Microbiology · Year 2 · from Microbiology

Case 1: Meningococcal Meningitis and Meningococcemia

Presentation

An 18-year-old male college freshman is brought to the emergency department by his roommate. The patient had been well until 12 hours ago when he developed fever, severe headache, and body aches that he thought was the flu. His symptoms rapidly worsened, and his roommate became alarmed when the patient became confused and developed a rash on his legs.

On examination, the patient is febrile (39.8°C), tachycardic (128 bpm), and hypotensive (85/52 mmHg). He is lethargic but arousable, oriented only to person. He has marked nuchal rigidity and photophobia. Scattered petechial lesions are present on his lower extremities and trunk, with some lesions beginning to coalesce into purpuric patches. Kernig and Brudzinski signs are positive.

The roommate mentions they attended a large party three days ago where the patient was "kissing a lot of people."

Clinical Image

Gram-negative diplococci with characteristic kidney-bean appearance - essential morphology for recognizing Neisseria species.

Image Source: Lecture image - Neisseria morphology

Questions

  1. What is the most likely diagnosis, and what organism is responsible? What immediate actions should be taken?
  1. What virulence factor is primarily responsible for the development of the petechial/purpuric rash and septic shock?
  1. What are the risk factors present in this case for developing invasive meningococcal disease?
  1. What public health measures are required following this diagnosis?

Answers

  1. Diagnosis and immediate actions:

Diagnosis: Meningococcal meningitis with meningococcemia caused by Neisseria meningitidis (the meningococcus).

Clinical features supporting this diagnosis:

  • Rapid onset and progression (12 hours)
  • Classic meningitis triad: fever, headache, nuchal rigidity
  • Altered mental status
  • Positive Kernig sign (pain on knee extension with hip flexed) and Brudzinski sign (hip flexion with neck flexion)
  • Petechial rash progressing to purpura - highly characteristic of meningococcemia

Immediate actions (within minutes):

  1. Empiric antibiotics: Ceftriaxone 2g IV IMMEDIATELY - do not wait for LP or imaging
  2. Blood cultures: Obtain before antibiotics if possible without delay
  3. IV fluid resuscitation: Aggressive volume replacement for septic shock
  4. Dexamethasone: 0.15 mg/kg IV before or with first antibiotic dose
  5. Lumbar puncture: After antibiotics started and if no contraindications (signs of elevated ICP)
  6. Vasopressors: If hypotension persists despite fluid resuscitation

Time to antibiotics is critical - mortality increases with each hour of delay.

  1. Virulence factor responsible for shock and rash:

Lipooligosaccharide (LOS) - the gram-negative endotoxin of Neisseria meningitidis.

Mechanism:

  • LOS (similar to LPS but without O-antigen repeats) is released during bacterial multiplication and death
  • Activates TLR4 signaling pathway → massive cytokine release (TNF-α, IL-1, IL-6)
  • Meningococcal LOS is particularly potent, causing extremely high cytokine levels

Pathophysiology of findings:

  • Petechiae/purpura: LOS activates endothelial cells → microvascular thrombosis → hemorrhagic skin necrosis
  • Septic shock: Vasodilation and capillary leak from cytokines
  • DIC (disseminated intravascular coagulation): Coagulation cascade activation with simultaneous consumption of clotting factors
  • Purpura fulminans: Progression to extensive purpuric lesions with skin necrosis

Mortality from meningococcemia with shock approaches 40% even with optimal treatment.

  1. Risk factors in this case:

Age and setting:

  • College freshman in dormitory: First-year college students living in dormitories have 3-5x increased risk
  • Adolescent/young adult: Peak age for invasive disease
  • Crowded living conditions: Facilitates transmission of respiratory secretions

Exposure:

  • Close contact exposure: "Kissing a lot of people" at party - intimate contact transmits nasopharyngeal colonization
  • Incubation period: 3 days from party to symptoms is typical (1-10 day range)

Host factors (not specifically identified in this case but important):

  • Complement deficiency (C5-C9, properdin): Dramatically increases risk
  • Asplenia: Impairs clearance of encapsulated bacteria
  • Eculizumab use: Complement inhibitor
  • HIV infection

Other factors:

  • Recent viral URI: Damages nasopharyngeal epithelium
  • Cigarette smoking: Alters respiratory epithelium
  1. Public health measures:

Chemoprophylaxis for close contacts (within 24 hours of diagnosis):

Who qualifies as close contact?

  • Household members
  • Roommates (college dormitory)
  • Intimate/kissing contacts
  • Anyone who shared saliva (utensils, beverages)
  • Childcare/daycare contacts
  • Healthcare workers who performed unprotected mouth-to-mouth or intubation

NOT close contact: Routine classroom or workplace exposure

Recommended prophylaxis regimens:

  • Ciprofloxacin: 500 mg PO x 1 dose (not for pregnant patients)
  • Rifampin: 600 mg PO q12h x 2 days
  • Ceftriaxone: 250 mg IM x 1 dose (safe in pregnancy)

Index patient prophylaxis:

  • If treated with ceftriaxone: No prophylaxis needed (eradicates carriage)
  • If treated with penicillin: Needs prophylaxis before discharge (penicillin doesn't eradicate nasopharyngeal carriage)

Additional measures:

  • Report to public health authorities (mandatory)
  • Evaluate for outbreak (≥2 cases in same setting)
  • Consider vaccination of exposed population

All cases for this lecture as Markdown