Detection of Chlamydia trachomatis by the polymerase chain reaction

Chlamydia trachomatis and Human Papillomavirus Infection in Women From Southern Hunan Province in China: A Large Observational Study

Chlamydia trachomatis and human papillomavirus (HPV) are the most common pathogens of sexually transmitted infections (STIs), which can increase the risk of cervical cancer and infertility. The purpose of this study was to evaluate the prevalence, genotype and risk factors of C. trachomatis and/or HPV infection in women attending the annual physical examination, assistant reproductive treatment and visiting the gynecology clinics from Southern Hunan province in China. Cervical-swab samples were collected from 5006 participants. We found that the overall prevalence of C. trachomatis, HPV infection and C. trachomatis/HPV coinfection was 4.7% (236/5006), 15.5% (778/5006) and 1.2% (59/5006), while the prevalence of asymptomatic infection of that was 3.8% (38/1006), 10.8% (109/1006) and 0.6% (6/1006), respectively. Furthermore, 25.0% (59/236) of C. trachomatis infection and 7.6% (59/778) of HPV infection were attributable to C. trachomatis and HPV coinfection. C. trachomatis and HPV infection were more often observed in young women of less than 25 years (10.4% and 21.3%, respectively) and in the outpatients from gynecology clinics (5.2% and 18.0%, respectively). Of note, a higher prevalence of C. trachomatis infection was observed in HPV-positive women (7.6%) than HPV- negative ones (4.2%), and vice versa. The top three C. trachomatis genotypes were E (1.4%), F (1.1%) and J (0.8%), and the counterparts of HPV genotypes were HPV52 (4.2%), HPV16 (2.3%) and HPV58 (2.2%), respectively. Among the 151 outpatients with colposcopy data, HPV infection was associated with severe cervical lesions with OR of 15.86 (95% CI 3.14–80.0, P < 0.001) while C. trachomatis infection was more likely associated with a low grade colposcopy impression (OR = 3.25, 95% CI: 1.22–8.65, P = 0.018). Our data highlight the high prevalence of asymptomatic C. trachomatis and HPV infection, particularly among women of <25 years. The two pathogens may serve as mutual risk factors to increase the risk of infections and cervical lesions. Widespread implementation of HPV and C. trachomatis screening programs, especially for young women, would be an effective strategy to relieve the burden of sexually transmitted infections.

Innovative Methods of Rapid Bacterial Quantification and Applicability in Diagnostics and in Implant Materials Assessment

In recent years, a variety of new technologies have been proposed that allow rapid qualitative and quantitative microbiological analyses. In this paper we discuss the urgent needs for reliable and rapid microbiological analytical techniques in different applicative fields involving the research, production and medical application of implant materials, and the potential benefits derived from the use of new methods for rapid bacterial quantification. Current compendial methods are easy to perform and have gained confidence over their long period of use, but the supplemental use of new technologies could represent real breakthroughs whenever sensitive and rapid responses are urgently required and not met by the tests currently in use. Overall, the new microbiological methods require critical evaluation depending on their specific type of application and they may still not be thought of as totally substitutive, but they certainly exhibit considerable potential for different areas of biomaterials, as well as for advanced therapy medicinal and tissue engineering treatments.

Cervicovaginal levels of proinflammatory cytokines are increased during chlamydial infection in bacterial vaginosis but not in lactobacilli-dominated flora

OBJECTIVE

The purpose of this study was to assess the cervicovaginal levels of proinflammatory cytokines in women with Chlamydia trachomatis (CT) infection in the presence of bacterial vaginosis (BV) and normal flora and to compare with those negative for CT.

MATERIALS AND METHODS

In this cross-sectional study, nonpregnant women were enrolled at 2 outpatient clinics and at 1 primary medical care unit in São Paulo State, Brazil. Cervicovaginal samples from 256 women with BV, of which 68 (26.6%) had concomitant CT infection and 188 (73.4%) were CT-negative, were measured for interleukin-1β (IL-1β), IL-6, and IL-8 by enzyme-linked immunosorbent assay. A matching number of samples from women with normal flora, CT-positive (n = 68) and negative (n = 188), were evaluated as control. Cytokine levels were compared by Mann-Whitney test and differences were considered significant at p < .05.

RESULTS

In CT-negative women, IL-1β was increased in BV (p < .001) when compared to normal flora, while the levels of IL-6 and IL8 were unchanged. The presence of CT infection was not associated with differences on cytokine levels in women with normal flora. However, women with BV had higher levels of IL-1β (p = .02), IL-6 (p = .02), and IL-8 (p = .03) in the presence of CT when compared to those who tested negative for CT.

CONCLUSIONS

Detection of endocervical CT is associated with increased cervicovaginal IL-1β, IL-6, and IL-8 levels in women with concomitant BV but not in those with normal flora.

Sialidase activity in aerobic vaginitis is equal to levels during bacterial vaginosis

OBJECTIVE

To evaluate levels of proinflammatory cytokines and sialidase activity in aerobic vaginitis (AV) in relation to normal vaginal flora and bacterial vaginosis (BV).

STUDY DESIGN

In this cross-sectional study, a total of 682 consecutive non-pregnant women attending the gynecology service were assessed and 408 women were included. Vaginal rinsing samples were collected from 223 women with microscopic finding of BV (n=98), aerobic vaginitis (n=25) and normal flora (n=100). Samples were tested for interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF)-α, and sialidase activity.

RESULTS

Compared to women with normal flora, vaginal levels of IL-1β were highly increased in both BV and AV (p<0.0001). Significantly higher vaginal IL-6 was detected in AV (p<0.0001) but not in BV, in relation to normal flora. Women with AV also presented increased IL-8 levels (p<0.001), while those with BV presented levels similar to normal flora. Sialidase was increased in BV and AV compared with the normal group (p<0.0001) but no difference in sialidase activity was observed between BV and AV.

CONCLUSION

A more intense inflammatory host response occurs for AV than for BV when compared with normal flora. Furthermore, the increased sialidase activity in AV and BV indicates that both abnormal vaginal flora types can be harmful to the maintenance of a healthy vaginal environment.

Rapid polymerase chain reaction-based test for the detection of female urogenital chlamydial infections

Objective: The purpose of this study was to evaluate the Amplicor Chlamydia trachomatis Test (Roche Molecular Systems, Branchburg, NJ), a polymerase chain reaction (PCR)-based technique, as a screening test for the detection of female urogenital C. trachomatis infections, comparing it to an enzyme immunoassay method.

Methods: Endocervical specimens for PCR and Chlamydiazyme (Abbott Laboratories, North Chicago, IL) analysis were obtained from 328 unselected patients at the outpatient Sexually Transmitted Diseases Clinic at the Allegheny County Health Department, Pittsburgh, PA. In addition, urethral swabs for PCR analysis were obtained from 256 of these patients.

