Chlamydia trachomatis serovars in 435 urogenital specimens typed by restriction endonuclease analysis of amplified DNA

Comparison of genovars and Chlamydia trachomatis infection loads in ocular samples from children in two distinct cohorts in Sudan and Morocco

Trachoma is a blinding disease caused by repeated conjunctival infection with different Chlamydia trachomatis (Ct) genovars. Ct B genovars have been associated with more severe trachoma symptoms. Here, we investigated associations between Ct genovars and bacterial loads in ocular samples from two distinct geographical locations in Africa, which are currently unclear. We tested ocular swabs from 77 Moroccan children (28 with trachomatous inflammation-follicular (TF) and 49 healthy controls), and 96 Sudanese children (54 with TF and 42 healthy controls) with a Ct-specific real-time polymerase chain reaction (PCR) assay. To estimate bacterial loads, Ct-positive samples were further processed by multiplex real-time qPCR to amplify the chromosomal outer membrane complex B and plasmid open reading frame 2 of Ct. Genotyping was performed by PCR-based amplification of the outer membrane protein A gene (~1120 base pairs) of Ct and Sanger sequencing. Ct-positivities among the Moroccan and Sudanese patient groups were 60·7% and 31·5%, respectively. Significantly more Sudanese patients than Moroccan patients were genovar A-positive. In contrast, B genovars were significantly more prevalent in Moroccan patients than in Sudanese patients. Significantly higher Ct loads were found in samples positive for B genovars (598596) than A genovar (51005). Geographical differences contributed to the distributions of different ocular Ct genovars. B genovars may induce a higher bacterial load than A genovars in trachoma patients. Our findings emphasize the importance of conducting broader studies to elucidate if the noted difference in multiplication abilities are genovar and/or endemicity level dependent.

We investigated the association between different Ct genovars, the approximate load of infection, and the distribution of Chlamydia genovars by comparing samples from one trachoma-endemic area (i.e., the city of El-Gadaref in Al Qadarif, Sudan) and one previously endemic area (i.e., the Zagora Province in Morocco), currently considered as non-endemic. This study is the first to reveal a significant difference between the genome copy numbers of Ct genovar A and B/Ba in children with TF. Evidence that Ct is still circulating in rural foci of countries like Morocco that are no longer considered endemic implies that the continuation of the trachoma surveillance must be warranted in future to avoid further spreading of Ct. The clinical significance of different infectious loads in the development of sequelae has to be determined as well as whether these differences are genovar specific or related to the given endemicity level.

Molecular typing of Chlamydia trachomatis: An overview

Urogenital infection due to Chlamydia trachomatis (CT) is one of the most common bacterial sexually transmitted infections (STIs) and is a major public health problem worldwide. Molecular characterisation of CT is important for understanding the pathophysiological mechanisms of chlamydial disease and its transmission dynamics in sexual networks. Traditionally, strain typing of CT was based on serotyping methods characterising the major outer membrane protein (MOMP). With the advent of polymerase chain reaction and sequencing the era of molecular typing began. Molecular characterization of CT strains is based on sequence analysis of ompA gene encoding MOMP. However, in due course of time, improvements were made to enhance the discriminatory power of sequencing and quality of epidemiological information. New high-resolution genotyping methods using multiple loci such as multilocus sequence typing (MLST) and multiple loci variable number of tandem repeats (MLVA) were developed but were unable to differentiate mixed infections (MIs). The development of DNA-hybridisation methods emerged as a major breakthrough in detecting MIs. Although MLST and MLVA are more discriminative than other genotyping methods, they are laborious and expensive. DNA microarray technique is an affordable alternative for genotyping. Since recombination is widespread in the CT genome, ompA is not a reliable marker for phylogenetic studies; hence, whole genome sequencing may provide maximum phylogenetic resolution of CT strains. A descriptive review is provided of the various molecular CT typing methods. The vital information gained can be used for formulating screening programmes, targeted prevention and optimising therapeutic measures aiming to reduce disease transmission.

