[The usefulness of a selective disk-broth media for the detection of group B streptococci in the vagina].

BACKGROUND

The detection of pregnant group B streptococci (GBS) carriers allows intrapartum administration of antibiotic prophylaxis to these women and prevents perinatal infection by this microorganism. The aim of this study was to determine the usefulness of a selective media to detect GBS in the vagina based on the disk-broth method.

MATERIAL AND METHODS

One thousand six hundred five vaginal swabs were seeded in blood agar with colistin and nalidixic acid (NDA) and in a selective disk-broth tube consisting of 2 ml of Mueller-Hinton broth with 5% serum and a disk of 30 micrograms of amikacin which was reseeded at 24 hours of incubation in blood agar with NDA.

RESULTS

GBS was isolated by either of the two methods in 209 samples (13.0%); in 160 (9.9%) in the initial dish of blood agar with NDA and in 205 (12.7%) in the subculture of the selective disk-broth media.

CONCLUSIONS

The selective disk-broth media used in this study is a simple method which allows detection of GBS in vaginal samples of women with GBS cultures in a negative agar blood dish.