Neisseria Gonorrhoeae

Microbiology

  • Member of Neisseria Genus
  • Characteristics
    • Gram-negative diplococcus
    • Oxidase positive
    • May produce beta-lactamase
  • Strains: at least 70 different strains exist
    • Differentiated by presence/absence of pili (hairlike appendages), opacity of colonies, auxotyping (nutritional requirements), serotyping, and genotyping
  • Infection: only known to infect humans

Physiology

  • Recruitment of Neutrophils: Neisseria Gonorrhoeae is able to recruit neutrophils -> accounts for purulence of infection
  • Piliated Strains: pili increased adherence and virulence by enhancing attachment to sperm and other cells
  • Opacity-Associated Strains: enhance virulence by enhancing adherence to cuboidal or columnar epithelial cells -> facilitates mucosal damage (and recruits neutrophils to the site
  • Ascending Infection: the affinity for blood of Neisseria Gonorrhoeae may faciltate retrograde spread of the organism from the vagina/cervix (lower genital tract) to endometrium/fallopian tubes/ovaries (upper genital tract) or even the peritoneal space via refluxed menstrual blood or attachment to sperm
    • Infection in females may present during menses with fever

Diagnosis

Nucleic Acid Amplification Test (NAAT)

  • Indications: second generation tests are indicated to detect both Neisseria Gonorrhoeae and Chlamydia Trachomatis in males/females with or without symptoms
  • Availability: commercially available from multiple manufacturers (Roche, etc)
  • Technique: PCR amplification, strand displacement amplification (SDA), or transcription-mediated amplification (TMA) of organism DNA/RNA in sample
    • Technique can theoretically detect as little as one organism per samples (the detection threshold of culture is approximately 1000 organisms per sample)
    • Sensitivity of various amplification methods varies
  • Optimal Specimen Type
    • Male: first void urine sample
      • Perform as well or better than urethral swabs
    • Female: vaginal swab
      • Vaginal swabs perform as well as cervical swabs (although cervical swabs may be substituted in cases when pelvic exam is performed)
      • Self-collected vaginal swabs are equivalent in sensitivity/specificity to clinician-collected vaginal swabs
      • Female urine specimens are 10% less effective than vaginal swabs for detection of Neisseria Gonorrhoeae (possibly related to the presence of urine inhibitory substances which may interfere with NAAT)
      • Female “clean catch” urine (if being performed at the same time) requires external cleansing of the urethra, which will impede optimal NAAT testing of urine -> therefore, NAAT of female urine should be performed using first void urine without external cleansing prior to collection
  • Cost-Effectiveness: cost effective in preventing sequelae of Neisseria Gonorrhoeae and Chlamydia Trachomatis infections
  • Cross-Reactivity with Non-Gonococcal Neisseria Species: none
  • Advantages of NAAT Over Urethral Swab Culture
    • Higher Sensitivity (100%) and Equal Specificity (99%) Than Urethral Swab Culture
    • Non-Invasive Collection Method: requires only urine to perform, rather than a urethral swab
    • Single Test Can Be Employed for Both Organisms
    • Faster Test Turnaround Time Than Urethral Swab Culture
  • Advantages of NAAT Over Other Molecular Testing Methods
    • NAAT’s are preferred over direct fluorescence antibody testing, ELISA’s, nucleic acid hybridization tests due to their superior sensitivity/specificity
  • Disadvantages of NAAT
    • NAAT does not enable determination of antibiotic sensitivities: therefore, cultures are still required in cases where antibiotic resistance is suspected
    • NAAT does not provide results at the point of care (specimens must be processed in the lab)
    • NAAT is expensive
  • Use of NAAT with Non-Genital Body Specimens
    • NAAT have higher sensitivity than culture to detect Chlamydia Trachomatis in oropharyngeal or rectal samples in males with have intercourse with other males: however, this use is not FDA-approved and needs to be validated in terms of performance at the local lab/clinical site

Urinalysis with Urine Culture

  • Specimen: first void urine specimen is required
    • Urination within 2 hrs of exam should be avoided, as it may impair the ability to detect organisms
  • Criteria: >10 WBC per hpf on first void urine is consistent with urethritis
  • Criteria: positive leukocyte esterase (on dipstick) on first void urine is consistent with urethritis

Urethral Swab with Culture

  • Used historically to diagnose Neisseria Gonorrhoeae and Chlamydia Trachomatis infections: however, NAAT above is now the preferred diagnostic method to detect these organisms
  • Culture is currently the only means of detecting Mycoplasma Genitalium and Ureaplasma Urealyticum infections
    • DNA-based testing methods (with 97% sensitivity) for these organisms have been developed, but are not commercially available yet
  • Criteria: >5 neutrophils per hpf indicates presence of urethritis
  • Disadvantages
    • Urethral swab procedure is uncomfortable

Other Testing

  • Herpes Simplex Virus (HSV) Culture and PCR: indicated in patients who have genital ulcer(s)
  • Affirm PCR Assay: indicated only in female cases to detect the 3 major causes of bacterial vaginosis (Candida, Gardnerella, and Trichomonas)
    • Utilizes vaginal/cervical swab
  • HIV Test: usually indicated in cases of suspected sexually-transmitted infection, due to possibility of co-infection with HIV
  • RPR: usually indicated in cases of suspected sexually-transmitted infection or genital ulcer(s), due to possibility of co-infection with syphilis

Clinical Manifestations

Genito-Urinary Manifestations

  • Epididymitis (see Epididymitis, [[Epididymitis]])
  • Pelvic Inflammatory Disease (PID)
  • Urethritis (see Urethritis, [[Urethritis]])

Other Manifestations

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Treatment

Antibiotics

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Public Health Reporting

  • Confirmation of a sexually-transmitted infection requires reporting to public health department

References

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