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
