Stability of ß -lactam antibiotics in bacterial growth media
Stability of ß -lactam antibiotics in bacterial growth media
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β-内酰胺类抗生素在细菌生长培养基中的稳定性
DOI：
10.1101/2020.04.15.044123
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Brouwers R
中科院分区：
文献类型：
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作者：
Brouwers R
MIC试验等实验室测定假定抗生素分子在所选生长培养基中是稳定的，但在某些条件下，在水溶液中观察到抗生素（包括β-内酰胺）的快速降解。在细菌生长培养基中的降解速率鲜为人知。在这里，我们开发了一种“延迟时间生物测定法”，提供了一种简单的方法来估计细菌生长培养基中的抗生素稳定性，仅使用酶标仪，而不需要直接测量抗生素浓度。我们使用生物测定法测量β-内酰胺类抗生素美西林、氨曲南和头孢噻肟在基于MOPS和Luria-Bertani（LB）肉汤的广泛使用的细菌生长培养基中的降解半衰期。我们发现美西林降解可以迅速发生，在37°C和pH 7.4的MOPS培养基中半衰期短至2小时，在LB中为4-5小时，但是调节pH和温度可以将其稳定性增加至约6小时的半衰期，而不会过度干扰生长。发现氨曲南和头孢噻肟在37°C和pH 7.4的MOPS培养基中的半衰期长于6小时，但仍短于典型的最小抑制浓度（MIC）测定的时间尺度。综上所述，我们的结果表明，在解释β-内酰胺抗生素的MIC试验和其他实验室生长试验时需要小心，因为在试验期间抗生素可能会发生显著降解。
Laboratory assays such as MIC tests assume that antibiotic molecules are stable in the chosen growth medium—but rapid degradation has been observed for antibiotics includingβ-lactams under some conditions in aqueous solution. Degradation rates in bacterial growth medium are less well known. Here, we develop a ‘delay time bioassay’ that provides a simple way to estimate antibiotic stability in bacterial growth media, using only a plate reader and without the need to measure the antibiotic concentration directly. We use the bioassay to measure degradation half-lives of theβ-lactam antibiotics mecillinam, aztreonam and cefotaxime in widely-used bacterial growth media based on MOPS and Luria-Bertani (LB) broth. We find that mecillinam degradation can occur rapidly, with a half-life as short as 2 hours in MOPS medium at 37°C and pH 7.4, and 4-5 hours in LB, but that adjusting the pH and temperature can increase its stability to a half-life around 6 hours without excessively perturbing growth. Aztreonam and cefotaxime were found to have half-lives longer than 6 hours in MOPS medium at 37°C and pH 7.4, but still shorter than the timescale of a typical minimum inhibitory concentration (MIC) assay. Taken together, our results suggest that care is needed in interpreting MIC tests and other laboratory growth assays forβ-lactam antibiotics, since there may be significant degradation of the antibiotic during the assay.