Meningitis, Meningococcal

Key Features

Essentials of Diagnosis

• Fever, headache, vomiting, delirium, convulsions

• Petechial rash of skin and mucous membranes

• Neck and back stiffness; positive Kernig and Brudzinski signs are characteristic

• Purulent spinal fluid with gram-negative intracellular and extracellular diplococci

• Culture of cerebrospinal fluid, blood, or petechial aspiration confirms the diagnosis

General Considerations

• Caused by Neisseria meningitidis of groups A, B, C, Y, W-135, and others

• Infection is transmitted by droplets

• The clinical illness may take the form of meningococcemia (a fulminant form of septicemia without meningitis), meningococcemia with meningitis, or predominantly meningitis

• Chronic recurrent meningococcemia with fever, rash, and arthritis can occur, particularly in those with terminal complement deficiencies

Demographics

• The prevalence of strains of N meningitidis with intermediate resistance to penicillin in vitro (MICs 0.1–1 mcg/mL) is increasing, particularly in Europe

Clinical Findings

Symptoms and Signs

• High fever, chills, nausea and vomiting, and headache as well as back, abdominal, and extremity pains are typical

• In older adults, fever or stiff neck is often missing, and altered mental status may dominate the picture

• Rapidly developing confusion, delirium, seizures, and coma can occur in some patients

• Nuchal and back rigidity are typical

• A petechial rash is found in most cases; it appears

  • All over the body, including on mucous membranes

  • On the lower extremities

  • At pressure points

• Petechiae may vary from pinhead sized to large ecchymoses or even areas of skin gangrene that may later slough

Differential Diagnosis

• Meningococcal meningitis must be differentiated from other meningitides

• Rickettsial, echovirus and, rarely, other bacterial infections (eg, staphylococcal infections, scarlet fever) can cause petechial rash

Diagnosis

Laboratory Tests

• The organism is usually found by smear or culture of the cerebrospinal fluid, oropharynx, blood, or aspirated petechiae

CEREBROSPINAL FLUID ANALYSIS

• See Table 30–1

• Typically, a cloudy or purulent fluid, with elevated pressure, increased protein, and decreased glucose content

• Usually contains more than 1000 cells/mcL (1.0 × 10⁹/L), with polymorphonuclear cells predominating and containing gram-negative intracellular diplococci

• The absence of organisms in a Gram-stained smear does not rule out the diagnosis

• The capsular polysaccharide can often be demonstrated in cerebrospinal fluid or urine by latex agglutination; this is especially useful in partially treated patients, though sensitivity is only 60–80%