Microbiology Diagnosis of chlamydia trachomatis infection

The in situ polymerase chain reaction for detection of chlamydia trachomatis

The in situ polymerase chain reaction (PCR) is a technique that has important applications in the diagnosis of viral and bacterial diseases. This study investigated an in situ PCR assay established to detect the presence of Chlamydia trachomatis in endocervical swabs. In addition, histological sections of endocervical squamous cell carcinoma were analyzed because previous studies had revealed a significant association with C. trachomatis. A total of 20 cervical neoplasms (squamous cell carcinoma in situ; n = 10; invasive squamous cell carcinoma; n = 10) and endocervical smears taken from five patients with and without inflammatory changes were analyzed by conventional PCR. Chlamydial DNA was found in 10 histological samples (six carcinomas in situ, four invasive carcinomas) and in one endocervical swab from a patient with known C. trachomatis infection. Positive specimens were used for establishing an in situ PCR assay (IS-PCR). After IS-PCR, these samples showed dense cytoplasmic staining of endocervical cells (smears) and non-neoplastic epithelial cells (cervical neoplasms). The other tumor samples and smears did not demonstrate positive PCR reaction. The results indicate that in situ PCR is an effective technique for localizing C. trachomatis in target cells because IS-PCR detection of chlamydial DNA correlated with histological and cytological features.

Comparison of Giemsa and fluorescent monoclonal antibody staining of inoculated cell cultures for diagnosis of Chlamydia trachomatis

Three methods of isolation and identification of Chlamydia trachomatis inclusions in cell monolayers were compared: Giemsa staining followed by darkfield microscopy of cycloheximide treated Buffalo green monkey kidney monolayers (BGM), fluorescent monoclonal antibody staining of cycloheximide treated BGM and of HeLa 229 monolayers. In an unselected group of 895 patients with suspected chlamydial infections including contacts of symptomatic patients, significantly more positive chlamydia isolates were detected with immunofluorescent monoclonal antibody staining of BGM and HeLa 229 than with Giemsa staining followed by darkfield microscopy on BGM. However, there was no disparity between the 2 staining methods with specimens from 156 patients with untreated non-gonococcal urethritis. In all chlamydia positive specimens, significantly more inclusions were seen after BGM-immunofluorescence than after HeLa-immunofluorescence or BGM-Giemsa. The extra cost associated with immunofluorescence staining was justified by the time saved in scanning.

Comparative evaluation of detection assays for Chlamydia trachomatis

The performances of a commercial nucleic acid hybridization test (Gen-Probe Pace 2 Chlamydia trachomatis) and two commercial enzyme immunoassays (EIAs) (Abbott Chlamydiazyme and Pharmacia Chlamydia EIA) were evaluated against cell culture for the detection of C. trachomatis infection, with cervical swabs obtained from 1,037 women visiting a public sexual health center. The positivity rate by cell culture was 4.7%. Sensitivity and specificity for each test were as follows: Gen-Probe, 95.8 and 98.3%; Chlamydiazyme, 80.4 and 99.3%; Pharmacia EIA, 80.8 and 99.1%. Analysis of discrepant results with probe confirmation assay (Gen-Probe) and direct immunofluorescence (Syva Microtrak) revealed 12 cases of C. trachomatis infection for which culture was negative, resulting in the definition of a true-positive case as opposed to a culture positive. The positivity rate by true-positive definition was 5.9%, and sensitivity and specificity for each test were as follows: Gen-Probe, 96.7 and 99.6%; Chlamydiazyme, 77.5 and 100%; Pharmacia EIA, 77.0 and 100%; cell culture, 80.0 and 100%. We conclude that the Gen-Probe Pace 2 C. trachomatis test is a sensitive and specific alternative to cell culture for the detection of C. trachomatis.

