Of nonchlamydial NGU cases, up to 20% recur after routine antibiotic
treatment -- so that aspect also is quite common. The CDC recommendations
for treatment, which I endorse, are that recurrent cases should be treated with a change in antibiotics. In particular, when the problem recurs after azithromycin, doxycycline should be used; and ideally metronidazole as well, to cover the possibility of trichomonas. (Trich is unlikely in gay men -- primarily a heterosexual problem.