The Swedish new variant of Chlamydia trachomatis

The serodiagnositic value of Chlamydia trachomatis antigens in antibody detection using luciferase immunosorbent assay

Introduction

Among the different antigens used in the detection of anti-Chlamydia trachomatis antibodies, significant differences in sensitivity and specificity have been observed. Further evaluation of C. trachomatis antigens in antibody detection is urgently needed for the development and application of C. trachomatis serologic assays.

Methods

Chlamydia trachomatis antigens Pgp3, TmeA, InaC, and HSP60 were selected and used in luciferase immunosorbent assay (LISA). The detection results obtained from well-defined C. trachomatis positive and negative samples were compared with the commercial C. trachomatis ELISA (Mikrogen) for performance evaluation.

Results

Pgp3, TmeA, InaC, and HSP60-based LISA showed sensitivity of 92.8, 88.8, 90.4, and 94.4%, and specificity of 99.2, 99.2, 99.2, and 92%, respectively. ROC analysis indicated that Pgp3-based LISA showed similar performance to Mikrogen ELISA (AUC 0.986 vs. 0.993, p = 0.207). Furthermore, four C. trachomatis antigens achieved strong diagnostic efficiency, i.e., positive likelihood ratios [+LR] ≥ 10 in C. trachomatis-infected women and negative likelihood ratios [-LR] ≤ 0.1 in C. trachomatis negative low exposure risk children, but only Pgp3 and TmeA showed strong diagnostic value in general adults. In addition, Pgp3, TmeA, and InaC, but not HSP60, achieved high performance, i.e., both positive predictive value (PPV) and negative predictive value (NPV) ≥ 90.9%, and showed no significant cross-reactivity with anti-Chlamydiapneumoniae.

Conclusion

Three C. trachomatis species-specific antigens Pgp3, TmeA, and InaC show superior performance in the detection of anti-C. trachomatis antibody, indicating the potential to be used in developing C. trachomatis serologic tests.

No widespread dissemination of Chlamydia trachomatis diagnostic-escape variants and the impact of Neisseria gonorrhoeae positivity on the Aptima Combo 2 assay

OBJECTIVES

A Finnish Chlamydia trachomatis (CT) new variant was detected in 2019 that escaped detection in the Hologic Aptima Combo 2 (AC2) assay due to a C1515T mutation in the CT 23S rRNA target region. Reflex testing of CT-negative/CT-equivocal specimens as well as those positive for Neisseria gonorrhoeae (NG) with the Hologic Aptima CT (ACT) assay was recommended to identify any CT variants.

METHODS

From June to October 2019, specimens with discrepant AC2/ACT CT results were submitted to Public Health England and screened for detectable CT DNA using an inhouse real-time (RT)-PCR. When enough DNA was present, partial CT 23S rRNA gene sequencing was performed. Analysis of available relative light units and interpretative data was performed.

RESULTS

A total of 317 discordant AC2/ACT specimens were collected from 315 patients. Three hundred were tested on the RT-PCR; 53.3% (n=160) were negative and 46.7% (n=140) were positive. Due to low DNA load in most specimens, sequencing was successful for only 36 specimens. The CT 23S rRNA wild-type sequence was present in 32 specimens, and two variants with C1514T or G1523A mutation were detected in four specimens from three patients. Of the discordant specimens with NG interpretation, 36.6% of NG-negative/CT-negative AC2 specimens had detectable CT DNA on the inhouse RT-PCR vs 53.3% of NG-positive/CT-negative specimens.

CONCLUSIONS

No widespread dissemination of AC2 diagnostic-escape CT variants has occurred in England. We however identified the impact of NG positivity on the discordant AC2/ACT specimens; a proportion appeared due to NG positivity and the associated NG signal, rather than any diagnostic-escape variants or low DNA load. Several patients with gonorrhoea may therefore receive false-negative AC2 CT results. Single diagnostic targets and multiplex diagnostic assays have their limitations such as providing selection pressure for escape mutants and potentially reduced sensitivity, respectively. These limitations must be considered when establishing diagnostic pathways.

Diagnosis of Chlamydia trachomatis genital infections in the era of genomic medicine

PURPOSE

Chlamydial genital infections constitute significant sexually transmitted infections worldwide. The often asymptomatic status of C. trachomatis (CT) infections leads to an increased burden on human reproductive health, especially in middle- and low-income settings. Early detection and management of these infections could play a decisive role in controlling this public health burden. The objective of this review is to provide an insight into the evolution of diagnostic methods for CT infections through the development of new molecular technologies, emphasizing on -omics' technologies and their significance as diagnostic tools both for effective patient management and control of disease transmission.

METHODS

Narrative review of the diagnostic methodologies of CT infections and the impact of the introduction of -omics' technologies on their diagnosis by review of the literature.

RESULTS

Various methodologies are discussed with respect to working principles, required specifications, advantages, and disadvantages. Implementing the most accurate methods in diagnosis is highlighted as the cornerstone in managing CT infections.

