Neisseria meningitidis is an exclusively human, gram negative, bean - shaped pathogenic diplococcus. Cells are nonmotile and do not produce endospore. Neisseria meningitidis has complex growth requirements. It is an aerobic bacteria and its optimal growth temperature is 35ºC, require humidity and 2 to 8% CO2. It produces acid from glucose and maltose, but not from lactose and sucrose. Traditionally, strains were characterized by using antibodies that recognized surface exposed epitopes on the capsule or outer membrane. By this technique, 13 serogrups 20 serotypes and 11 subtypes have been defined. Twelve inmunotypes have been defined by lipopolisacharide. Transmission of meningococal strain usually occurs by air borne droplets. Like most bacterial pathogens, Neisseria meningitidis initiate infection by colonization of the host at the site of entry, the epittelial cells lining the mucosal surfaces of the nasopharynx. Pili are the mayor adhesins that contribute to the attachment to mucosal cells. After primary binding, further contact with the host cell is established via class 5 OMPs, capsule and lipooligosacarides. Meningococci pass through the mucosal epithelium to the bloodstream where survive and proliferate or progress to the cerebrospinal fluid to cause meningitis. During periods of endemic infection, approximately 10% of the population harbor meningococci in the nose, but 9 of 10 strain isolated are considered nonpathogenic because they are not associated with the clones cultured from patients. Others conditions for meningococal naso-oropharyngeal carrier are age, sex, social condition, exposure to passive or active cigarette smoke, immune status and viral infection.

Have been defined tree class of carriers :

Transitory , the harbored status is very short (days or weeks); Chronic , colonization may persist for long times (2 years or more), and Intermittent , harboring repeatedly during short times. A capsule-based vaccine is available commercially and proven safe and effective in preventing meningitis caused by serogrup A and C, but not serogrup B. Moreover to prevent disease by means of eradication of carriers. Rifampicin is the drug of choise, ciprofloxacin, ofloxacin,minocicline (not in children) and ceftriaxone are good alternatives.