A 5-year-old girl from Mumbai presents with a 3-day history of fever, headache, and vomiting. On day 3, she develops a non-blanching petechial rash over the trunk and extremities. Her parents report she attends a crowded school. On examination, she is febrile (38.8°C), alert, with neck stiffness and a positive Kernig's sign. CSF analysis shows: protein 150 mg/dL, glucose 65 mg/dL (serum glucose 110 mg/dL), WBC 200/μL (60% neutrophils, 40% lymphocytes), Gram stain is negative, culture pending. Blood culture grows gram-negative diplococci. What is the most likely causative organism and the immediate management priority?

Explanation

## Clinical Diagnosis **Key Point:** The combination of meningitis with a non-blanching petechial rash in a child from a crowded setting (school) is pathognomonic for meningococcal meningitis caused by *Neisseria meningitidis*. ## Identifying Features of Meningococcal Meningitis **High-Yield:** Meningococcal meningitis is the only bacterial meningitis that classically presents with a petechial or purpuric rash. This rash is due to vasculitis and is a medical emergency. | Feature | *N. meningitidis* | *H. influenzae* | *S. agalactiae* | *E. coli* K1 | | --- | --- | --- | --- | --- | | Rash | Petechial/purpuric (80%) | Rare | None | None | | Gram stain | Gram-negative diplococcus | Gram-negative coccobacillus | Gram-positive coccus | Gram-negative rod | | Age group | Any age (peak 5–19 yrs) | <5 years | Neonates (0–3 mo) | Neonates | | CSF glucose | Low (often <40% serum) | Low | Variable | Low | | Epidemiology | Crowded settings, droplet | Vaccine-preventable | Maternal flora | Maternal flora | **Mnemonic:** RIPE — **R**ash (petechial), **I**ntense headache, **P**etechiae, **E**pidemic setting = *N. meningitidis* ## Immediate Management Priorities 1. **Antibiotic therapy:** Ceftriaxone 2 g IV 6-hourly (or cefotaxime 2 g IV 4–6-hourly) is the first-line agent. Vancomycin may be added if penicillin resistance is a concern, but in this case the organism is gram-negative and vancomycin is not indicated. 2. **Chemoprophylaxis for close contacts:** This is a critical and often-tested point. Close contacts (household members, school classmates, healthcare workers with direct contact) must receive prophylaxis within 24 hours of diagnosis to prevent secondary cases. - **Rifampicin:** 600 mg orally 12-hourly for 2 days (adult dose) - **Ciprofloxacin:** 500 mg orally once (single dose) - **Ceftriaxone:** 250 mg IM once (if rifampicin/ciprofloxacin unavailable) **Clinical Pearl:** Meningococcal meningitis can progress to fulminant septicemia with septic shock and disseminated intravascular coagulation (DIC) within hours. The presence of petechiae indicates systemic involvement and warrants ICU admission and aggressive supportive care including fluid resuscitation, vasopressors, and management of DIC. 3. **Isolation:** Respiratory isolation for 24 hours after starting antibiotics. 4. **Vaccination:** Meningococcal vaccine (if not previously given) should be offered to the patient after recovery and to close contacts. **High-Yield:** The question tests both organism identification (gram-negative diplococcus + rash) AND the critical public health intervention (contact chemoprophylaxis), which is unique to meningococcal disease. [cite:Harrison 21e Ch 384]