The Epidemiology of Chlamydia trachomatis Organism Load During Genital Infection: A Systematic Review

BACKGROUND

The role of organism load in Chlamydia trachomatis infection is not well understood. We conducted a systematic review to investigate the epidemiology of C. trachomatis organism load in human genital chlamydia infection.

METHODS

Embase, PubMed, and Medline databases were searched for literature published through August 2014. English-language publications that quantified load in humans were eligible. Participant characteristics and laboratory data were extracted.

RESULTS

A total of 737 records were identified, and 29 publications involving 40 883 participants were included. In women, load was highest for cervical swabs and lowest for urine specimens. In men, load was highest for rectal swabs and similar for urethral swabs and urine specimens. Evidence of any association between load and age, serovar, risk of transmission, hormone levels, and concurrent sexually transmitted infections was inconsistent. Eight of 9 culture-based studies found an association between load and signs and symptoms, in contrast with only 3 of 8 nucleic acid amplification test (NAAT)-based studies (P = .03).

CONCLUSION

Chlamydia organism load varies by specimen type and site of sampling, and viable chlamydia organism load may be a more important indicator of severity of infection than total load measured by NAAT.

Observations on Chlamydia trachomatis and other microbes in reactive arthritis

There are problems in attributing causality in inflammatory arthritis. So far as C. trachomatis and sexually acquired reactive arthritis are concerned, there is much in favour of a causal relationship, although there are important caveats which need to be explored before it is possible to say unreservedly that C. trachomatis plays a causative role in reactive arthritis. For example, micro-organisms have never been cultured from synovial effusions in early disease, and only once has substantial benefit of antimicrobial treatment been reported. The claim that ocular strains of C. trachomatis are of over-riding importance in pathogenesis needs confirmation before it can be accepted. No conclusion can be made about the possibility of other small intracellular bacteria in joints having a role in causing disease. However, if it can be shown that eradication of the micro-organism, which may be difficult to prove, coincides with clinical recovery, it would go some way to recognising causality. In spite of the recognised difficulties, antibiotic studies have an important role in identifying aetiology. They need to focus on very early disease and on eradication of intra-articular bacteria. Treatment of established disease is likely to be less informative. Although a combination of antibiotics might have a future in treating established disease, diagnosing and treating non-gonococcal urethritis as soon as possible should be the aim in order to prevent the development of reactive arthritis.

Evolution, phylogeny, and molecular epidemiology of Chlamydia

The Chlamydiaceae are a family of obligate intracellular bacteria characterized by a unique biphasic developmental cycle. It encompasses the single genus Chlamydia, which involves nine species that affect a wide range of vertebral hosts, causing infections with serious impact on human health (mainly due to Chlamydia trachomatis infections) and on farming and veterinary industries. It is believed that Chlamydiales originated ∼700mya, whereas C. trachomatis likely split from the other Chlamydiaceae during the last 6mya. This corresponds to the emergence of modern human lineages, with the first descriptions of chlamydial infections as ancient as four millennia. Chlamydiaceae have undergone a massive genome reduction, on behalf of the deletional bias "use it or lose it", stabilizing at 1-1.2Mb and keeping a striking genome synteny. Their phylogeny reveals species segregation according to biological properties, with huge differences in terms of host range, tissue tropism, and disease outcomes. Genome differences rely on the occurrence of mutations in the >700 orthologous genes, as well as on events of recombination, gene loss, inversion, and paralogous expansion, affecting both a hypervariable region named the plasticity zone, and genes essentially encoding polymorphic and transmembrane head membrane proteins, type III secretion effectors and some metabolic pathways. Procedures for molecular typing are still not consensual but have allowed the knowledge of molecular epidemiology patterns for some species as well as the identification of outbreaks and emergence of successful clones for C. trachomatis. This manuscript intends to provide a comprehensive review on the evolution, phylogeny, and molecular epidemiology of Chlamydia.

