Office laboratory identification of Neisseria gonorrhoeae

Current literature is contradictory regarding what tests are necessary to establish an adequate presumptive diagnosis for office identification of Neisseria gonorrhoeae. This is especially true in light of recent reports of N meningitidis causing acute genital infection. This study was designed to look at the various criteria recommended and to establish guidelines for the office identification of N gonorrhoeae. Four hundred thirty-six isolates grown on Thayer-Martin selective agar were studied. Of these, 156 were found to be oxidase-positive. Gram stain of the isolates showed that 31.4 percent of the oxidase-positive isolates were gram-negative diplococci, 59 percent were yeastlike mole, and 9.7 percent were gram-negative bacilli. All of the gram-negative diplococci were confirmed to be N gonorrhoeae by sugar fermentation studies. No isolates of N meningitidis or saprophytic Neisseria were found. On the basis of this finding, it is recommended that office identification of N gonorrhoeae from genital or anal cultures should include (1) growth on Thayer-Martin (or comparable) medium, (2) positive reaction to oxidase reagent, and (3) identification of gram-negative diplococci on Gram stain of the Thayer-Martin isolate.