Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA, USA.
Pathobiology Graduate Program, Brown University, Providence, RI, USA.
J Antimicrob Chemother. 2024 Nov 4;79(11):2867-2876. doi: 10.1093/jac/dkae299.
Burkholderia cepacia complex (Bcc) is a collection of intrinsically drug-resistant Gram-negative bacteria that cause life-threatening disease in people with cystic fibrosis (CF). Standard antimicrobial susceptibility testing methods have poor predictive value for clinical outcomes in Bcc infections, probably due in part to differences between in vitro testing conditions and the environment in which Bcc grow in the lungs of people with CF.
To compare the activity of commonly used antibiotics under standard in vitro testing conditions with activity in conditions mimicking those found in vivo.
Two Bcc strains were grown alone and with six different antibiotics (minocycline, ceftazidime, meropenem, tobramycin, levofloxacin, trimethoprim-sulfamethoxazole) in two different media: standard cation-adjusted Mueller-Hinton broth and an artificial sputum medium designed to simulate the environment in the lungs of people with CF through addition of components including mucin, free DNA and amino acids. Two different starting conditions were used for time-kill assays: a standard ∼5 × 106 cfu/mL inoculum, and a high-density inoculum in which bacteria were grown for 72 hours before addition of antibiotics. Growth detection was performed by colony enumeration and by detection of resazurin reduction.
There were major discrepancies between standard susceptibility results and activity in our models. Some antibiotics, including ceftazidime, showed minimal activity in all time-kill assays despite low minimal inhibitory concentrations, while others, notably tobramycin, were more active in high-density growth conditions than in standard time-kill assays.
This work underscores the urgent need to develop more clinically relevant susceptibility testing approaches for Bcc.
洋葱伯克霍尔德菌复合群（Bcc）是一组固有耐药的革兰氏阴性细菌，可导致囊性纤维化（CF）患者发生危及生命的疾病。Bcc 感染的标准抗菌药物敏感性测试方法对临床结果的预测价值较差，这可能部分归因于体外测试条件与 Bcc 在 CF 患者肺部生长环境之间的差异。
比较标准体外测试条件下常用抗生素的活性与模拟体内条件下的活性。
单独培养两种 Bcc 菌株，并在两种不同的培养基中与六种不同的抗生素（米诺环素、头孢他啶、美罗培南、妥布霉素、左氧氟沙星、复方磺胺甲噁唑）共培养：标准阳离子调整 Mueller-Hinton 肉汤和人工痰液培养基，该培养基通过添加包括粘蛋白、游离 DNA 和氨基酸在内的成分来模拟 CF 患者肺部的环境。使用两种不同的起始条件进行时间杀伤测定：标准的约 5×106cfu/mL 接种物和高浓度接种物，在添加抗生素之前，细菌在高浓度接种物中培养 72 小时。通过菌落计数和还原-resazurin 检测来进行生长检测。
标准药敏结果与我们模型中的活性之间存在很大差异。一些抗生素，包括头孢他啶，尽管最低抑菌浓度较低，但在所有时间杀伤测定中活性都很低，而其他抗生素，特别是妥布霉素，在高密度生长条件下比标准时间杀伤测定更活跃。
这项工作强调了迫切需要为 Bcc 开发更具临床相关性的药敏测试方法。
