A 5-year-old boy has been irritable for the past 2 days and has complained of an earache for the past 5 days. On physical examination, he has a temperature of 39.1°C. Laboratory examination of the CSF from a lumbar punctureshows numerous neutrophils, slightly increased protein level, and decreased glucose concentration. On Gram staining of the CSF, which of the following is most likely to be seen microscopically?
Short Gram-positive rods
Answer :B Gram-positive cocci
This patient has acute bacterial meningitis. In his age group, the most common etiologic organism is now Streptococcus pneumoniae, a gram-positive coccus.
The number of CNS infections with Haemophilus influenzae, a gram negative bacillus, in this age group has decreased because of widespread immunization.
Pneumococci also are likely to be seen in an adult. The gram-negative diplococci of Neisseria meningitidis are seen in young adults. The short, gram positive rods of Listeria monocytogenes appear sporadically or in epidemics caused by food contamination.
The gram negative bacilli of Escherichia coli are most often seen in neonates. With these clinical and CSF features, it would be unusual if bacteria were not present in the CSF.