Marton A, Major P
Heim Pál Children's Hospital, Budapest, Hungary.
Microb Drug Resist. 1996 Fall;2(3):361-9. doi: 10.1089/mdr.1996.2.361.
Minimum inhibitory concentrations (MICs) of a total of 68 Streptococcus (S.) pneumoniae strains (21 susceptible, 23 intermediate, and 24 resistant to penicillin) were tested for 9 beta-lactam antibiotics such as penicillin, cefpirome, cefotaxime, ceftriaxone, cefuroxime, ceftazidime, cefpodoxime, cefodizime, and amoxycillin. MICs to penicillin, cefotaxime, cefpirome, and ceftriaxone were also tested on Muller-Hinton blood agar supplemented with 50% human serum. Killing kinetics of 0.5, 2, and 4 times the MIC of cefpirome and cefotaxime and synergistic bactericidal activity of combinations of cephalosporins with vancomycin or gentamicin were investigated. The synergism studies were conducted with drug concentrations half of the MICs. On the basis of MIC50 values cefpirome, cefotaxime, ceftriaxone, and cefpodoxime were 8, 4, 2, and 2 times more active than penicillin, while on the basis of MIC90 values they were 8, 8, 4, and 2 times superior to penicillin for the penicillin-resistant S. pneumoniae. Cefuroxime, cefodizime, and amoxycillin showed an identical or a 2-fold higher MIC50 or MIC90 than penicillin for the same group of isolates. Ceftazidime showed the lowest activity against S. pneumoniae. MIC50 and MIC90 values for ceftriaxone increased 4-fold when human serum was added to the test medium. Cefpirome was the only drug with MIC50 for the penicillin-resistant S. pneumoniae below the new resistance breakpoint of the NCCLS (> or = 2 mg/liter), while these values for cefotaxime and ceftriaxone were identical to or 2-fold higher than the resistance breakpoint. The MIC50 and MIC90 of the other drugs tested exceeded the breakpoint 2 to 16 times. The combination of vancomycin with cefpirome or cefotaxime showed a higher killing activity to two penicillin-resistant strains tested than 2- and 4-fold concentrations of the MICs of the two cephalosporins alone.
对总共68株肺炎链球菌（21株对青霉素敏感、23株中介、24株对青霉素耐药）进行了9种β-内酰胺类抗生素（如青霉素、头孢匹罗、头孢噻肟、头孢曲松、头孢呋辛、头孢他啶、头孢泊肟、头孢地嗪和阿莫西林）的最低抑菌浓度（MIC）测试。还在补充有50%人血清的Muller-Hinton血琼脂上测试了对青霉素、头孢噻肟、头孢匹罗和头孢曲松的MIC。研究了头孢匹罗和头孢噻肟的0.5、2和4倍MIC的杀菌动力学以及头孢菌素与万古霉素或庆大霉素联合用药的协同杀菌活性。协同作用研究采用MIC一半的药物浓度进行。基于MIC50值，头孢匹罗、头孢噻肟、头孢曲松和头孢泊肟对青霉素的活性分别高8倍、4倍、2倍和2倍，而基于MIC90值，对于耐青霉素的肺炎链球菌，它们比青霉素分别高8倍、8倍、4倍和2倍。对于同一组分离株，头孢呋辛、头孢地嗪和阿莫西林的MIC50或MIC90与青霉素相同或高2倍。头孢他啶对肺炎链球菌的活性最低。当在测试培养基中添加人血清时，头孢曲松的MIC50和MIC90值增加了4倍。头孢匹罗是唯一一种对耐青霉素肺炎链球菌的MIC50低于NCCLS新的耐药界点（≥2mg/L）的药物，而头孢噻肟和头孢曲松的这些值与耐药界点相同或高2倍。所测试的其他药物的MIC50和MIC90超过界点2至16倍。万古霉素与头孢匹罗或头孢噻肟联合用药对所测试的两株耐青霉素菌株的杀菌活性高于单独使用两种头孢菌素的2倍和4倍MIC浓度。
