Takahashi I, Sawai T, Ando T, Yamagishi S
J Antibiot (Tokyo). 1980 Sep;33(9):1037-42. doi: 10.7164/antibiotics.33.1037.
Cefoxitin resistance, an unique property found in clinical isolates of Escherichia coli was investigated. Cefoxitin resistant strains, 255 and GN206, produced cephalosporinase constitutively. The cephalosporinase was located in the periplasm, and its production was considered to be mediated by chromosomal gene(s). Cephalosporinase-less mutants from both strains were susceptible to cefoxitin as well as other beta-lactam antibiotics, suggesting that the cephalosporinase was responsible for the resistance to beta-lactam antibiotics including cefoxitin. The cephalosporinases from the E. coli strains were partially purified and their enzymological properties were compared with those of cephalosporinases of Citrobacter freundii and Proteus morganii. Although the cephalosporinases of E. coli, as well as other cephalosporinases, showed little activity for cefoxitin-hydrolysis, the E. coli cephalosporinases exhibited a significantly higher affinity for cefoxitin than other cephalosporinases. It was assumed that the E. coli enzyme located around the targets of cefoxitin protected the targets from the antibiotic by its high affinity for the antibiotic.
对在临床分离的大肠杆菌中发现的一种独特特性——头孢西丁耐药性进行了研究。头孢西丁耐药菌株255和GN206组成性地产生头孢菌素酶。该头孢菌素酶位于周质中，其产生被认为是由染色体基因介导的。来自这两种菌株的无头孢菌素酶突变体对头孢西丁以及其他β-内酰胺类抗生素敏感，这表明头孢菌素酶是对包括头孢西丁在内的β-内酰胺类抗生素产生耐药性的原因。对来自大肠杆菌菌株的头孢菌素酶进行了部分纯化，并将其酶学特性与弗氏柠檬酸杆菌和摩根氏变形杆菌的头孢菌素酶进行了比较。尽管大肠杆菌的头孢菌素酶以及其他头孢菌素酶对头孢西丁水解的活性很低，但大肠杆菌的头孢菌素酶对头孢西丁的亲和力明显高于其他头孢菌素酶。据推测，位于头孢西丁靶点周围的大肠杆菌酶因其对抗生素的高亲和力而保护靶点免受抗生素的作用。