Results: By PCR analysis, the prevalence of urogenital chlamydial infections was 15.6% and that of cervical chlamydial infections was 10.7%. The sensitivity of PCR in the detection of endocervical chlamydial infections was 89.7% and the specificity was 100%. The positive and negative predictive values of PCR were 100% and 99%, respectively. The sensitivity of Chlamydiazyme in the detection of cervical infections was 61.5% and the specificity was 99.7%, with a positive predictive value of 96.0%. Among all patients with urogenital chlamydial infections, concomitant infections in the urethra and cervix occurred in 52.5%, whereas the urthra or cervix was solely infected in 35.0% and 12.5%, respectively.

Conclusions: This PCR-based technique is a rapid screening tool for the diagnosis of urogenital chlamydial infections and is more sensitive than Chlamydiazyme for endocervical infections in a sexually transmitted disease clinic population.

Molecular Diagnostics and Comparative Genomics in Clinical Microbiology

Initially, the availability of molecular diagnostics was considered a panacea, but replacement of conventional tests for detection and identification of microorganisms by molecular procedures eventually gathered momentum. This chapter describes current state-of-the-art molecular diagnostics and comparative genomics in medical microbiology to provide an understanding of infectious disease over the coming years. Nucleic acid-based tests are being introduced with increasing speed into routine clinical microbiology laboratories. Some of the problems remaining to be solved prior to general acceptance of nucleic acid-mediated detection and identification of microbial pathogens are reviewed. Historic objections are slowly being taken apart, and an accelerated introduction of molecular diagnostics is being pursued in many cases. Clear improvement in clinical testing is achieved by introducing molecular tests. Therefore, swift introduction of such tests into clinical practice is important to be pursued. Several PCR tests show increased sensitivity, excellent specificity, and cost effectiveness highlighting the success of the novel applications in the field of bacterial infections. Finally, some of the problems remaining to be solved prior to general acceptation of nucleic acid-mediated detection and identification of microbial pathogens are also reviewed.

Persistence and clearance of human papillomavirus infection: a prospective cohort study

OBJECTIVE

The objective of the study was to identify epidemiological correlates for persistence and clearance of human papillomavirus (HPV) infection.

STUDY DESIGN

Cervical smears collected in a prospective cohort study to perform Papanicoloau cytology and HPV deoxyribonucleic acid (DNA) detection at baseline and during the follow-up. Outcomes analyzed were: (1) persistence of HPV DNA; (2) conversion; and (3) clearance of HPV.

RESULTS

Among 501 women the incidence of HPV was 12.3%. Thirty-four women were persistently infected with HPV, which was associated with age below 21 years at first intercourse and 4 or more sexual partners during their lifetime. In a median of 19 months, 80.7% of women had clearance of HPV, which was associated with black race, coinfection with Chlamydia trachomatis at baseline, and a history of previous Papanicoloau smear.

CONCLUSION

Strategies for sexual orientation may modify the rates of HPV persistence. The association of HPV clearance with a history of previous Papanicolaou smear screening highlights the importance of improving cervical screening programs. Further studies on the association of gynecological infections with HPV clearance are needed.

Application of an oligonucleotide array assay for rapid detecting and genotyping of Chlamydia trachomatis from urogenital specimens

An oligonucleotide array technology was established for rapidly detecting and genotyping Chlamydia trachomatis in urogenital infections. The VS1-VS2 region of the omp1 gene was used to design oligonucleotide probes. Eleven serovar-specific probes to serovars A, B, C, D, E, F, G, H, I, J, and K, and 3 group-specific probes to group B (B, Ba, D, E, L1, and L2), group C (A, C, H, I, J, K, and L3), and an intermediate group (F and G) were synthesized and spotted onto the nylon membrane. Two pairs of universal primers were designed for the nested polymerase chain reaction (PCR) amplification of the VS1-VS2 gene. Digoxigenin-labeled amplicons of the VS1-VS2 gene of C. trachomatis were hybridized to the membrane array. Hybridization signals were read by the nitroblue tetrazolium/5-bromo-4-chloro-3-indolylphosphate color development. The assay developed was tested with reference strains of C. trachomatis serovars and clinical samples. The sensitivity was evaluated for 57 samples previously found to be positive for C. trachomatis by using plasmid PCR, and 98.2% (56/57) concordance was obtained. Fourteen oligonucleotide probes were optimized by trying different reaction conditions, showing specific hybridization with the corresponding reference strains, but no cross-reactions with other urogenital microorganisms. Using this procedure, a total of 59 strains were detected from 56 chlamydial samples. Eight genotypes were found, and type D, E, F, and H were the most frequently observed types (77.9%). Three cases (5.4%) had multiple infections with serovars: 1.D/E, 2.D/F, and 3.F/K. To validate the reference strains and confirm the genotype identity as determined by the oligonucleotide array technology, we sequenced all reference strains and 10 selected specimens across variable sequence VS1 and VS2. No discrepancies were found between the array typing and the genotype identity confirmed by nucleotide sequencing of the PCR product. The findings from this study indicated that the oligonucleotide array is a simple, fast, and specific assay for directly detecting and genotyping C. trachomatis from clinical samples.

A multiplexed real-time PCR assay for rapid detection of Chlamydia trachomatis and identification of serovar L-2, the major cause of Lymphogranuloma venereum in New York

Lymphogranuloma venereum (LGV) is caused by a rare form of Chlamydia trachomatis that is difficult to diagnose, since culture is not readily available, and since other methods are not reliable or lack sensitivity. We report here a rapid, sensitive, and specific real-time multiplex polymerase chain reaction (PCR) assay capable of detecting C. trachomatis and identifying serovar L-2 in the same reaction, directly from rectal swabs. The analytical sensitivity of the assay was 25 genome copies for C. trachomatis, and 50 genome copies for L-2. The analytical specificity was 100%, as demonstrated with a diverse range of C. trachomatis serovars and other site-specific bacterial pathogens. With the use of a rapid DNA extraction method, a blinded validation of spiked rectal swabs correctly identified 30 samples containing C. trachomatis cells, L-2 DNA, or negative samples. The multiplexed PCR assay also identified serovar L-2 in 13 of 70 rectal swab samples taken from symptomatic patients. Twelve additional samples were positive for C. trachomatis only, and omp1 sequencing determined these samples as either serovar D, E, G, J, or K. This assay represents the first real-time PCR method capable of detecting C. trachomatis DNA, and of simultaneously identifying C. trachomatis infection as serovar L-2.

Comparison of DNA extraction from cervical cells collected in PreservCyt solution for the amplification of Chlamydia trachomatis

OBJECTIVE

The aim of this study was to compare and evaluate three methods of DNA extraction for the amplification of Chlamydia trachomatis in uterine cervical samples collected in PreservCyt solution. ThinPrep is the trade name for the slide preparation.

