Doxycycline is regarded as an effective therapy for early syphilis, and there is increasing interest in using doxycycline for prophylaxis of this infection. However, the MIC of doxycycline for Treponema pallidum subsp. pallidum has not been reported previously. In this study, an in vitro culture system was utilized to determine that the MIC of doxycycline is 0.06 to 0.10 μg/ml for four strains of T. pallidum subsp. pallidum (Nichols, SS14, UW231B, and UW249B). The Nichols strain cultured in vitro with doxycycline was also tested for infectivity in rabbits, and the minimum bactericidal concentration (MBC) was found to be ≤0.1 μg/ml using this method. The low MIC and MBC values are consistent with the previously demonstrated clinical efficacy of doxycycline for the treatment of early syphilis. This study represents the first report of the in vitro susceptibility of T. pallidum to doxycycline, and the resulting information may be useful in the consideration of doxycycline for use in prevention of syphilis.

中文翻译：

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梅毒螺旋体亚种的体外敏感性。苍白球变强力霉素。


强力霉素被认为是治疗早期梅毒的有效疗法，并且人们对使用强力霉素预防这种感染越来越感兴趣。然而，强力霉素对梅毒螺旋体亚种的 MIC。此前未见苍白球的报道。本研究利用体外培养系统测定强力霉素对四种梅毒螺旋体亚种菌株的 MIC 为 0.06 至 0.10 μg/ml。苍白球（Nichols、SS14、UW231B 和 UW249B）。还用多西环素体外培养的Nichols菌株对家兔进行了感染性测试，使用该方法发现最低杀菌浓度（MBC）≤0.1μg/ml。低 MIC 和 MBC 值与先前证明的多西环素治疗早期梅毒的临床疗效一致。这项研究首次报告了梅毒螺旋体对多西环素的体外敏感性，所得信息可能有助于考虑将多西环素用于预防梅毒。