[Evaluation of various culture media for use in isolating group B streptococci from clinical specimens]

The author compares the potentialities of several nutrient media for the isolation of Group B streptococci. The media used have been as follows: agar, manufactured by the Daghestan Research Institute for Nutrient Media, with 5% of human defibrinated blood (HBA), and blood agar containing 5% of sheep red blood cells (BAS). Gentamicin (8 micrograms/ml) and nalidixic acid (15 micrograms/ml) have been added into the media selectively, and the media have been then labeled as SHBA or SBAS. Liquid nutrient medium: placental broth with the same selective agents in the same concentrations (PBS), prepared by the author, has also been employed. 213 lochia samples and 196 urine samples from pregnant women have been examined. Urine cultivation in PBS has yielded a 4-fold increase (p less than 0.01) of the isolation rate of streptococci vs. other media. The difference in the isolation rates of streptococci cultivated in HBA and SHBA has been insignificant. Addition of donor or sheep red cells to solid nutrient media has provided similar isolation rates of streptococci. The best results have been achieved when liquid selective medium and blood agar have been simultaneously employed.