CONCLUSION

Diagnostics based on -omics' technologies are considered to be the most pertinent modalities in CT testing when compared to other available methods. There is a need to modify these effective and accurate diagnostic tools in order to render them more available and feasible in all settings, especially aiming on turning them to rapid point-of-care tests for effective patient management and disease control.

Chlamydia trachomatis intra-bacterial and total plasmid copy number in clinical urogenital samples

Chlamydia trachomatis (CT) increases its plasmid numbers when stressed, as occurs in clinical trachoma samples. Most CT tests target the plasmid to increase the test sensitivity, but some only target the chromosome. We investigated clinical urogenital samples for total plasmid copy numbers to assess its diagnostic value and intra-bacterial plasmid copy numbers to assess its natural variation. Both plasmid and chromosome copies were quantified using qPCR, and the plasmid:chromosome ratio (PCr) calculated in two cohorts: (1) 383 urogenital samples for the total PCR (tPCr), and (2) 42 vaginal swabs, with one half treated with propium-monoazide (PMA) to prevent the quantification of extracellular DNA and the other half untreated to allow for both tPCr and intra-bacterial PCr (iPCr) quantification. Mann–Whitney U tests compared PCr between samples, in relation to age and gender. Cohort 1: tPCr varied greatly (1–677, median 16). Median tPCr was significantly higher in urines than vaginal swabs (32 vs. 11, p < 0.001). Cohort 2: iPCr was more stable than tPCr (range 0.1–3 vs. 1–11). To conclude, tPCr in urogenital samples was much more variable than previously described. Transport time and temperature influences DNA degradation, impacting chromosomal DNA more than plasmids and urine more than vaginal samples. Data supports a plasmid target in CT screening assays to increase clinical sensitivity.

A molecular screening assay to identify Chlamydia trachomatis and distinguish new variants of C. trachomatis from wild-type

Chlamydia trachomatis is the most common sexually transmitted pathogen globally, causing serious health problems and representing a burden on public health. A new variant of C. trachomatis (nvCT) that carries mutations (C1514T, C1515T and G1523A) in the 23S rRNA gene has eluded detection in Aptima Combo 2 assays. This has led to false negatives in diagnostics tests and poses a challenge for C. trachomatis diagnostics on a global level. In this study, we developed a simple and cost‐effective assay to identify C. trachomatis, with a potential application to screen for nvCT. We developed a screening assay based on high‐resolution melting (HRM), targeting the 23S rRNA gene and cryptic plasmid. To evaluate the performance of the assay, 404 archived C. trachomatis DNA specimens and 570 extracted clinical specimens were analysed. Our HRM assay not only identified C. trachomatis in clinical specimens, but also correctly differentiated nvCT carrying C1514T, C1515T and G1523A mutations from the wild‐type. We observed no cross‐reactions with other clinically related agents, and the limit of detection was 11.26 (95% CI; 7.61–31.82) copies per reaction. Implementation of this screening assay could reduce detection times and costs for C. trachomatis diagnoses, and facilitate increased research on the presence and monitoring of nvCT.

Validation of an Aptima-format Finnish new variant of Chlamydia trachomatis (FI-nvCT) surveillance assay, 2019

The Finnish new variant of Chlamydia trachomatis (FI-nvCT) is escaping diagnostics in Finland, Norway and Sweden. We have developed and validated an Aptima-format nucleic acid amplification test (NAAT) designed specifically to detect the FI-nvCT. This NAAT has high sensitivity (100%) and specificity (100%) for the FI-nvCT strain, enabling further investigation of the geographic distribution, prevalence and transmission of this diagnostic-escape mutant in screening populations in Europe.

False-negative Chlamydia polymerase chain reaction result caused by a cryptic plasmid-deficient Chlamydia trachomatis strain in Australia

Background The 7.5-kb chlamydial cryptic plasmid remains a widely used sequence target for Chlamydia trachomatis nucleic acid amplification tests, but sequence variation in this plasmid, particularly a previously reported 377-bp deletion, can cause false-negative results. Here we report the presence in Australia of a C. trachomatis strain lacking the cryptic plasmid.

METHODS

A rectal swab from a male in his 50s provided a positive result for C. trachomatis using the Roche Cobas 4800 test, but a negative result in our confirmatory in-house polymerase chain reaction (PCR) method targeting the chlamydial cryptic plasmid. This result was unexpected given our in-house PCR assay targeted a region of sequence outside the recognised 377-bp deletion. To further investigate this discrepancy, the sample was retested using a second in-house PCR targeting a chromosomal (ompA) gene as well as six primer sets flanking various regions of the cryptic plasmid.

RESULTS

The sample provided positive results in the second in-house method, confirming the presence of C. trachomatis DNA. All other primer sets targeting the cryptic plasmid failed to amplify, indicating a lack of the chlamydial cryptic plasmid in this sample.

