Orefici G, Scopetti F
Laboratory of Medical Bacteriology and Mycology, Istituto Superiore di Sanità, Rome, Italy.
Boll Ist Sieroter Milan. 1988;67(2):97-104.
The possible in vitro synergistic effect between amikacin and cefoxitin against 29 clinical isolates of M.fortuitum was studied either by the agar dilution checkerboard technique and by the killing curve on Mueller Hinton agar plus OADC enrichment and on 7H11. As evaluated by FIC index on MHA a synergistic effect was noted on 20 (68.96%) strains tested, an additive effect on 8 (27.60%) isolates, and a possible antagonistic effect only on 1 (3.44%) isolate. On 7H11 a synergistic effect was shown on 10 (38.50%) isolates, an additive effect on 12 (46.10%) and an antagonistic effect on 4 (15.40%) isolates. The killing curve observed on three strains (562, 565 and 505), specially selected as representative of synergistic (562), additive (565) and antagonistic effect (505) on the basis of their checkerboard results, showed synergistic effect on strains 562 and 565 as well as on strain 505 where complete killing was obtained in 24 h by a combination of two antibiotics used at 1/2 Mic. By the killing curve technique both antibiotics were found to be bactericidal but the effect was earlier for amikacin than for cefoxitin.
采用琼脂稀释棋盘法以及在添加了油酸白蛋白富集物的穆勒-欣顿琼脂和7H11培养基上绘制杀菌曲线的方法，研究了阿米卡星和头孢西丁对29株偶然分枝杆菌临床分离株的体外协同作用。根据在MHA上的FIC指数评估，在测试的20株（68.96%）菌株上观察到协同作用，在8株（27.60%）分离株上观察到相加作用，仅在1株（3.44%）分离株上观察到可能的拮抗作用。在7H11培养基上，10株（38.50%）分离株表现出协同作用，12株（46.10%）表现出相加作用，4株（15.40%）表现出拮抗作用。根据棋盘试验结果，特别挑选了三株菌株（562、565和505）分别代表协同作用（562）、相加作用（565）和拮抗作用（505），对其绘制的杀菌曲线显示，在菌株562和565以及菌株505上均表现出协同作用，在菌株505上，两种抗生素以1/2 MIC联合使用时，在24小时内实现了完全杀菌。通过杀菌曲线技术发现两种抗生素均具有杀菌作用，但阿米卡星的杀菌效果比头孢西丁更早出现。
