"For the microbiologic diagnosis of gonorrhea, culture is necessary for anti-microbial susceptibility testing, due to the large numbers of resistant strains.

In males, the diagnosis is based upon Gram staining of a urethral exudate.

• The presence of intracellular Gram-negative diplococci is diagnostic of gonorrhea.

 In females, the normal flora of the vagina confounds direct diagnosis by Gram stain.

• Culture is required.

Due to the fact that N. gonorrheae is rapidly killed by drying, the culture plate must be streaked in the examination room.

• A Thayer-Martin (or equivalent) bi-plate is normally used.

The left side of the plate contains chocolate agar, whereas the right side of the plate contains chocolate agar plus antibiotics.

• This inhibits normal flora and allows primarily the gonococcus to grow.

 Occasional strains of gonococcus will be resistant to the antibiotics in the agar, so both sides must be streaked."

Some institutions have recombinant DNA test for the gonococcus that eliminates the need for Thayer-Martin plates, but you may still have to use this culture method in many hospitals or clinics.

Ó 1999 KUMC Pathology and the University of Kansas, used with permission; courtesy of Dr. James Fishback, Department of Pathology, University of Kansas Medical Center.