Jin C
Department of Bacteriology, Juntendo University School of Medicine.
Nihon Saikingaku Zasshi. 1992 Mar;47(2):373-85. doi: 10.3412/jsb.47.373.
The beta-lactam resistance of genus Streptococcus has been explained by the low binding affinity of penicillin-binding proteins (PBPs) to the drug. This study was carried out to resolve the mechanisms of resistance to beta-lactam antibiotics in the species of genus Enterococcus by means of binding affinities of PBPs. Streptococcus pyogenes, Enterococcus faecalis, Enterococcus faecium and Enterococcus avium were employed as assay microbes. Cefepime (CFPM) and ampicillin (ABPC) were used as representatives of cephems and penicillins, respectively. All the PBP fractions of S. pyogenes manifested high binding affinities to CFPM and ABPC, whereas PBPs 1 and 4 of E. faecalis showed high binding affinities to ABPC but not to CFPM. In E. faecium, PBPs of an exceptionally penicillin-susceptible strain manifested a high binding affinity to ABPC, but PBPs 5 and 6 showed low affinities to CFPM. beta-lactam resistant strains of E. faecium possessed PBPs 5 and 6 with low binding affinities to CFPM and ABPC. All the fractions of PBPs but PBP 1 in E. avium showed low binding affinities to CFPM. Although all the PBP fractions but PBPs 3 and 6 manifested high binding affinities to ABPC, PBPs 3 and 6 showed low binding affinities to ABPC. A strain of E. avium, which is susceptible to ABPC but moderately resistant to CFPM, lacked PBP 6. In conclusion, the resistance of E. avium to CFPM is based upon low binding affinities of the many fractions to this drug, and ABPC resistance is based upon PBPs 3 and 6 with low binding affinities to ABPC.
链球菌属对β-内酰胺类抗生素的耐药性被解释为青霉素结合蛋白（PBPs）与药物的低结合亲和力。本研究旨在通过PBPs的结合亲和力来解析肠球菌属物种对β-内酰胺类抗生素的耐药机制。化脓性链球菌、粪肠球菌、屎肠球菌和鸟肠球菌被用作检测微生物。头孢吡肟（CFPM）和氨苄西林（ABPC）分别作为头孢菌素类和青霉素类的代表药物。化脓性链球菌的所有PBP组分对CFPM和ABPC均表现出高结合亲和力，而粪肠球菌的PBPs 1和4对ABPC表现出高结合亲和力，但对CFPM无此表现。在屎肠球菌中，一株对青霉素异常敏感的菌株的PBPs对ABPC表现出高结合亲和力，但PBPs 5和6对CFPM表现出低亲和力。屎肠球菌的β-内酰胺耐药菌株所具有的PBPs 5和6对CFPM和ABPC的结合亲和力较低。鸟肠球菌除PBP 1外的所有PBP组分对CFPM表现出低结合亲和力。尽管鸟肠球菌除PBPs 3和6外的所有PBP组分对ABPC表现出高结合亲和力，但PBPs 3和6对ABPC表现出低结合亲和力。一株对ABPC敏感但对CFPM中度耐药的鸟肠球菌菌株缺乏PBP 6。总之，鸟肠球菌对CFPM的耐药性基于许多组分对该药物的低结合亲和力，而对ABPC的耐药性基于对ABPC结合亲和力较低的PBPs 3和6。
