Multiplex AMPLICOR PCR screening for Chlamydia trachomatis and Neisseria gonorrhoeae in women attenting non-sexually transmitted disease clinics. The European Chlamydia Epidemiology Group

Low-cost conventional PCR techniques enable simultaneous detection of bacterial sexually transmitted infections with enhanced sensitivity and specificity

PURPOSE

Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Mycoplasma hominis (MH), the three most common treatable bacterial sexually transmitted infections (STIs) worldwide can lead to many complications if remain untreated. Screening of high-risk population with highly sensitive methods will lead to significant improvement in patient outcomes and will prevent downward transmission. The advantages of Polymerase chain reaction (PCR) based assay are not only high sensitivity and specificity, but also detection of multiple organisms in a single reaction which reduce the result turn-around time. The aim of the present study was to evaluate the feasibility of a multiplex PCR assay method targeting 16S rRNA gene for simultaneous detection of NG, CT and MH infection along with their trend and occurrence among high-risk population in Assam, Northeast India.

METHODS

A cross-sectional study was undertaken, where a total of 200 randomly selected patients from high-risk population were included. After validation of singleplex PCR, Multiplex PCR (M-PCR) was performed along with the traditional culture method for NG.

RESULTS & CONCLUSION

The overall agreement of M-PCR with singleplex PCR was very high (100%). The occurrence of STI was found to be very high (101/200; 50.5%). Furthermore, co-infection was detected in 10/200; 5%) individuals. Infection was more common among young individuals (p < 0.05) and males out-numbered females (p < 0.05). The most common organism detected was CT (42/200; 21%) followed by NG (41/200; 20.5%) and MH (20/200; 10%). The M-PCR assay workflow is simple, cost effective and can be used in routine diagnostic laboratories with basic molecular facilities.

A systematic review and meta-analysis of different diagnostic procedures to detect gonococcus infection in resource-limited scenario

Context

Neisseria gonorrhoeae is a Gram-negative diplococcus, an obligate human pathogen, and the etiologic agent of the sexually transmitted infection (STI), gonorrhoea. culture is the standard procedure for diagnosis, which may be supported by nucleic acid tests and microscopy.

Aims

To determine the best possible method of diagnosis for Gonococcus infection in resource-limited settings.

Settings and Design

The meta-analyses were designed to determine the difference in diagnosis between Culture and nucleic acid amplification tests (NAATs) and also between the different Amplification Tests and widely available Roche COBAS AMPLICOR test.

Subjects and Methods

Databases searched were Pubmed, Medline, Google Scholar and Cochrane reviews. Risk ratio (RR) with 95% confidence intervals was estimated for the dichotomous outcomes. The random-effect model was applied for all the studies in the analysis.

Statistical Analysis Used

The meta-analysis was computed in RevMan Version 5.3, Copenhagen, Denmark.

Results

In the first analysis, NAATs significantly improved the chances of detection in comparison to the standard culture and final RR was 1.24 (1.05-2.51), which put the diamond on the right of no-effect axis, indicating more positives by NAATs. In the second analysis, AMPLICOR had the more positive results, which may have indicated better detection rate, as well as less specificity and final RR was 0.809 (0.737-0.888), which put the diamond on the left of the non-effect axis, indicating more positives by AMPLICOR.

Conclusions

In a resource-limited scenario like India, the syndromic management of STIs are considered to be the norm. A positive diagnosis is only given if the tests are confirmed by Culture, as it is still considered to be the gold standard of diagnosis. However, in many cases, due to suboptimal transportation and lack of proper handling, culture in unable to grow even if the patient is infected. In such cases, Nucleic Acid Tests should be able to detect an infection.

Detection of genital chlamydial and gonococcal infection using urine samples: A community-based study from India

Sexually transmitted infections (STI) have a major impact on the reproductive health of women. Among the different etiological agents of STIs, Chlamydia trachomatis and Neisseria gonorrhoeae are the main bacterial pathogens that cause sexually transmitted infections in women. The aim of the study was to estimate the prevalence of genital chlamydial and gonococcal infection among women in the age group of 18-65 years from a community-based setting. A community-based cross-sectional study was performed using the archived urine samples (n=811) of women in the age group of 18-65 years for C. trachomatis and N. gonorrhoeae using a multiplex conventional Polymerase Chain Reaction (PCR). Out of 811 samples tested in the present study, 2 (0.24%) were tested positive for C. trachomatis and none were positive for N. gonorrhoeae. The study demonstrates the very low prevalence of C. trachomatis and N. gonorrhoeae infection in a rural community. For large population-based screening, urine samples were observed to be more socially acceptable and cost-effective.

Comparison between conventional culture and NAATs for the microbiological diagnosis in gonococcal infection

Gonorrhea is a public health problem. Fast diagnostics is necessary. The aim of this study was to compare the diagnostic yield of culture with that of polymerase chain reaction (PCR) in gonococcal infection. This is a study comparing the results of Neisseria gonorrhoeae detection by culture versus PCR from July to December 2012. Molecular diagnosis was performed by real-time PCR using the Versant CT/GC DNA 1.0 assay. In the 768 specimens, 96.9% the results were concordant. In 3.1%, the results were discordant, being PCR-positive and culture-negative in 21 cases and PCR-negative and culture-positive in 3. The sensitivity, specificity, positive predictive value, and negative predictive value for culture were 86.2%, 99.8%, 99.2%, and 96.7%, and for PCR, 98.7%, 100%, 100% and 99.7%, respectively. In laboratories where antimicrobial susceptibility is monitored, an effective approach would be to perform culture in addition to PCR in symptomatic patients.