Distribution of Chlamydia trachomatis serotypes in clinical urogenital samples from north-eastern Croatia

The purpose of this study was to determine prevalence of Chlamydia trachomatis (Ct) urogenital infection and its serotype distribution from clinical samples in north-eastern Croatia. During a 3-year period, 2,379 urogenital samples were analyzed by real-time polymerase chain reaction (A group), while 4,846 genital swabs were analyzed by direct fluorescent antibody test (B group). 132 Ct positive specimens were genotyped by omp1 gene sequencing. The prevalence rate of Ct was 3.2 % in A and 1 % in B group. The most prevalent chlamydial genotype was E (44 %), followed by F (33 %), K (11.5 %), G (8 %), J/UW (5.3 %), D-IC (4.4 %), D-B120 (1.8 %), and B/IU, J/IU, Ia/IU (0.9 % each) serotypes. Single-nucleotide polymorphisms (SNPs) of omp1 gene were detected in E, K, and G serotypes. Some of these SNPs (C/T at position 272 and G/A at position 813 in E strain; C/T at position 884 in D strain) might represent novel omp1 variants.

Chlamydia trachomatis serovar distribution and Neisseria gonorrhoeae coinfection in male patients with urethritis in Greece

The distribution of Chlamydia trachomatis serovars and Neisseria gonorrhoeae coinfection was studied in a group of 100 C. trachomatis-positive males with urethritis in Greece. The serovar distribution revealed that apart from the predominant worldwide types E and F, the relatively uncommon type G is also prevalent. Gonococcal coinfection was frequent (30%) and was associated with genovariant Ja (75%, P = 0.008).

Highly discriminative genotyping of Chlamydia trachomatis using omp1 and a set of variable number tandem repeats

This article reports the development of a method for genotyping Chlamydia trachomatis, using PCR and sequencing of omp1, supplemented with three new variable number tandem repeat (VNTR) loci of C. trachomatis. Typeability, reproducibility and discriminatory power were assessed using four groups of samples: two groups (I and II) of C. trachomatis-positive patients and their positive partner(s), one group (III) of patients with recurrent or persistent C. trachomatis infections, and one group (IV) comprising samples containing a newly discovered mutant strain with a 377-bp deletion in the cryptic plasmid, the new variant C. trachomatis (nvCT). The VNTR loci (designated CT1335, CT1299, and CT1291) were all single nucleotide repeats chosen for maximal mutability and variation. In the study material, nine variants of CT1335, eight variants of CT1299 and five variants of CT1291 were found. The discriminatory power (D) of omp1 in the present material was D(omp1) = 0.69. Ds for VNTRs CT1335, CT1299 and CT1291 were 0.53, 0.74 and 0.74, respectively. The resolution power of the omp1-VNTR assay was 0.94. Stability over time of the VNTRs was investigated and found to be adequate for epidemiological studies. Using this genotyping assay, it was confirmed that the nvCT strain was indeed a clone. These results indicate that, with this novel method, strains of C. trachomatis can be individually identified, and epidemiological associations established.

Cervicovaginal HIV-1 and herpes simplex virus type 2 shedding during genital ulcer disease episodes

OBJECTIVE

To investigate correlates of herpes simplex virus type 2 (HSV-2) DNA and HIV-1 RNA among women with genital ulcer disease (GUD).

DESIGN

Baseline data from a randomized placebo-controlled trial of episodic herpes treatment in Ghana and the Central African Republic.

METHODS

GUD aetiology was determined by polymerase chain reaction (PCR) from a lesional swab. Real-time PCR was used to quantify HIV-1 RNA, and HSV-2 DNA in cervicovaginal lavages (CVL) and HIV-1 RNA in plasma. Genital infection was defined as the presence of virus in the lesion or CVL.

