CASE HISTORY A Young Mother Who Recently Emigrated from Uganda Brought Her

CASE HISTORY
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) selective.
B) differential.
C) chemically defined.
D) synthetic.