Powley L, Meeson J, Greenwood D
Department of Microbiology, University Hospital, Queen's Medical Centre, Nottingham.
J Clin Pathol. 1989 Jan;42(1):77-80. doi: 10.1136/jcp.42.1.77.
Tolerance to penicillin was investigated in 40 isolates of optochin-resistant, alpha-haemolytic streptococci. Thirteen strains exhibited tolerance to penicillin (MBC:MIC ratio greater than or equal to 32) when stationary phase inocula were used, but only seven strains retained the tolerance phenotype in experiments with logarithmic phase inocula. There was a striking association between tolerance and Eagle's optimum dosage effect, particularly among strains that displayed tolerance in both the stationary and the logarithmic growth phases. Sequential viable counts on representative strains showed that reliance on the arbitrary criterion of bactericidal activity of 99.9% reduction of the original inoculum after 24 hours' exposure may occasionally lead to difficulties in the recognition of penicillin tolerance. In general, however, the 99.9% killing criterion provided a useful discriminator between strains that were rapidly killed by penicillin and those (tolerant strains) in which the bactericidal activity was much reduced.
对40株对奥普托欣耐药的α溶血性链球菌进行了青霉素耐受性研究。当使用稳定期接种物时，13株菌株表现出对青霉素的耐受性（MBC:MIC比值大于或等于32），但在对数期接种物实验中，只有7株菌株保留了耐受性表型。耐受性与伊格尔最佳剂量效应之间存在显著关联，特别是在稳定期和对数生长期均表现出耐受性的菌株中。对代表性菌株的连续活菌计数表明，依赖于暴露24小时后原始接种物减少99.9%的杀菌活性这一任意标准，偶尔可能会导致识别青霉素耐受性出现困难。然而，一般来说，99.9%的杀菌标准为快速被青霉素杀死的菌株与杀菌活性大大降低的菌株（耐受菌株）之间提供了一个有用的区分标准。
