Genetic analysis of chromosomal resistance to trimethoprim derived from clinical isolates of Escherichia coli.

Chromosomal genes conferring resistance to trimethoprim were transferred from three independently isolated thy+ clinical strains of Escherichia coli to Escherichia coli K12 by using P1 transduction. Trimethoprim-resistant transductants were obtained less frequently than transductants of other chromosomal markers, suggesting that there were problems related to the expression of the trimethoprim resistance genes in E. coli K12. Mapping studies revealed that one of the resistance determinants was located at a similar position on the chromosome (1 min) to the fol-type mutations previously described in E. coli K12. The two remaining resistance determinants mapped at separate positions between 2.5 and 3 min on the chromosome. The presence of one of these determinants reduced the efficiency with which either donor or recipient cells carrying it could participate in conjugation mediated by the sex factor F and also resulted in phenotypic interaction with the azi gene. The mechanisms of trimethoprim resistance in the three clinical E. coli isolates studied were more complex and diverse than was expected from previous studies of E. coli K12 mutants.

The carriage of Escherichia coli on the peri-urethral area and in the feces in patients on long term low dose cotrimoxazole therapy.

Peri-urethral and fecal carriage of E. coli has been studied in 30 patients maintained on long term low dose cotrimoxazole and in abacteriuric subjects not receiving any antibiotic. Cotrimoxazole treatment is associated with a dramatic reduction in E. coli carriage both in the feces and especially on the peri-urethral area which persists over months or years. Recovery of trimethoprim-resistant E. coli from the feces was uncommon but when observed antedated subsequent relapse due to resistant organisms. Possible mechanisms for low peri-urethral carriage rates include reduction in fecal carriage, vaginal secretion of trimethoprim or low urinary concentrations of that drug.

Trial of phenoxymethylpenicillin, phenethicillin, and lincomycin in treatment of staphylococcal sepsis in a casualty department.

A comparative trial of phenoxymethylpenicillin (penicillin V), phenethicillin (Broxil), and lincomycin (Lincocin) against superficial staphylococcal infections seen in a casualty department showed no difference in the efficacy of the three agents, though half the staphylococci isolated were resistant to penicillin. Possible reasons include the fact that antibiotic treatment may not affect superficial staphylococcal infections, or that the organisms concerned may have been weak formers of penicillinase.Half the patients treated with lincomycin complained of diarrhoea and 5% of those treated with phenethicillin suffered from nausea.