Subpopulations of Helicobacter pylori Are Responsible for Discrepancies in the Outcome of Nitroimidazole Susceptibility Testing

Metronidazole susceptibility testing by E test was compared to that by disk diffusion for 263 Helicobacter pylori isolates and to that by breakpoint agar dilution for 90 H. pylori isolates. In 5% and 6% of the cases, respectively, results were discrepant. For each of 52 clinical isolates an E test was performed on 10 separate colonies. Subpopulations of resistant and susceptible bacteria were found in five cases. From three isolates, each colony was subcultured and tested up to 10 times. All but 1 of 292 tests showed the same result. We conclude that the E test is reliable and that subpopulations are responsible for discordant results.

本研究针对263株幽门螺杆菌（Helicobacter pylori）分离株，采用E试验（E test）开展甲硝唑药敏检测，并将其结果与纸片扩散法（disk diffusion）的检测结果进行对比；同时针对90株幽门螺杆菌分离株，将E试验的检测结果与断点琼脂稀释法（breakpoint agar dilution）的检测结果进行比对。针对263株分离株的配对检测中，结果不一致率为5%；针对90株分离株的配对检测中，结果不一致率为6%。针对52株临床分离株，分别对其10个独立菌落实施E试验检测。本研究在5份样本中检出了耐药与易感细菌亚群。针对3株分离株，对其每个菌落进行传代培养并开展至多10次重复检测，292项检测中仅1项结果存在差异。综上，本研究证实E试验具备良好的可靠性，细菌亚群是导致检测结果不一致的核心原因。