A microbiologist is reading plates from a CSF culture. She notices that there is growth on CHOC, but no growth on SBA or MAC agar. The Gram stain showed a gram-negative bacillus. What organism should be suspected?

Question

Quizplus · Accepted Answer

Haemophilus influenzae is a fastidious gram-negative cocci that grows best on chocolate agar (CHOC) and requires factors X and V from blood for its growth. It does not grow on SBA or MAC agar. It is a common cause of meningitis and epiglottitis in children. Streptococcus pneumoniae and Staphylococcus aureus are both gram-positive cocci and do not match the characteristics of the organism described. Escherichia coli is a gram-negative bacillus but is not fastidious and can grow on SBA and MAC agar.

A Microbiologist Is Reading Plates from a CSF Culture