Sirot D, Chanal C, Henquell C, Labia R, Sirot J, Cluzel R
Clermont-Ferrand, France.
J Antimicrob Chemother. 1994 Jun;33(6):1117-26. doi: 10.1093/jac/33.6.1117.
Twenty clinical isolates of Escherichia coli resistant to amoxycillin and ticarcillin, both in combination with clavulanic acid, were studied. The ranges of MICs for these strains as determined by the agar dilution method were as follows: amoxycillin, 2048- > 4096 mg/L; ticarcillin, 512- > 4096 mg/L; piperacillin, 32-256 mg/L; mecillinam, 0.5-8 mg/L; and cephalothin 4-16 mg/L. Combining amoxycillin with beta-lactamase inhibitors, each at a fixed concentration of 4 mg/L, had only modest potentiating effects on the activities of this agent, the ranges of MICs falling to 256- > 2048 mg/L in the presence of clavulanic acid or sulbactam and to 64-1024 mg/L and 128-2048 mg/L in the presence of tazobactam and brobactam respectively. The pI values for the beta-lactamases produced by the 20 isolates were 5.2 for 15 strains, 5.4 for four strains and 7.4 for a single strain. Colony hybridization with oligonucleotides was performed in order to detect substitutions of arginine at position 241 (Arg-241) and methionine at position 67 (Met-67). Based on this technique, the four beta-lactamases with pI values of 5.4 were grouped into two oligotypes (+ = hybridization, - = non-hybridization)-Arg-241+, Met-67- (n = 3) and Arg-241+, Met-67+ (n = 1); in one of the three mutants which did not hybridize with the Met-67 probe, leucine had been substituted for methionine at position 67. The beta-lactamases with pI values of 5.2 which were identified in 15 strains were grouped into the following three oligotypes: Arg-241-, Met-67+ (n = 7); Arg-241-, Met-67- (n = 6); and Arg-241+, Met-67- (n = 2). In three of the 13 mutants which failed to hybridize with the Arg-241 probe, serine residues had replaced arginine residues at position 241. Substitutions of Arg-241 or Met-67 led to reduced affinities of the mutant enzymes for the beta-lactams tested. The results of the hybridization studies demonstrate that, amongst E. coli clinical isolates, there is a diversity of mutant TEM enzymes mediating resistance to beta-lactamase inhibitors.
对20株对阿莫西林和替卡西林（二者均与克拉维酸联合使用）耐药的大肠埃希菌临床分离株进行了研究。通过琼脂稀释法测定，这些菌株的最低抑菌浓度（MIC）范围如下：阿莫西林，2048～＞4096mg/L；替卡西林，512～＞4096mg/L；哌拉西林，32～256mg/L；美西林，0.5～8mg/L；头孢噻吩，4～16mg/L。将阿莫西林与β-内酰胺酶抑制剂各以4mg/L的固定浓度联合使用时，对该药物活性仅有适度的增强作用，在克拉维酸或舒巴坦存在时MIC范围降至256～＞2048mg/L，在他唑巴坦和溴巴坦存在时分别降至64～1024mg/L和128～2048mg/L。20株分离株产生的β-内酰胺酶的pI值，15株为5.2，4株为5.4，1株为7.4。进行了寡核苷酸菌落杂交，以检测第241位精氨酸（Arg-241）和第67位甲硫氨酸（Met-67）的取代情况。基于该技术，4株pI值为5.4的β-内酰胺酶被分为两种寡核苷酸类型（+ =杂交，- =非杂交）——Arg-241+，Met-67-（n = 3）和Arg-241+，Met-67+（n = 1）；在3株未与Met-67探针杂交的突变体中，有1株在第67位甲硫氨酸被亮氨酸取代。在15株中鉴定出的pI值为5.2的β-内酰胺酶被分为以下三种寡核苷酸类型：Arg-241-，Met-67+（n = 7）；Arg-241-，Met-67-（n = 6）；和Arg-241+，Met-67-（n = 2）。在13株未与Arg-241探针杂交的突变体中，有3株在第241位丝氨酸残基取代了精氨酸残基。Arg-241或Met-67的取代导致突变酶对所测试的β-内酰胺类药物的亲和力降低。杂交研究结果表明，在大肠埃希菌临床分离株中，存在多种介导对β-内酰胺酶抑制剂耐药的突变TEM酶。
