Comparison of different medium bases for the semiquantitative isolation of anaerobes from vaginal secretions.

Two studies were performed to determine the best medium for the isolation of anaerobes from vaginal secretions. In the first, three different medium bases (brucella, Centers for Disease Control [CDC], and Schaedler) were compared semiquantitatively for ability to support the growth of gram-negative anaerobes from vaginal fluid. Media were supplemented with laked sheep blood, kanamycin, and vancomycin. The brucella base agar formulation supported the growth of anaerobic gram-negative bacilli better than either the CDC or Schaedler base agar formulation. In a second study, nonselective brucella and CDC base sheep blood agar were compared for ability to support the growth of anaerobic gram-positive cocci. Anaerobic gram-positive cocci grew in higher concentrations on CDC base agar than on brucella base agar. On the basis of these observations, we recommend that a CDC base sheep blood agar be used for the nonselective plate and a brucella base plate supplemented with laked sheep blood, kanamycin, and vancomycin be used for isolation of gram-negative bacilli in studies of the anaerobic flora of the female genital tract.