Topic: Meningococcus, Salmonella
Question: A 5-year-old girl was brought in by her mother with the symptoms of fever, vomiting (7-8 episodes) and altered sensorium for the last 24 h. Central nervous system examination showed that she was drowsy, had signs of meningeal irritation, neck rigidity. Examination of CSF showed neutrophilic predominance. (a) What is the clinical diagnosis. (b) Name SIX common probable causes of this clinical condition. (c) Name two rapid tests to detect these causes. (d) What are the confirmatory tests that can be done in the laboratory.
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(a) The clinical diagnosis is acute bacterial meningitis based on the symptoms and CSF findings.
(b) Six common probable causes:
– Streptococcus pneumoniae
– Neisseria meningitidis
– Haemophilus influenzae
– Staphylococcus aureus
– Escherichia coli
– Listeria monocytogenes
(c) Rapid tests:
– Gram stain of CSF
– Latex agglutination tests for bacterial antigens
(d) Confirmatory laboratory tests and findings:
– CSF culture: Isolation of the causative bacteria
– Blood culture: May be positive, especially for S. pneumoniae, N. meningitidis, S. aureus
– CSF PCR: Detection of bacterial DNA
– CSF cell count: Neutrophilic pleocytosis >100 cells/μL
– CSF chemistries: Low glucose <40 mg/dL, elevated protein >50 mg/dL
– Hematological tests: Leukocytosis, elevated CRP
– Serology for viruses
– Microscopic examination for fungi and parasites
– Biochemical tests like adenosine deaminase for tuberculosis
The gram stain, culture and antibiotic susceptibility testing will help identify the causative organism and guide appropriate antimicrobial therapy
