N. meningitidis is responsible for a wide array of clinical manifestations. Most frequently, the organism causes meningitis, which may be seen with or without meningococcemia. Acute dissemination, heralded by petechiae, can progress to disseminated intravascular coagulation and death. Chronic meningococcemia is clinically similar to chronic gonococcemia with recurring fevers and arthralgias.

Epidemiology: Meningococcal conjunctivitis occurred in two time periods: around World War II and from 1970 to the present. Whereas almost half of the cases in the earlier era were in army personnel, almost all of the cases currently are in civilians. 95% of patients with primary meningococcal conjunctivitis are younger than 25 years, and 50% are younger than 5 years. The male to female ratio is 1.76 to 1.

Clinical Manifestations: Meningococcal conjunctivitis, like gonococcal conjunctivitis, is an acute or hyperacute conjunctivitis accompanied by a purulent exudate that can occur bilaterally but is usually unilateral. Gonococcal conjunctivitis in neonates tends to occur at 2 to 5 days of age (representing infection acquired at birth), whereas meningococcal conjunctivitis tends to occur in older infants, beyond the first week of life (representing infection from direct contact or airborne sources). However, rare cases of meningococcal conjunctivitis in infants less than a week old have been reported (likely representing infection from the maternal genital tract). Ocular complications of meningococcal conjunctivitis are infrequent (15% of patients) and do not portend poor ocular outcomes. The most frequent ocular complication is corneal ulceration.

Diagnosis: Although a gram stain of conjunctival exudate or scraping can be suggestive of N. meningitidis, it is unreliable for distinguishing N. meningitidis from N. gonorrhoeae or Moraxella catarrhalis, and diagnosis should rely on isolation and identification in culture. The organism is fastidious and grows in a moist environment at 35C-37C with 5% to 10% carbon dioxide. N. meningitidis produce large, smooth non-pigmented colonies and metabolize glucose and maltose (N. gonorrhoeae usually produce small, convex greyish white colonies and do not metabolize maltose). Serologic subtyping should not delay reporting but is useful for epidemiologic purposes.

Therapy: As the risk of developing systemic meningococcal disease in patients who receive only topical therapy is almost twenty fold greater than in patients who receive systemic therapy, systemic therapy with a third generation cephalosporin is mandatory for all patients with meningococcal conjunctivitis. Prophylaxis for family members and caretakers of infected neonates with rifampin should be encouraged. Blood and cerebrospinal fluid cultures in neonates should be considered.