137 - Gonococcus: Neisseria Gonorrhoeae

Summary

Neisseria gonorrhoeae is the second most common sexually transmitted bacterial pathogen after Chlamydia trachomatis, resulting in an estimated 600 000 cases per year in the United States. The gonococcus causes disease by attaching primarily to columnar or cuboidal epithelial cells (Table 137.1) via pili and outer membrane proteins. It then penetrates between and through the cells to submucosal areas, where it elicits a neutrophilic host response. The clinical spectrum of primary infection with Neisseria gonorrhoeae mirrors that of Chlamydia trachomatis, which is the most important etiological differential diagnosis.

Acute urethritis, manifesting as some combination of urethral discharge and dysuria, is the most common presentation of disease in men, although some infected men are asymptomatic. Gram stain of urethral discharge may be used for presumptive diagnosis of gonococcal urethritis. Polymorphonuclear neutrophils (PMN) with gram-negative, intracellular diplococci (Figure 137.1) are observed in 95% of infected, symptomatic men, and the finding is 98% specific. Observing PMN without gram-negative intracellular diplococci (GNID) supports a diagnosis of nongonococcal urethritis (see Chapter 58, Urethritis and Dysuria), but the sensitivity of GNID in asymptomatic men is only about 75%, and Gram stain cannot be used to rule out gonorrhea in these patients.