A 14-month-old boy is brought in by his parents with fever, fussiness and lethargy, and apparent headache. On examination, the neck is stiff. His parents have not allowed his routine childhood vaccines. Very short Gramnegative rods are seen in the CSF, so antibiotics are immediately started. The organism grows on chocolate agar but not blood agar. No one else in the family is ill. What is the most likely causative agent?

Question

Quizplus · Accepted Answer

Although Haemophilus influenzae type b is rarely seen in vaccinated children younger than 2 years of age, it still occurs in unvaccinated children. The description of a chocolate agar-positive organism should suggest either Neisseria meningitidis or H. influenzae type b. The descriptor as a short rod (from CSF) or pleomorphic rod (from culture) suggests H. influenzae type b. Although both Klebsiella pneumonia and Escherichia coli (a cause of neonatal meningitis) are both Gram-negative rods, neither is likely to cause meningitis in a healthy child, and, like all other Enterobacteriaceae, will grow on blood agar. Streptococcus is Gram-positive.

A 14-Month-Old Boy Is Brought in by His Parents with Fever