Qureshi Nadia N, Gallaher Brandon, Schiller Neal L
Division of Biomedical Sciences, School of Medicine, University of California , Riverside, Riverside, California.
Microb Drug Resist. 2014 Dec;20(6):509-16. doi: 10.1089/mdr.2014.0019.
Helicobacter pylori is the major cause of peptic ulcers and gastric cancer in humans. Treatment involves a two or three drug cocktail, typically including amoxicillin. Increasing levels of resistance to amoxicillin contribute to treatment failures, and higher levels of resistance are believed to be due to multiple genetic mutations. In this study, we examined the progression of spontaneous genetic mutations that contribute to amoxicillin resistance in H. pylori when exposed to increasing concentrations of amoxicillin in vitro. During the selection process, we isolated five strains each of which had progressively higher levels of resistance. Using a whole genome sequencing approach, we identified mutations in a number of genes, notably pbp1, pbp2, hefC, hopC, and hofH, and by sequencing these genes in each isolate we were able to map the order and gradual accumulation of mutations in these isolates. These five isolates, each expressing multiple mutated genes and four transformed strains expressing individually mutated pbp1, hefC, or hofH, were characterized using minimum inhibitory concentrations, amoxicillin uptake, and efflux studies. Our results indicate that mutations in pbp1, hefC, hopC, hofH, and possibly pbp2 contribute to H. pylori high-level amoxicillin resistance. The data also provide evidence for the complexity of the evolution of amoxicillin resistance in H. pylori and indicate that certain families of genes might be more susceptible to amoxicillin resistance mutations than others.
幽门螺杆菌是人类消化性溃疡和胃癌的主要病因。治疗通常采用两药或三药联合方案，其中一般包括阿莫西林。对阿莫西林耐药性的不断增加导致治疗失败，而更高水平的耐药性被认为是由于多种基因突变所致。在本研究中，我们检测了体外暴露于浓度不断增加的阿莫西林时，幽门螺杆菌中导致阿莫西林耐药性的自发基因突变的进展情况。在筛选过程中，我们分离出了五株耐药水平逐渐升高的菌株。采用全基因组测序方法，我们在多个基因中鉴定出了突变，特别是pbp1、pbp2、hefC、hopC和hofH基因，通过对每个分离株中的这些基因进行测序，我们能够确定这些分离株中突变的顺序和逐渐积累情况。使用最低抑菌浓度、阿莫西林摄取和外排研究对这五株分别表达多个突变基因的分离株以及四株分别表达单个突变的pbp1、hefC或hofH基因的转化菌株进行了表征。我们的结果表明，pbp1、hefC、hopC、hofH以及可能的pbp2基因中的突变导致了幽门螺杆菌对阿莫西林的高水平耐药。这些数据也为幽门螺杆菌阿莫西林耐药性进化的复杂性提供了证据，并表明某些基因家族可能比其他基因家族更容易发生阿莫西林耐药性突变。