RESULTS

Of 441 women enrolled, 79.0% were HSV-2 seropositive, 46.6% were HIV-1 seropositive, and 50.0% had an HSV-2 ulcer. Among 180 HSV-2/HIV-1 co-infected women, cervicovaginal HIV-1 RNA was detected more frequently in women with HSV-2 ulcers (67.9%) or cervicovaginal HSV-2 DNA only (72.3%) compared with women without genital HSV-2 infection (42.4%) (P = 0.004). Women with genital HSV-2 infection had higher median cervicovaginal HIV-1-RNA loads (3.14 log10 copies/mL versus 2.10 log10 copies/mL; P = 0.003), higher plasma HIV-1-RNA loads (median 5.10 versus 4.65 log10 copies/mL; P = 0.07), and lower median CD4 cell counts) (198 versus 409 cells/mm, P = 0.03). Cervicovaginal HIV-1 RNA and HSV-2 DNA were significantly correlated after adjusting for plasma HIV-1 RNA and CD4 cell counts (P < 0.001) and a 10-fold increase in cervicovaginal HSV-2 DNA was associated with a 1.7-fold increase in plasma HIV-1 RNA (P = 0.003).

CONCLUSION

Genital HSV-2 infection is associated with increased cervicovaginal and plasma HIV-1 RNA among co-infected women with genital ulcers, independently of the level of immunodeficiency, highlighting the close interaction between these two viruses and the role of HSV-2 as a co-factor for the sexual transmission of HIV-1.

Association of Chlamydia trachomatis Serovar Ia Infection With Black Race in a Sexually Transmitted Diseases Clinic Patient Population in Birmingham, Alabama

BACKGROUND

Black race is a risk marker for Chlamydia trachomatis infection. Because chlamydial serovar and race could both influence the transmission dynamics of chlamydia, studies characterizing serovars in a predominantly black population are of interest, yet remain sparse. STUDY DESIGN AND GOALS: C. trachomatis isolates collected consecutively from 109 female and 98 male patients presenting to a sexually transmitted disease clinic in Birmingham, Alabama, were serotyped. Our goal was to evaluate serovar distribution and associated demographic characteristics in a predominantly black population.

RESULTS

The median age was 23 years and 91% were black. Serovars E (29%), D (19%), F (19%), Ia (16%), and J (9%) were the most prevalent. Blacks were less often infected with serovar E (30% vs. 41%) and J (9% vs. 24%), but more often infected with serovar Ia (17% vs. 0%) compared with individuals of other racial groups (P = 0.07). The overall serovar distribution did not significantly differ by gender or age; however, serovar Ia infections were associated with older age (21% in age >or=23 years vs. 10% in those age <23 years; P = 0.03).

CONCLUSIONS

Although the overall C. trachomatis serovar distribution in this predominantly black population in Birmingham was similar to that reported elsewhere, serovar Ia was only found in blacks, in whom it was commonly isolated. Finding differences in serovar distribution by race, particularly serovar Ia, may be of epidemiologic significance and deserves verification in similar cohorts.

Diagnosis and assessment of trachoma

Trachoma is caused by Chlamydia trachomatis. Clinical grading with the WHO simplified system can be highly repeatable provided graders are adequately trained and standardized. At the community level, rapid assessments are useful for confirming the absence of trachoma but do not determine the magnitude of the problem in communities where trachoma is present. New rapid assessment protocols incorporating techniques for obtaining representative population samples (without census preparation) may give better estimates of the prevalence of clinical trachoma. Clinical findings do not necessarily indicate the presence or absence of C. trachomatis infection, particularly as disease prevalence falls. The prevalence of ocular C. trachomatis infection (at the community level) is important because it is infection that is targeted when antibiotics are distributed in trachoma control campaigns. Methods to estimate infection prevalence are required. While culture is a sensitive test for the presence of viable organisms and nucleic acid amplification tests are sensitive and specific tools for the presence of chlamydial nucleic acids, the commercial assays presently available are all too expensive, too complex, or too unreliable for use in national programs. There is an urgent need for a rapid, reliable test for C. trachomatis to assist in measuring progress towards the elimination of trachoma.