CONCLUSIONS

The recognition of a plasmid-deficient strain of C. trachomatis within Australia highlights further limitations of using the chlamydial cryptic plasmid for C. trachomatis diagnostics and re-emphasises the benefits of using multitarget assays to avoid false-negative results.

Finnish new variant of Chlamydia trachomatis escaping detection in the Aptima Combo 2 assay also present in Örebro County, Sweden, May 2019

We identified the first two cases of the Finnish new variant of Chlamydia trachomatis (F-nvCT) beyond Finland in two clinical urogenital specimens in Örebro County, Sweden. These Aptima Combo 2 assay-negative specimens were Aptima Chlamydia trachomatis (CT) assay positive and had the characteristic C1515T mutation in the 23S rRNA gene. From 22 March to 31 May 2019, 1.3% (2/158) of the CT-positive cases in Örebro County were missed because of the F-nvCT. International awareness, investigations and actions are essential.

The 'Finnish new variant of Chlamydia trachomatis' escaping detection in the Aptima Combo 2 assay is widespread across Norway, June to August 2019

The ‘Finnish new variant of Chlamydia trachomatis’ (FI-nvCT), escaping detection in the Aptima Combo 2 assay (AC2), is widespread across Norway. From June to August 2019, 84% (81/97) of available AC2/Aptima CT discordant samples from five laboratories were confirmed as FI-nvCT. Two additional CT variants (CT 23S rRNA C1514T and G1523A) also escaped AC2 detection. The high FI-nvCT proportion might indicate a long-term national spread and it cannot be excluded that FI-nvCT emerged in Norway.

Sensitivity, specificity, inclusivity and exclusivity of the updated Aptima Combo 2 assay, which provides detection coverage of the new diagnostic-escape Chlamydia trachomatis variants

Background

Four new variants of Chlamydia trachomatis (nvCTs), detected in several countries, cause false-negative or equivocal results using the Aptima Combo 2 assay (AC2; Hologic). We evaluated the clinical sensitivity and specificity, as well as the analytical inclusivity and exclusivity of the updated AC2 for the detection of CT and Neisseria gonorrhoeae (NG) on the automated Panther system (Hologic).

Methods

We examined 1004 clinical AC2 samples and 225 analytical samples spiked with phenotypically and/or genetically diverse NG and CT strains, and other potentially cross-reacting microbial species. The clinical AC2 samples included CT wild type (WT)-positive (n = 488), all four described AC2 diagnostic-escape nvCTs (n = 170), NG-positive (n = 214), and CT/NG-negative (n = 202) specimens.

Results

All nvCT-positive samples (100%) and 486 (99.6%) of the CT WT-positive samples were positive in the updated AC2. All NG-positive, CT/NG-negative, Trichomonas vaginalis (TV)-positive, bacterial vaginosis-positive, and Candida-positive AC2 specimens gave correct results. The clinical sensitivity and specificity of the updated AC2 for CT detection was 99.7 and 100%, respectively, and for NG detection was 100% for both. Examining spiked samples, the analytical inclusivity and exclusivity were 100%, i.e., in clinically relevant concentrations of spiked microbe.

Conclusions

The updated AC2, including two CT targets and one NG target, showed a high sensitivity, specificity, inclusivity and exclusivity for the detection of CT WT, nvCTs, and NG. The updated AC2 on the fully automated Panther system offers a simple, rapid, high-throughput, sensitive, and specific diagnosis of CT and NG, which can easily be combined with detection of Mycoplasma genitalium and TV.

Chlamydia trachomatis: when the virulence-associated genome backbone imports a prevalence-associated major antigen signature

Chlamydia trachomatis is the most prevalent sexually transmitted bacterium worldwide and the causative agent of trachoma. Its strains are classified according to their ompA genotypes, which are strongly linked to differential tissue tropism and disease outcomes [ocular disease, urogenital disease and lymphogranuloma venereum (LGV)]. While the genome-based species phylogenetic tree presents four main clades correlating with tropism/prevalence, namely ocular, LGV, urogenital T1 (more prevalent genotypes) and urogenital T2 (less prevalent genotypes), inter-clade exchange of ompA is considered a rare phenomenon probably mediating marked tropism alterations. An LGV epidemic, associated with the clonal expansion of the L2b genotype, has emerged in the last few decades, raising concerns particularly due to its atypical clinical presentation (ulcerative proctitis) and circulation among men who have sex with men (MSM). Here, we report an LGV outbreak, mostly affecting human immunodeficiency virus-positive MSM engaging in high-risk sexual practices, caused by an L2b strain with a rather unique non-LGV ompA signature that precluded the laboratory notification of this outbreak as LGV. C. trachomatis whole-genome capture and sequencing directly from clinical samples was applied to deeply characterize the genomic backbone of this novel LGV outbreak-causing clone. It revealed a chimeric genome structure due to the genetic transfer of ompA and four neighbouring genes from a serovar D/Da strain, likely possessing the genomic backbone associated with the more prevalent urogenital genotypes (T1 clade), to an LGV (L2b) strain. The hybrid L2b/D-Da strain presents the adhesin and immunodominant antigen MOMP (major outer membrane protein) (encoded by ompA) with an epitope repertoire typical of non-invasive genital strains, while keeping the genome-dispersed virulence fingerprint of a classical LGV strain. As previously reported for inter-clade ompA exchange among non-LGV clades, this novel C. trachomatis genomic mosaic involving a contemporary epidemiologically and clinically relevant LGV strain may have implications on its transmission, tissue tropism and pathogenic capabilities. The emergence of variants with epidemic and pathogenic potential highlights the need for more focused surveillance strategies to capture C. trachomatis evolution in action.

