription-repair coupling factor involved in strand-specific DNA repair. Mutation of the mfd gene resulted in an approximately 100-fold reduction in the rate of spontaneous mutation to ciprofloxacin resistance, while overexpression of mfd elevated the mutation frequency. In addition, loss of mfd in C. jejuni significantly reduced the development of fluoroquinolone-resistant Campylobacter in culture media or chickens treated with fluoroquinolones. These findings indicate that Mfd is important for the development of fluoroquinolone resistance in Campylobacter, reveal a previously unrecognized function of Mfd in promoting mutation frequencies, and identify a potential molecular target for reducing the emergence of fluoroquinolone-resistant Campylobacter.
空肠弯曲菌是一种主要的食源性病原体，也是人类小肠结肠炎的常见病原体。氟喹诺酮类药物是用于临床治疗包括弯曲菌病在内的肠道感染的一类关键抗生素，但在抗生素选择压力下，耐氟喹诺酮的弯曲菌很容易出现。为了解耐氟喹诺酮弯曲菌产生的机制，我们使用DNA微阵列比较了在有和没有环丙沙星的情况下空肠弯曲菌的基因表达谱。我们的分析表明，在高于抑制浓度的环丙沙星存在下，多个基因的表达发生了显著变化。最重要的是，环丙沙星诱导了mfd的表达，mfd编码一种参与链特异性DNA修复的转录修复偶联因子。mfd基因突变导致对环丙沙星耐药的自发突变率降低约100倍，而mfd的过表达则提高了突变频率。此外，空肠弯曲菌中mfd的缺失显著降低了在含氟喹诺酮的培养基或鸡中耐氟喹诺酮弯曲菌的产生。这些发现表明，Mfd对弯曲菌中氟喹诺酮耐药性的产生很重要，揭示了Mfd在促进突变频率方面以前未被认识的功能，并确定了一个减少耐氟喹诺酮弯曲菌出现的潜在分子靶点。
