Objective Severe drug resistances to the first line antibiaotics used in eradication therapy have been observed in clinical isolates of Helicobacter pylori in China. The study conducted a multi-center drug susceptibility testing for minocycline, a second-generation semi-synthetic tetracycline, in clinical isolates of H. pylori, and set the epidemiological cutoff value （ECOFF） to provide scientific evidence for the selection of antibiotics for H. pylori eradication and the development of H. pylori infection prevention and control strategies.

Methods A total of 131 clinical isolates of H. pylori were obtained from Hubei, Yunnan, and Shaanxi provinces, representing the central, southwestern and northwestern regions of China. The minimum inhibitory concentration （MIC） range of minocycline to H. pylori was detected by using the standardized agar dilution method, and the ECOFF was calculated.

Results The MIC range of minocycline for the 131 clinical isolates included in the study was ≤ 0.03 mg/L to 2 mg/L. No statistically significant differences were observed in MIC distributions among isolates from different provinces (P=0.330). Based on a combined analysis using visual (eyeball) method and the ECOFFinder software, an MIC value of 0.5 mg/L is proposed as the ECOFF to differentiate wild type from non-wild type H. pylori isolates.

Conclusion H. pylori is generally sensitive to minocycline.in China. The ECOFF value of minocycline is low, and the use of minocycline in clinical eradication therapy is expected to have good effect.