Laboratory Capacity for Antimicrobial Susceptibility Surveillance of Neisseria gonorrhoeae-District of Columbia, 2007-2012

BACKGROUND

In the District of Columbia (DC), Neisseria gonorrhoeae (gonorrhea) infections accounted for more than 25% of 9321 incident sexually transmitted infections reported in 2011; untreated infections can lead to reproductive complications and a higher risk for HIV transmission. In DC, limited capacity to measure the prevalence of antibiotic-resistant N. gonorrhoeae is available; culture-based antibiotic susceptibility testing (AST) is needed to monitor antimicrobial resistance. We examined the capacity of laboratories that report to the DC Department of Health to perform AST for ongoing surveillance of antibiotic-resistant N. gonorrhoeae and to identify suspected treatment failures.

METHODS

We created a survey about diagnostic methods for gonorrhea testing and identified 33 laboratories that reported gonorrhea results to Department of Health in 2007 to 2012. Laboratories were assessed for use of bacterial culture or nucleic acid amplification testing (NAAT) for gonorrhea testing, prevalence of AST on gonorrhea-positive cultures, and types of antibiotics tested during AST. We estimated the prevalence of laboratory practices on the basis of self-report by staff.

RESULTS

Nineteen (58%) laboratories completed the survey, representing 92% of the gonorrhea reporting. Seventeen (89%) of 19 laboratories conducted testing by culture; only 6 (35%) performed AST; 79% performed NAAT. Barriers to AST included longer completion times and limited number of provider requests for AST. Commercial laboratories (32%) were more likely to conduct both culture and NAAT, compared with health care facilities (11%).

CONCLUSIONS

We report a low prevalence of laboratories performing AST because of multiple barriers. State-specific strategies addressing these barriers are needed to improve detection of antibiotic-resistant gonorrhea stains circulating among the population.

Development and evaluation of a next-generation digital PCR diagnostic assay for ocular Chlamydia trachomatis infections

Droplet digital PCR (ddPCR) is an emulsion PCR process that performs absolute quantitation of nucleic acids. We developed a ddPCR assay for Chlamydia trachomatis infections and found it to be accurate and precise. Using PCR mixtures containing plasmids engineered to include the PCR target sequences, we were able to quantify with a dynamic range between 0.07 and 3,160 targets/μl (r² = 0.9927) with >95% confidence. Using 1,509 clinical conjunctival swab samples from a population in which trachoma is endemic in Guinea Bissau, we evaluated the specificity and sensitivity of the quantitative ddPCR assay in diagnosing ocular C. trachomatis infections by comparing the performances of ddPCR and the Roche Amplicor CT/NG test. We defined ddPCR tests as positive when we had ≥95% confidence in a nonzero estimate of target load. The sensitivity of ddPCR against Amplicor was 73.3% (95% confidence interval [CI], 67.9 to 78.7%), and specificity was 99.1% (95% CI, 98.6 to 99.6%). Negative and positive predictive values were 94.6% (95% CI, 93.4 to 95.8%) and 94.5% (95% CI, 91.3 to 97.7%), respectively. Based on Amplicor CT/NG testing, the estimated population prevalence of C. trachomatis ocular infection was ∼17.5%. Receiver-operator curve analysis was used to select critical cutoff values for use in clinical settings in which a balance between higher sensitivity and specificity is required. We concluded that ddPCR is an effective diagnostic technology suitable for both research and clinical use in diagnosing ocular C. trachomatis infections.

Female genital Chlamydia trachomatis infection: where are we heading?

INTRODUCTION

Urogenital infection by Chlamydia trachomatis is the most common bacterial sexually transmitted disease in the world. C. trachomatis is the etiologic agent of several common genital tract syndromes such as urethritis, cervicitis, and pelvic inflammatory disease in women.

MATERIALS AND METHODS

In this review, the pathophysiology of a chlamydial infection as well as diagnosis, therapy and prevention strategies regarding female chlamydial infection are reviewed.

RESULTS

A chlamydial infection results in minimal or even no symptoms in approximately two-thirds of women, remaining therefore clinically apparent and undiagnosed. C. trachomatis infections are of great socioeconomic and public health concern due to the potential for severe long-term consequences in women, including an increased risk of ectopic pregnancy, tubal infertility and chronic pelvic pain. Moreover, if the bacterium is transmitted during labor to a newborn, it can cause ophthalmia neonatorum and atypical neonatal pneumonia. Due to the documented increased risk of morbidity, several national guidelines are available, including a routine screening for young women and screening during pregnancy that is recommended in several countries.

DISCUSSION

A routine screening for young women and screening during pregnancy is recommended in several countries. However, additional prospective studies of the effectiveness of chlamydia screening are warranted and might be feasible within established screening programs. Moreover, the transition from cervicitis to infertility should be also evaluated in future controlled studies to underline the existing evidence. Additionally, there is an urgent need to educate and inform health-care providers about implementation of screening programs to reduce the spread of chlamydial infection. Moreover, awareness and use of screening programs by the public is needed, which requires informational campaigns for the general public using different media. For improved screening strategies and public awareness, novel approaches have to be developed and evaluated. Finally, guidelines should be actively disseminated to all medical practitioners to increase their use in daily practice. Although the major socioeconomic and public health concerns of C. trachomatis infection are recognized, several considerations and additional measures for addressing this increasingly urgent health problem remain.

Self-collection of specimens for nucleic acid-based diagnosis of pharyngeal, cervicovaginal, urethral, and rectal Neisseria gonorrhoeae and Chlamydia trachomatis infections

Commercially available nucleic acid amplification tests (NAATs) for Neisseria gonorrhoeae and Chlamydia trachomatis detection allow for self-collection including home-based collection from multiple anatomic sites such as the urethra, cervicovagina, rectum, and pharynx. Verification studies need to be done prior to processing pharyngeal and rectal specimens. We review specimen collection and test characteristics of NAATs at different anatomical sites.