METHODS

Thirty-eight samples collected in LCx buffer medium, which were identified as C. trachomatis infected by ligase chain reaction (LCR), were selected for this study. DNA from the PreservCyt samples was extracted by three methods: (i) QIAamp kit, (ii) boiling in Tris-EDTA buffer with Chelex purification, and (iii) Proteinase K digestion with Chelex purification. Sample DNA was tested for the presence of C. trachomatis by PCR using cryptic plasmid research (CTP) primers and major outer membrane protein research momp gene (MOMP) primers. Real-time (LightCycler) PCR for relative C. trachomatis quantification following DNA extraction was performed using primers (Hsp 60) for the 60 kDa heat-shock protein hsp60 gene.

RESULTS

Amplification using CTP primers was the most successful with each of the extraction protocols. Boiling in buffer was the least successful extraction method. QIAamp was the best extraction method, yielding the most positives with both the CTP and MOMP primers. Proteinase K-Chelex extraction gave similar sensitivity to QIAamp extraction with CTP primers but lower for MOMP primers.

CONCLUSIONS

The DNA extraction method must be carefully selected to ensure that larger PCR amplicons can be successfully produced by PCR and to ensure high sensitivity of detection of C. trachomatis. In this study it was found that the QIAamp extraction method followed by PCR with the CTP primers was the most successful for amplification of C. trachomatis DNA.

Application of touchdown enzyme time release (TETR)-PCR for diagnosis of Chlamydophila abortus infection

Chlamydophila abortus-DNA was detected using a touchdown enzyme time-release (TETR)-polymerase chain reaction (PCR) assay as an improved test for sensitive and rapid diagnosis of abortion in small ruminants. Two hundred and fifty two placentae, liver or spleen tissue samples from aborting ewes and goats or aborted lambs and kids in which C. abortus infection was suspected were examined by TETR-PCR and the results were compared with cell culture. Sixty-five tissue samples were found to be TETR-PCR positive while only 56 samples were cell culture-positive. After resolution of discrepant samples with a confirmatory nested PCR assay, TETR-PCR had a sensitivity of 97% and a specificity of 99.5% while culture had a sensitivity of 84.8% and a specificity of 100%. The analytical sensitivity of the TETR-PCR assay was determined with DNA extracted from 4-fold serial dilution of C. abortus B577 culture and found to be 0.25 inclusion-forming unit per PCR. No reduction in the analytical sensitivity was noted when the assay was tested with mouse liver samples spiked with 4-fold serial dilution of C. abortus B577 culture. No target product was amplified when DNA from Chlamydophila pecorum was tested. TETR-PCR used in this study is a practical, rapid, sensitive and specific assay that could be used for the detection of C. abortus in infected tissue samples. We recommend the use of this assay as a supplemental diagnostic tool for detection of C. abortus in infected tissue samples.

Construction and evaluation of internal control DNA for PCR amplification of Chlamydia trachomatis DNA from urine samples

An internal control DNA (ICD) with the same primer binding sequences as the target Chlamydia trachomatis DNA was constructed and evaluated in a PCR assay with immunoenzymatic detection. One hundred urine specimens were tested, and 23 were found to contain inhibitors of the PCR, if not subjected to DNA extraction prior to amplification. Coamplification and detection of the ICD appeared to be a useful method for estimating the effects of inhibitors on C. trachomatis DNA amplification.

Evaluation of the Hybrid Capture 2 CT/GC DNA tests and the GenProbe PACE 2 tests from the same male urethral swab specimens

BACKGROUND

A previous study demonstrated that Digene's Hybrid Capture 2 (HC2) DNA tests for detection of and (CT/GC) could be performed using cervical swab specimens collected in GenProbe transport media with significantly greater sensitivity for the detection of than with the GenProbe PACE 2 system.

GOAL

The goal was to assess the performance of HC2 tests in comparison with GenProbe PACE 2 tests for the detection of CT/GC in male urethral swab specimens.

STUDY DESIGN

A total of 1,202 male urethral swab specimens were collected in GenProbe PACE transport medium. All specimens were first tested with the PACE 2 system, followed by masked HC2 CT/GC testing. The GenProbe AMPLIFIED CT Assay (AMP CT) and PCR/SHARP Signal System (SHARP) were used for adjudication of discrepant results.

RESULTS

The prevalence rates for this population were 8.4% for and 14.6% for, based on the adjudicated results. The relative sensitivity and specificity for the detection of were 97.0% and 99.8% for HC2 and 69.3% and 98.3% for PACE 2, respectively. The relative sensitivities for the detection of were 98.9% for HC2 and 99.4% for PACE 2, with the same specificity of 99.9% for both tests. Agreement between the two testing methods was 95.4% for and 99.6% for.

CONCLUSION

The HC2 test is compatible with the GenProbe collection medium, with significantly greater sensitivity than the GenProbe PACE 2 test for detecting and similar sensitivities for detecting.

PCR assessment of Chlamydia trachomatis infection of semen specimens processed for artificial insemination

In order to ascertain the microbiological quality of stored semen specimens processed for artificial insemination by a donor (AID), we developed a PCR assay targeting the chlamydial plasmid to detect Chlamydia trachomatis in semen. The lower limit of detection of this assay corresponded to 2.5 to 5 elementary bodies per microl of semen. A total of 669 cryopreserved ejaculates from 97 asymptomatic donors were tested for C. trachomatis infection. Twelve ejaculates, originating from four donors, were found to be positive, indicating a 4% prevalence of C. trachomatis infection among the donor population studied. Cross-contamination between the cryopreserved specimens in the storage container was studied by typing using sequence analysis of PCR-amplified omp1 genes of the strains. Two donors were infected with serovar E, one was infected with serovar F, and one was infected with serovar K. For two donors, the duration of C. trachomatis positivity could be assessed. One donor donated C. trachomatis-positive semen for at least 4 successive months, and the other did so for at least 16 months. The occurrence of C. trachomatis infection in cryopreserved donor semen indicates that ejaculates from donors not tested for a C. trachomatis infection just prior to donation should be tested for infection by a direct test such as the PCR described here. Direct testing of semen specimens will detect not only donors with an active infection but also C. trachomatis-infected ejaculates already stored and will thus improve the microbiological quality of AID, since discrepancies in the presence of C. trachomatis in urine and semen specimens have been reported.

Detection of Chlamydia trachomatis and Neisseria gonorrhoeae in swab specimens by the Hybrid Capture II and PACE 2 nucleic acid probe tests

BACKGROUND AND OBJECTIVES

The Digene Hybrid Capture II (HC II) CT/GC Test (Digene Corp., Beltsville, MD) is a new nucleic acid signal amplification-based test for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in specimens from the genital tract. For optimal results, the HC II CT/GC Test employs a special conical shaped brush for cervical specimen collection from nonpregnant women and swabs from pregnant women.