The Finnish New Variant of Chlamydia trachomatis with a Single Nucleotide Polymorphism in the 23S rRNA Target Escapes Detection by the Aptima Combo 2 Test

In 2019, more than 200 cases of Chlamydia trachomatis negative/equivocal by the Aptima Combo 2 assay (AC2, target: 23S rRNA) with slightly elevated relative light units (RLUs), but positive by the Aptima Chlamydia trachomatis assay (ACT, target: 16S rRNA) have been detected in Finland To identify the cause of the AC2 CT false-negative specimens, we sequenced parts of the CT 23S rRNA gene in 40 specimens that were AC2 negative/equivocal but ACT positive. A single nucleotide polymorphism (SNP; C1515T in the C. trachomatis 23S rRNA gene) was revealed in 39 AC2/ACT discordant specimens. No decrease in the number of mandatorily notified C. trachomatis cases was observed nationally in Finland in 2010–2019. When RLUs obtained for AC2 negative specimens were retrospectively evaluated in 2011–2019, a continuous increase in the proportion of samples with RLUs 10–19 was observed since 2014, and a slight increase in the proportion of samples with RLUs 20–84 in 2017–2019, indicating that the Finnish new variant of C. trachomatis might have been spreading nationally for several years. This emphasizes that careful surveillance of epidemiology, positivity rate and test performance are mandatory to detect any changes affecting detection of infections.

An Asymptomatic Patient with Fatal Infertility Carried a Swedish Strain of Chlamydia trachomatis with Additional Deletion in The Plasmid orf1 that Belonged to A Different MLST Sequence Type

Here, we present the first case of asymptomatic genital Chlamydial infection caused by the new emerging Chlamydia trachomatis (C.t.) ST13 strain genovar E, which has a double deletion of 377 bp and 17 bp in orf1 gene of the cryptic plasmid (ddCT). This case occurred in an infertile patient (case-patient) with a detectable level of Chlamydial antibodies and a spermatozoa deficiency known as azoospermia. Additionally, the ddCT strain showed the presence of a duplication of 44 bp in the plasmid orf3 and SNP in orf4, which were known as the typical characteristics of the Swedish variant of C.t. (nvCT) genovar E. Multilocus sequence typing (MLST) determined a significant difference between ddCT and nvCT in four alleles (oppA, hfiX, gitA and enoA). Both ddCT and nvCT were assigned to different genetic lineages and could be allocated to two different non-overlapping clonal complexes. Furthermore, ddCT demonstrated a considerable difference among 4–5 alleles in comparison with other C.t. strains of genovar E of ST4, ST8, ST12, and ST94, including the founder of a single relevant cluster, wtCT E/SW3 (Swedish genetic lineage). In contrast to other genovar E strains, ddCT had identical alleles with seven out of seven loci found in ST13 strains of genovars D and G, including the founder for this clonal group, D/UW-3/CX, and six out of seven loci found in its derivatives, such as ST6, ST10, and ST95 of genovars G and H. Nevertheless, MSTree V2 showed that ddCT and nvCT could have a common early ancestor, which is a parental C.t. G/9301 strain of ST9. A significant difference between ddCT and nvCT of genovar D (nvCT-D) that was recently found in Mexico was also determined as: (i) ddCT belonged to genovar E but not to genovar D; (ii) ddCT had a 44 bp duplication within the orf3 of the plasmid typical for nvCT; (iii) ddCT possessed an additional 17 bp deletion in the orf1. In conclusion, improved case management should include the clinical physician’s awareness of the need to enhance molecular screening of asymptomatic Chlamydia patients. Such molecular diagnostics might be essential to significantly reducing the global burden of Chlamydial infection on international public health.

Chlamydia trachomatis samples testing falsely negative in the Aptima Combo 2 test in Finland, 2019

Since February 2019, over 160 Chlamydia trachomatis (CT) cases testing negative or equivocal by Aptima Combo 2 (AC2) but positive by Aptima CT test run with Panther instruments occurred in Finland. The AC2 test targets chlamydial 23S rRNA while the CT test targets 16S rRNA. Sequencing of 10 strains revealed a nucleotide substitution in 23S rRNA. The significance of this for the failure of the AC2 test to detect the variant is not yet known.

