Anaerobic curved rods in genital samples of women. Performance of different selective media, comparison of detection by microscopy and culture studies, and recovery from different sampling sites

Abstract

Anaerobic curved rods (CR) frequently occur in the vaginal flora of women with non-specific vaginitis, more recently referred to as bacterial vaginosis (BV). The reasons for difficulties in culturing CR include their anaerobic nature, slow rate of growth and presence in a highly mixed flora. The present study concerns the efficiency of three culture media--blood agar, a gonococcal medium, and Columbia agar--for recovery of CR. The possibility of improving selectivity by adding various antibiotics (e.g. nalidixic acid, colistin and tinidazole) to the media was also explored. The MICs for 157 CR strains and for 80 strains of anaerobic or facultatively anaerobic bacteria isolated from vaginal samples from women with BV were therefore determined. Columbia agar containing 1 micrograms/ml tinidazole in combination with either colistin (10 micrograms/ml) or nalidixic acid (15 micrograms/ml) proved the most efficient medium for recovery of CR. These antibiotic combinations effectively suppressed growth of Gardnerella vaginalis, anaerobic cocci and species of Bacteroides.--In 291 women, comparison was made of the detection of CR morphotype bacteria in methylene-blue-stained smears and the results of vaginal cultures for CR. A long variant (2-4 micron) was found in 42% by direct microscopy and 43% by culture. A short variant (approx 1 micron), which, with two exceptions, was always concomitant with the long variant, was demonstrable in only 3% of vaginal smears and in 14% of the cultures.--Vaginal samples were approximately four times more often culture-positive for CR than were cervical samples from the same women.