GOALS

To validate a protocol for HC II C. trachomatis and N. gonorrhoeae testing of specimens collected for the GenProbe PACE 2 System.

STUDY DESIGN

Specimens were collected from 1,746 patients with a swab and placed in GenProbe transport media according to the manufacturer's recommended procedure. The specimens were first tested at two clinical laboratories by the PACE 2 system, and then blindly tested by HC II CT/GC using an adjusted cutoff value. Discrepant specimens were adjudicated by polymerase chain reaction (PCR), and the result common to two of the three testing methods (HC II, PACE 2, and PCR) was defined as the consensus result.

RESULTS

Combining the data from both sites, the relative sensitivity of the HC II Test compared with the consensus result for the detection of 1,761 specimens for C. trachomatis and 1,750 specimens for N. gonorrhoeae was 100% for both organisms. The relative specificities for C. trachomatis and N. gonorrhoeae detection were 99.8% and 99.7%, respectively. The relative sensitivities of the PACE 2 CT and GC Systems were 86.5% and 87.1%, respectively, with relative specificities of 99.9% and 100%. The difference in sensitivity between HC II and PACE 2 for C. trachomatis detection was significant (P < 0.016).

CONCLUSION

The HC II CT/GC Test can be performed using specimens collected in GenProbe transport media and has a significantly greater sensitivity for C. trachomatis detection than the PACE 2 System.

RNA amplification by nucleic acid sequence-based amplification with an internal standard enables reliable detection of Chlamydia trachomatis in cervical scrapings and urine samples

In the present study, the suitability of RNA amplification by nucleic acid sequence-based amplification (NASBA) for the detection of Chlamydia trachomatis infection was investigated. When comparing different primer sets for their sensitivities in NASBA, use of both the plasmid and omp1 targets resulted in a detection limit of 1 inclusion-forming unit (IFU), while the 16S rRNA appeared to be the most sensitive RNA target for amplification (10(-3) IFU). In contrast, for DNA amplification by PCR, the plasmid target was optimal (10(-2) IFU), which is 10 times less sensitive than rRNA NASBA. To exclude false negativity in NASBA detection because of inhibition of amplification and/or inefficient sample preparation, an internal standard was developed. The internal control was added prior to sample preparation. This 16S rRNA NASBA with an internal control was compared with a plasmid DNA PCR by using a group of C. trachomatis-negative (n = 41) and -positive (n = 37) cervical scrapings, as determined by enzyme immunoassay (EIA). In addition, urine samples from the EIA-positive women were tested (n = 17). Both NASBA and PCR assays were able to detect C. trachomatis in all EIA-positive cervical scrapings, the corresponding urine samples, and two samples from the EIA-negative group. The internal NASBA standard was found clearly in all EIA-negative samples. In conclusion, these results indicate that detection of C. trachomatis by RNA amplification by NASBA with an internal standard is a suitable and highly sensitive detection method, with potential use in the diagnosis of urogenital C. trachomatis infections with cervical scrapings as well as urine specimens.

Choosing highly specific primers for the polymerase chain reaction using the octomer frequency disparity method: application to Chlamydia trachomatis

The eight-nucleotide sequence (octomer) at the 3' end of PCR primers is important to PCR specificity. We describe a correlation between the specificity of PCR primers used with human DNA and the frequency of the 3' octomer in a human database. We therefore applied a methodology (OFD) based on octomer frequency disparity to identify 16 PCR targets in the chromosome of the intracellular bacterium, Chlamydia trachomatis (Ct). In addition, the 16 sets of primers were tested with a standard procedure. All the primer pairs were highly specific for Ct and did not lead to non-specific amplification when used with human DNA. This work shows that the choice of specific PCR primers is possible using a method based on the statistical representativeness of octomers in genomes.

Prevalence and serovar distribution of asymptomatic cervical Chlamydia trachomatis infections as determined by highly sensitive PCR

The prevalence rates and serovar distributions of Chlamydia trachomatis cervical infections were investigated in two different groups of women. Group I consisted of 393 asymptomatic young women (aged 17 to 30 years) who were invited to participate in a C. trachomatis screening program. Group II consisted of 734 randomly selected patients (aged 17 to 68 years) attending an inner-city gynecological outpatient clinic. C. trachomatis was detected in cervical scrapes by PCR specific for endogenous plasmid. These plasmid PCR-positive samples were subsequently subjected to genotyping by C. trachomatis-specific omp1 PCR-based restriction fragment length polymorphism analysis (J. Lan, J. M. M. Walboomers, R. Roosendaal, G. J. van Doornum, D. M. MacLaren, C. J. L. M. Meijer, and A. J. C. van den Brule, J. Clin. Microbiol. 31:1060-1065, 1993). The overall prevalence rates of C. trachomatis found in patients younger than 30 years were 9.2 and 11.8% in groups I and II, respectively. A clear age dependency was seen in group II, with the highest prevalence rate (20%) found in patients younger than 20 years, while the rate declined significantly after 30 years of age (5.9%). In women younger than 30 years, the genotyping results showed that serovars E, I, and D (in decreasing order) were frequent in group I, while serovars F, E, and G (in decreasing order) were predominantly found in group II. The study shows that C. trachomatis infections are highly prevalent in asymptomatic young women. The different serovar distributions found most likely reflect the different compositions of the study groups, but additional analysis of the case histories of individual patients suggests that certain serovars might be associated with symptomatic (i.e., serovar G) or asymptomatic (i.e., serovars D and I) infections.

Detection of Chlamydia trachomatis by ligase chain reaction compared with polymerase chain reaction and cell culture in urogenital specimens

OBJECTIVE

The aim of this study was to evaluate the newly developed ligase chain reaction (LCR) assay for the detection of Chlamydia trachomatis in urogenital specimens using cell culture and Amplicor PCR for comparison.

SUBJECTS

Two hundred and eighty patients attending hospital or urban STD clinics (high-risk population, 62 men and 84 women) and obstetric/gynaecology clinics (low-risk population, 134 women) in Bordeaux, France.

METHODS

Specimens from men were tested with LCR on urethral swabs and urine, with Amplicor or urine, with cell culture on urethral swabs. Specimens from women were tested with LCR, Amplicor and cell culture on endocervical swabs and with LCR on urine. When the three methods generated different results, the LCR and Amplicor tests were repeated on the remaining samples. Samples with discordant LCR and Amplicor results and a negative culture were further analysed by major outer membrane protein gene omp1-PCR.

RESULTS

After analysis of discrepant results, the overall prevalence was 7.5% (21/280) calculated on the basis of an expanded "gold standard" defined as culture positive or LCR plus Amplicor positive or omp1-PCR positive for discrepant results between LCR and Amplicor tests. Of the 21, 20 were detected by LCR, 17 by Amplicor and culture. The specificity of LCR and Amplicor was 99.6%.