Evaluating PCR, culture & histopathology in the diagnosis of female genital tuberculosis

BACKGROUND & OBJECTIVES

Genital tuberculosis (GTB) is one of the major causes for severe tubal disease leading to infertility. Unlike pulmonary tuberculosis, the clinical diagnosis of GTB is difficult because in majority of cases the disease is either asymptomatic or has varied clinical presentation. Routine laboratory values are of little value in the diagnosis. An absolute diagnosis cannot be made from characteristic features in hysterosalpingogram (HSG) or laparoscopy. Due to the paucibacillary nature of GTB, diagnosis by mycobacterial culture and histopathological examination (HPE) have limitations and low detection rate. The objective of this study was to evaluate the efficacy of PCR technique, culture and histopathological examination in the diagnosis of GTB in female infertility.

METHODS

This study included 72 infertile women who met the inclusion and exclusion criteria. After a detailed history and clinical examination all patients were subjected to investigations including pelvic sonogram, HSG and laparoscopy. Endometrial samples from were allocated for AFB smear, culture and HPE examination. Only 49 samples were available for PCR using IS 6110 and TRC 4 primers. In seven patients peritoneal fluid was also taken for culture and PCR. Based on the clinical profile and laparoscopic findings, a diagnostic criteria was derived to suspect GTB. Specific diagnostic tests were evaluated against this diagnostic criterion.

RESULTS

Laparoscopy was suggestive of tuberculosis in 59.7 per cent of cases, AFB smear was positive in 8.3 per cent, culture was positive in 5.6 per cent, HPE positive in 6.9 per cent and PCR was positive in 36.7 per cent of cases. Based on the diagnostic criteria, GTB was suspected in 28 of the 49 cases. On evaluating against the diagnostic criteria, the sensitivity of PCR, HPE and culture were 57.1, 10.7, 7.14 per cent respectively. The concordance of results between the clinical criteria and specific diagnostic tests were analysed by Kappa measure of agreement. The culture and HPE showed mild agreement with the clinical criteria, whereas PCR showed a moderate agreement. PCR was positive in Two of the 21 cases in whom GTB was not suspected. False positive PCR in these two cases were ruled out by multiple areas of sampling and re-sampling in one case. The PCR results were negative in 12 of the 28 cases. PCR using TRC 4 primers had a higher sensitivity (46.4%) than IS 6110 primers (25%) in detecting clinically suspected GTB.

INTERPRETATION & CONCLUSIONS

Our results showed that conventional methods of diagnosis namely, HPE, AFB smear and culture have low sensitivity. PCR was found to be useful in diagnosing early disease as well as confirming diagnosis in clinically suspected cases. False negative PCR was an important limitation in this study.

Gynaecological and microbiological findings in women attending for a general health check-up

Two hundred apparently healthy sexually active women, 17-34 years of age, who had presented for a general health check-up at the Clinic of Dermatology and Venereology, Medical University, Plovdiv, Bulgaria, were asked about genital symptoms, sexual behaviour, contraceptive use and smoking habits, and examined for signs of genital infections. They were searched for genital chlamydial infection, gonorrhoea, trichomoniasis, bacterial vaginosis (BV) and vulvovaginal candidosis, syphilis and HIV. Polymerase chain reaction (PCR) was used for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in urine samples and the results were compared with direct immunofluorescence (DFA) and enzyme immunoassays (EIA) for C. trachomatis in urethral, cervical and urine samples. In 56 (28%) women, an STD and/or an STD-related condition were diagnosed. The prevalence of genital chlamydial infection, trichomoniasis, BV and vulvovaginal candidosis was 4.5%, 0.5%, 17.5% and 7.5% respectively. On direct questioning 39 (19.5%) women reported symptoms suggestive of an infection, while 58 (29%) had signs that may have been caused by genital infection. In urine the PCR tests detected more (3.5%) chlamydia-positive women than the DFA (2.5%) and EIA tests (1.5%). The urine PCR test was as sensitive as the DFA when testing cervical samples. The chlamydia-positive women and women with BV were less likely to have a steady partner than the controls. No woman had syphilis or HIV infection. The women with BV were more frequent users of an intrauterine device and were more likely to smoke heavily compared with other women. STDs and STD-related conditions are common among adult women who consider themselves gynaecologically healthy. Screening for genital infections among women in reproductive age attending for health check-up could improve women's reproductive health.

Neisseria species identification assay for the confirmation of Neisseria gonorrhoeae-positive results of the COBAS Amplicor PCR

Screening assays for Neisseria gonorrhoeae exhibit low positive predictive values, particularly in low-prevalence populations. A new real-time PCR assay that detects and identifies individual Neisseria spp. using melt curve analysis was compared to two previously published supplementary assays. NsppID, a 16S rRNA real-time PCR/melt curve assay developed to distinguish N. gonorrhoeae from other Neisseria spp., was compared to real-time PCR assays targeting genes reportedly specific for N. gonorrhoeae, the cppB gene and the porA pseudogene. A total of 408 clinical specimens (324 female endocervical swabs and 84 male urine or urogenital swab specimens) were screened using the COBAS Amplicor assay for Chlamydia trachomatis and N. gonorrhoeae (CT/NG) (Roche Diagnostics, Indianapolis, IN) followed by confirmatory testing via real-time PCR. The NsppID assay detected Neisseria spp. in 150/181 COBAS-positive specimens (82%), including six dual infections, and identified N. gonorrhoeae in 102 (56%) specimens. Sixty-nine of 181 (38%) specimens were positive for N. gonorrhoeae by porA pseudogene, and 115/181 (64%) were positive for cppB. However, cppB was also positive in 15% of COBAS-negative specimens, more than either NsppID (4%) or porA pseudogene (2%) assays. The porA pseudogene assay had the highest specificity for both genders but the lowest sensitivity, especially in female specimens. NsppID had a slightly lower specificity but greater sensitivity and overall accuracy. The least desirable confirmatory assay was cppB, due to poor specificity. The NsppID assay is an accurate confirmatory assay for N. gonorrhoeae detection. In addition, the NsppID assay can identify the non-N. gonorrhoeae species responsible for the majority of false-positive results from the COBAS Amplicor CT/NG assay.

