In patients with symptomatic gonococcal urethritis, how efficacious is a Gram stain of the exudate in comparison to a culture utilizing selective media for gonococcus?

A Gram stain of a urethral discharge in symptomatic males is an excellent method of diagnosing gonorrhea. A positive Gram stain showing multiple neutrophils, some containing clusters of gram-negative diplococci with the sides flattened toward one another, is cited as having a sensitivity of 98%. With such a Gram stain, a culture is expensive and adds little diagnostic yield (about 2%). Cultures are usually done in males with a urethritis and a negative or nondiagnostic Gram stain of the urethral exudates. In women suspected of having gonorrhea, the site of choice for obtaining specimens is the endocervix. However, gram-stained smears are relatively insensitive (30% to 60%), and their interpretation is difficult. A culture on selective media is essential to diagnose gonorrhea in women.

Holder NA: Gonococcal infections, Pediatr Rev 29:228–234, 2008.