The role of polymerase chain reaction and ligase chain reaction for the detection of Chlamydia trachomatis

Strategies to control trachoma

Trachoma is a significant public health problem that is endemic in 57 countries, affecting 40.6 million people and contributing to 4% of the global burden of blindness. Repeated episodes of infection from Chlamydia trachomatis lead to long-term inflammation, scarring of the tarsal conjunctiva and distortion of the upper eyelid with in-turning of eyelashes that abrade the surface of the globe. This constant abrasion, in turn, can cause irreversible corneal opacity and blindness. The Alliance for the Global Elimination of Trachoma by 2020 (GET2020) has adopted the SAFE (Surgery, Antibiotics, Facial cleanliness and Environmental improvement) strategy as the main action against trachoma. Trichiasis surgery reduces the risk of blindness by reversing the in-turning of eyelashes and also improves the quality of life from non-visual symptoms. However, future efforts need to aim at increasing accessibility to surgery and improving acceptance. Antibacterials are required to reduce the burden of infection. Oral azithromycin is as close to the perfect antibacterial as we will get for mass distribution: it is safe, requires only a single oral dose, treatment is usually repeated every 6-12 months, resistance is not seen as a problem, and cost is not a limiting factor with a large donation programme and newer generic versions of the drug. Future focus should be on the details of antibacterial distribution such as coverage, frequency of distribution and target population. The promotion of facial cleanliness through education may be the key to trachoma elimination as it will stop the frequent exchange of infected ocular secretions and thus reduce the transmission of infection. However, innovative methods are required to translate health education and promotion activities into sustainable changes in hygiene behaviour. Environmental improvements should focus on the barriers to achieving facial cleanliness and cost-effective means need to be identified. There are a number of countries already eligible for certification of trachoma elimination and if current momentum continues, blinding trachoma can be eliminated by the year 2020.

Effect of endocervical-specimen adequacy on detection of Chlamydia trachomatis by the APTIMA COMBO 2 assay

Six hundred one endocervical specimens were analyzed for Chlamydia trachomatis by the APTIMA Combo 2 assay and evaluated for columnar epithelial cell adequacy by direct fluorescent-antibody staining. With 5.5% positive adequate and 7.8% positive inadequate specimens (P=0.27), the study suggested no difference in positivity rates due to specimen adequacy when this amplified technology was used.

Molecular genetic methods for diagnosis and characterisation of Chlamydia trachomatis and Neisseria gonorrhoeae: impact on epidemiological surveillance and interventions

One of the mainstays in the prevention of Chlamydia trachomatis and Neisseria gonorrhoeae infections is the availability of laboratory diagnostics with high sensitivity and specificity. Assays for diagnosis of C. trachomatis include cell culture and nucleic acid amplification tests (NAATs). The major target sequences for C. trachomatis diagnosis by NAATs are located at the cryptic plasmid and the major target used for characterisation is the omp1 gene. The gold standard for diagnosis of N. gonorrhoeae is culture. However, numerous NAATs for identification of N. gonorrhoeae and a number of molecular genetic methods for characterisation of N. gonorrhoeae have been developed. Probably no routine laboratory can attain as high sensitivity by culturing C. trachomatis or N. gonorrhoeae as by using NAATs. For that reason NAATs can be recommended for diagnosing C. trachomatis, but not as the only diagnostic assay for N. gonorrhoeae, due to lack of antibiotic susceptibility testing and specificity problems, most pronounced for pharyngeal and rectal samples. Genotyping of C. trachomatis or N. gonorrhoeae provides additional information for contact tracing. It is recommended for N. gonorrhoeae, at least in low prevalence geographic areas, but cannot today be recommended for C. trachomatis. This is due to the low genetic variability and hence the limited benefits for partner notification. However, genotyping of C. trachomatis may play an important role under special circumstances.

Polymorph count for predicting non-gonococcal urethral infection: a model using Chlamydia trachomatis diagnosed by ligase chain reaction

BACKGROUND/OBJECTIVES

The criteria for the diagnosis of non-gonococcal urethritis (NGU) on a Gram stained urethral smear are derived from previous studies which used culture as a diagnostic test for Chlamydia trachomatis. Our objectives were (1). to re-assess the relation between urethral polymorph count and C trachomatis infection, using ligase chain reaction (LCR) as the diagnostic test; and (2). to assess other possible predictors of C trachomatis infection such as symptoms, signs, demographic and behavioural variables.