A fast real-time polymerase chain reaction method for sensitive and specific detection of the Neisseria gonorrhoeae porA pseudogene

Ever since the advent of molecular methods, the diagnostics of Neisseria gonorrhoeae has been troubled by false negative and false positive results compared with culture. Commensal Neisseria species and Neisseria meningitidis are closely related to N. gonorrhoeae and may cross-react when using molecular tests comprising too-low specificity. We have devised a real-time polymerase chain reaction (PCR), including an internal amplification control, that targets the N. gonorrhoeae porA pseudogene. DNA was automatically isolated on a BioRobot M48. Our subsequent PCR method amplified all of the different N. gonorrhoeae international reference strains (n = 34) and N. gonorrhoeae clinical isolates (n = 176) but not isolates of the 13 different nongonococcal Neisseria species (n = 68) that we tested. Furthermore, a panel of gram-negative bacterial (n = 18), gram-positive bacterial (n = 23), fungal (n = 1), and viral (n = 4) as well as human DNA did not amplify. The limit of detection was determined to be less than 7.5 genome equivalents/PCR reaction. In conclusion, the N. gonorrhoeae porA pseudogene real-time PCR developed in the present study is highly sensitive, specific, robust, rapid and reproducible, making it suitable for diagnosis of N. gonorrhoeae infection.

Use of a reliable PCR assay for the detection of Neisseria gonorrhoeae in Peruvian patients

Neisseria gonorrhoeae is the most common sexually transmitted disease-causing bacterium worldwide. An in-house PCR assay targeting the carbamoyl-phosphate synthase subunit A (carA) gene was developed for the specific detection of N. gonorrhoeae in clinical specimens. Samples from 605 patients were cultured on selective medium and assayed by PCR in a double-blind fashion. Of 605 urethral/cervical samples analysed, 13 were PCR-positive, of which 11 were culture-positive. The PCR showed a sensitivity and specificity of 100% and 99.7% with these samples. PCR targeting the carA gene appears to be a reliable method for the detection of N. gonorrhoeae in clinical specimens.

Nucleic acid amplification testing for Neisseria gonorrhoeae: an ongoing challenge

Nucleic acid amplification tests (NAATs) for the detection of Neisseria gonorrhoeae became available in the early 1990s. Although offering several advantages over traditional detection methods, N. gonorrhoeae NAATs do have some limitations. These include cost, risk of carryover contamination, inhibition, and inability to provide antibiotic resistance data. In addition, there are sequence-related limitations that are unique to N. gonorrhoeae NAATs. In particular, false-positive results are a major consideration. These primarily stem from the frequent horizontal genetic exchange occurring within the Neisseria genus, leading to commensal Neisseria species acquiring N. gonorrhoeae genes. Furthermore, some N. gonorrhoeae subtypes may lack specific sequences targeted by a particular NAAT. Therefore, NAAT false-negative results because of sequence variation may occur in some gonococcal populations. Overall, the N. gonorrhoeae species continues to present a considerable challenge for molecular diagnostics. The need to evaluate N. gonorrhoeae NAATs before their use in any new patient population and to educate physicians on the limitations of these tests is emphasized in this review.

Specific and sensitive detection of Neisseria gonorrhoeae in clinical specimens by real-time PCR

Early diagnosis of Neisseria gonorrhoeae infections is important with regard to patients' health and infectivity. We report the development of a specific and sensitive TaqMan assay for the detection of N. gonorrhoeae in clinical samples. The target sequence is a 76-bp fragment of the 5' untranslated region of the opa genes that encode opacity proteins. A panel of 448 well-defined N. gonorrhoeae isolates was used to evaluate and optimize the assay. The method employs two minor-groove binding probes, one of them recognizing a newly identified sequence in the opa genes. Testing a large panel of related and unrelated microorganisms revealed that other Neisseria strains and other microorganisms tested negative in the opa test. With a lower detection limit of one genome per reaction, the opa test appeared more sensitive than both the COBAS AMPLICOR (Roche Diagnostics Nederland BV, Almere, The Netherlands) and a LightCycler 16S rRNA test. Analysis of a panel of 122 COBAS AMPLICOR-positive samples revealed that 68% were negative in both the 16S rRNA test and the opa assay (confirming that the COBAS AMPLICOR test produces false positives), while 30% were positive in both assays. Three samples were opa positive and 16S rRNA negative, which may be due to the higher sensitivity of the opa assay. We conclude that the opa gene-based real-time amplification assay offers a sensitive, specific, semiquantitative, and reliable assay suitable for the detection of N. gonorrhoeae in clinical specimens and/or for confirmation of less specific tests.