Population-based genetic and evolutionary analysis of Chlamydia trachomatis urogenital strain variation in the United States

Chlamydia trachomatis is a major cause of ocular and sexually transmitted diseases worldwide. While much of our knowledge about its genetic diversity comes from serotyping or ompA genotyping, no quantitative assessment of genetic diversity within serotypes has been performed. To accomplish this, 507 urogenital samples from a multicenter U.S. study were analyzed by phylogenetic and statistical modeling. No B, Da, or I serotypes were represented. Based on our analyses, all but one previous urogenital B serotype was identified as Ba. This, coupled with the lack of B serotypes in our population, suggests that B has specific tropism for ocular mucosa. We identified a Ba/D recombinant (putative crossover nucleotide 477; P < 0.0001) similar to a B/D mosaic we described previously from an African trachoma patient. Computational analyses of the Ba/D recombinant indicated that upstream changes were less important for tissue tropism than downstream incorporation of the D sequence. Since most serotypes had nonsynonymous/synonymous ratios of <1.0, the major outer membrane protein, encoded by ompA, has many functional constraints and is under purifying selection. Surprisingly, all serotype groups except for J had a unimodal population structure indicating rapid clonal expansion. Of the groups with a unimodal structure, E and Ia and, to a lesser extent, G and K were prevalent, had infrequent incorporation of mutations, and, compared to other groups, had a relatively greater degree of diversifying selection, consistent with a selective sweep of mutations within these groups. Collectively, these data suggest a diverse evolutionary strategy for different serogroups of the organism.

Genotyping of Chlamydia trachomatis strains from cultured isolates and nucleic acid amplification test-positive specimens

Urogenital strains of Chlamydia trachomatis are divided into several serogroups (D-K). Since these serovars are represented with differing prevalence in the population a serotyping of strains is necessary, when characterising the epidemiological situation. The aim of this study was the genotyping of C. trachomatis strains, the comparison of the results with those of serotyping, and the genotyping of positive specimens using commercial nucleic acid amplification tests (NAAT). The Chlamydia trachomatis major outer membrane protein gene (omp1) from 55 isolated strains and 36 NAAT-positive specimens was amplified by polymerase chain reaction (PCR). The restriction fragment length polymorphism (RFLP) patterns of these amplicons were compared with those of reference strains. The genotypes E and F were found to be most prevalent. The results are discussed considering other studies, genovariants and epidemiology.

Longitudinal assessment of infecting serovars of Chlamydia trachomatis in Seattle public health clinics: 1988-1996

BACKGROUND

There have been few longitudinal studies of fluctuations in the prevalence of Chlamydia trachomatis serovars in a given community; such studies could improve our understanding of the epidemiology and transmission of C trachomatis.

STUDY DESIGN

This was a longitudinal study of 7110 female patients (62%) and 4344 male patients (38%) presenting with first-time infections to health department clinics between 1988 and 1996.

GOAL

The goal was to ascertain trends in the proportion of infecting serovars over the 9-year study period and determine independent relationships between serovar and age, gender, race, and year of infection.

RESULTS

Serovar E was the most prevalent (32%), followed by F (18%) and D (13%). Being female, African American, and infected with serovar B was associated with young age (P < 0.001, P < 0.001, and P = 0.09, respectively). Class C serovars were found in older patients (P < 0.001). Over the 9-year period, the percentage of infections with serovar types F and G increased (P = 0.007, P = 0.009), those with I and K decreased (P < 0.001, P = 0.008), and those with B, D, D-, E, H, Ia, and J remained stable. The age of those with positive Chlamydia cultures decreased (P < 0.001).

CONCLUSION

In this population, while the major serovars appeared stable over 9 years, significant changes in the distribution of minor serovars, especially G, were observed over time.

Prevalence of Chlamydia trachomatis in human immunodeficiency virus-infected women in Cuba

To determine the prevalence rates and serovar distribution of Chlamydia trachomatis cervical infections in Cuban women, two different groups were selected. Group I consisted of 60 human immunodeficiency virus (HIV-1) seropositive women from different regions of Cuba and group II of 60 randomly selected women HIV seronegative and apparently healthy. C. trachomatis was detected in cervical scrapes by mean of nested polymerase chain reaction (PCR) specific for major out membrane protein. The overall prevalence rate of C. trachomatis in cervical scrapes determined by nested PCR was 10% in group I and the estimated prevalence was 6.6% for group II; 83.3% of HIV seropositive women with C. trachomatis infection reported history of pelvic inflammatory disease followed by cervicitis (50%). The control group C. trachomatis-infected women referred a history of cervicitis in 75% of cases. Other reports in the latter group included infertility and pelvic inflamatory disease in 50%. The present study is the first report of C. trachomatis prevalence in Cuba. It showed that there was not significantly difference in the prevalence rate of C. trachomatis between both groups.