CONCLUSION

The LCR Chlamydia trachomatis test is a highly sensitive nonculture technique and a good alternative test for the detection of chlamydial infections.

Chlamydia trachomatis and ectopic pregnancy: retrospective analysis of salpingectomy specimens, endometrial biopsies, and cervical smears

AIMS

To examine the role of Chlamydia trachomatis in ectopic pregnancy by detection of DNA in archival salpingectomy specimens, and in their preceding cervical specimens and endometrial biopsies, by using the polymerase chain reaction (PCR).

METHODS

Archival paraffin embedded salpingectomy tissues (n = 48) from 37 women with ectopic pregnancy were examined for the presence of C trachomatis plasmid and omp1 DNA by PCR. In addition, preceding cervical specimens (n = 58) stored either as cervical cell suspensions or as archival cervical smears, and preceding endometrial biopsies (n = 18), taken 0-5.8 years before the ectopic pregnancy, were examined by PCR for the presence of C trachomatis.

RESULTS

C trachomatis DNA was detected in only one of the 48 salpingectomy specimens from 37 women. However, in six of the 37 women, C trachomatis DNA was detected in the genital specimens (cervix and/or endometrial) taken before salpingectomy. C trachomatis infections were mostly found in endometrial or cervical specimens taken more than three years before ectopic pregnancy. No chlamydial DNA was found in endometrial or cervical specimens taken at the same time of the ectopic pregnancy.

CONCLUSIONS

Although no C trachomatis DNA was found in salpingectomy specimens, several women with ectopic pregnancy had C trachomatis infections in endometrial and cervical specimens in the past. This suggests that at least in these cases the ectopic pregnancy is a late post-inflammatory complication of an ascending C trachomatis infection resulting in a scarred fallopian tube.

Comparison of the Amplicor Chlamydia trachomatis test and cell culture for the detection of urogenital chlamydial infections

OBJECTIVE

To compare the polymerase chain reaction (PCR) Amplicor Chlamydia trachomatis test with the cell culture method, in diagnosing urogenital chlamydial infections.

SUBJECTS

439 patients (327 women and 112 men) attending one STD clinic and Family Planning and Gynaecological Clinics in Lisbon, Portugal, between November 1993 and March 1994.

METHODS

In women, two endocervical swab samples were collected: one for PCR Amplicor and one for standard culture technique. Men were asked to submit 20 ml of urine (first pass urine) for PCR Amplicor and one urethral specimen was taken for culture. The order of collection of the specimens was rotated every 50 patients. Discrepant results were further analysed by a second PCR with primers directed against the C trachomatis major outer membrane protein (MOMP) and by direct fluorescent antibody (DFA).

RESULTS

After analysis of discrepancies, the adjusted sensitivity and specificity of PCR on endocervical specimens were 92.9% and 100% and the positive and negative predictive values were 100% and 99.7% respectively; on the urine samples these values were 100%, 99.1%, 100% and 99.1%, respectively.

CONCLUSION

These results indicate that the PCR Amplicor test is a rapid sensitive and specific assay for the detection of C trachomatis in urogenital infections and provides a non-invasive technique for screening chlamydia infection in men.

Amplification of plasmid and chromosome Chlamydia DNA in synovial fluid of patients with reactive arthritis and undifferentiated seronegative oligoarthropathies

OBJECTIVE

To investigate the hypothesis that whole bacteria might be found in the joints of patients with Chlamydia-associated reactive arthritis.

METHODS

The presence of 2 plasmid- and 2 chromosome-specific sequences of Chlamydia DNA was investigated by amplification with the polymerase chain reaction, in synovial fluid (SF) samples from 71 patients with various arthropathies.

RESULTS

Chlamydia DNA was found in SF samples from 22 patients.

CONCLUSION

Whole chlamydiae are likely present in the SF of patients with Chlamydia-associated reactive arthritis.

Use of the polymerase chain reaction for the detection of Chlamydia trachomatis in clinical specimens and its comparison to commercially available tests

A polymerase chain reaction (PCR) was developed to detect Chlamydia trachomatis in genital tract specimens. Two sets of primers for the PCR were used; one set amplifies a region of the plasmid present in all C trachomatis strains and the other amplifies a conserved region of the genome coding for the major outer membrane protein. The sensitivity of these PCRs were compared with each other, and with the sensitivities of antigen ELISA, Clearview and culture. Southern blotting and probing was used to increase sensitivity of detection.

Influence of volume of sample processed on detection of Chlamydia trachomatis in urogenital samples by PCR

In the present study, it was demonstrated that the sensitivity of the PCR for the detection of Chlamydia trachomatis is influenced by the volume of the clinical sample which is processed in the PCR. An adequate sensitivity for PCR was established by processing at least 4%, i.e., 80 microliters, of the clinical sample volume per PCR. By using this preparation procedure, 1,110 clinical samples were evaluated by PCR and by cell culture, and results were compared. After discordant analysis, cell culture resulted in a sensitivity of 79.1% and PCR resulted in a sensitivity of 92.7%. Furthermore, it was shown that treatment with antibiotics immediately resulted in negative cell culture results but that PCR could give positive results up to 2 weeks posttreatment.

Role of confirmatory PCRs in determining performance of Chlamydia Amplicor PCR with endocervical specimens from women with a low prevalence of infection

The role of confirmatory PCR assays for determining the performance of Chlamydia Amplicor PCR for endocervical specimens from women with a low prevalence of infection was evaluated. An endocervical swab was collected from 770 women and tested by culture or direct fluorescent antibody (DFA) staining. A second swab was tested by Chlamydia Amplicor PCR (Roche Molecular Systems, Branchburg, N.J.). Discordant results were resolved by three confirmatory PCRs: one targeting the plasmid by using different primers and two directed to the major outer membrane protein (MOMP) gene. Of the 30 swabs that were positive by culture or DFA (3.9%), 27 were positive by Amplicor PCR. An additional five swabs were positive by Amplicor PCR but negative by culture or DFA. Both plasmid and MOMP confirmatory PCRs identified the five culture-DFA negatives and the three Amplicor negatives as true positives. The three specimens originally classified as negative by Amplicor PCR were positive on repeat Amplicor testing. After resolution of the discordant results by confirmatory PCR testing, the sensitivity of the initial Amplicor PCR was 91.4% (32 of 35 specimens), changing to 100% after storage and repeat testing. The specificity of Amplicor PCR was 100% (735 of 735 specimens). Our results demonstrated that plasmid and MOMP confirmatory PCRs worked equally well in resolving false-positive and false-negative Amplicor PCR results. Some specimens may contain inhibitors of Amplicor PCR which may disappear with time.