The Hidden Genomics of Chlamydia trachomatis

The application of whole-genome sequencing has moved us on from sequencing single genomes to defining unravelling population structures in different niches, and at the -species, -serotype or even -genus level, and in local, national and global settings. This has been instrumental in cataloguing and revealing a huge a range of diversity in this bacterium, when at first we thought there was little. Genomics has challenged assumptions, added insight, as well as confusion and glimpses of truths. What is clear is that at a time when we start to realise the extent and nature of the diversity contained within a genus or a species like this, the huge depth of knowledge communities have developed, through cell biology, as well as the new found molecular approaches will be more precious than ever to link genotype to phenotype. Here we detail the technological developments and insights we have seen during the relatively short time since we began to see the hidden genome of Chlamydia trachomatis.

Implementation and evaluation of the Presto combined qualitative real-time assay for Chlamydia trachomatis and Neisseria gonorrhoeae in Rwanda

Background

The Presto combined qualitative real-time assay for Chlamydia trachomatis and Neisseria gonorrhoeae (Presto CT/NG PCR assay) is appealing for developing countries, because it can be used with multiple DNA extraction methods and polymerase chain reaction (PCR) platforms.

Objectives

The objective of the study was to implement and evaluate the Presto CT/NG PCR assay at the National Reference Laboratory (NRL) in Kigali, Rwanda, where no real-time PCR assays for the detection of C. trachomatis or N. gonorrhoeae were available.

Methods

The Presto CT/NG PCR assay was first evaluated at the Institute of Tropical Medicine (ITM) in Antwerp, Belgium. Next, NRL laboratory technicians were trained to use the assay on their ABI PRISM 7500 real-time PCR instrument and their competencies were assessed prior to trial initiation. During the trial, endocervical swabs were tested at the NRL, with bi-monthly external quality control testing monitored by the ITM. The final NRL results were evaluated against extended gold standard testing at the ITM, consisting of the Abbott m2000 RealTime System with confirmation of positive results by an in-house real-time PCR assay for C. trachomatis or N. gonorrhoeae.

Results

Of the 192 samples analysed using the Presto assay at the NRL, 16 samples tested positive for C. trachomatis and 17 tested positive for N. gonorrhoeae; four of these were infected with both. The sensitivity and specificity of the Presto assay were 93.3% (95% confidence interval [CI]: 68.1% – 99.8%) and 99.4% (95% CI: 96.8% – 100%) for C. trachomatis and 100% (95% CI: 76.8% – 100%) and 98.8% (95% CI: 95.8% – 99.9%) for N. gonorrhoeae.

Conclusion

C. trachomatis and N. gonorrhoeae testing with the Presto assay was feasible in Kigali, Rwanda, and good performance was achieved.

Keywords

qPCR; Chlamydia trachomatis; Neisseria gonorrhoeae.

First Detection of Chlamydia trachomatis 'Swedish' Variant (nvCT) in a Russian Couple with Infertility

BACKGROUND

Chronic asymptomatic chlamydial genital infection caused by the wild-type of Chlamydia trachomatis (wtCT) is the most common bacterial infection causing human infertility. The novel 'Swedish' variant of С.trachomatis (nvCT) which contains a 377 bp deletion in a region that is specifically targeted in some nucleic acid amplification tests may impede diagnosis.

OBJECTIVE

The study aimed to investigate whether nvCT may be a possible cause of infertility in a couple undergoing in vitro fertilization (IVF).

METHOD

Clinical specimens from both genital (urethra and cervix) and extra-genital sites (pharynx, conjunctive, blood) of a couple who experienced multiple unsuccessful attempts at pregnancy by natural fertilization and IVF procedures were analyzed before and after antibiotic therapy. Both partners had neither somatic nor endocrinal abnormality nor any clinically apparent genital manifestations of Chlamydia or other STIs.

RESULTS

Before antibiotic therapy all the samples of the Female Partner (FP) contained DNA of only the nvCT. After antibiotic therapy, additionally, DNA of wtCT of genovars E and D was detected in specimens from her conjunctiva and oropharynx. All samples of the Male Partner (MP) revealed co-infection of nvCT and wtCT. Identical SNP within the variable region 4 (VD4) of the ompA gene confirmed the identity of the wtCT strains found in both partners. The FP had a positive anti-chlamydial IgG titer. The sperm characteristics of the MP, motility (immotile spermatozoa was 51.1% versus 21.6%) and vitality (46% versus 68%) declined progressively, and the MP anti-chlamydial IgG titer was negative.

CONCLUSION

Infertility in this couple may have been caused by chronic asymptomatic and persistent nvCT-associated infection that was complicated by re-infection later with wtCT. This study illustrates the importance of including detection methods for nvCT strains in the investigation of infertility cases.

Anorectal Lymphogranuloma Venereum in Madrid: A Persistent Emerging Problem in Men Who Have Sex With Men

BACKGROUND

Since 2003, outbreaks of lymphogranuloma venereum (LGV) with anorectal syndrome have been increasingly recognized in many Western countries. All of them have been classified as LGV serovar L2b, mainly occurring in human immunodeficiency virus (HIV)-infected men who have had sex with men (MSM). We describe a series of 26 diagnosed cases of LGV proctitis in downtown Madrid, Spain, in 2014, after implementing routine diagnostic procedures for this disease in symptomatic MSM.

