Evaluation of a radioactive rRNA:cDNA-hybridisation assay for the direct detection of Chlamydia trachomatis in urogenital specimens

Detection of C trachomatis in urogenital specimens by polymerase chain reaction

OBJECTIVE

To establish a polymerase chain reaction (PCR) protocol for the detection of urogenital C trachomatis infection and to compare it with the detection in cell culture.

SPECIMENS

Urethral specimens were collected from 62 male patients and cervical specimens from 106 female patients.

SETTING

Department of Dermatology and Venereology, Ruprecht-Karls-Universität, Heidelberg.

METHODS

Urogenital specimens were simply boiled for 15 minutes and subsequently subjected to amplification without prior extraction of nucleic acid. The DNA sequence selected for amplification is located in the third open reading frame of the ubiquitous C trachomatis plasmid pCTT1. The amplified products were demonstrated by agarose gel electrophoresis followed by Southern blot hybridization. In addition, specimens were investigated with cell culture.

MAIN OUTCOME MEASURES

Results of PCR and cell culture.

RESULTS

PCR detected all C trachomatis serovars relevant for urogenital infections (D-L2). Serial dilution experiments revealed that the PCR procedure was 100 fold more sensitive than cell culture. The investigation of 168 urogenital specimens showed that the PCR confirmed all 30 cell culture positive results, however, out of the 138 cell culture negative specimens 16 were positive using the PCR.

CONCLUSIONS

A substantial number of urogenital C trachomatis infections detectable by PCR may be missed by the cell culture technique.

Detection of Chlamydia trachomatis in clinical specimens by the polymerase chain reaction

Sequences derived from the endogenous plasmid of Chlamydia trachomatis and from the genes coding for ribosomal 16S RNA of Chlamydia psittaci were used as primers and oligonucleotide probes for detection of chlamydiae by the polymerase chain reaction. The endogenous plasmid primers generated specific amplified products of 517 bp with all known Chlamydia trachomatis serovars. No specific products of Chlamydia psittaci and Chlamydia pneumoniae could be detected using these primers. With the rRNA primers specific amplified products of 208 bp were generated with Chlamydia psittaci, Chlamydia trachomatis and Chlamydia pneumoniae. No specific amplified products were detected with DNA isolated from a variety of microorganisms from the urogenital and the respiratory tract. Of 156 clinical specimens used for evaluation of the polymerase chain reaction, 26 were found to be positive for Chlamydia trachomatis on culture. All 26 culture positive samples were also found to be positive for Chlamydia trachomatis DNA by the polymerase chain reaction with both primer sets. Two culture negative samples were also found to be positive by this technique. The polymerase chain reaction thus seems to be a sensitive and reliable method for detection of Chlamydia trachomatis.