Evaluation of the Amplicor Chlamydia trachomatis test versus culture in genital samples in various prevalence populations

OBJECTIVE

To evaluate a newly developed polymerase chain reaction (PCR) assay, Amplicor C trachomatis for the detection of C trachomatis in genital samples using cell culture for comparison.

SUBJECTS

501 patients (431 women and 70 men) attending an STD clinic in Hôpital Pellegrin (high-risk population) and gynaecological clinics (low-risk population) in Bordeaux, France.

METHODS

The genital samples (cervical and urethral) were tested for the presence of C trachomatis using the Amplicor test and using standard cell culture identified by the immunofluorescence test using a monoclonal antibody to C trachomatis. Discrepancies between the results of culture and Amplicor were further analysed by major outer membrane protein gene (omp1)-PCR of the specimens taken in transport media and by direct fluorescent antibody (DFA) staining of elementary bodies in culture transport tubes.

RESULTS

After analysis of discrepancies, the revised sensitivity and specificity of PCR were 95.3% and 100% and the positive and negative predictive values were 100% and 99.5%, respectively.

CONCLUSION

The present results indicate that the Amplicor assay is rapid, specific and more sensitive than the culture method. This test provides an excellent non-culture method for the detection of C trachomatis in various prevalence populations.

Interlaboratory agreement study of a double set of PCR plasmid primers for detection of Chlamydia trachomatis in a variety of genitourinary specimens

We conducted a tricenter interlaboratory agreement study to assess the agreement of PCR results obtained for detection of Chlamydia trachomatis in genitourinary specimens. A total of 120 specimens (49 positive and 71 negative), including 20 first-void urine samples, 50 endocervical and 50 urethral swabs (40 males), were coded and sent from a reference laboratory (laboratory A) to two other laboratories. Laboratories B and C were provided with a standardized protocol and reagent package including two sets of plasmid PCR primers (KL1-KL2 and T1-T2) and were asked to test each specimen with the first set of primers (KL1-KL2) and to confirm positives with the second set of primers (T1-T2). Laboratory B identified 47 of 49 positives and 69 of 70 negatives (one specimen dried up on shipping) following the initial PCR, for an accuracy of 97.5% (116 of 119), and 47 of 49 positives and 70 of 70 negatives after confirmatory testing of the positives, for an accuracy of 98.3% (117 of 119). Laboratory C identified 42 of 49 positives and 70 of 70 negatives for the initial PCR, for an accuracy of 94.1% (112 of 119), and 39 of 42 positives and 70 of 70 negatives for the confirmatory PCR, for an accuracy of 91.6% (109 of 119). The overall accuracy of PCR testing was 96.6% (345 of 357). The kappa agreement statistics for agreement between pairs of laboratories after confirmation of positives were 0.97 for laboratories A and B, 0.83 for laboratories B and C, and 0.83 for laboratories A and C. Use of the confirmatory PCR improved the specificity and overall accuracy of results for individual laboratories but reduced slightly the results obtained for agreement between laboratories. These results demonstrate that when standardized reagents and protocols are used, PCR results are highly reproducible and excellent agreement between laboratories is obtainable.

Microtiter assay for colorimetric detection of in vitro amplified Chlamydia trachomatis sequences

An integrated diagnostic method for colorimetric detection of polymerase chain reaction (PCR) products in a microtitre format is described. The amplified material is labelled by using modified PCR primers introducing a biotin molecule and a lac operator handle. Positive samples are identified, after immobilization onto streptavidin-coated microtitre wells, using a reporter fusion protein consisting of the Escherichia coli lac repressor and beta-galactosidase. The analysis of the PCR products is thus, from a practical point of view, identical with the enzyme-linked immunosorbent assay (ELISA) using the enzymatic activity of beta-galactosidase. Here, we show that the assay can be used for rapid and simple detection of Chlamydia trachomatis in an automated format. The reported analysis of 90 urethral patient samples, using this microtitre assay, indicates that this technique is more sensitive and more specific than culture technique.

Sensitive detection and typing of Chlamydia trachomatis using nested polymerase chain reaction

OBJECTIVES

A method based on a nested polymerase chain reaction (PCR) was developed to detect and to type Chlamydia trachomatis from low titre samples by amplifying a large portion of the major outer membrane protein gene. The sensitivity of this procedure was evaluated in urogenital clinical samples in comparison with culture.

SPECIMENS

A series of 787 urogenital specimens, including 37 (4.7%) positive by culture, together with 227 other samples that had been found to yield less than 25 chlamydial inclusions in culture were tested.

METHODS

Samples were pelleted, resuspended in 1 mM NaOH, heated and amplified without further purification. After 40 cycles of PCR, 1 microliters of product was amplified by a further 30 cycles of PCR using a second set of primers nested within the initial pair. Positives were detected by agarose gel electrophoresis and confirmed by repeating the PCR analyses and determining the serovar of both amplified samples by restriction fragment length polymorphism.

RESULTS

Nested PCR allowed detection of 96% and culture 77% of positives with only three samples repeatedly positive by PCR but considered false positives because a different serovar was identified in the two amplifications. Of culture-positive samples with less than 11 chlamydia inclusion-forming-units 97% could be detected by nested PCR and most still gave a positive signal when diluted hundred fold.

CONCLUSIONS

Nested PCR provided the basis for a very sensitive C trachomatis detection and typing strategy. Repetition and typing positive samples facilitated detection of false-positive PCR specimens resulting from contamination of the PCR process or any reagent except the original sample.

Comparison of plasmid- and chromosome-based polymerase chain reaction assays for detecting Chlamydia trachomatis nucleic acids

Several laboratories have demonstrated that the polymerase chain reaction (PCR) is more sensitive than culture or enzyme immunoassay (EIA) for detecting Chlamydia trachomatis in genitourinary tract specimens when various DNA targets are used for amplification, including the cryptic plasmid, major outer membrane protein (MOMP), or rRNA genes. We compared the performances of five different PCR assays, including assays with two plasmid, two MOMP, and one rRNA targets, by amplifying serial dilutions of C. trachomatis DNA and testing genitourinary tract specimens. By using published procedures, two different plasmid primers had sensitivities of 0.1 fg for C. trachomatis plasmid DNA and 10 fg for total cellular DNA. The sensitivities of the assays with the two MOMP primers were 0.1 and 10 pg, and the sensitivity for the assay with the rRNA primers was 1 pg for cellular DNA. Both plasmid-based assays detected 38 of 38 confirmed Chlamydiazyme-positive specimens, whereas the assays with the MOMP and rRNA primers detected 36 of 38 and 29 of 38 confirmed Chlamydiazyme-positive specimens, respectively. Six of 18 Chlamydiazyme-negative specimens collected from individuals whose specimens were positive by culture or immunofluorescence were positive by both plasmid-based PCRs; 4 of these were positive by PCR with the MOMP primers and 3 were positive by PCR with the rRNA primers. The results obtained with both purified DNA and genitourinary tract specimens indicated that the plasmid-based PCRs are more sensitive than bacterial chromosome-based PCRs for detecting C. trachomatis.

