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