Löwdin E, Odenholt-Tornqvist I, Bengtsson S, Cars O
Department of Infectious Diseases, University Hospital, Uppsala, Sweden.
Antimicrob Agents Chemother. 1993 Oct;37(10):2200-5. doi: 10.1128/AAC.37.10.2200.
It has been shown that bacteria in a postantibiotic (PA) phase exposed to subinhibitory concentrations (sub-MICs) of antibiotics show a long delay before regrowth. This effect has been named the PA sub-MIC effect (PA SME). In the present study, we have used a new method to demonstrate this phenomenon. A computerized incubator for bacteria, Bioscreen C (Lab Systems, Helsinki, Finland), which incubates the bacteria, measures growth continuously by vertical photometry, processes the data, and provides a printout of the results was used. With this method, one may easily test several antibiotics against different bacteria for PA effects (PAEs), PA SMEs, and SMEs. In this study, the effects of benzylpenicillin against beta-hemolytic streptococci and pneumococci were examined. The bacteria were exposed to 2, 10, or 50x MIC for 2 h, washed and diluted, incubated in the Bioscreen C incubator, and then exposed to 0.1 to 0.9x MIC. The regrowth was monitored for 20 h. The PAE was calculated as the difference in the time required for the exposed and unexposed bacteria to grow to a defined point (A50) on the absorbance curve. A50 was defined as 50% of the maximum absorbance for the control cultures. The PA SMEs were calculated as the difference in the time required for the reexposed cultures and the unexposed controls to reach A50. The PAEs ranged between 0.6 and 3.2 h and varied little with the concentration used for the induction of the PAEs. At 0.2x MIC, the PA SMEs were 2 to 3 h longer than the PAEs. Higher sub-MICs increased this delay before regrowth. Most cultures exposed to sub-MICs alone were only slightly affected compared with the controls.
已表明，处于抗生素后（PA）期的细菌在暴露于亚抑制浓度（亚 MIC）的抗生素后，再生长前会出现长时间延迟。这种效应被命名为 PA 亚 MIC 效应（PA SME）。在本研究中，我们使用了一种新方法来证明这一现象。使用了一种用于细菌的计算机化培养箱，即 Bioscreen C（芬兰赫尔辛基的 Lab Systems 公司），它培养细菌，通过垂直光度法连续测量生长情况，处理数据，并提供结果打印输出。通过这种方法，可以轻松地针对不同细菌测试几种抗生素的 PA 效应（PAE）、PA SME 和 SME。在本研究中，检测了苄青霉素对β溶血性链球菌和肺炎球菌的影响。将细菌暴露于 ２、10 或 50 倍 MIC 浓度下 2 小时，洗涤并稀释，在 Bioscreen C 培养箱中培养，然后暴露于 0.1 至 0.9 倍 MIC 浓度下。监测再生长情况 20 小时。PAE 计算为暴露和未暴露细菌生长至吸光度曲线上定义点（A50）所需时间的差值。A50 定义为对照培养物最大吸光度的 50％。PA SME 计算为再次暴露培养物和未暴露对照达到 A50 所需时间的差值。PAE 范围在 0.6 至 3.2 小时之间，并且随用于诱导 PAE 的浓度变化不大。在 0.2 倍 MIC 时，PA SME 比 PAE 长 2 至 3 小时。更高的亚 MIC 浓度增加了再生长前的这种延迟。与对照相比，大多数仅暴露于亚 MIC 浓度的培养物仅受到轻微影响。