METHODS

We collected data from 363 men consecutively attending a genitourinary medicine clinic (excluding those with gonorrhoea and follow up visits) who had a urethral smear and a urethral LCR test for C trachomatis. The sensitivity and specificity of a discrete cut off in urethral polymorphonuclear leucocyte (PMNL) count as a diagnostic test for chlamydia urethritis were calculated. The associations between other variables, such as age and symptoms, and this infection were also estimated.

RESULTS

8% of men had C trachomatis infection and 26% of men had a PMNL count of 5 or more. Of those men with chlamydia 37% did not have NGU; 20% of men with NGU had chlamydia. Adjusted odds ratios for risk of chlamydial infection were significant for age less than 30 relative to 40 years and over (adj OR 13.6; 95% confidence interval 1.69 to 110), a PMNL count of 20 or more (6.56; 2.15 to 20.0), a PMNL count of 5-19 (3.59; 1.41 to 9.15), and the symptom of dysuria (3.27; 1.32 to 8.08). However a PMNL count of 5 or more was only 63% sensitive and 77% specific for C trachomatis infection. No association between sexual behaviour and chlamydial infection was found in this setting.

CONCLUSIONS

The PMNL count is associated with presence of chlamydial infection but a large proportion of men with chlamydia have PMNL counts below the recommended cut off for a diagnosis of NSU. Lower age and the presence of symptoms may be as predictive as the urethral polymorph count for chlamydial urethritis and possibly for other urethral infections.

Screening and genotyping of genital Chlamydia trachomatis in urine specimens from male and female clients of youth-health centers in Stockholm County

BACKGROUND

The current study was conducted in the context of the current increase in cases of Chlamydia trachomatis infections, the development of new diagnostic strategies, and an outreach to community-based youth center screening sites.

GOAL

The goal was to define the prevalence of genital C trachomatis infection among clients of youth-health clinics and to evaluate the feasibility of implementing genotyping as a tool for epidemiologic studies with use of urine specimens.

STUDY DESIGN

This was a prospective pilot study at two community-based youth-health clinics for teenagers and adolescents. Enrollment followed a high school educational program and public advertising campaign on the common occurrence of nonsymptomatic or only mildly symptomatic chlamydial infection among sexually active young people. Voluntary, confidential, free screening of first-void urine was provided, and the samples were tested by polymerase chain reaction (PCR). Demographic and behavioral data were obtained. Positive samples were differentiated into genovars by genotyping with restriction fragment length polymorphism analysis of the PCR-amplified omp1 gene.

RESULTS

The prevalence of nonsymptomatic or mildly symptomatic chlamydial infection was 6.0% among women and 9.3% among men. A significant increase in the risk of infection was associated with a history of sexually transmitted disease (STD) (P < 0.01). There was no statistical risk correlating with partner change during the past year, infrequent or inconsistent condom use during the past year, present use of contraceptive pills, smoking habits, or recent alcohol consumption. Genotype E was most common (60%) among both sexes. Genotypes F and K were second most prevalent for men (20%), and genotype D was second most prevalent for women (15%). Genotype K or F was found in 23% of cases.

CONCLUSION

Screening programs targeting sexually active adolescents attending youth-health clinics are important for detection of C trachomatis. Genotyping might become an efficient tool in epidemiologic studies. The impact of educational school- and community-based programs on STD among young people needs further evaluation.

Comparison of urine, first and second endourethral swabs for PCR based detection of genital Chlamydia trachomatis infection in male patients

OBJECTIVES

To compare endourethral swabs and urine as diagnostic specimens for the detection of genital Chlamydia trachomatis infection using the polymerase chain reaction (PCR), in male patients attending a genitourinary clinic and to assess whether the first endourethral swab used solely for diagnosing gonococcal infection could be used for C trachomatis detection as well.

METHODS

Two endourethral swabs were taken from 80 male patients, in whom the likelihood of genital C trachomatis infection was high. The first swab was used for microscopy and culture for Neisseria gonorrhoeae, before being used for C trachomatis detection. First voided urine specimens were collected from 61 of these patients. All three specimens were processed for C trachomatis DNA detection using the Roche Cobas Amplicor PCR. A diagnosis of genital C trachomatis infection was made if any one of the specimens tested reproducibly positive. Samples from 13 patients showing discrepant PCR results between swabs and/or urine were retested by ligase chain reaction (LCR).

