Direct FA Technique Using Flazo Orange Counterstain in Identification of Neisseria gonorrhoeae

Abstract

IN THE immunofluoreseent diagnosis of gonorrhea previously described (1-3), a direct and a delayed procedure for identifying gonococci in exudates have been used. When sufficient number of gonococci are present in the exudate, direct fluorescent antibody (FA) staining of smears permits detection and identification of the gonococci within less than an hour even when many contaminating bacteria are present. When the direct FA method is used, the presence of only a few gonococci in an exudate results in a 50 percent loss of sensitivity compared with results by the delayed FA method (1). By the delayed FA method, exudate collected with a swab is incubated 16 to 20 hours on chocolate agar slants, and gonococci too few to detect by the direct FA technique groiw to easily observable numbers. Rapid diagnosis of gonorrhea is often necessary, and the longer time required with the delayed FA method is undesirable. When the simpler, faster, direct FA procedure is used, differentiation of specific Neisseria gonorrhoeae fluorescence is difficult even when the organisms are present in sufficient numbers to permit identification. Various counterstains have been reported to increase the effectiveness of the FA method (4-6). These counterstains allow faster and more specific detection of microorganisms in smears by increasing the background contrast. Careful attention to the collection of specimens for direct smears is necessary for the successful detection of gonococci. It has been suggested (7) that the use of a bacteriological loop is preferable to a swab for the collection of specimens from female gonorrheal patients, particularly when a small amount of exudate is present. In this study the results of examination of smears by the direct FA (DFA) method and by the direct FA method using Flazo orange counterstain (FFA) were compared with the cultural results when specimens were obtained with a bacteriological loop.