Microbiological aspects of the diagnosis of Chlamydia trachomatis

The available diagnostic methods for Chlamydia trachomatis infection comprise serology (indirect detection) and culture, antigen detection and nucleic acid amplification (direct detection). The rationale, applications, advantages and disadvantages of the methods and diagnostic targets are discussed. Compared to conventional methods, nucleic acid amplification tests have increased sensitivity. This allows samples to be taken at home by the patient herself and mailed directly to the laboratory. Public health strategies implying home sampling for asymptomatic men and women result in a lower prevalence and a lower risk of short-term complications in terms of pelvic inflammatory disease (PID). The importance of predictive values and the association with prevalence are highlighted.

The role of serology, antibiotic susceptibility testing and serovar determination in genital chlamydial infections

Systemic and local antibodies regularly develop in genital infections caused by Chlamydia trachomatis. Such antibodies cannot be used as a sign of current infection as they often persist for years after the infection has resolved. Chlamydial antibodies have, however, been extremely useful for demonstrating associations between C. trachomatis and clinical conditions such as ectopic pregnancy and tubal factor infertility. In particular, antibodies to the chlamydial heat shock protein 60 predict the presence of tubal scarring.C. trachomatis has been divided into 15 (or 18) serovars, with many genotypes within each serovar. Differences in pathogenicity between serovars have been reported but no general pattern has emerged. Genotyping is a powerful epidemiological tool but is not yet ready for routine clinical use.C. trachomatis infections can be successfully treated by tetracycline or macrolides. Some resistant strains have been reported, causing treatment failures, and the problem of emerging antibiotic resistance cannot be neglected.

Improvement of clinical algorithms for the diagnosis of Neisseria gonorrhoeae and Chlamydia trachomatis by the use of Gram-stained smears among female sex workers in Accra, Ghana

BACKGROUND

Screening for cervical infection is difficult in developing countries. Screening strategies must be improved for high-risk women, such as female sex workers.

GOAL

To evaluate the sensitivity and specificity of screening algorithms for cervical infection pathogens among female sex workers in Accra, Ghana.

STUDY DESIGN

A cross-sectional study among female sex workers was conducted. Each woman underwent an interview and a clinical examination. Biologic samples were obtained for the diagnosis of HIV, syphilis, bacterial vaginosis, yeast infection, Trichomonas vaginalis, Neisseria gonorrhoeae, and Chlamydia trachomatis infection. Signs and symptoms associated with cervicitis agents were identified. Algorithms for the diagnosis of cervical infection were tested by computer simulations.

RESULTS

The following prevalences were observed: HIV, 76.6%; N. gonorrhoeae, 33.7%; C. trachomatis, 10.1%; candidiasis, 24.4%; T. vaginalis, 31.4%; bacterial vaginosis, 2.3%; serologic syphilis, 4.6%; and genital ulcers on clinical examination, 10.6%. The best performance of algorithms were reached when using a combination of clinical signs and a search for gram-negative diplococci on cervical smears (sensitivity, 64.4%; specificity, 80.0%).

CONCLUSIONS

In the algorithms, examination of Gram-stained genital smears in female sex workers without clinical signs of cervicitis improved sensitivity without altering specificity for the diagnosis of cervical infection.

