Evaluation of the fluorescent gonococcal test-heated

Limulus lysate assay in detection of gonorrhea in women from a low-incidence population

An evaluation of the limulus amebocyte lysate assay for detection of gonococcal endotoxin in cervical secretions was undertaken in 48 women from an ambulatory population with a low incidence of gonococcal infection. When cervical secretions were diluted 1 : 2,000, positive limulus amebocyte lysate assay results were obtained in four women (100%) with culture-proved gonococcal infection, and negative results were obtained in 25 of 44 women (57%) with culture-negative specimens. The limulus amebocyte lysate assay was not sufficiently specific in a low-incidence, largely asymptomatic population to be recommended as a rapid diagnostic procedure (60 minutes) in such a group. Standardization of sampling technique, size, and reagent preparation and elimination of vaginal contamination of cervical secretions may produce a limulus amebocyte lysate test with more consistent performance characteristics in varied populations. Since the predictive value of a test varies with the prevalence of the disease in the populations tested, a test proposed for use in a population with a low likelihood of disease must be tested in such a population.

Enzymatic detection of Neisseria gonorrhoeae

In a study using a non-serological enzymatic approach for the detection of Neisseria gonorrhoeae in cervical and urethral swabs, the technique was shown to be technically feasible. The enzyme, 1, 2-propanediol oxidoreductase, was used as a presumptive diagnostic marker for N gonorrhoeae. Enzymatic activity was measured with a fluorometer. Two assay procedures were performed: (a) enzyme detection (two-tube and three-tube assays) requiring 60 minutes; and (b) enzyme inhibition (EI) (90-minute and modified 20-minute assays). Sensitivities of the two-tube, three-tube, and the 90-minute EI assays with male urethral specimens from a high-prevalence population were 80%, 84%, and 91% respectively. The specificities of these assays in a low-prevalence male population were not determined. Sensitivity of the 90-minute EI assay in a high-prevalence female group was 77% and specificity in a low-prevalence female group was 75%. The modified EI assay was tested only in a low-prevalence female group and had 87% specificity. Although the specificity of the assays needs improvement, several advantages--including early case detection, rapid availability of results, detection of current active infections, and the possibility of automation--are intrinsic in this enzymatic approach.

Purification of Neisseria gonorrhoeae surface L-antigen

A purified preparation of the L-antigen of Neisseria gonorrhoeae with a 40-fold increase of antigenic activity over the crude extract was prepared. The antigen was extracted from the cell envelope by mild treatment with sodium dodecyl sulfate and purified by Sepharose 4B, diethylaminoethyl-cellulose, and diethyl-(2-hydroxypropyl)aminoethyl (QAE)-Sephadex column chromatography. The purified antigen was heat labile and trypsin sensitive. The smallest antigenically active subunit appeared to have a molecular weight of 38,500, as shown by polyacrylamide gel electrophoresis of the product incubated with sodium dodecyl sulfate.