Laboratory Diagnosis, Treatment, Prevention and Control of Chlamydia trachomatis 5/5 (9)

Laboratory Diagnosis, Treatment, Prevention and Control of Chlamydia trachomatis

Laboratory Diagnosis of Chlamydia trachomatis

Specimen

  • Urethral discharge, cervix swab, rectum, oropharynx, and conjunctiva swab are the frequently collected specimens.
  • In addition, other specimens such as, blood, urine, respiratory secretions, sputum, lung, and other tissues are collected and examined.
  • Pus from bubo is also useful for diagnosis of LGV.

Microscopy

  • Demonstration of chlamydial inclusion bodies stained by Giemsa, Castaneda, Machiavello, Gimenez stains or Lugol’s iodine.
  • C. trachomatis infections of conjunctiva, urethra, and cervix are diagnosed by demonstration of typical reniform inclusion bodies surrounding the nucleus.
  • Direct Immunofluorescence test (DIF) is used as for direct detection of inclusion bodies in clinical material, particularly from the genital tract and eye.
  • In DIF, fluorescent tagged monoclonal antibodies directed against group-specific LPS antigen or species-specific MOMP antigens are added.

Culture

  • Isolation of C. trachomatis in cell cultures is the more specific method for diagnosis of C. trachomatis infection.
  • Centrifugation of specimens onto cycloheximide treated McCoy or HeLa cell monolayers, followed by incubation and then staining with a fluorescent monoclonal antibody or with a vital dye, to detect inclusions, has been widely used for the diagnosis of C. trachomatis infection.

Chlamydia trachomatis is grown in cell cultures


Figure: Chlamydia trachomatis is grown in cell cultures and detected by staining inclusion bodies (arrows) with either iodine- or specific fluorescein-labeled antibodies.

Antigen detection

  • Two general approaches have been used to detect chlamydial antigens in clinical specimens: direct immunofluorescence staining with fluorescein-conjugated monoclonal antibodies and enzyme-linked immunosorbent assays.
  • In both assays, antibodies are used that have been prepared against either the chlamydial MOMP or the cell wall LPS.
  • The DFA uses monoclonal antibodies directed against a species-specific antigen on the chlamydial MOMP.
  • The EIA detects the presence of genus-specific antigens extracted from EBs in the specimen.

Nucleic Acid–Based Tests

  • Nucleic acid probe tests most commonly measure the presence of a species-specific sequence of 16S ribosomal RNA.
  • The advantage of these tests is that the nucleic acid does not have to be amplified, making the tests rapid and relatively inexpensive; however, these tests are relatively insensitive for the detection of small numbers of chlamydiae.
  • Various methods available are:
    • Polymerase chain reaction (PCR)
    • Ligase chain reaction (LCR)
    • Transcription-mediated amplification (TMA)
    • Strand displacement assay (SDA).

Antibody Detection

  • Serologic testing is of limited value in the diagnosis of trachomatis urogenital infections in adults because the test cannot differentiate between current and past infections.
  • C. trachomatis IgM antibody is the ‘gold standard’ for the diagnosis of chlamydial pneumonia in babies.
  • Antibody tests for the diagnosis of LGV can be helpful.
  • Infected patients produce a vigorous antibody response that can be detected by complement fixation (CF), microimmunofluorescence (MIF), or enzyme immunoassay (EIA).

Laboratory Diagnosis, Treatment, Prevention and Control of Chlamydia trachomatis

Treatment of Chlamydia trachomatis Infection

  • Tetracyclines and macrolides are the mainstay of treatment.
  • Tetracyclines (eg, doxycycline) are commonly used in nongonococcal urethritis and in nonpregnant infected women.
  • Azithromycin is effective and can be given to pregnant women.
  • Ophthalmia neonatorum and neonatal pneumonia due to trachomatis should be treated with erythromycin.
  • Erythromycin may be administered orally and topically for treatment of ophthalmia neonatorum.
  • Systemic erythromycin is effective treatment in severe cases.
  • Recommended treatment for LGV is doxycycline or erythromycin.
  • Azithromycin has been used successfully in some cases.
  • Ocular infection can be effectively treated with a single oral dose of azithromycin.

Prevention and Control of Chlamydia trachomatis Infection

  • Health education and condom promotion, especially for the youngest sexually active age groups may help to reduce the incidence of genital C. trachomatis infection.
  • Periodic screening of high risk groups, such as young women having multiple sex partners.
  • Use of barrier methods of contraception such as condoms.
  • Chlamydia conjunctivitis and genital infections are prevented through the use of safe sex practices and the prompt treatment of symptomatic patients and their sexual partners.
  • The blindness associated with advanced stages of trachoma can be prevented only by prompt treatment of early disease and the prevention of re-exposure.
  • Screening of mother giving birth to a child for Chlamydial infections.

Laboratory Diagnosis, Treatment, Prevention and Control of Chlamydia trachomatis

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