Wong C K, Harding G K, Ronald A R, Hoban S
Can Med Assoc J. 1975 Jun 14;112(13 Spec No):54-8.
The incidence of trimethoprim-resistant Enterobacteriaceae has not increased since the introduction of the combination trimethoprim-sulfamethoxazole (TMP-SMX) into the clinical use at our centre in 1973. Using the minimum inhibitory concentration (MIC) as the index of trimethoprim resistance, this ranged from 1.6 to 800 mug/ml; for the majority of isolates it lay between 1.6 and 12.5 mug/ml. About half of these trimethoprim-resistant organisms were sensitive to sulfonamide. In vitro data suggest that organisms resistant to sulfonamide as well as to trimethoprim, where the MIC for the former drug is 3.1 mug/ml or less, will be susceptible to the combination. More resistant organisms, i.e., those for which the MIC of trimethoprim is 6.2 mug/ml or more, often appear quite resistent to the combination. There is no evidence that previous therapy with TMP-SMX is a significant predisposing factor to infection with these organisms, although there is a significant correlation between previous TMP-SMX therapy and infection with organisms with a high level of trimethoprim resistance. Organisms harbouring R-factor resistance or thymine-dependent mutants were not encountered during the course of this study.
自1973年甲氧苄啶-磺胺甲恶唑（TMP-SMX）联合用药在我们中心投入临床使用以来，耐甲氧苄啶肠杆菌科细菌的发生率并未增加。以最低抑菌浓度（MIC）作为甲氧苄啶耐药性指标，其范围为1.6至800μg/ml；大多数分离株的MIC介于1.6至12.5μg/ml之间。这些耐甲氧苄啶的微生物中约有一半对磺胺类药物敏感。体外数据表明，对磺胺类药物和甲氧苄啶均耐药的微生物（前一种药物的MIC为3.1μg/ml或更低）对联合用药敏感。耐药性更强的微生物，即甲氧苄啶MIC为6.2μg/ml或更高的微生物，通常对联合用药表现出相当的耐药性。没有证据表明先前使用TMP-SMX治疗是这些微生物感染的重要易感因素，尽管先前使用TMP-SMX治疗与感染甲氧苄啶高耐药性微生物之间存在显著相关性。在本研究过程中未发现携带R因子耐药性或胸腺嘧啶依赖性突变体的微生物。
