Apparent failure of brain heart infusion broth to cultivate meningococci from clinically infected patients.

Brain Heart Infusion broth is a widely used medium for the isolation of pathogenic bacteria from body fluids. Cerebro spinal fluid and blood inoculated into this medium from clinically meningitic infants infected with Neisseria meningitidis appeared not to support the growth of this organism. In laboratory experiments the broth did not support the growth of Neisseria meningitidis unless adequately vented and with addition of blood. Thorough mixing was necessary to disperse microcolonies that formed in the base blood layer of blood cultures. When this was done they were isolated using standard sub-culture techniques. Broths used for specimens other than blood must be used with blood or a blood supplement if this organism is suspected, and should be incubated aerobically or vented to 5% carbon dioxide, and thoroughly mixed. Awareness of these deficiencies may prevent false negative results.