Clarithromycin-induced alterations in vaginal flora

Many antibiotics have been shown to alter both the bacterial and the fungal flora of the vagina, in some cases potentially increasing a woman's propensity toward urinary tract infections and vaginal candidiasis. The effects of some of the newer macrolide antibiotics on women's vaginal flora have not been previously studied, and almost none of the previous studies specifically cultured for effects on vaginal lactobacillus. Young women (ages 18-45 years) who were about to go onto therapy with clarithromycin, who did not have any conditions known to affect the vaginal flora (eg, diabetes mellitus, spermicide use, menopausal status without hormone replacement therapy), and who agreed to participate in the study were cultured with aerobic and anaerobic and fungal vaginal cultures before starting the antibiotic. These same women were then retested about 4 to 6 weeks after the start of their antibiotic course, and the results of their preantibiotic and postantibiotic cultures were compared. Lactobacillus was present in 33% of patients by vaginal culture before treatment, but this decreased to 0% after treatment. Escherichia coli was present in only 8% of patients before treatment, but this increased to 17% of patients after treatment. Enterococcus was present in 25% of patients before treatment but in only 8% of patients after treatment. The incidence of Gardnerella vaginalis was not affected by the treatment. Candida species incidence increased from 17% to 33% with treatment. The overall effects of clarithromycin on the vaginal flora are similar to other older antibiotics that have been tested.