Objectives

This study aimed to explore the interactions of polymyxin B in combination with 13 other antibiotics against carbapenemase-producing Klebsiella pneumoniae.

Methods

Five clinical isolates of multidrug-resistant K. pneumoniae producing KPC-2, KPC-3, NDM-1, OXA-48 and VIM-1 carbapenemases were used. Polymyxin B was tested alone and in combination with amikacin, aztreonam, cefepime, chloramphenicol, ciprofloxacin, fosfomycin, linezolid, meropenem, minocycline, rifampicin, temocillin, thiamphenicol and trimethoprim. Inhibition of growth during antibiotic exposure was evaluated in 24-hr automated time-lapse microscopy experiments. Combinations that showed positive interactions were subsequently evaluated in static time-kill experiments.

Results

All strains carried multiple (≥9) resistance genes as determined by whole-genome sequencing. In the initial screening the combination of polymyxin B and minocycline was most active with enhanced activity compared with the single antibiotics detected against all strains. Positive interactions were also observed with polymyxin B in combination with rifampicin and fosfomycin against four of five strains and less frequently with other antibiotics. Time-kill experiments demonstrated an additive or synergistic activity (1–2 log₁₀ or ≥2 log₁₀ CFU/mL reduction, respectively, compared with the most potent single antibiotic) with 21 of 23 tested combinations. However, because of regrowth, only 13 combinations were synergistic at 24 hr. Combinations with minocycline or rifampicin were most active, each showing synergy and bacteriostatic or bactericidal effects resulting in 1.93–3.97 and 2.55–5.91 log₁₀ CFU/mL reductions, respectively, after 24 hr against four strains.

Discussion

Polymyxin B in combination with minocycline, rifampicin or fosfomycin could be of potential clinical interest. Time-lapse microscopy showed some discrepancy in results compared with the time-kill data but was useful for screening purposes.

中文翻译：

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在延时显微镜和时间杀灭实验中，评估多粘菌素B与其他13种抗生素的结合，以对抗产生碳青霉烯酶的肺炎克雷伯菌。

目标

这项研究旨在探讨多粘菌素B与其他13种抗生素的结合对产生碳青霉烯酶的肺炎克雷伯菌的相互作用。

方法

使用了五个临床分离株，它们分别产生KPC-2，KPC-3，NDM-1，OXA-48和VIM-1碳青霉烯酶多重耐药肺炎克雷伯菌。多粘菌素B单独或与阿米卡星，氨曲南，头孢吡肟，氯霉素，环丙沙星，磷霉素，利奈唑胺，美洛培南，米诺环素，利福平，替莫西林，甲砜霉素和甲氧苄氨嘧啶联用进行测试。在24小时自动延时显微镜实验中评估了抗生素暴露期间的生长抑制。随后在静态时间杀灭实验中评估了显示出积极相互作用的组合。

结果

通过全基因组测序确定，所有菌株均携带多个（≥9）抗性基因。在最初的筛选中，与针对所有菌株检测到的单一抗生素相比，多粘菌素B和米诺环素的组合活性最高，活性增强。还观察到多粘菌素B联合利福平和磷霉素对五种菌株中的四种有积极的相互作用，而与其他抗生素的相互作用较少。时间杀灭实验显示出加性或协同活性（1-2 log ₁₀或≥2log ₁₀ 与23种测试组合中的21种相比，与最有效的单一抗生素相比，CFU / mL降低了。但是，由于再生长，在24小时内只有13种组合具有协同作用。与米诺环素或利福平的组合最有效，每种都表现出协同作用和抑菌或杀菌作用 ，分别对四种菌株在24小时后分别降低1.93–3.97和2.55–5.91 log ₁₀ CFU / mL。

讨论区

多粘菌素B与米诺环素，利福平或磷霉素合用可能具有潜在的临床意义。延时显微镜显示的结果与时间杀灭数据相比有一些差异，但对于筛选目的很有用。