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A young mother who recently emigrated from Uganda brought her sick 18-month-old infant, Mirembe, to a New York City emergency room. The infant was crying uncontrollably, especially when the physician tried to move her head. Meningitis (an infection of the spinal fluid and membrane surrounding the brain) was suspected, and a spinal tap was performed to collect cerebrospinal fluid (CSF). The fluid, which appeared cloudy, was sent to the laboratory. CSF should be free of microbes, but a microscopic examination revealed Gram-negative bacilli. The technician cultured the sample on various solid media. The organism failed to grow on blood agar plates containing intact red blood cells (RBCs) but did grow on a medium containing lysed RBCs (called chocolate agar because of its color). The organism recovered from the CSF also grew on a relatively simple medium containing growth factors known as X and V. The diagnosis was meningitis caused by the bacterium Haemophilus influenzae. The child received antibiotics and made a full recovery. The blood agar plates used to culture Mirembe's sample contain intact red blood cells and agar. Organisms that are capable of lysing the red blood cells may produce green-appearing zones of partial hemolysis or clear-appearing zones of complete hemolysis around colonies that are easily visually distinguishable. This medium is best described as:

          A young mother who recently emigrated from Uganda brought her sick 18-month-old infant, Mirembe, to a New York City emergency room. The infant was crying uncontrollably, especially when the physician tried to move her head. Meningitis (an infection of the spinal fluid and membrane surrounding the brain) was suspected, and a spinal tap was performed to collect cerebrospinal fluid (CSF). The fluid, which appeared cloudy, was sent to the laboratory. CSF should be free of microbes, but a microscopic examination revealed Gram-negative bacilli. The technician cultured the sample on various solid media. The organism failed to grow on blood agar plates containing intact red blood cells (RBCs) but did grow on a medium containing lysed RBCs (called chocolate agar because of its color). The organism recovered from the CSF also grew on a relatively simple medium containing growth factors known as X and V.
The diagnosis was meningitis caused by the bacterium Haemophilus influenzae. The child received antibiotics and made a full recovery.
The blood agar plates used to culture Mirembe's sample contain intact red blood cells and agar. Organisms that are capable of lysing the red blood cells may produce green-appearing zones of partial hemolysis or clear-appearing zones of complete hemolysis around colonies that are easily visually distinguishable. This medium is best described as:

Added by Jennifer W.

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