Chlamydia trachomatis antigen detection by Chlamydiazyme combined with Chlamydia Blocking Reagent verification

Several options exist for the detection of chlamydial infection in a routine laboratory setting. Enzyme immuno assay (EIA) technology offers rapid turn around of results and is less technically demanding than chlamydial cell culture. In addition, recently introduced EIA confirmatory reagents have the potential to improve the accuracy of EIA detection. We have evaluated one such confirmatory reagent (Chlamydia Blocking Reagent, Abbott Laboratories) to determine the accuracy of the Chlamydiazyme EIA with special regard to interpretation of low absorbance values. An initial series of 192 male urethral specimens showed that use of a lowered cut off level (absorbance value 0.05) compared with that recommended by the manufacturer increased sensitivity of the EIA from 0.73 to 0.83, thus motivating studies on this interpretative modification. Of 1101 EIA reactive specimens, 65% were determined to be chlamydia positive by the Chlamydia Blocking Reagent. The proportion of female cervical specimens that did not confirm positive was elevated compared with male urethral specimens, 43% vs. 5.7% respectively. In samples yielding absorbance from the recommended cut off level to 0.05 (approximately 50% below), the corresponding figures were 78% and 14% respectively. In 85 selected EIA reactive samples, examination by a direct immunofluorescence staining assay (DFA) (MicroTrak, Syva Inc.) revealed elementary bodies in 85% of 67 blocking test positive and in 24% of 18 blocking test negative samples. The possibility that Gram-negative bacteria were responsible for unconfirmed EIA reactive specimens was investigated using bacterial suspensions. While EIA reactivity was noted with several strains for Gram-negative bacteria, both the blocking reagent and DFA correctly verified the absence of chlamydial antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of urogenital Chlamydia trachomatis infections by cell culture and the polymerase chain reaction using a closed system

Two hundred and fifty-four specimens from males and females consulting a clinic for sexually transmitted diseases were analyzed for genital Chlamydia trachomatis infection. Each clinical sample was tested by the cell culture technique and the polymerase chain reaction using a closed system. When the two test systems were compared, the overall sensitivity of the polymerase chain reaction was 96% and the specificity 94% when compared to the cell culture technique. By use of a closed system for DNA extraction and sample transfer for the polymerase chain reaction, contamination of the samples was minimized. The polymerase chain reaction detected a higher number of Chlamydia trachomatis infections among both symptomatic and asymptomatic females and males, and it also detected Chlamydia trachomatis at an earlier stage of infection when compared to cell culture. The polymerase chain reaction did not detect Chlamydia trachomatis after sufficient antibiotic treatment of the chlamydial infections.

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.

Use of HL cells for improved isolation and passage of Chlamydia pneumoniae

We compared growth of the recently discovered respiratory pathogen Chlamydia pneumoniae in McCoy, HeLa 229, BHK-21, and HL cells. When cells were not pretreated with DEAE-dextran, HL cells had significantly higher mean numbers of inclusion-forming units (IFUs) on initial inoculation than the other cell lines. When cells were pretreated with DEAE-dextran, HeLa 229 and HL cells had equivalent mean numbers of IFUs on initial inoculation. HL cells had strikingly higher mean numbers of IFUs in passage than HeLa 229, BHK-21, or McCoy cells. In addition, HL cells did not require pretreatment with DEAE-dextran and could be used from 2 to 4 days after seeding. We conclude that HL cells are an excellent cell culture system for laboratory propagation of C. pneumoniae and may be a more sensitive cell line for initial isolation.

Age and sex correlation of Chlamydia trachomatis infections evaluated by the culture technique and by an enzyme immunosorbent assay, IDEIA

A total number of 1358 patients were examined for genital infections with Chlamydia trachomatis. 252 urethral smears from men and 1106 cervical smears from women were obtained. The average age of infected patients was 24.8 years (females 24.1, males 27.7). The overall prevalence was 10.6% (females 10.0%, males 13.1%). At the age below 20 years, the prevalence was 21% for both women and men, and 25% when data were restricted to patients consulting general practitioners. Above that age the overall prevalence was lower in all age intervals, and higher among males than females. All samples were tested by the tissue-culture technique, and the results were confirmed by the IDEIA (Boots-Celltech) enzyme-linked immunosorbent assay kit (EIA) for detection of C. trachomatis. The original smear was used for both culture and EIA. The EIA test was evaluated to have a sensitivity of 90.8% and a specificity of 95.4% when using a cut-off level of 0.05 mean extinction values (MEV), as described by the manufacturer.

