Paper I
Question
A five year old boy was brought to emergency department with history of fever, headache, vomiting and altered sensorium for last 48 hours. On examination, neck stiffness was present. Examination of CSF showed neutrophilic predominance
- (a) What is the most probable clinical diagnosis 1 mark(s)
- (b) Enumerate the etiological agents causing this condition 2 mark(s)
- (c) Describe the laboratory diagnosis 4 mark(s)
- (d) Write about the vaccine prophylaxis of this condition according to the etiological agents 3 mark(s)
Answer
a) Most probable clinical diagnosis: Acute bacterial (pyogenic) meningitis — fever, headache, vomiting, altered sensorium, neck stiffness, and neutrophilic CSF pleocytosis is classical.
b) Etiological agents (varies by age): Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b are the classical agents in children beyond the neonatal period; E. coli and Group B Streptococcus are more typical in neonates.
c) Laboratory diagnosis
- CSF examination: raised opening pressure, turbid/cloudy appearance, neutrophilic pleocytosis, raised protein, and markedly reduced glucose (low CSF:blood glucose ratio) — distinguishing it from viral meningitis’s lymphocytic pleocytosis with normal glucose.
- Gram stain of CSF — rapid presumptive identification: Gram-positive diplococci (S. pneumoniae), Gram-negative diplococci (N. meningitidis), or small Gram-negative coccobacilli (H. influenzae).
- CSF culture — definitive test, on blood agar and chocolate agar in a CO2-enriched atmosphere; allows antibiotic susceptibility testing.
- Latex agglutination test — rapid detection of bacterial capsular antigen directly in CSF, useful after antibiotics have already been given.
- Blood culture — often positive concurrently.
- PCR — rapid, sensitive detection, particularly useful after antibiotics have started.
d) Vaccine prophylaxis by etiological agent
- Streptococcus pneumoniae — Pneumococcal conjugate vaccine (PCV), part of the routine infant immunization schedule, covering the major invasive serotypes.
- Haemophilus influenzae type b — Hib conjugate vaccine, given as part of the pentavalent/DPT-based schedule in infancy.
- Neisseria meningitidis — Meningococcal conjugate vaccine (covering serogroups such as A, C, W, Y, and separately, serogroup B vaccines), recommended in endemic/epidemic areas or for specific risk groups (e.g., travellers to the meningitis belt, asplenic patients).
- Conjugate vaccine technology (linking the polysaccharide antigen to a carrier protein) is used for all three, since it converts a T-independent polysaccharide response (poorly immunogenic in young children, without memory) into a T-dependent response with strong immunogenicity and immunological memory even in infants.