meningokocker

Meningokocker refers to Neisseria meningitidis, a Gram-negative diplococcus that colonizes the human nasopharynx. In most carriers the bacteria are asymptomatic, but transmission occurs via respiratory droplets and close contact, enabling outbreaks in settings such as dormitories, barracks, and schools. Serogroups A, B, C, W, X and Y are the main pathogenic lineages; distribution varies by region and age, and vaccination programs target several of these serogroups.

Pathogenesis begins with mucosal colonization, followed by invasion of the nasopharyngeal epithelium and, in some cases, bacteremia. The capsule, a major virulence factor, helps the organism evade phagocytosis. Other virulence factors include pili, opacity proteins, porins, and lipooligosaccharide. Meningococcal disease manifests primarily as meningitis or meningococcemia; meningitis presents with fever, headache, neck stiffness, and photophobia, while meningococcemia may cause a rapidly progressive septic shock with a characteristic petechial or purpuric rash. Waterhouse-Friderichsen syndrome is a potential, severe complication.

Diagnosis relies on rapid identification from blood or cerebrospinal fluid. Laboratory methods include Gram stain and culture (oxidase-positive, Gram-negative diplococci; glucose and maltose fermentation patterns), latex agglutination for serogroup, and PCR.

Treatment typically involves empiric therapy with a third-generation cephalosporin such as ceftriaxone or cefotaxime, adjusted to susceptibility when available. Adjunctive therapy is determined by clinical status. Antibiotic resistance remains uncommon but is monitored.

Prevention emphasizes vaccination and contact notification. Vaccines cover serogroups A, C, W and Y (MenACWY) and serogroup B (MenB vaccines). Close contacts of a case may require chemoprophylaxis with rifampin, ciprofloxacin, or ceftriaxone to reduce transmission.