Nucleic acid amplification tests for gonorrhea and chlamydia: practice and applications

Nucleic acid amplification tests (NAATs), which are highly sensitive and specific, have provided the ability to use alternative sam-ple types for the diagnosis of sexually transmitted infections (STIs). Self-collected genital specimens, such as urine or even vaginal swabs, can now be accurately used to diagnose gonorrhea or chlamydia infections. In many cases, use of these sample types can decrease the necessity for a clinician to perform a pelvic examination on women or to collect a urethral swab from men, thus extending the diagnostic capability for detecting these infections to nonclinic screening venues. As most chlamydia infections and many gonorrhea infections are asymptomatic, the use of NAATs for self-collected samples greatly increases the types and numbers of patients that can be screened outside of clinic settings. Self-sampling also allows clinicians to easily screen patients in the clinic for STIs who are not presenting for pelvic or urogenital examinations. The application of NAATs to self-collected specimens has the potential to augment public health programs designed to control the epidemic of STIs in the community.

Comparison of strand displacement and ligase chain amplification for detection of Chlamydia trachomatis infection in urogenital specimens

Two amplification tests for the diagnosis of Chlamydia trachomatis infection, namely the ligase chain reaction (LCx) and the strand displacement assay (ProbeTec), were compared using samples from 1183 patients at sexually transmitted disease clinics. The overall prevalence of positive results was 8.0%, with agreement between the two assays of 98.8%. For endocervical, urethral and male urine samples, agreement was 99.3%, 99.4% and 97.7%, respectively. For ten discrepant samples, alternative amplification assays suggested that the LCx and ProbeTec assays gave erroneous results in six and four cases, respectively. Inhibition of amplification was observed with three (0.25%) urine specimens.

Appropriate use of nonculture tests for the detection of sexually transmitted diseases in children and adolescents

The introduction of nucleic acid amplification tests (NAATs) has been the most important advance in the diagnosis of sexually transmitted diseases (STDs) since tissue culture replaced inoculation of eggs for culture and isolation of Chlamydia trachomatis from clinical specimens. Because nucleic acid amplification is exquisitely sensitive, theoretically capable of detecting as little as a single gene copy, and highly specific, it offers the opportunity to use noninvasive sampling (ie, urine). This ability in turn means that these tests might be used in nontraditional settings, such as schools and in the field, which may be very helpful in providing services to homeless adolescents. However, none of these tests is approved or recommended by the manufacturers for rectal specimens from adults, and they are not approved for rectogenital specimens from children. In addition to medical implications, the identification of a sexually transmitted disease (STD), especially in a young child, also has legal implications. Because of the legal implications, the highest specificity is needed and is more important than is sensitivity in this situation. Data on the use of these tests in prepubertal children are insufficient to permit their use at this time. What may be appropriate for screening a sexually active adult in an STD clinic may not be appropriate for evaluating a child victim of suspected sexual abuse. Although missing possible sexual abuse is a major concern, the ramifications of a false-positive test for an STD, which can lead to erroneous reports of sexual abuse and possibly unjustified prosecution and incarceration, also must be considered.

Molecular diagnostics of viral hemorrhagic fevers

This review addresses the diagnostics of viral hemorrhagic fevers (VHFs). In the first part, an overview is given on classical methods of VHF diagnostics as well as novel molecular diagnostic tools. Currently available polymerase chain reaction (PCR) assays for diagnosis of VHF are summarized and discussed. In the second part, VHF diagnostics are described in particular for Lassa fever, yellow fever, and Crimean-Congo hemorrhagic fever, based on cases that were imported into or occurred within Europe. The third part is focussed on important differential diagnoses of VHF.

The accuracy and efficacy of screening tests for Chlamydia trachomatis: a systematic review

Screening women for lower genital tract infection with Chlamydia trachomatis is important in the prevention of pelvic inflammatory disease, ectopic pregnancy and infertility. This systematic review aims to state clearly which of the available diagnostic tests for the detection of C. trachomatis would be most effective in terms of clinical effectiveness. The review included all studies published from 1990 onward that evaluated diagnostic tests in asymptomatic, young, sexually active populations. Medline and Embase were searched electronically and key journals were hand-searched. Further studies were identified through the Internet and contact with experts in the field. All studies were reviewed by two reviewers and were scored by Irwig's assessment criteria. Additional quality assessment criteria included a documented sexual history and recording of previous chlamydial infection. The reviews were subjected to meta-analysis and meta-regression. The 30 studies that were included examined three types of DNA-based test--ligase chain reaction (LCR), PCR and gene probe--as well as enzyme immuno-assay (EIA). The results showed that while specificities were high, sensitivities varied widely across the tests and were also dependent on the specimen tested. Pooled sensitivities for LCR, PCR, gene probe and EIA on urine were 96.5%, 85.6%, 92% and 38%, respectively, while on cervical swabs the corresponding sensitivities of PCR, gene probe and EIA were 88.6%, 84% and 65%. Meta-analysis demonstrated that DNA amplification techniques performed best for both urine and swabs in low prevalence populations. We conclude that nucleic acid amplification tests used on non-invasive samples such as urine are more effective at detecting asymptomatic chlamydial infection than conventional tests, but there are few data to relate a positive result with clinical outcome.

Prevalence of gonococcal and chlamydial infections and sexual risk behavior among youth in Addis Ababa, Ethiopia

BACKGROUND

No community-based study on the magnitude of sexually transmitted diseases (STDs) has ever been conducted among young people in Ethiopia.

GOAL

To assess the magnitude of Chlamydia trachomatis and Neisseria gonorrhoeae infections and status of sexual risk behavior among youths (15-24 years old) in Addis Ababa, Ethiopia.

