Diagnosis & treatment Of Chlamydia Infection

TESTING TECHNOLOGY:
  • Culture
  • Non-culture tests
  1. Nucleic Acid Amplification Tests (NAATs)
  2. Non-Nucleic Acid Amplification Tests (Non-NAATs)
  3. Serology
CULTURE:
  • Historically the “gold standard”
  • Variable sensitivity (50%-80%)
  • High specificity
  • Use in legal investigations
  • Not suitable for widespread screening
  • Cell culture is usually used for the cultivation 
  • Many cell lines are susceptible but those commonly used are McCoy and HeLa cells.
  1. Yolk sac inoculation
  2. Yolk sac inoculation is used for diagnosing chlamydia from tissue specimen.
  3. Yolk sac inoculation , Tissue culture using irradiated McCoy cells , Tissue culture using irradiated BHK cells are the method of isolation of chlamydia from clinical specimens C. trachomatis in embryonated hens' eggs, McCoy cells (mouse fibroblasts), HeLa 229 (derived from human cervical carcinoma cells) and BHK-21 cells (baby hamster kidney cells) are the cell types regularly used for the culture of C. trachomatis.
  • Cell cultures used for isolation are pretreated by irradiation or chemicals such as 5-iodo-2-dexoyuridine or cycloheximide to enhance chlamydial replication and facilitate detection of inclusion antibodies.
NAATs:
  • NAATs amplify and detect organism-specific genomic or plasmid DNA or rRNA
  • FDA cleared for urethral swabs from men/women, cervical swabs from women, and urine from both
  • PCR and LCR are both sensitive and specific methods for detecting cervical Chlamydia trachomatis infection in women.
  • PCR is a method to amplify minute amounts of genetic material.The reaction can thus be used for detecting very tiny amounts of pathogen.Prerquisite is the preparation of pathogen specific DNA primer.
  1. Commercially available NAATs include:
  2. Becton Dickinson BDProbeTec
  3. Gen-Probe AmpCT, Aptima
  4. Roche Amplicor
  5. Significantly more sensitive than other tests
Non-NAATs:
  • Direct fluorescent antibody (DFA)
  1. Detects intact bacteria with a fluorescent antibody
  2. Variety of specimen sites
  3. Can be used to determine quality of endocervical specimens
  • Enzyme immunoassay (EIA)
  1. Detects bacterial antigens with an enzyme-labeled antibody
  • Nucleic acid hybridization (NA probe)
Detects specific DNA or RNA sequences of C. trachomatis and N. gonorrhoeae
Gram staining:
  1. Presence of pus cells with absence of any microorganisms on gram stain
  • Fries test (skin hypersensitivity test) was used for LGV (caused by chlamydia trachomatis).But it is not used now because of high false positive results.
Serology:
  • Rarely used for uncomplicated infections (results difficult to interpret)
  • Criteria used in LGV diagnosis
  1. Complement fixation titers >1:64 suggestive
  2. Complement fixation titers > 1:256 diagnostic
  3. Complement fixation titers < 1:32 rule out
TREATMENT: Treatment of Uncomplicated Genital Chlamydial Infections
CDC-recommended regimens
  1. Azithromycin 1 g orally in a single dose, OR
  2. Doxycycline 100 mg orally twice daily for 7 days
Treatment of chlamydial Cervicits:
Tetracycline
Treatment of Chlamydial Infection in Pregnant Women
CDC-recommended regimens
  1. Azithromycin 1gm as a single dose(latest )
  2. Erythromycin base 500 mg orally 4 times a day for 7 days, OR
  3. Amoxicillin 500 mg orally 3 times a day for 7 days
Treatment of Neonatal Conjunctivitis and/or Pneumonia
CDC-recommended regimen
  • Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into 4 doses daily for 14 days
Treatment of Chlamydial Infection in Children
Children who weigh
  • Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into 4 doses daily for 14 days
Children who weigh ≥45 kg, but are
Azithromycin 1 g orally in a single dose
Children ≥8 years of age:
  • Azithromycin 1 g orally in a single dose, OR
Doxycycline 100 mg orally twice a day for 7 days
Treatment of Lymphogranuloma Venereum (LGV)
CDC-recommended regimen
  • Doxycycline 100 mg orally twice a day for 21 days
Alternative regimen
Erythromycin base 500 mg orally 4 times a day for 21 days
REPEAT TEST AFTER TREATMENT:
Pregnant women
  • Repeat testing, preferably by culture, 3 weeks after completion of recommended therapy
Non-pregnant women
  • Screen 3-4 months after treatment, especially adolescents
  • Screen at next health care visit
  • Consider test of cure 3 weeks after completion of therapy for anyone treated with erythromycin
Exam Question
  • A patient with discharge per vagina was evalu­ated and on endocervical biopsy Chlamydia was found. Treatment to be given in this case is Azithromycin 1 g orally in a single dose + Contact tracing
  • In chlamydial cervicitis drug of choice is Tetracycline
  • Most sensitive investigation for diagnosis of asymptomatic chlamydial infection is Nucleic acid amplification
  • Yolk sac inoculation is used for diagnosing chlamydia from tissue specimen.
  • PCR and LCR are both sensitive and specific methods for detecting cervical Chlamydia trachomatis infection in women.
  • Fries test (skin hypersensitivity test) was used for LGV (caused by chlamydia trachomatis)
  • Treatment of chlamydia pneumonia is Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into 4 doses daily for 14 days
  • Presence of pus cells with absence of any microorganisms on gram stain favour the diagnosis of chlamydia
  • McCoy and HeLa cells is usually used for the cultivation of chlamydia
  • Yolk sac inoculation , Tissue culture using irradiated McCoy cells , Tissue culture using irradiated BHK cells are the method of isolation of chlamydia from clinical specimens Drug of choice for treatment of chlamydia in pregnant women is Azithromycin 1gm as a single dose/Erythromycin base 500 mg orally 4 times a day for 7 days

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