What is the criterion standard for diagnosis of gonorrhea?

Updated: Sep 07, 2018
  • Author: Brian Wong, MD; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Answer

Specific culture of a swab from the site of infection is a criterion standard for diagnosis at all potential sites of infection. Bacterial culture has high sensitivity and specificity, is relatively low cost, and is suitable for different types of specimen sources. Cultures are particularly useful when the clinical diagnosis is unclear, when a failure of treatment has occurred, when contact tracing is problematic, and when legal questions arise. However, culturing for Neisseria is problematic because the bacteria’s viability is difficult to maintain during transport and storage in various settings. Another drawback is the time; 24-72 hours may be needed before a preliminary culture result is available. Therefore, empiric treatment is often necessary in patients awaiting diagnosis via culture. [40]

A small percentage (approximately 5%) of isolated gram-negative diplococci from genital, rectal, and pharyngeal cultures are actually Neisseria meningitidis, which can cause clinical disease that is identical to gonococcal infections of the urethra, cervix, or rectum. Hence, speciation from samples from pharyngeal and rectal sites should be standard, while samples from genital sites are recommended.

Antimicrobial susceptibility testing is generally unnecessary except in cases of resistance surveillance testing or cases of disseminated infection.

N gonorrhoeae is a fastidious organism that requires an enriched medium, such as Thayer-Martin or Martin-Lewis medium, and must be incubated at 35-36.5°C with supplemental 5% CO2. Poor technique, failure to store collected specimens appropriately, and slow transport to the microbiology laboratory drastically reduce test sensitivity.

If multiple specimens are to be collected from one anatomic site, it is recommended that the N gonorrhoeae culture specimen be obtained first, as this will increase likelihood of successful culture. [36] Gonorrheal cultures should be obtained with a plastic or wire shaft with rayon, Dacron, or calcium alginate tip, as wooden shafts and cotton-tip swabs might be inhibitory and may prevent optimal recovery of the organism. Culture swabs should be inserted 2-3 cm into the male urethra or 1-2 cm into a female endocervical canal followed by 2-3 rotations of the swab. If there is urethral discharge, exudate collection is adequate for gonorrheal culture.


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