STUDY DESIGN

Youths in or out of school residing in two (of the six) administrative zones in Addis Ababa served as the study population. Participants filled out a self-administered questionnaire related to sexuality and its sociocultural determinants. First-void urine (FVU) was analyzed for gonorrhea and chlamydial infection by polymerase chain reaction (PCR).

RESULTS

A total of 561 youths took part in the study. Urine PCR was performed for 522 of them. Nine subjects (1.7%) were found to have and N gonorrhoeae and C trachomatis infections. There were five cases (1.0%) involving each agent. Double infection was noted in one female subject. All but one of the infections were detected among the out-of-school youths (chi-square = 4.5; < 0.05). None of these subjects complained of symptoms suggestive of an active STD. One-third (188/561) reported having had sexual intercourse. The prevalence among sexually active youths was thus 4.8% (9/188) for both infections combined (2.7% for each agent). While 7/52 (13.5%) of the sexually active females were found to also have STDs, only 2/136 (1.5%) of the males had an STD (chi-square = 8.0; < 0.01). Report of sexual activity was significantly associated with being male, an age of >/=20 years, out-of-school status, and report of alcohol/khat (amphetamine-like substance) consumption. Females reported less condom use, whether they were in or out of school and independent of age.

CONCLUSIONS

Out-of-school youths, especially females, took more sexual risk and were exceedingly susceptible to STDs. This calls for alternative group-targeted strategies for sex education, disease prevention, and STD screening and management.

Confirmation by 16S rRNA PCR of the COBAS AMPLICOR CT/NG test for diagnosis of Neisseria gonorrhoeae infection in a low-prevalence population

The COBAS AMPLICOR CT/NG test is widely used for the diagnosis of Neisseria gonorrhoeae infection using genital swabs or urine samples. Although highly specific, cross-reactivity occurs with some nonpathogenic strains of Neisseria and Lactobacillus species. In low-prevalence populations, even highly specific assays may require confirmatory testing of positive results. We assessed the positive predictive value (PPV) of this test in a low-prevalence (0.5%) setting. Genital and urine specimens testing positive using the COBAS AMPLICOR NG test were retested using an investigational 16S rRNA PCR assay. Additionally, 737 specimens were tested in parallel by both culture and the above PCR protocol. Of 9,772 specimens tested in-house, 168 were positive by the AMPLICOR test; in addition, 62 AMPLICOR-positive specimens were referred to our laboratory for confirmatory testing, yielding 230 positive specimens. Of these, 72 were confirmed positive by 16S rRNA PCR, yielding a specificity of 98.7% and a PPV of 31.3%. Specificity was similar for all specimen types, whereas PPV varied with prevalence: specimens from males, females, urine specimens, and genital swabs had PPVs of 70.8, 13.3, 51.9, and 20.1%, respectively. The PPV was higher when the initial AMPLICOR optical density (OD) was > or =3.5 versus initial and repeat OD readings in an equivocal zone of > or =0.2 to <3.5 (65.1 versus 10.1%; P < 0.001). On repeat testing of specimens with ODs in the equivocal zone, 54 gave ODs of > or =0.2 and <2.0, 35 gave ODs of > or =2.0 and <3.5, and 12 gave ODs of > or =3.5, with 3.7, 20, and 33.3% confirmed positive, respectively (P = 0.004). Comparing PCR to culture as the "gold standard," specificity increased from 96.8 to 99.9% when 16S rRNA PCR was performed on specimens positive by the COBAS AMPLICOR NG test. Confirmatory testing with a more specific method such as 16S rRNA PCR should be considered in low-prevalence populations, especially for specimens with an OD in the equivocal zone.

Performance characteristics of the Becton Dickinson ProbeTec System for direct detection of Chlamydia trachomatis and Neisseria gonorrhoeae in male and female urine specimens in comparison with the Roche Cobas System

OBJECTIVE

The Becton Dickinson BDProbeTec ET System is a new semiautomated system using strand displacement amplification technology that simultaneously amplifies and detects Chlamydia trachomatis and Neisseria gonorrhoeae DNA. The strand displacement amplification products are hybridized with a fluorescent detector probe and are captured by a chemiluminescent assay in a microwell format. An amplification control is also included to monitor assay inhibition. This study evaluated the performance of the BDProbTec ET system in detecting C trachomatis and N gonorrhoeae in male and female urine specimens, calculated its ability to process large volumes of specimens, and determined the inhibition rate.

MATERIALS AND METHODS

Eight hundred twenty-five male and 399 female urine specimens were tested for both C trachomatis and N gonorrhoeae with the BDProbeTec ET system, and results were compared with those of the Roche Amplicor Cobas system. All urine specimens were processed on both assays on the same day they were received, according to the manufacturers' instructions. Discrepant results were resolved by in-house polymerase chain reaction assays. Internal or amplification controls were also used in each specimen assay to monitor inhibition. The throughput of the BDProbTec ET system was further tested with 150 urine specimens on an 8-hour shift for 2 days.

RESULTS

The overall sensitivity, specificity, positive predicative value, and negative predicative value for for detection of chlamydia were 95.3%, 99.3%, 95.9%, and 99.2% for strand displacement amplification and 95.9%, 98.3%, 90.6%, and 99.3% for the Roche Amplicor system. For detection of gonorrhea, these values were 100%, 99.7%, 88.2%, and 100% and 96.7%, 98.9%, 69%, and 99.9%, respectively. The overall inhibition rates for both strand displacement amplification and Roche Amplicor were less than 3.5%. The BDProbTec ET system was able to produce 150 results each for chlamydia and gonorrhea and the internal control within the 8-hour shift.