Detection of Chlamydia trachomatis in semen of artificial insemination donors by the polymerase chain reaction

OBJECTIVE

To assess the feasibility of detecting Chlamydia trachomatis in cryopreserved donor semen by a specific, direct polymerase chain reaction (PCR).

DESIGN

Cryopreserved donor semen was tested for the presence of C. trachomatis by a specific PCR, directly applied to semen without prior DNA purification.

SETTING

Tertiary care fertility center in a teaching hospital and university-based laboratory for molecular pathology.

PARTICIPANTS

Cryopreserved semen from 30 donors was investigated. These semen samples had previously given negative results in cell culture for C. trachomatis. Two different ejaculates of each donor, cryopreserved with an interval of 2 years, were retrospectively analyzed.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

The presence of C. trachomatis as demonstrated by PCR.

RESULTS

In 3 of 30 donors C. trachomatis was detected in both ejaculates, whereas in 2 additional donors only one of the two samples tested positive. Additional samples from 2 positive donors, together with samples from 3 negative donors, were studied more extensively, to test the reproducibility and reliability of PCR results. All ejaculates of the donors, previously positive for C. trachomatis by PCR, indeed appeared to be positive, whereas the samples of the negative donors remained negative.

CONCLUSIONS

The direct PCR is a reliable, sensitive, and valuable method for detection of C. trachomatis in semen. The incidence of contamination of donor semen with C. trachomatis in the donor population in this study stresses the need for rigorous screening of donor semen before artificial insemination, preferably using a sensitive method such as the PCR.

Direct detection and genotyping of Chlamydia trachomatis in cervical scrapes by using polymerase chain reaction and restriction fragment length polymorphism analysis

Detection and genotyping of Chlamydia trachomatis were optimized by using a polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis performed directly with crude cells of cervical scrapes. Different PCR pretreatment methods were evaluated on samples which were positive for C. trachomatis by cell culture. In comparison with DNA extraction and different proteolytic digestion methods, a simple pretreatment of 10 min of boiling appeared to be optimal for PCR amplification. Crude samples (n = 209) were first screened for C. trachomatis by both cell culture and plasmid PCR. Subsequently, positive samples found by plasmid PCR were subjected to a direct omp1 PCR-based RFLP analysis to differentiate C. trachomatis serovars A to K, Ba, Da, and L1 to L3 and serovariant D-. All cervical scrapes that were found positive for C. trachomatis by cell culture (n = 30) were also positive by plasmid PCR and omp1 PCR and could be easily genotyped. In addition, of the culture-negative group, eight samples were found positive by plasmid PCR. Five of these eight samples were also positive by omp1 PCR; of these five, two were positive by a nested omp1 PCR. Genotyping by RFLP analysis of the 35 omp1 PCR-positive samples showed that serovars D, E, and F are the most prevalent types found in cervical scrapes, while serovariant D- was also detected. This study shows that direct PCR and PCR-based RFLP analysis are feasible for detection and genotyping of C. trachomatis in cervical scrapes and are more sensitive than culture-based serotyping.

Detection of Chlamydia trachomatis by the polymerase chain reaction in the cervices of women with acute salpingitis

OBJECTIVE

Our objective was to determine whether an increased prevalence of Chlamydia trachomatis could be detected by the polymerase chain reaction as opposed to culture in the cervices of women with acute salpingitis.

STUDY DESIGN

Endocervical samples from 15 women with laparoscopy-verified acute salpingitis and 20 women seeking medical help for conditions other than pelvic pain were tested for Chlamydia trachomatis with the polymerase chain reaction. The oligonucleotide primer pairs used were specific for a 144 bp region of the major outer membrane protein that contained a single EcoRI endonuclease cleavage site. The detection of a 144 bp band that was cleaved by EcoRI to a 103 bp band denoted a Chlamydia trachomatis-positive sample. Cervical samples were cultured for Chlamydia trachomatis with the use of McCoy cells. The lymphocyte proliferative response to Chlamydia trachomatis elementary bodies was also determined.

RESULTS

Nine of the 15 women (60%) with salpingitis had positive results when tested with the polymerase chain reaction for cervical Chlamydia trachomatis. Only two of these women (13%), both of whom had positive results when tested with the polymerase chain reaction, had cultures that were positive for Chlamydia trachomatis (p < 0.02). Among the 20 other women, only two patients with cervicitis had positive cultures for Chlamydia. Those women plus two women with unexplained recurrent abortions had positive polymerase chain reaction test results for Chlamydia trachomatis. A lymphocyte proliferative response to Chlamydia trachomatis was detected in five of eight women with salpingitis, as well as three of the other four patients, all of whom had positive polymerase chain reaction test results; lymphocytes from the remaining women were unresponsive. Follow-up cervical samples were obtained 4 to 6 months after treatment from six of the patients with salpingitis who had positive polymerase chain reaction test results; at that time five had negative polymerase chain reaction test results for Chlamydia trachomatis.

CONCLUSION

The polymerase chain reaction appeared to be more sensitive and more rapid than culture in detecting Chlamydia trachomatis in the cervices of women with acute salpingitis. This assay may be of value for the early diagnosis of chlamydial infections.

Amplification of Chlamydia trachomatis DNA by ligase chain reaction

Amplification of Chlamydia trachomatis DNA by polymerase chain reaction was compared with amplification by ligase chain reaction (LCR). Both amplification procedures were able to consistently amplify amounts of DNA equivalent to three C. trachomatis elementary bodies. All 15 C. trachomatis serovars were amplified to detectable levels by LCR, and no DNA from 16 organisms potentially found in clinical specimens or from Chlamydia psittaci and Chlamydia pneumoniae was amplified by LCR.

PCR detection and differentiation of Chlamydia pneumoniae, Chlamydia psittaci and Chlamydia trachomatis

A PCR-based system was developed for the detection and differentiation of Chlamydia trachomatis, Chlamydia psittaci and Chlamydia pneumoniae. A conserved 145 bp fragment of the chlamydial omp1 gene was amplified from all three species. The three species were then differentiated from each other by digestion of this PCR product with restriction enzymes Eco RI and either Hind III or Pst I. The system was shown to work for two strains of C. pneumoniae, 11 strains of C. psittaci and 10 serovars of C. trachomatis, and had a sensitivity of less than 10 chlamydial elementary bodies. This method was also applicable to the detection of C. trachomatis in conjunctival and nasopharyngeal swabs.