Analysis of Chlamydia trachomatis serovars in endocervical specimens derived from pregnant Japanese women

The polymerase chain reaction (PCR) method has been employed to amplify a chlamydial genome encoding four variable segments of the major outer membrane protein and genotyping of different Chlamydia trachomatis serovars was successfully achieved by means of restriction fragment length polymorphism (RFLP) analysis and sequencing of amplified DNA. These methods were applied to identify the serotypes of C. trachomatis in endocervical specimens obtained from asymptomatic pregnant Japanese women at 28-30 weeks of gestation. Among the 218 specimens, 207 were serotyped 43 (19.3%) as serovar D, 53 (24.3%) as E, 24 (11.0%) as F, 39 (17.9%) as G, 15 (6. 9%) as H, 15 (6.9%) as I, five (2.3%) as J, nine (4.1%) as K and four (1.8%) as mixed. Among the 11 unclassified strains by RFLP, six (2.8%) were identified as serovar B variants and five (2.3%) were identified as D/IC-Cal-8. It was suggested that variants of endemic trachoma serovars also have affinity for the urogenital tract of Japanese pregnant women.

Genotyping of Portuguese Chlamydia trachomatis urogenital isolates

OBJECTIVE

To determine the prevalence of the different Chlamydia trachomatis genotypes in Portuguese patients.

METHODS

Urogenital isolates (n = 240) derived from attenders of various clinics in the Lisbon area were differentiated into genovars by genotyping with restriction fragment length polymorphism (RFLP) analysis of the PCR amplified omp1 gene.

RESULTS

Genotype E was the most common for both men (47.9%) and women (43.8%). Genotypes D and F were the second most prevalent for men (11.3%) and genotype H was the second most prevalent for women (19.5%). Genotypes F, G, D, in women and H, G, I, in men, were found in a lower percentage of cases. Genotypes B, Ba, J, K, L1 and L2 were very rarely detected.

CONCLUSIONS

With one exception, the overall distribution of Chlamydia trachomatis genotypes in our study is similar to what has been observed in other western countries. The only exception is the unusual prevalence of genotype H among women. The clinical manifestations associated with this and other genotypes were similar.

Evaluation of a screening algorithm for the diagnosis of genital infections with Neisseria gonorrhoeae and Chlamydia trachomatis among female sexworkers in Bénin

BACKGROUND AND OBJECTIVES

In developing countries, simple and cheap procedures for the diagnosis of sexually transmitted diseases (STDs) are urgently needed, especially for screening purposes in high risk groups.

GOALS

To evaluate the sensitivity and specificity of a screening algorithm for STDs among 364 female sex workers in Bénin, in comparison with reference laboratory tests.

STUDY DESIGN

The algorithm relied on the following criteria, which were evaluated in sequence: the presence of endocervical mucopus on visual inspection of the cervix, a positive swab test, or a microscopic examination of vaginal fluid showing more than 10 polymorphonuclear cells per field. The algorithm diagnosed an infection if any one of these criteria was fulfilled. True infectious status was determined by the combined results of culture for Neisseria gonorrhoeae, enzyme immunoassay for Chlamydia trachomatis, and polymerase chain reaction assays for both infections.

RESULTS

Gonococcal or chlamydial infection was diagnosed in 39.8% of the study population according to the reference tests. The algorithm had a sensitivity of 57.9% and a specificity of 61.2%. In the presence of Candida sp or Trichomonas vaginalis, specificity decreased to 39.1%, but sensitivity increased to 67.5%.

CONCLUSIONS

These results underscore the limitations of simple, nonlaboratory diagnostic tools for screening STDs in high-risk groups in developing countries. Further research is needed to increase the validity--especially the sensitivity--of these algorithms.

Quantitation of Chlamydia trachomatis by culture, direct immunofluorescence and competitive polymerase chain reaction

OBJECTIVES

Methods to quantitate Chlamydia trachomatis have never been compared although it would be relevant to periodically evaluate the sensitivity of a detection system. We compared the sensitivity and reproducibility of culture, direct immunofluorescence and the polymerase chain reaction (PCR) to quantitate C trachomatis.

METHODS

A competitive semiquantitative PCR procedure was developed. The number of inclusions in culture, particles by direct immunofluorescence and DNA copies by PCR were measured for 12 patient specimens. Variation was determined by measuring a sample 10 times for each method.

