Chlamydia Trachomatis

Microbiology

  • Member of Chlamydia Genus (Family: Chlamydiaceae)
  • Characteristics: small, obligate intracellular, Gram-negative organism
    • Major Outer Membrane Protein (MOMP): functions as adhesin for binding to epithelial cells
    • Lipopolysaccharide (LPS): functions to elicit immune response to organism
  • Life Cycle
    • Inactive Form: inactive elementary bodies attach to and penetrate into cells -> changing into the active form (reticulate bodies) within 6-8 hrs
    • Active Form: active reticulate bodies form large intracellular inclusions
      • Reticulate bodies reorganize into elementary bodies and within 2-3 days, cell ruptures and releases newly formed elementary bodies
  • Antibiotic Resistance: appears to be very rare

Physiology

  • Immunity to Chlamydia Trachomatis Infection: typically not long-lasting -> this may explain persistent or recurrent infections
    • The intracellular location of Chlamydia Trachomatis infection eliminates the need for rapid evolution of cell surface components that might contribute to antibiotic resistance
    • As elementary bodies are relatively inert, opportunities for replication and the generation of antibiotic resistance mutations are limited
    • These features may explain the relatively asymptomatic nature of many Chlamydia Trachomatis infections

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]])
  • Lymphogranuloma Venereum (LGV) (Climatic Bubo, Durand–Nicolas–Favre Disease, Poradenitis Inguinale, Strumous Bubo)
  • Urethritis (see Urethritis, [[Urethritis]])

Ophthalmalogic Manifestations

Pulmonary Manifestations

Other Manifestations

  • Trachoma

Treatment

  • xxx:

References

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