Then R L, Hermann F
Chemotherapy. 1981;27(3):192-9. doi: 10.1159/000237977.
Dihydrofolate reductases (DHFR) were studied in two groups of trimethoprim (TMP)-resistant Enterobacteria, isolated in Turku, Finland. The first group consisted of six strains with a high level of TMP resistance (MIC greater than 1,000 mg/l) and all of them were found to harbour an additional TMP-insensitive DHFR thought to be responsible for the high degree of resistance. Three Proteus mirabilis strains in this group synthesized chromosomal reductases with reduced TMP sensitivity as well. A second group of six strains, exhibiting MIC values for TMP between 16 and 512 mg/l was seen to be resistant by the production of a chromosomally altered TMP-insensitive DHFR, produced either in normal or slightly elevated amounts. With one exception these strains were all fully susceptible to sulfadiazine and strong synergism with TMP was present. Resistance to nalidixic acid was also frequently observed in this group. In conclusion, three different basic mechanisms were found to be responsible for TMP resistance in Enterobacteria from Finland and these were seen to occur not only independently but also simultaneously in the same strain.
对在芬兰图尔库分离出的两组耐甲氧苄啶（TMP）的肠杆菌中的二氢叶酸还原酶（DHFR）进行了研究。第一组由六株对TMP具有高水平抗性（MIC大于1000mg/L）的菌株组成，发现它们都含有一种额外的对TMP不敏感的DHFR，认为该酶是高抗性程度的原因。该组中的三株奇异变形杆菌菌株也合成了对TMP敏感性降低的染色体还原酶。第二组有六株菌株，其TMP的MIC值在16至512mg/L之间，通过产生一种染色体改变的对TMP不敏感的DHFR而表现出抗性，该酶的产生量正常或略有增加。除了一株菌株外，这些菌株对磺胺嘧啶均完全敏感，并且与TMP存在强协同作用。该组中也经常观察到对萘啶酸的抗性。总之，发现三种不同的基本机制导致了芬兰肠杆菌对TMP的抗性，并且这些机制不仅独立出现，而且在同一菌株中同时出现。
