Ureaplasma urealyticum organisms (ureaplasmas) were isolated in large numbers (up to 10(8) colour changing units (ccu)/ml) over a period of four years from the urethra of a man with hypogammaglobulinaemia and non-gonococcal
urethritis. Elimination of Mycoplasma hominis by
antibiotic treatment early in the course of the
urethritis did not diminish the severity of his condition, which indicated that this mycoplasma was not a cause. Courses of treatment with
tetracyclines,
spectinomycin,
erythromycin,
rosaramicin, and
clindamycin on each occasion reduced the numbers of ureaplasma isolated from the urethra and the severity of disease. The organisms were not eliminated, however, sometimes due to the development of antibiotic resistance, and the
urethritis recurred. Though
netilmicin was not particularly effective in vitro, it was effective clinically, the disease resolving and the organisms disappearing for five months. Recurrence of
urethritis, accompanied by
epididymitis, was associated this time with the recovery of a different (
tetracycline sensitive) ureaplasma strain; the
urethritis and
epididymitis were treated successfully with a combination of
netilmicin and
doxycycline. The administration of ureaplasma antiserum did not seem to be instrumental in eradicating the ureaplasmas. The various
antibiotics had a greater influence on the mycoplasmas in the urethra than on those in the throat and joints, perhaps because the
antibiotics were concentrated in the urogenital tract. The close association between the occurrence of
urethritis and the ureaplasmas suggests strongly that they were responsible for it.