The laboratory diagnosis of Neisseria gonorrhoeae

The present article describes the laboratory diagnosis of Neisseria gonorrhoeae by culturing of the organism from different types of clinical specimens followed by confirmatory tests. The success of culture methods requires good quality collection and transport of clinical specimens. The present guide describes the media requirements and cultural conditions for N gonorrhoeae growth and the characteristics for a presumptive identification of N gonorrhoeae. Confirmatory tests include biochemical tests, chromogenic enzyme substrate tests, immunoassays and nucleic acid methods. Nucleic acid detection methods include either amplification-based methods or nonamplification tests, and are increasingly used in clinical laboratories where a viable culture is not possible to obtain. Nucleic acid methods can also be used to detect the presence of low numbers in a specimen. Nucleic acid detection methods need confirmation with another amplification method or gene target. Controls must be included to ensure true positive and negative results, and to rule out nucleic acid contamination. Monitoring of antimicrobial susceptibilities of N gonorrhoeae is important to investigate treatment failure and to evaluate the efficacy of currently recommended therapies. Many methods for the characterization of N gonorrhoeae require cultures. The useful typing methods for determining strain relatedness include auxotyping, serotyping, plasmid profile analysis, DNA sequencing of the porB gene and pulsed-field gel electrophoresis. Quality assurance programs for diagnostic testing and antimicrobial susceptibility testing is reviewed.