METHODS

We conducted an observational study of patients with symptomatic proctitis attending an outpatient infectious diseases clinic in Madrid, Spain during calendar year 2014. Clinical, epidemiological, laboratory, and therapeutic data were gathered and analyzed.

RESULTS

Twenty-six patients were included in the analysis. All were MSM, and 24 of them were HIV-positive. All patients reported having acute proctitis symptoms including tenesmus (85%), pain (88%), constipation (62%), or anal discharge (96%). Proctoscopy showed mucopurulent exudate (25 patients [96%]), and rectal bleeding, with mucosal erythema and/or oedema in all cases. Rectal swabs were obtained from all patients, and LGV serovar L2 was confirmed in all of them. The cure rate was 100% after standard treatments with doxycycline 100 mg twice per day for 3 weeks. Simultaneous rectal infections with other sexually transmitted pathogens (gonorrhoea, herpes simplex virus, Mycoplasma genitalium) and systemic sexually transmitted diseases (STDs) (syphilis, acute HIV, and hepatitis C infections) were also documented in 12 patients (46%), but these co-infections did not appear to influence the clinical manifestations of LGV.

CONCLUSIONS

Anorectal LGV is a common cause of acute proctitis and proctocolitis among HIV-infected MSM who practice unprotected anal sex, and it is frequently associated with other rectal STDs. The implementation of routine screening and prompt diagnosis of these rectal infections should be mandatory in all clinical settings attended by HIV and STD patients.

A simple and rapid DNA extraction method for Chlamydia trachomatis detection from urogenital swabs

A highly sensitive and specific Chlamydia trachomatis (CT) diagnostic test was developed by combining filtration isolation of nucleic acid (FINA) extraction with quantitative polymerase chain reaction including an internal control to identify test inhibition. A pilot study of 40 clinical specimens yielded 100% sensitivity and specificity.

Comprehensive global genome dynamics of Chlamydia trachomatis show ancient diversification followed by contemporary mixing and recent lineage expansion

Chlamydia trachomatis is the world's most prevalent bacterial sexually transmitted infection and leading infectious cause of blindness, yet it is one of the least understood human pathogens, in part due to the difficulties of in vitro culturing and the lack of available tools for genetic manipulation. Genome sequencing has reinvigorated this field, shedding light on the contemporary history of this pathogen. Here, we analyze 563 full genomes, 455 of which are novel, to show that the history of the species comprises two phases, and conclude that the currently circulating lineages are the result of evolution in different genomic ecotypes. Temporal analysis indicates these lineages have recently expanded in the space of thousands of years, rather than the millions of years as previously thought, a finding that dramatically changes our understanding of this pathogen's history. Finally, at a time when almost every pathogen is becoming increasingly resistant to antimicrobials, we show that there is no evidence of circulating genomic resistance in C. trachomatis.

Improvement of laboratory diagnostics of urogenital chlamydial infection in patients with impaired reproductive functions found to be infected with Chlamydia trachomatis

The dominant role in human infertility has been attributed to sexually transmitted infections (STIs) with a leading contribution of urogenital chlamydial infection (UGCI) caused by Chlamydia trachomatis (CT). the two variants of this pathogen are represented by the wild-type (wtCT) and new Swedish (nvCT) strains containing 377 bp deletion within the cryptic plasmid orf1 gene. Objective. The purpose of the study was investigation of the clinical specimens obtained from the urogenital tract of couples coping with infertility for the presence of genetic material of wtCT and nvCT. Material and methods. Clinical samples (scrapings from the urethra and cervix) obtained from 25 to 41 years old couples (n = 14) were tested for the presence of identifiable wtCT and nvCT chlamydia DNA by monoplex and duplex PCR, specific antigens C. trachomatis in elementary bodies by using immunofluorescence analysis (IFA), while detection of anti-chlamydia antibodies in sera was determined by immunoenzymatic assay (IEA). Results. The nvCT variant with typical deletion of 377 bp within the orf1 gene that belongs to the genovar e subtype E1 was detected in 100% of couples with infertility. The negative results of DNA testing for wtcT were registered in 87.5% of patients from this group, while one individual (12.5%) was likely coinfected with nvCT and wtCT of E1 and D genovars, respectively. The wtCT strains of genovar E (subtypes E1, E2, E6), g (subtypes G1, G2), F (subtypes F1), and K were identified in control group among patients with UGCI. The study revealed difficulties in detection of nvCT by nucleic acid amplification test (NAAT), IFA, and IEA; data on comparison of the efficacy of these methods are presented. Conclusion. Chronic UGCI in patients with reproductive dysfunctions can be caused by nvCT alone or as result of co-infection with nvCT and wtCT. The negative results in NAAT may not 100% correlate with the absence of UGCI that requires further confirmation in tests allowing detection of all known variants of C. trachomatis.

