BHI CC Agar Slant w/ 10% Sheep Blood and Gentamicin

Principle And Interpretation

Brain Heart CC Agar is formulated as per Ajello et al. (1) and McDonough, et al. (4). This medium is recommended for selective isolation of pathogenic fungi (5). Chloramphenicol is a broad-spectrum antibiotic, which inhibits the growth of wide range of gram-positive and gram-negative bacteria. Cycloheximide inhibits most saprophytic moulds and enhances the isolation of pathogenic fungi.

This medium contains HM Infusion powder, BHI powder and proteose peptone to supply the necessary nutrients to support the growth of fastidious pathogenic fungi. Dextrose is a carbohydrate source and disodium phosphate buffers the medium. The medium may be further enriched with 10% sheep blood to isolate systemic fungi that grow poorly on non-enriched medium. Also the addition of Gentamicin, 50 mcg/ml of medium, improves the selectivity. The antibiotics in this medium may inhibit some fungi. The addition of blood makes Brain Heart Infusion CC Agar suitable for the isolation of the tissue phase of Histoplasma capsulatum and other pathogenic fungi, including Coccidioides immitis.

While handling Histoplasma capsulatum extreme care should be taken to avoid dissemination of its infective spores. The culture should be examined in a closed filtered air cabinet. Isolation of fungi from contaminated specimens can be done by inoculating selective medium along with nonselective medium and incubated at 25-30°C. For isolation of fungi causing systemic mycoses two sets of media should be inoculated with one set incubated at 23-30°C and a duplicate set at 35-37°C. Examine the plates for at least a week.Defibrinated sheep blood added to the basal medium provides essential growth factors for the more fastidious fungal organisms.