Edwards R, Greenwood D
Division of Microbiology, University Hospital, Queen's Medical Centre, Nottingham, UK.
J Antimicrob Chemother. 1996 Dec;38(6):941-51. doi: 10.1093/jac/38.6.941.
The mechanisms responsible for reduced susceptibility to imipenem (MIC 2-16 mg/L) were investigated in eight strains of Bacteroides fragilis. All the strains produced elevated levels of beta-lactamase. Four B. fragilis strains produced metallo-beta-lactamase capable of marked imipenem hydrolysis, and these enzymes were shown to be responsible for resistance. There was evidence, from testing susceptibility to imipenem in the presence of clavulanic acid, that increased resistance in two strains was associated with susceptibility to beta-lactamases other than metallo-enzymes. With the remaining two strains there was no evidence of enzymic breakdown of imipenem. Neither of these strains showed evidence of decreased permeability to nitrocefin as judged by a method which takes into account the substrate concentration in the periplasmic space. A low molecular weight PBP, that was not seen in fully sensitive strains of B. fragilis, was detected in four strains in which reduced susceptibility to imipenem was not associated with metallo-beta-lactamase activity.
对8株脆弱拟杆菌中对亚胺培南敏感性降低（MIC为2-16mg/L）的机制进行了研究。所有菌株均产生高水平的β-内酰胺酶。4株脆弱拟杆菌产生能够显著水解亚胺培南的金属β-内酰胺酶，这些酶被证明是耐药的原因。在克拉维酸存在下测试对亚胺培南的敏感性的结果表明，两株菌耐药性增加与对金属酶以外的β-内酰胺酶敏感性有关。对于其余两株菌，没有证据表明亚胺培南发生酶解。通过一种考虑周质空间中底物浓度的方法判断，这两株菌均未显示对硝噻吩的通透性降低。在4株对亚胺培南敏感性降低但与金属β-内酰胺酶活性无关的菌株中，检测到一种在脆弱拟杆菌完全敏感菌株中未见到的低分子量青霉素结合蛋白。