Background review for the '2015 European guideline on the management of Chlamydia trachomatis infections'

SummaryChlamydia trachomatis infections are major public health concerns globally. Of particular grave concern is that the majority of persons with anogenital Chlamydia trachomatis infections are asymptomatic and accordingly not aware of their infection, and this silent infection can subsequently result in severe reproductive tract complications and sequelae. The current review paper provides all background, evidence base and discussions for the 2015 European guideline on the management of Chlamydia trachomatis infections (Lanjouw E, et al. Int J STD AIDS 2015). Comprehensive information and recommendations are included regarding the diagnosis, treatment and prevention of anogenital, pharyngeal and conjunctival Chlamydia trachomatis infections in European countries. However, Chlamydia trachomatis also causes the eye infection trachoma, which is not a sexually transmitted infection. The 2015 European Chlamydia trachomatis guideline provides up-to-date guidance regarding broader indications for testing and treatment of Chlamydia trachomatis infections; clearer recommendation of using validated nucleic acid amplification tests only for diagnosis; advice on (repeated) Chlamydia trachomatis testing; recommendation of increased testing to reduce the incidence of pelvic inflammatory disease and prevent exposure to infection and recommendations to identify, verify and report Chlamydia trachomatis variants. Improvement of access to testing, test performance, diagnostics, antimicrobial treatment and follow-up of Chlamydia trachomatis patients are crucial to control its spread.

2015 European guideline on the management of Chlamydia trachomatis infections

Chlamydia trachomatis infections, which most frequently are asymptomatic, are major public health concerns globally. The 2015 European C. trachomatis guideline provides: up-to-date guidance regarding broader indications for testing and treatment of C. trachomatis infections; a clearer recommendation of using exclusively-validated nucleic acid amplification tests for diagnosis; advice on (repeated) C. trachomatis testing; the recommendation of increased testing to reduce the incidence of pelvic inflammatory disease and prevent exposure to infection; and recommendations to identify, verify and report C. trachomatis variants. Improvement of access to testing, test performance, diagnostics, antimicrobial treatment and follow-up of C. trachomatis patients are crucial to control its spread. For detailed background, evidence base and discussions, see the background review for the present 2015 European guideline on the management of Chlamydia trachomatis infections (Lanjouw E, et al. Int J STD AIDS. 2015).

2015 UK national guideline for the management of infection with Chlamydia trachomatis

This guideline offers recommendations on the diagnostic tests, treatment regimens and health promotion principles needed for the effective management of Chlamydia trachomatis genital infection. It covers the management of the initial presentation, as well the prevention of transmission and future infection. The guideline is aimed at individuals aged 16 years and older presenting to healthcare professionals working in departments offering Level 3 care in sexually transmitted infections management within the UK. However, the principles of the recommendations should be adopted across all levels, using local care pathways where appropriate.

External Quality Assessment for the Detection of Chlamydia trachomatis in Urine Using Molecular Techniques in Belgium

Chlamydia trachomatis is a major cause of sexually transmitted bacterial disease worldwide. C. trachomatis is an intracellular bacterium and its growth in vitro requires cell culture facilities. The diagnosis is based on antigen detection and more recently on molecular nucleic acid amplification techniques (NAAT) that are considered fast, sensitive, and specific. In Belgium, External Quality Assessment (EQA) for the detection of C. trachomatis in urine by NAAT was introduced in 2008. From January 2008 to June 2012, nine surveys were organized. Fifty-eight laboratories participated in at least one survey. The EQA panels included positive and negative samples. The overall accuracy was 75.4%, the overall specificity was 97.6%, and the overall sensitivity was 71.4%. Two major issues were observed: the low sensitivity (45.3%) for the detection of low concentration samples and the incapacity of several methods to detect the Swedish variant of C. trachomatis. The reassuring point was that the overall proficiency of the Belgian laboratories tended to improve over time.

High-resolution typing of Chlamydia trachomatis: epidemiological and clinical uses

PURPOSE OF REVIEW

A state-of-the-art overview of molecular Chlamydia trachomatis typing methods that are used for routine diagnostics and scientific studies.

RECENT FINDINGS

Molecular epidemiology uses high-resolution typing techniques such as multilocus sequence typing, multilocus variable number of tandem repeats analysis, and whole-genome sequencing to identify strains based on their DNA sequence. These data can be used for cluster, network and phylogenetic analyses, and are used to unveil transmission networks, risk groups, and evolutionary pathways. High-resolution typing of C. trachomatis strains is applied to monitor treatment efficacy and re-infections, and to study the recent emergence of lymphogranuloma venereum (LGV) amongst men who have sex with men in high-income countries. Chlamydia strain typing has clinical relevance in disease management, as LGV needs longer treatment than non-LGV C. trachomatis. It has also led to the discovery of a new variant Chlamydia strain in Sweden, which was not detected by some commercial C. trachomatis diagnostic platforms.

