Gonorrhoeae Information and Courses from MediaLab, Inc.

Superoxol is an additional spot test that may be helpful in the presumptive identification of N. gonorrhoeae. Superoxol is 30% hydrogen peroxide, in contrast to the 3% solution that is used in the catalase test. Other Neisseria species and Moraxella catarrhalis are either negative for this test or give a weak, delayed reaction.

Smith KR, Fisher HC III, Hook, EW III: Prevalence of fluorescent monoclonal antibody-nonreactive Neisseria gonorrhoeae in five North American sexually transmitted disease clinics. J Clin Microbiol 34:1551-1552, 1996 We compared a direct fluorescent monoclonal antibody (DFA) test with alternative enzymatic and fermention tests for identifying presumptive gonococcal isolates in a systematic sample from patients attending five sexually transmitted disease clinics in five cities. Fourteen (2.5%) of 556 isolates from three clinics were nonreactive with the DFA confirmatory reagent and reactive by both the Quad-Ferm and Rapid NH tests. The prevalence of DFA-nonreactive Neisseria gonorrhoeae isolates varies geographically and is independent of local methods for the identification of possible gonococci. On the basis of our findings, we recommend that for use in medicolegal and other instances in which a diagnosis of gonorrhea has the potential to have far-reaching effects, it is appropriate to test DFA reagent-nonreactive, oxidase-positive, gram-negative diplococci by alternative methods of gonococcal confirmation. Although the prevalence of such isolates could change, the fluorescent monoclonal antibody confirmation reagents remain useful for many clinical situations. Their ease of use and ready applicability for screening large numbers of isolates make them useful for many laboratories.

Molecular methodologies can be useful in the detection of a variety of diseases that are important public health issues such as:Chlamydia trachomatis (CT) Neisseria gonorrhoeae (GC)Human papillomavirus (HPV)Human immunodeficiency virus(HIV)Herpes simplex virus(HSV)Cytomegalovirus(CMV)In many clinical laboratories, traditional methods have been replaced by molecular methodologies because testing can occur for several pathogens in a single specimen. This is termed multiplex testing.

In 1988, Gen-Probe marketed the PACE® System, using non-amplified probes for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae. This product was later followed by the PACE® 2 product line.Amplified assays for both Chlamydia and Neisseria followed in subsequent years, offered by several manufacturers. Automation of at least some parts of the process made it more feasible for clinical laboratories to incorporate molecular methods into their test menus.Roche developed a polymerase chain reaction (PCR) methodology focusing on specific nucleic acid sequences for both organisms. The Roche COBAS® AMPLICOR assay, on a semi-automated platform, obtained Food and Drug Administration (FDA) clearance in 1999. The Abbott LCx® semi-automated platform, based on ligase chain reaction, was also introduced around the same time. Shortly thereafter, Gen-Probe offered their APTIMA Combo 2® Assay, an amplification assay that utilized target capture. Later on, the TIGRIS® automated system by PROCLEIX® was added to provide automated specimen processing, enhancing the efficiency of the product line. Becton Dickenson then entered the arena, with the ProbeTec™, another semi-automated system based on strand displacement amplification.Digene also marketed its hybrid capture assay for Chlamydia and Neisseria. Unlike the other commercial assays, this method did not amplify the target DNA sequence, but instead employed a chemiluminescent methodology to amplify the signal of RNA:DNA hybrids.

Gram-negative cocci that occur in pairs with their adjacent sides flattened, giving them a "coffee bean" appearance, are typical of the genus Neisseria. The presence of intracellular gram-negative diplococci on a smear made from a purulent urethral discharge from a male can be confirmatory of the diagnosis of gonorrhea. In this case, cultures may not even be needed unless susceptibilities are required. However, if the genital specimen is from a female (cervical specimen), the presence of gram-negative diplococci is not specific enough to confirm the diagnosis, and a culture or other confirmatory testing must be performed. Organisms such as Acinetobacter sp. and Moraxella sp. may mimic the appearance of N. gonorrhoeae and can lead to false-positive results.Direct smears read specifically for the presence of Neisseria gonorrhea should include a direct reference to gram-negative intracellular diplococci.

Identification of bacteria in direct smears may be of lifesaving importance. For example, a rapid diagnosis of bacterial meningitis, made after examining a gram-stained smear of the patient's cerebrospinal fluid, allows the physician to begin treatment immediately. The appearance of bacteria on gram-stained smears is suggestive of a certain species, but identification may not be made on the basis of the stain alone. An exception to this rule is the presence of gram-negative intracellular diplococci from a male urogenital specimen, which is presumptive identification of Neisseria gonorrhoeae. In addition, culture results can be correlated with the direct smear report.