Evaluation of Gonochek-II as a rapid identification system for pathogenic Neisseria species

Abstract

The Gonochek-II test kit (E-Y Laboratories, San Mateo, Calif.) may be used to rapidly identify (within 30 min) Neisseria gonorrhoeae, Neisseria meningitidis, Neisseria lactamica, and Branhamella catarrhalis. The kit consists of oxidase swabs, chromogenic substrates, and EY-20 reagent (diazonium salt derivative). A beta-lactamase tube is also included. Fifty-two clinical isolates were tested from cervical (22 isolates), urethral (13), throat (11), rectal (5), and urine (1) sources. All strains were oxidase-positive, gram-negative diplococci isolated on Thayer-Mayer plates incubated at 35° C in 5% CO2 for 18 to 24 h. Each strain was tested by Gonochek-II, RapID NH (Innovative Diagnostics, Decatur, Ga.), and conventional rapid carbohydrate utilization. Forty-four isolates of N. gonorrhoeae and six N. meningitids were identified. Only two isolates tested (4%) were identified as species other than these two. Gonochek-II outperformed all other methods for identification of N. gonorrhoeae from cervical and urethral areas. N. meningitidis strains were correctly identified in all cases. Ease and rapidity of the procedure, coupled with a small inoculum requirement and reliable results, led us to favor Gonochek-II for routine identification of pathogenic Neisseria species.