CONCLUSIONS

The performance characteristics of the BDProbeTec ET assay are similar to those of the Roche Amplicor polymerase chain reaction for detection of chlamydia and gonorrhea in male and female urine specimens. The system was able to produce 300 results in an 8-hour shift.

Diagnostic performance of the Roche AMPLICOR PCR in detecting Neisseria gonorrhoeae in genitourinary specimens from female sex workers in Cotonou, Benin

The objective of this study was to evaluate the diagnostic performance of the Roche multiplex AMPLICOR Chlamydia trachomatis/Neisseria gonorrhoeae PCR test for the detection of Neisseria gonorrhoeae infection in female urine specimens and wet and dry endocervical swabs. Endocervical swabs and urine specimens were collected from 342 female sex workers from Cotonou, Benin, and were tested using the AMPLICOR C. trachomatis/N. gonorrhoeae test (Roche Diagnostic Systems, Inc., Branchburg, N.J.) with internal control detection. Endocervical swabs were also cultured on Thayer-Martin medium. A series of alternate standards that included a combination of all the tests but not the test being evaluated was used to assess the performance of the test with each type of specimen. The sensitivity, specificity, and positive and negative predictive values for the urine were 53.8, 98.9, 93.5, and 87.5%, respectively. Corresponding figures for the wet swab were 91.5, 100, 100, and 97.4%, respectively. Those for the dry swab were 96.3, 96.2, 88.5, and 98.8%, respectively. Based on this study, the AMPLICOR PCR assay showed a low sensitivity for detection of N. gonorrhoeae infection in urine specimens, whereas the test was found to be highly sensitive and specific with endocervical specimens.

Correlation between an early sexual debut, and reproductive health and behavioral factors: a multinational European study

OBJECTIVE

To investigate whether women who made an early sexual debut differ from those with a later debut regarding genital signs and symptoms.

METHODS

The study included women who considered themselves gynecologically healthy and who attended 17 family planning centers in 13 European countries for contraceptive advice. There were 629 women who made their sexual debut at the age of 16 years or earlier (study population) and 927 women who had their first sexual intercourse at the age of 19 years or later (comparison group). Genital symptoms and signs, contraceptive use, smoking, and genital hygiene habits and previous genital infections were recorded on a structured patient record form. Detection of Chlamydia trachomatis was made by means of a polymerase chain reaction on first-void urine. The study was made, on average, 7-10 years after the women's sexual debut.

RESULTS

The mean age of first intercourse was 15.3 years for the study group versus 20.7 years for the control group (p < 0.001). The study population had significantly more symptoms, such as vaginal discharge and pruritus, and signs, such as abnormal discharge, erythema of the vaginal mucosa and lower genital tract infections, than the comparison group. Twice as many women in the study group were smokers and there was a ten-fold increase among these subjects of using low-pH solutions for genital hygiene. The prevalence of C. trachomatis infection did not differ between the two groups (p = 0.22).

CONCLUSION

Age at first intercourse is not only a predictor of sexual risk behavior, but also a predictor, regarding both signs and symptoms, of future gynecological problems.

Chlamydia screening--yes, but of whom, when, by whom, and with what?

The importance of screening programs in reducing the prevalence of genital chlamydial infections is stressed by the fact that the majority of infected persons are more or less asymptomatic. The use of oral contraceptives may mask infections affecting the upper genital tract. This imposes selective screening and rescreening of women with a history of pelvic inflammatory disease. The recent knowledge that vaginal introital samples will provide a detection rate equal to or even higher than that of cervical samples collected in the same women opens up the possibility of screening women in health units lacking a gynecological examination chair. It also opens up the possibility of outpatient screening programs, for example, home sampling and mailing samples to laboratories that will perform analyses. The use of nucleic acid-based assays means increased sensitivity and specificity compared with earlier used techniques such as ELISA. These former methods can also be used in low-prevalence populations with acceptable positive predictable value, but may be misleading if used in post-therapy check-ups because the antigen may persist in microbiologically cured cases.

Update on Chlamydia trachomatis

Chlamydia trachomatis is one the most important sexually transmitted diseases; it can cause serious sequelae despite the absence of symptoms in some people. It's estimated that about 25% of women who have acute salpingitis become infertile, and chlamydial infection is the commonest cause. The introduction of screening programs for its detection are still a topic of discussion. The literature shows that the total cost of examination and treatment of complications known to be associated with genital chlamydial infection (PID, chronic pelvic pain, tubal factor infertility) is generally higher than the total cost of a large-scale Chlamydia screening program. The selection of a diagnostic test for detection of chlamydial genital infection depends on availability, local expertise, and prevalence of Chlamydia trachomatis in the test population. Cell culture is too expensive in nonendemic regions, so the use of non-culture techniques is very attractive. PCR (polymerase chain reaction) and LCR (ligase chain reaction) are actually the two most commonly used alternatives to conventional methods for detecting STD agents. In fact, PCR and LCR have proved useful for detection of Chlamydia trachomatis in cervical and urethral samples both in symptomatic and asymptomatic women. Recently, testing of first-void urine (FVU) specimens with these techniques has shown that the amplification tests are as sensitive as tests with endocervical swab cultures.

Multiplex polymerase chain reaction for the simultaneous detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia psittaci in respiratory samples

AIMS

To develop a multiplex polymerase chain reaction (PCR) for the simultaneous detection of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia psittaci in respiratory samples.

METHODS

Oligonucleotide primers for the amplification of the DNA of these three organisms were optimised for use in combination in the same reaction. PCR products were detected by hybridisation with pooled internal probes using an enzyme linked immunosorbent assay. Those with positive signals were further differentiated using species specific probes. Quality of DNA extraction and PCR inhibition were controlled by amplification of a human mitochondrial gene. A panel of 53 respiratory samples with known results was evaluated blindly. This was followed by a retrospective study on sputa collected from 244 patients with suspected community acquired pneumonia.

