庆大霉素血浓度微生物测定法的改进

A MODIFIED AGAR WELL DIFFUSION TECHNIQUE FOR DETERMINATION OF SERUM GENTAMICIN CONCENTRATION

以短小芽胞杆菌为检测菌,以生理盐水配制庆大霉素标准液,用校正抑菌圈直径计算血清庆大霉素浓度。结果表明:庆大霉素的MIC为0.5μg/ml,在1～16μg/ml内,抑菌圈直径与血药浓度对数呈线性相关。平均回收率为103％,但β-内酰胺类MIC均在100μg/ml以上。本法简便,不用血清配标标准液,不必应用β-内酰胺酶,结果准确,可满足临床监测庆大霉素血药浓度要求。

A modified agar well diffusion technique for serum gentamicin level assay, using Bacillus pumillus 63202 as indicator strain and using normal saline solution containing standard concentration of gentamicin instead of serum, is described. The experimental results indicated that the zone diameters of microbial growth inhibitions induced by gentamicin with standard levels in normal saline solution were correlated linearly with those in serum, the flope of the regression line was close to 1 (r = 0.99); In the concentration range of gentamicin 1-16 μg/ml, the corrected zone diameters after incubation at 37℃ for 6 hr were correlated linearly with logarithmic concentration of gentamicin (r = 0.99); The MIC of gentamicin was 0.5μg/ml, alternatively the MICs of β-lacctarns, including ampici-11in, oxacillin, carbenicillin, penicillin, cephazolin and cephoranide, were all exceeded 100 μg/ml. Therefore, this assay saving β-lactamase was not affected when gentamicin was combined with β-lactams, and this was a simple, inexpensive and reliable technique acceptable for routine clinical use.