RESULTS

Chlamydia trachomatis DNA was detected in 35 (43.8%) of the 80 patients. In 17 of the 35 patients (48.6%), all the genital specimens were positive. However, in 18 (51.4%) patients, one or more of the genital specimens had negative PCR results. Among the 18 patients with discrepant results, urine was found to be a more sensitive diagnostic specimen than the second urethral swab picking up 13 out of 16 positives (81.3%) as opposed to five out of 18 (27.8%). There was no significant difference between the two swabs. Retesting by LCR, of the samples from 13 of the 18 patients with discrepant PCR results confirmed them all as true positives, although as with PCR, not all specimens in the set were concordantly positive. LCR detected all the 13 positives in urine, while there was no difference in the detection rate between the first and the second urethral swabs.

CONCLUSIONS

Urine appeared to be a better diagnostic specimen than the conventional second endourethral swab for C trachomatis detection by PCR in this cohort of male patients. There was no difference between the first swab, intended primarily for N gonorrhoeae testing and the second swab intended for C trachomatis detection. This raises questions over the need for the conventional second swab for detecting C trachomatis.

Evaluation of self-taken samples for the presence of genital Chlamydia trachomatis infection in women using the ligase chain reaction assay

The aim of this study was to evaluate the sensitivity and acceptability of self-taken vulval-introital (VI) samples, first-catch urine (FCU) samples and clinician-obtained cervical samples for the presence of genital Chlamydia trachomatis infections in women using the ligase chain reaction (LCR) assay. One hundred and four patients were enrolled, of whom 54 patients had chlamydial DNA in at least one of the samples tested. The sensitivity of the cervical sample was 96.3%, vulval-introital sample in LCR buffer 92.6%, vulval-introital swab collected dry 88.9%, FCU stored at +2-8 degrees C 81.5%, FCU stored at room temperature 77.8% and FCU stored with 2% w/v boric acid at room temperature 87.0%. Self-taken vulval-introital LCR samples were shown to be an acceptable alternative to a clinician-obtained LCR sample. The addition of boric acid may overcome the need for a continuous cold chain for FCU samples.

Evaluation of a rapid assay for detection of Chlamydia trachomatis infections in outpatient clinics in South Kalimantan, Indonesia

A multicenter cross-sectional survey was conducted comparing a commercially available chlamydial optical immunoassay (OIA) to the chlamydial ligase chain reaction (LCR). Endocervical samples from 415 outpatients visiting clinics from three hospitals in South Kalimantan, Indonesia, were evaluated. Relative to the LCR, the overall sensitivity and specificity of the OIA were 31.6 and 98.9%, respectively. The sensitivity of the OIA varied among the three hospital laboratories, ranging from 20 to 50%. The OIA performance was slightly lower on samples from patients attending dermatovenereology clinics than on samples from nondermatovenereology clinic patients. The results indicate that the OIA did not perform well compared to LCR.

Pelvic inflammatory disease. From diagnosis to prevention

Pelvic inflammatory disease (PID) refers to infection of the uterus, fallopian tubes, and adjacent pelvic structures that is not associated with surgery or pregnancy. PID causes major medical, social, and economic problems worldwide. Long-term sequelae, most notably tubal factor infertility and ectopic pregnancy, are common and extremely costly to the healthcare system. The most important causative micro-organisms are Chlamydia trachomatis, Neisseria gonorrhoeae, and micro-organisms associated with bacterial vaginosis. The clinical spectrum of PID ranges from subclinical endometritis to severe salpingitis, pyosalpinx, tubo-ovarian abscess, pelvic peritonitis, and perihepatitis. Clinical diagnosis of PID has limitations. The clinical diagnostic criteria are insensitive and nonspecific, and false-positive and false-negative diagnosis is common; however, direct visual diagnosis is not always feasible, requires general anesthesia, and is costly. More research is needed of noninvasive diagnosis of PID. Current treatment guidelines call for broad-spectrum antimicrobial coverage. Screening for asymptomatic chlamydial infection is the mainstay of prevention of PID. Emerging evidence from randomized controlled trials provides strong evidence that intervention with selective screening for chlamydial infection effectively reduces the incidence of PID.