RESULTS

The multiplex assay had a lower sensitivity than PCR with individual primers by about one log. The resultant sensitivity was considered acceptable for diagnostic use. Of the panel of 53 samples, nine of 11 M pneumoniae, 11 of 11 C pneumoniae, six of seven C psittaci, and 24 of 24 negative samples were correctly identified. Of the 244 patients with pneumonia, seven (2.9%) had detectable M pneumoniae, six (2.5%) had C pneumoniae, and one (0.4%) had C psittaci. The case notes from 11 patients were studied. The PCR finding was of possible significance in at least eight of these patients.

CONCLUSIONS

This multiplex PCR assay has the potential to be used as a diagnostic and epidemiological tool. Further prospective studies are needed to establish its clinical value.

Use of lambda phage DNA as a hybrid internal control in a PCR-enzyme immunoassay to detect Chlamydia pneumoniae

An inherent problem in the diagnostic PCR assay is the presence of ill-defined inhibitors of amplification which may cause false-negative results. Addition of an amplifiable fragment of foreign DNA in the PCR to serve as a hybrid internal control (HIC) would allow for a simple way to identify specimens containing inhibitors. Two oligonucleotide hybrid primers were synthesized to contain nucleic acid sequences of the Chlamydia pneumoniae 16S rRNA primers in a position flanking two primers that target the sequences of a 650-bp lambda phage DNA segment. By using the hybrid primers, hybrid DNA comprising a large sequence of lambda phage DNA flanked by short pieces of chlamydia DNA was subsequently generated by PCR, cloned into a plasmid vector, and purified. Plasmids containing the hybrid DNA were diluted and used as a HIC by adding them to each C. pneumoniae PCR test. Consequently, C. pneumoniae primers were able to amplify both chlamydia DNA and the HIC DNA. The production of a 689-bp HIC DNA band on an acrylamide gel indicated that the specimen contained no inhibitors and that internal conditions were compatible with PCR. Subsequently, a biotinylated RNA probe for the HIC was transcribed from a nested sequence of the HIC and was used for its hybridization. Detection of the HIC DNA-RNA hybrid was achieved by enzyme immunoassay (EIA). This PCR-EIA system with a HIC was initially tested with 12 previously PCR-positive and 14 previously PCR-negative specimens. Of the 12 PCR-positive specimens, 11 were reconfirmed as positive; 1 had a negative HIC value, indicating inhibition. Of the 14 previously PCR-negative specimens, 13 were confirmed as true negative; 1 had a negative HIC value, indicating inhibition. The assay was then used with 237 nasopharyngeal specimens from patients with pneumonia. Twenty-one of 237 (8.9%) were positive for C. pneumoniae, and 42 (17.7%) were found to inhibit the PCR. Specimens showing inhibitory activity were diluted 1:10 and were retested. Ten specimens were still inhibitory to the PCR and required further DNA purification. No additional positive samples were detected and 3 nasopharyngeal specimens remained inhibitory to PCR. Coamplification of a HIC DNA can help confirm true-negative PCR results by ruling out the presence of inhibitors of DNA amplification.

Use of ligase chain reaction with urine versus cervical culture for detection of Chlamydia trachomatis in an asymptomatic military population of pregnant and nonpregnant females attending Papanicolaou smear clinics

Ligase chain reaction (LCR) (Abbott Laboratories, Abbott Park, Ill.) with first-catch urine specimens was used to detect Chlamydia trachomatis infections in 465 asymptomatic military women attending clinics for routine Papanicolaou smear tests. Results were compared to results of cervical culture to determine the sensitivity of the urine LCR and the possible presence of inhibitors of amplification in pregnant and nonpregnant women. Discrepant results for LCR and culture were resolved by direct fluorescent antibody staining of culture sediments, two different PCR assays, and LCR for the outer membrane protein 1 gene. The prevalence of Chlamydia in specimens by urine LCR was 7.3% compared to 5% by culture. For 434 women with matching specimens, there were 11 more specimens positive by LCR than were positive by culture, of which all but one were determined to be true positives. There were four culture-positive, LCR-negative specimens, all from nonpregnant women. The sensitivity, specificity, and positive and negative predictive values of urine LCR after discrepant results were resolved were 88.6, 99.7, 96.9, and 99.0%, respectively. The sensitivity of culture was 71.4%. From the 148 pregnant women (prevalence by LCR, 6.8%), there were no patients who were cervical culture positive and urine LCR negative to indicate the presence in pregnant women of inhibitors of LCR. Additionally, a subset of 55 of the LCR-negative frozen urine specimens from pregnant women that had been previously processed in LCR buffer were inoculated with 5 cell culture inclusion forming units of C. trachomatis each and retested by LCR; all tested positive, indicating the absence of inhibitors of LCR in urine from these pregnant women. The use of LCR testing of urine specimens from asymptomatic women, whether pregnant or not, offers a sensitive and easy method to detect C. trachomatis infection in women.

Are oral contraceptives masking symptoms of chlamydial cervicitis and pelvic inflammatory disease?

Tubal factor infertility is often diagnosed without any documented history of pelvic inflammatory disease. Chlamydial infection is one of the most common causes of pelvic inflammatory disease and likely also of infertility and ectopic pregnancy. Oral contraceptives may alter the course of chlamydial infections which may mask the clinical expression of the disease. This paper considers a number of unresolved matters related to oral contraceptive use and its possible influence on the epidemiology and course of chlamydial pelvic inflammatory disease.