title: Trimethoprim-resistant Enterobacteriaceae in urinary tract infection.
abstract: 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.
mesh_terms: D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D004756:Enterobacteriaceae Infections / Q000188:drug therapy* / Q000382:microbiology; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000188:drug therapy; D005260:Female; D006801:Humans; D007709:Klebsiella / Q000187:drug effects; D007710:Klebsiella Infections / Q000188:drug therapy; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011511:Proteus / Q000187:drug effects; D011512:Proteus Infections / Q000188:drug therapy; D013420:Sulfamethoxazole / Q000494:pharmacology* / Q000627:therapeutic use; D014295:Trimethoprim / Q000494:pharmacology* / Q000627:therapeutic use; D014552:Urinary Tract Infections / Q000188:drug therapy / Q000382:microbiology*
chemical_list: D004338:Drug Combinations; D014295:Trimethoprim; D013420:Sulfamethoxazole