Resistance in Escherichia coli after single dose ampicillin to treat gonorrhoea.

Patients with uncomplicated gonorrhoea were treated with a single dose of either ampicillin 3 g orally or procaine penicillin 2.4 MIU by injection, both with probenecid 1 g orally. The proportion of faecal Escherichia coli resistant to ampicillin before and a week after treatment was assessed. Of 55 patients treated with ampicillin who initially possessed sensitive flora, 25 (45.5%) became colonised subsequently by resistant E coli. Resistance to ampicillin, together with resistance to some other antimicrobials, was transferable in vitro. Penicillin, however, selected resistant E coli in only four (14.3%) out of 28 patients with initially sensitive flora. There was no difference in therapeutic response between the two agents. Intramuscular penicillin appeared to offer appreciably greater microbiological benefits than oral ampicillin in treating gonorrhoea.