RESULTS

Patient C trachomatis major outer membrane protein gene DNA was measured semiquantitatively by amplifying together with reference DNA. DNA molecules, particles and infectious units were quantitated in clinical samples with, on average, 595 DNA molecules and 87 immunofluorescent particles observed per inclusion-forming-unit. Similar coefficients of variation (47-52%) were observed for the 3 procedures.

CONCLUSION

Competitive PCR and counting immunofluorescent particles provide reproducible and sensitive methods of quantitating C trachomatis.

Variation outside variable segments of the major outer membrane protein distinguishes trachoma from urogenital isolates of the same serovar of Chlamydia trachomatis

OBJECTIVES--Whereas serovars A, B, Ba and C of Chlamydia trachomatis are usually associated with trachoma, two of these serovars (Ba and C) are occasionally observed in urogenital infections. Variation in the gene encoding the major outer membrane protein (MOMP) was explored to distinguish urogenital from trachoma specimens of the same serovar. METHODS--A large portion of the MOMP gene was amplified by nested PCR directly from clinical samples from trachoma or urogenital infection and the serovar of the infecting C trachomatis was determined by restriction fragment length polymorphism (RFLP). Amplified DNA from trachoma serovars B, Ba and C and from urogenital serovars Ba, C, D and E was sequenced by the dideoxy chain termination method. RESULTS--While almost identical in variable segment (VS)I, three urogenital Ba samples differed from all trachoma B and Ba samples at eight nucleotides including two sites which changed amino acids in the constant region upstream of VSI. An identical sequence in this region was observed for the reference urogenital D serovar. Variation in this same region upstream of VSI also distinguished 40% of serovar D samples from prototype D including three that were sequenced. Two urogenital C differed from trachoma C samples at four sites that changed the MOMP amino acid sequence including two changes in the constant region between VSII and III and single changes in VSII and III. On the basis of these sequence determinations, RFLP was predicted which allowed extension of these observations to 20 other urogenital Ba, 12 trachoma B or Ba, seven variant D, 12 D, four urogenital C and three trachoma C samples without further sequencing. CONCLUSION--Urogenital Ba and C samples have VSI or II and III sequences identical or very similar to trachoma strains of the same serovar, but resemble more closely other serovars in the constant regions. Urogenital serovar D samples can also be divided into two genotypes on the basis of sequence differences in the constant region preceding VSI.

Comparison of two panels of monoclonal antibodies for determination of Chlamydia trachomatis serovars

A panel of monoclonal antibodies was developed for serovar typing of clinical isolates of Chlamydia trachomatis. The panel could distinguish all 15 established serovars from one another, although the hybridomas of the panel were developed by fusions of myeloma cells and spleen cells from mice immunized with antigen derived from the urogenital serovars D to L3. The typing assay was based on a dot enzyme immunoassay, and the monoclonal antibodies that were included in the panel reacted strongly in this assay. A collection of 289 clinical isolates from The Netherlands was typed. The observed serovar frequency distribution was 51 isolates of serovar D (17.6%), 103 isolates of serovar E (35.6%), 62 isolates of serovar F (21.5%), 28 isolates of serovar G (9.9%), 14 isolates of serovar H (4.8%), 2 isolates of serovar I' (0.7%), 20 isolates of serovar J (6.9%), and 9 isolates of serovar K (3.1%). These results were confirmed by typing these isolates with a panel of monoclonal antibodies purchased from the Washington Research Foundation, Seattle. No strain variation was observed within serovar D with both panels. However, restriction fragment length polymorphism analysis of the gene encoding the major outer membrane protein showed that 32 isolates were similar to the prototype D and 17 were similar to the variant D-. The two others showed a new restriction pattern. Our panel of monoclonal antibodies contained one monoclonal antibody that divided the serovar G isolates into two groups. This differentiation was confirmed by restriction fragment length polymorphism analysis, confining this difference to a known sequence variation in variable domain IV. These data support the subdivision of serovar G into serovars G (prototype strain UW-57) and Ga (prototype strain IOL-238).