Effect of short term treatment of non-gonococcal urethritis with minocycline.

Two hundred and forty four men with non-gonococcal urethritis (NGU) took part in a trial of minocycline. Chlamydiae were isolated from 34%, ureaplasmas from 47.1%, and Mycoplasma hominis from 10.2%. These micro-organisms were isolated least often from men suffering their third or more attack of NGU, and men in this group failed most often to respond to minocycline. Irrespective of the micro-organisms isolated originally or the number of previous attacks, the failure rate (10%) for men receiving minocycline for 10 days was significantly less than for those receiving this antibiotic for one or two days. More than half of the men suffering third attacks from whom micro-organisms were not isolated failed to respond to these short regimens. One of the lowest failure rates (4%) after short term treatment, however, was seen in men experiencing first attacks who yielded only ureaplasmas with or without M hominis, which indicates the importance of ureaplasmas in this group of patients. Chlamydiae were not reisolated from any patient after treatment, irrespective of its duration, and the only ureaplasmas that were reisolated were from nine patients who carried tetracycline resistant strains. Reasons for the absence of chlamydiae and ureaplasmas in the presence of disease and the need to look for other microorganisms as a cause of NGU are discussed among other issues raised by these results.