Intrafamilial spreading of Escherichia coli resistant to trimethoprim.

Bacterial resistance to trimethoprim has mainly been considered a problem confined to hospitals. The present investigation was undertaken to check for any possible spread of trimethoprim resistance borne by uropathogenic Escherichia coli among families of outpatients. Family members, living in the same household as outpatients with urinary tract infections caused by a trimethoprim-resistant E. coli strain, were asked to deliver faecal specimens. Of a total number of 51 family members 16 were found to be carrying trimethoprim-resistant E. coli in their faecal flora. A comparison of serotypes showed 8 of the 16 family members to have the same E. coli strain in their faeces as originally isolated in the urine of the index patient from the same family. The results indicate that resistance to trimethoprim not only spreads in hospitals with intensive use of antibiotics, but also among the families of trimethoprim-treated outpatients.