Visalli M A, Jacobs M R, Moore T D, Renzi F A, Appelbaum P C
Department of Pathology (Clinical Microbiology), Hershey Medical Center, Pennsylvania 17033, USA.
Antimicrob Agents Chemother. 1997 Apr;41(4):767-70. doi: 10.1128/AAC.41.4.767.
The agar dilution MIC method was used to test activities of ticarcillin, ticarcillin-clavulanate, amoxicillin, amoxicillin-clavulanate, ampicillin, ampicillin-sulbactam, piperacillin, piperacillin-tazobactam, inhibitors alone, ceftazidime, and imipenem against 237 Acinetobacter genospecies. A total of 93.2% of strains were beta-lactamase positive by the chromogenic cephalosporin method. Overall, ampicillin-sulbactam was the most active combination against all strains (MIC at which 50% of the isolates are inhibited [MIC50] and MIC90, 4.0 and 32.0 microg/ml; 86.9% susceptible at < or = 16 microg/ml), followed by ticarcillin-clavulanate (16.0 and 128.0 microg/ml; 85.7% susceptible at < or = 64 microg/ml), piperacillin-tazobactam (16.0 and 128.0 microg/ml; 84.8% susceptible at < or = 64 microg/ml), and amoxicillin-clavulanate (16.0 and 64.0 microg/ml; 54.4% susceptible at < or =16 microg/ml). Ceftazidime and imipenem yielded MIC50s and MIC90s of 8.0 and 64.0 microg/ml (ceftazidime) and 0.5 and 1.0 microg/ml (imipenem), respectively; 71.3% of strains were susceptible to ceftazidime at < or = 16 microg/ml, and 99.2% were susceptible to imipenem at < or = 8 microg/ml. Sulbactam was the most active beta-lactamase inhibitor alone (MIC50 and MIC90, 2.0 and 16.0 microg/ml); clavulanate and tazobactam were less active (16.0 and 32.0 microg/ml for both compounds). Enhancement of beta-lactams by beta-lactamase inhibitors was not always seen in beta-lactamase-positive strains, and activity of combinations such as ampicillin-sulbactam was due to the inhibitor alone. Acinetobacter baumannii was the most resistant genospecies. By contrast, Acinetobacter haemolyticus, Acinetobacter calcoaceticus, Acinetobacter johnsonii, Acinetobacter junii, Acinetobacter radioresistens, and other non-Acinetobacter baumannii strains were more susceptible to all compounds tested. E-test MICs were within 1 dilution of agar dilution MICs in 38.4 to 89.6% of cases and within 2 dilutions in 61.6 to 98.6% of cases.
采用琼脂稀释法测定替卡西林、替卡西林-克拉维酸、阿莫西林、阿莫西林-克拉维酸、氨苄西林、氨苄西林-舒巴坦、哌拉西林、哌拉西林-他唑巴坦、单独的抑制剂、头孢他啶和亚胺培南对237株不动杆菌属菌种的活性。采用显色头孢菌素法检测，共有93.2%的菌株β-内酰胺酶呈阳性。总体而言，氨苄西林-舒巴坦对所有菌株的活性最强（50%的分离株被抑制时的最低抑菌浓度[MIC50]和MIC90分别为4.0和32.0μg/ml；在≤16μg/ml时86.9%的菌株敏感），其次是替卡西林-克拉维酸（16.0和128.0μg/ml；在≤64μg/ml时85.7%的菌株敏感）、哌拉西林-他唑巴坦（16.0和128.0μg/ml；在≤64μg/ml时84.8%的菌株敏感）以及阿莫西林-克拉维酸（16.0和64.0μg/ml；在≤16μg/ml时54.4%的菌株敏感）。头孢他啶和亚胺培南的MIC50和MIC90分别为8.0和64.0μg/ml（头孢他啶）以及0.5和1.0μg/ml（亚胺培南）；在≤16μg/ml时71.3%的菌株对头孢他啶敏感，在≤8μg/ml时99.2%的菌株对亚胺培南敏感。舒巴坦是活性最强的单独β-内酰胺酶抑制剂（MIC50和MIC90分别为2.0和16.0μg/ml）；克拉维酸和他唑巴坦的活性较低（两种化合物均为16.0和32.0μg/ml）。在β-内酰胺酶阳性菌株中，β-内酰胺酶抑制剂对β-内酰胺类药物的增强作用并非总是可见，氨苄西林-舒巴坦等联合制剂的活性仅归因于抑制剂。鲍曼不动杆菌是耐药性最强的菌种。相比之下，溶血不动杆菌、醋酸钙不动杆菌、约翰逊不动杆菌、琼氏不动杆菌、抗辐射不动杆菌以及其他非鲍曼不动杆菌菌株对所有测试化合物更为敏感。E-test法测定的最低抑菌浓度在38.4%至89.6%的情况下与琼脂稀释法测定的最低抑菌浓度相差1个稀释度，在61.6%至98.6%的情况下相差2个稀释度。
