Darland G, Birnbaum J
Antimicrob Agents Chemother. 1977 Apr;11(4):725-34. doi: 10.1128/AAC.11.4.725.
Toluene-treated cell suspensions of Bacteroides fragilis were used to screen clinical isolates for the production of beta-lactamase. Approximately one-third of the isolates possessed considerable cephalosporinase activity. A significant correlation was found between beta-lactamase production and resistance to cephalosporin antibiotics. Several isolates were resistant to cefuroxime and cefamandole and produced enzymes capable of hydrolyzing these antibiotics. However, none of the 79 strains tested could hydrolyze the cephamycin derivative, cefoxitin. A large percentage (>90%) of the strains were susceptible to cefoxitin. Therefore, resistance to lactamase hydrolysis is a major factor for the effectiveness of cefoxitin against B. fragilis. Detailed studies of four isolates suggest that two different enzymes may be produced. Both are cephalosporinases but differ with regard to cellular distribution and substrate specificity. Cefoxitin is not a substrate for either enzyme, but it is an excellent competitive inhibitor (K(i) approximately 0.1 muM).
用甲苯处理的脆弱拟杆菌细胞悬液来筛选临床分离株的β-内酰胺酶产生情况。大约三分之一的分离株具有相当的头孢菌素酶活性。发现β-内酰胺酶产生与对头孢菌素抗生素的耐药性之间存在显著相关性。有几种分离株对头孢呋辛和头孢孟多耐药，并产生能够水解这些抗生素的酶。然而，所测试的79株菌株中没有一株能够水解头孢霉素衍生物头孢西丁。很大比例（>90%）的菌株对头孢西丁敏感。因此，对β-内酰胺酶水解的耐药性是头孢西丁对脆弱拟杆菌有效性的一个主要因素。对四株分离株的详细研究表明可能产生两种不同的酶。两者都是头孢菌素酶，但在细胞分布和底物特异性方面有所不同。头孢西丁不是这两种酶的底物，但它是一种极好的竞争性抑制剂（抑制常数约为0.1μM）。
