What is the most likely cause of a 19-year-old military recruit's condition, characterized by fever, headache, stiff neck, maculopapular rash, tachycardia, hypotension, elevated white blood cell (WBC) count with a left shift, thrombocytopenia, and growth of Gram-negative cocci in blood cultures?

Meningococcal Sepsis with Disseminated Intravascular Coagulation

The most likely organism is Neisseria meningitidis (meningococcus), characterized by lipopolysaccharide (endotoxin) that induces disseminated intravascular coagulation, as evidenced by the thrombocytopenia (80,000/μl) and clinical presentation of septic shock in this young military recruit.

Clinical Reasoning for Meningococcal Disease

This 19-year-old military recruit living in barracks presents with the classic constellation of meningococcal disease:

• Age and setting: Meningococcal infection predominantly affects adolescents and young adults, with military recruits in barracks representing a high-risk population due to close-quarter living conditions 1

• Rash characteristics: The maculopapular rash can occur with meningococcal sepsis, though it may take other forms including purpuric or petechial patterns; when a rash is present in the context of meningitis, N. meningitidis is the causative organism in 92% of cases 1

• Meningeal signs: The combination of severe headache, photophobia, stiff neck, and blurred vision indicates meningeal involvement, which occurs in approximately 60% of meningococcal disease presentations 1

• Septic shock features: The hypotension (100/60 mm Hg), tachycardia (126/min), and high fever (40°C) indicate shock resulting from hypovolemia (capillary leak syndrome), myocardial dysfunction, and altered vasomotor tone characteristic of meningococcal sepsis 1

Laboratory Findings Supporting Meningococcemia

• Gram-negative cocci in blood cultures: This definitively identifies N. meningitidis, a gram-negative diplococcus 2

• Thrombocytopenia (80,000/μl): This indicates disseminated intravascular coagulation (DIC), a hallmark complication of meningococcal sepsis caused by the lipopolysaccharide endotoxin 2, 3

• Leukocytosis with left shift: The WBC count of 26,000/μl with 25% band forms indicates severe bacterial infection, though this can vary in meningococcal disease 1

Why Lipopolysaccharide (LPS) is the Correct Answer

The lipopolysaccharide (oligosaccharide) component of the meningococcal outer membrane is the key virulence factor that induces DIC through the following mechanism:

• LPS triggers massive cytokine release and activates the coagulation cascade 2

• Platelets adhere to damaged vascular surfaces in meningococcemia, leading to consumption and thrombocytopenia 3

• The capillary leak syndrome and vascular damage result from endotoxin-mediated injury 1

• This explains the clinical triad of hypotension, thrombocytopenia, and multiorgan dysfunction seen in this patient 1, 2

Excluding Other Answer Choices

• Poly-glutamic acid capsule: This describes Bacillus anthracis, not N. meningitidis; anthrax does not present with this clinical picture

• Protein toxin from vaginal tampons: This describes toxic shock syndrome from Staphylococcus aureus, which would not grow as gram-negative cocci

• Tropism for placental tissue with erythritol: This describes Brucella species, which cause undulant fever without this acute presentation

• Toxins A and B in large bowel: This describes Clostridioides difficile, which causes antibiotic-associated colitis, not bacteremia with meningitis

Critical Management Implications

• Immediate antibiotic therapy: This patient requires urgent ceftriaxone or cefotaxime without waiting for confirmatory testing, as meningococcal sepsis can progress from initial symptoms to death within 12-48 hours if untreated 2

• Risk factors for fatal outcome: This patient exhibits multiple poor prognostic features including hypotension, shock, thrombocytopenia, and coagulopathy 1

• Close contact prophylaxis: Military barracks contacts require prophylactic antibiotics to prevent secondary cases 2