Epidemiology of Neisseria gonorrhoeae

Epidemiology

◗ Geographical distribution

Gonococcal infection is reported throughout the world. However, the incidence is much lower in the European coun-tries, and this condition has virtually been eliminated in Sweden. The highest incidence of gonorrhea and its complica-tions occurs in developing countries. The median prevalence of gonorrhea in pregnant women has been estimated to be 4% in Asia, 5% in Latin America, and 10% in Africa.

◗ Habitat

N. gonorrhoeae is exclusively a human pathogen. The gonococciare only found in infected conditions. In infected women, the gonococci are most commonly found in the endocervix, and in infected men found in the urethra. In both men and women gonococci can also be found in the pharynx, rectum, and eyes. The gonococci are not found as normal human flora in the mucosa of the urethra, cervix, or vagina.

◗ Reservoir, source, and transmission of infection

Only humans, especially asymptomatic infected men and women, are reservoirs of infections. Asymptomatic carriage is more common in women than in men. Purulent urethra or cer-vical discharge is the most common source of infection. The infection is transmitted:

·           Primarily by sexual contact. N. gonorrhoeae infection occurs following mucosal inoculation during vaginal, anal, or oral sexual contact. Increased sexual contact with infected part-ners increases the risk of acquiring the infection.

·           Less frequently, by nonsexual contact. Ophthalmia neona-torum is acquired nonsexually. This infection occurs follow-ing a conjunctival inoculation during vaginal delivery. Less frequently, the disease is transmitted through rectum, oro-pharynx, or through the birth canal.

Fomites do not play any role in transmission of the disease, because gonococci die rapidly outside the human body.

Strain typing: Strains ofN. gonorrhoeaecan be typed by(a) auxotyping and (b) serotyping.

·           Auxotyping is based on addition of specific nutrients andcofactors in the medium for the growth of gonococci. There are over 30 auxotypes. The most common auxotypes are prototrophic or wild type (Proto), praline-requiring type (Pro), and the strains requiring arginine, hypoxanthine, and uracil (AHU).

·           Serotyping is based on the OMP “Porin”, which is furtherdivided into serovars (e.g., 1A-4, 1B-12) based on agglutina-tion with a panel of monoclonal antibodies.