奥马环素对脓肿分枝杆菌体外抑菌及细胞内杀菌活性

In vitro inhibitory and intracellular bactericidal activity of omadacycline against Mycobacterium abscessus

目的:研究奥马环素对脓肿分枝杆菌的体外抑菌和细胞内杀菌活性,为探索治疗脓肿分枝杆菌病更优的药物组合提供数据支撑。方法:选取分离自2015—2016年首都医科大学附属北京胸科医院就诊患者的58株脓肿分枝杆菌临床分离株及保存于北京结核病临床数据与样本资源库(北京胸科医院)的脓肿分枝杆菌标准菌株(ATCC 199777)作为研究菌株。采用微孔板法测定奥马环素对脓肿分枝杆菌标准株的最低抑菌浓度(minimal inhibitory concentration,MIC)和最小杀菌浓度(minimal bactericidal concentration,MBC),以及对58株临床分离株的MIC_(90)。采用棋盘法测定奥马环素与常用抗脓肿分枝杆菌药物两药联合对脓肿分枝杆菌标准株的抑菌效果;采用胞内杀菌法测定不同两药组合对胞内菌的杀伤能力。结果:奥马环素对脓肿分枝杆菌标准株的MIC为0.5μg/ml,MBC为4μg/ml;奥马环素对58株脓肿分枝杆菌临床分离株的MIC_(90)为0.5μg/ml。奥马环素与克拉霉素、利奈唑胺、贝达喹啉联用有协同作用,其分数抑制浓度指数分别为0.250、0.375和0.375;与氯法齐明、阿奇霉素、利福布汀联用有加和作用,其分数抑制浓度指数分别为0.750、0.625和0.560。奥马环素与贝达喹啉联合后MBC变化最显著,由4μg/ml下降至0.05μg/ml,比单药作用下降98.75%。对胞内细菌的杀灭作用显示,在24 h时,奥马环素联用阿奇霉素对于胞内菌的杀菌作用最明显,胞内菌量从(7.02±0.06)log_(10)CFU下降至(5.36±0.10)log_(10)CFU,差异有统计学意义(t=3.241,P<0.001);在48 h时,奥马环素联用氯法齐明胞内菌量从(7.36±0.10)log_(10)CFU下降至(5.33±0.35)log_(10)CFU,差异有统计学意义(t=8.265,P=0.004);联用亚胺培南胞内菌量从(6.87±0.15)log_(10)CFU下降至(5.10±0.17)log_(10)CFU,差异有统计学意义(t=13.190,P<0.001);联用利奈唑胺胞内菌量从(6.95±0.05)log_(10)CFU下降至(5.26±0.24)log_(10)CFU,差异有统计学意义(t=11.920,P=0.005);联用利福布汀胞内菌量从(6.98±0.07)log_(10)CFU下降至(5.65±0.16)log_(10)CFU,差异有统计学意义(t=13.440,P=0.001)。结论:奥马环素联合其他药物对脓肿分枝杆菌具有抑制作用和杀菌作用,具有治疗脓肿分枝杆菌病的潜力。

Objective:To evaluate the antimicrobial and bactericidal activities of omadacycline against Mycobacterium abscessus(MAB)and provide insights into optimizing drug combinations for the treatment of MAB infections.Methods:A total of 58 clinical isolates of MAB,obtained from patients at the Beijing Chest Hospital between 2015 and 2016,as well as a reference strain(ATCC 19977),were included in this study.The minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of omadacycline against the reference strain were measured using microdilution,alongside determining the MIC_(90)for the clinical isolates.The checkerboard assay was employed to evaluate the effects of drug combinations on the reference strain,while intracellular bactericidal activity was assessed to measure the drugs’efficacy against intracellular bacteria.Results:Omadacycline demonstrated MIC of 0.5μg/ml and MBC of 4μg/ml against the reference strain,with MIC_(90)of 0.5μg/ml for the clinical isolates.Synergistic effects were observed when omadacycline was combined with clarithromycin,linezolid,and bedaquiline,with fractional inhibitory concentration indices(FICIs)of 0.250,0.375,and 0.375,respectively.Additive effects were noted when combined with clofazimine,azithromycin,and rifabutin,with FICIs of 0.750,0.625 and 0.560.The combination of omadacycline and bedaquiline produced the most substantial reduction in MBC,decreasing from 4μg/ml to 0.05μg/ml,representing a 98.75%reduction compared to omadacycline monotherapy.For intracellular bacteria,the combination of omadacycline and azithromycin demonstrated the most pronounced bactericidal effect at 24 hours,reducing the bacterial count from(7.02±0.06)log_(10)CFU to(5.36±0.10)log_(10)CFU(t=3.241,P<0.001).At 48 hours,the combination of omadacycline and clofazimine reduced the intracellular bacterial load from(7.36±0.10)log_(10)CFU to(5.33±0.35)log_(10)CFU(t=8.265,P=0.004).Similarly,the combination of omadacycline and imipenem resulted in a reduction of intracellular bacteria from(6.87±0.15)log_(10)CFU to(5.10±0.17)log_(10)CFU(t=13.190,P<0.001).The combination of omadacycline and linezolid reduced the intracellular bacterial count from(6.95±0.05)log_(10)CFU to(5.26±0.24)log_(10)CFU(t=11.920,P=0.005).Similarly,the combination of omadacycline and rifabutin lowered the intracellular bacterial load from(6.98±0.07)log_(10)CFU to(5.65±0.16)log_(10)CFU(t=13.440,P=0.001).Conclusion:Omadacycline combined with other drugs demonstrates significant inhibitory and bactericidal activity against MAB.These findings suggest that omadacycline holds promise as a therapeutic option for treating MAB infections.