Evaluation of the polymerase chain reaction (PCR) for detection of Chlamydia psittaci in abortion material from ewes

The polymerase chain reaction (PCR) was evaluated as a diagnostic tool for detection of Chlamydia (C.) psittaci in abortion material from 40 ewes. For this purpose, PCR results of 87 samples were compared with direct microscopic identification after chemical staining, cell culture isolation and a commercially available enzyme-linked immunosorbent assay (ELISA). The value for sensitivity as compared to cell culture was 97.7% whereas the specificity-value was calculated to be 84.1%.

Confirmatory polymerase chain reaction testing for Chlamydia trachomatis in first-void urine from asymptomatic and symptomatic men

First-void urine specimens from 683 men (592 without symptoms) were tested for Chlamydia trachomatis by a polymerase chain reaction (PCR) with KL1 and KL2 plasmid primers and by a Chlamydiazyme enzyme immunoassay (EIA). Thirty-seven specimens were confirmed to be positive by using the EIA blocking reagent and a second set of plasmid primers (T1 and T2). By comparing unconfirmed PCR results (KL1 and KL2 primers only) with the blocked Chlamydiazyme EIA results, the sensitivity and specificity of PCR were 100% (37 of 37 specimens) and 99.5% (643 of 646 specimens), respectively. Three additional specimens were negative by EIA but positive by PCR and were confirmed to be positive with primers T1 and T2. Two of the three specimens were from men with symptoms. The confirmatory PCR assay performed equally well in detecting positive specimens from symptomatic (31 of 31) and asymptomatic (9 of 9) men. Comparison of confirmatory testing of first-void urine specimens by PCR and EIA showed that PCR was 100% sensitive (40 of 40 specimens) and that the EIA was 92.5% sensitive (37 of 40 specimens) but that the assays were equally specific (100%).

Development and clinical evaluation of a polymerase chain reaction test for detection of Chlamydia trachomatis

A polymerase chain reaction (PCR) for the detection of Chlamydia trachomatis was developed and evaluated. Two primer-probe sets were designed; one detected a specific sequence of the plasmid, and the other detected the gene encoding the major outer membrane protein. Both sets reacted species specifically and amplified sequences from all human serovars. A simple protocol was used for sample pretreatment. The PCR was optimized by addition of tetramethylammonium chloride and bovine serum albumin. The results of the PCR with the plasmid primer-probe set were compared with those of culture and the Chlamydiazyme and Gen-Probe PACE 2 tests for urogenital specimens from 220 patients. The rates of prevalence of infection with C. trachomatis were 22.7, 16.4, 15.0, and 14.5%, respectively. The sensitivities of the Chlamydiazyme and Gen-Probe PACE 2 assays compared with culture were 66.7 and 61.1%, respectively, and their sensitivities compared with PCR were 60.0 and 60.0%, respectively. The sensitivity of culture compared with PCR was 70.0%. Forty-eight of the 50 specimens positive by PCR with the plasmid primer-probe set could be confirmed by PCR with the major outer membrane protein primer-probe set or culture. It is concluded that the PCR is the most sensitive technique for laboratory detection of C. trachomatis.

Demonstration of chlamydial RNA and DNA during a culture-negative state

Trachoma is a common blinding disease of humans caused by ocular infections with Chlamydia trachomatis. The cynomolgus monkey is a valuable primate model for the detection, pathobiology, and treatment of this infection. We have used this model system to compare the relative ability of tissue culture, direct fluorescence cytology, a modified polymerase chain reaction, and RNA blotting to detect C. trachomatis following primary infection and reinfection over 34 weeks. Six cynomolgus monkeys were given a primary ocular chlamydia infection, and 20 weeks later they were reinoculated with the same organism. All animals showed brisk inflammatory responses to the primary infection and milder inflammatory reactions to reinfection. All four diagnostic techniques detected chlamydia at 1 week after primary infection, but both nucleic acid detection methods suggested that organisms were present longer after primary infection than did either tissue culture or direct fluorescence cytology (16 weeks for RNA blotting versus 12 weeks for tissue culture). Following reinoculation at 20 weeks, the period of C. trachomatis detection by tissue culture or direct fluorescence cytology (4 weeks) was much shorter than after primary infection. In contrast, nucleic acid detection was positive for up to 5 weeks longer than tissue culture or direct fluorescence cytology. Both polymerase chain reaction and RNA blotting, which involved no amplification step, indicated the presence of organisms during the culture-negative period. These data suggest that live chlamydiae may remain at a site of infection and produce inflammation beyond the time at which standard microbiological techniques are able to detect them.

Detection of Chlamydia trachomatis by use of polymerase chain reaction

A polymerase chain reaction (PCR) assay was developed for detection of Chlamydia trachomatis DNA. One primer set was used, from the published sequence of the common C. trachomatis plasmid. Detection of amplified sequences was carried out by agarose gel electrophoresis. Analysis of 106 clinical samples tested by cell culture and PCR showed a sensitivity of 100% when PCR was compared with cell culture.

Typing of Chlamydia trachomatis by restriction endonuclease analysis of the amplified major outer membrane protein gene

A procedure was developed for characterization of Chlamydia trachomatis strains by using restriction endonuclease analysis of amplified genes of the major outer membrane protein (MOMP). Reference strains of the 15 serovars (A through K and L1 through L3) and clinical isolates were tested. The nucleotide sequences of the MOMP genes of each of the 15 serovars were arbitrarily constructed by using the sequences of the four variable domains known for each serovar and the constant domains of serovar L1. Computer analysis of these sequences indicated that two restriction digestions performed in parallel, one with AluI and the other with IIpaII, followed by HinfI and EcoRI, would allow the theoretical differentiation of 13 serovars. Serovars Ba and L1 presented the same theoretical restriction profile. Our typing method consisted of polymerase chain reaction amplification of a fragment of about 1,200 bp of the MOMP gene, followed by restriction endonuclease digestion with the aforementioned enzymes. From the 15 serovars, we obtained 14 different patterns; 13 profiles were serovar specific, while serovars B and Ba presented the same pattern. Application of this typing method to C. trachomatis strains isolated from clinical material gave the same results as the immunotyping method for 14 of 17 strains. Furthermore, restriction endonuclease analysis detected differences within a serovar. This method seems to be promising for epidemiological studies.

New strategies in microbiological diagnosis

With the advent of the polymerase chain reaction (PCR), molecular biology is at last poised to enter the clinical microbiology laboratory. We describe this technique, and review its present and future applications in the diagnosis of infectious disease, with particular emphasis on its potential in diagnostic bacteriology. We discuss the suitability of different sequences as targets for DNA amplification. The disadvantages of PCR as a diagnostic strategy are covered, and current technical problems with the method are surveyed. We briefly mention two alternative strategies--the transcript-based amplification system and replicatable RNA reporter systems based on the Q beta replicase.