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

A radioactive cDNA probe complementary to chlamydial ribosomal RNA was used to detect C trachomatis in urogenital specimens. Of 37 specimens positive with cell culture 31 were confirmed by the rRNA:cDNA hybridisation test, the sensitivity being 83.8%. The specificity of the hybridisation test was 94.4%, as 186 of 197 specimens that were negative by cell culture were also negative when assessed by the hybridisation method. Given a prevalence of 15.8% the predictive values for positive and negative results were 73.8% and 96.9%, respectively. In additional experiments the possible role of microorganisms added to the specimen collection medium was investigated. However, no indication for crosshybridisation was found; at high concentrations microorganisms interfered with the test procedure.

Immunodiagnosis of ocular chlamydial infection

The diagnostic roles of enzyme immunoassay and indirect immunofluorescence tests were studied in 99 patients with various grades of active trachoma and in 72 patients with inactive trachoma. Normal individuals and patients with non-specific chronic conjunctivitis were used as a control group. Chlamydial antigens were detected in the conjunctival swabs from a large proportion of patients with severe or moderate trachoma. Cases with 'antigen-negative' but clinically severe trachoma showed presence of specific IgG in the blood, thus indicating that serological tests may complement the ELISA test for the detection of chlamydia in infected tissues. The nature of cellular reaction in the conjunctiva seems to be related to the severity of trachoma and presence of the infective organism. 'Antigen-negative' trachoma thus represents either an error of diagnosis or limited sensitivity of currently available immunologic techniques, or a predominantly hypersensitivity state triggered by transient tissue parasitism. Recombinant DNA technology and chronobiologic study of infiltrating lymphocytes are likely to provide some insight in such cases.

Comparison of two enzyme immunoassays and an immunofluorescence test for detection of Chlamydia trachomatis

Three rapid methods for the detection of Chlamydia trachomatis were compared: one immunofluorescence test and two enzyme immunoassays. Cervical and urethral specimens were obtained from 75 women in an outpatient clinic for therapeutic abortions and from 50 women in a sexually transmitted disease clinic. Urethral specimens were also obtained from 154 men in the same clinic. One hundred and nineteen cervical and 272 urethral specimens of a total 391 specimens were tested by the three methods. The direct immunofluorescence test detected Chlamydia trachomatis in 8% and the two enzyme immunoassays in 10% and 12% of the patients. The sensitivity of the immunofluorescence test was 76% compared to 91% and 80% for the two enzyme immunoassay tests. All three tests had a specificity of 99%. Dilution experiments confirmed that one immunoassay test, Chlamydiazyme, detected most of the positive specimens. The rapid and easily automated enzyme immunoassays are a valuable complement to the culture technique.

Detection of experimental Chlamydia trachomatis eye infection in conjunctival smears and in tissue culture by use of fluorescein-conjugated monoclonal antibody

The immunofluorescent staining of conjunctival cytology smears with an antichlamydial monoclonal antibody is a new method for the detection of chlamydial eye infection. Using a monkey model of chlamydial eye infection, we compared the monoclonal antibody staining cytology with the established methods of Giemsa-stained cytology and chlamydial culture with cycloheximide-treated McCoy cells. Compared with either culture or monoclonal antibody-stained cytology, Giemsa cytology had a low sensitivity (30 and 24%, respectively) but was highly specific (100% in each case). Compared with culture, monoclonal antibody-stained cytology was highly sensitive (94%) but appeared to lack specificity (70%). However, examination of the changes in identification rates with time suggested that monoclonal antibody-stained cytology may be even more sensitive than culture and detect lower levels of infection. This study showed that monoclonal antibody-stained cytology of conjunctival smears might be a rapid, efficient, and inexpensive method of diagnosing ocular chlamydial infection.