SUMMARY

After a brief history and comparison of the various Chlamydia typing methods, the applications of the current techniques are described and future endeavors to extend scientific understanding are formulated. High-resolution typing will likely help to further unravel the pathophysiological mechanisms behind the wide clinical spectrum of chlamydial disease.

A multiplex PCR assay for the simultaneous detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis

INTRODUCTION

For developing countries, sexually transmitted infections (STIs) and their complications are ranked in the top 5 disease categories for which adults seek medical treatment. Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) are the three most common STIs worldwide, with TV accounting for over half of the cases. In developing countries, traditional methods for diagnosing STIs are laborious, often not very sensitive, and have a long turnaround time with most recent commercially available diagnostic tests targeting one or, at most, two of these STIs at a time. Here, we describe the development of a highly sensitive, rapid and affordable sample-to-answer multiplex PCR-based assay for the simultaneous detection of Trichomonas vaginalis, Neisseria gonorrhoeae, and Chlamydia trachomatis.

MATERIALS AND METHODS

We designed a multiplex PCR assay for the detection of 4 targets (CT, TV, NG, and process/PCR control) using melt curve analysis. To establish the limit of detection (LOD) for each pathogen, we used previously extracted and quantified TV, NG, and CT genomic DNA (Vircell, Spain). For each target, the LOD was determined by lowering its copy number while increasing the other two STI loads in a stepwise fashion. The process/PCR control remained constant in the optimized assay and was spiked into each sample before extraction. For a concordance study, we tested urine, vaginal and rectal swab specimens from 26 patients positive for one or more of the tested STIs. In addition, 56 liquid cytology specimens (Thinprep) were used to assess specificity.

RESULTS

This assay has a turnaround time of less than 2h and has a limit of detection as low as 7-31 copies for each STI in the presence of the other 2 targets. Our assay also demonstrated 100% concordance with 26 known clinical samples from urine, vaginal and rectal swab specimens. TV, NG, CT, and our process/PCR control were consistently identified at 78°C, 82.3°C, 85.7°C, and ~92°C, respectively. When applied to DNA extracted from residual Thinprep specimens, the assay was negative in 54/56 samples. Two samples were found to be co-infected with CT.

CONCLUSIONS

Our multiplex assay combines a rapid and cost-effective approach to molecular diagnostics with the versatility required for use within a variety of laboratory settings. These performance characteristics make this multiplex STI assay highly suitable for use in a clinical laboratory.

Recent advances in understanding and managing Chlamydia trachomatis infections

Worldwide, Chlamydia trachomatis infections rank among the most common sexually transmitted infections (STI), and cause notable reproductive morbidity in women. Although advances in highly accurate and non-invasive diagnostic testing have allowed for better estimation of the burden of disease—especially the asymptomatic state—we still lack a true point-of-care test, and many infections go undetected and untreated. Moreover, limited resources and effort for managing sexual partners of those in whom infection is actually identified comprise a major challenge to control. Here, we review the current state of understanding of this common infection, and efforts to control it.

Minimum spread of the new Swedish variant of Chlamydia trachomatis and distribution of C. trachomatis ompA genotypes in three geographically distant areas of Spain, 2011-2012

PURPOSE

The aim of this study was to determine the presence of the new Swedish Chlamydia trachomatis (C. trachomatis) variant (nvCT) and the distribution of C. trachomatis ompA genotypes in three geographically distant regions of Spain.

METHODS

The genotypes of strains causing 624 episodes of infection (January 2011-September 2012) were studied using a nested PCR that amplifies a fragment of the ompA gene, followed by sequencing. To detect nvCT, a real-time PCR was used that amplifies a fragment of the cryptic plasmid with a 377 base pair deletion, which identifies the nvCT.

RESULTS AND CONCLUSION

The ompA genotype was identified in 565 (90.5%) episodes. Eleven genotypes were detected, of which nine were found in all three regions. Only one nvCT strain was detected (0.4%), despite the predominance of genotype E (41%). Other frequent genotypes were genotypes D (19%), F (13%), G (11 %), and J (7%). Genotype L2b, causing lymphogranuloma venereum, was detected in men who have sex with men (MSM) in all three regions. Genotypes E and F were more frequent in women and heterosexual men, and genotypes D, G, J and L2b in MSM. In men, the main factor causing differences in the distribution of C. trachomatis was sexual behavior (MSM versus heterosexual men), while the distribution of C. trachomatis genotypes was similar in women and heterosexual men.

Evaluation of Abbott RealTime CT/NG assay for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in cervical swabs from female sex workers in China

Background

To evaluate the performance of the Abbott RealTime CT/NG assay for detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) among female sex workers (FSWs) in China.

Methods

Cervical swabs from 997 participants were blindly detected by the Abbott RealTime CT/NG assay on the automated m2000 molecular platform and Roche Cobas Amplicor CT/NG assay. Discrepant analysis were confirmed by the Qiagen care CT PCR assay. The sample was defined as candidate nvCT-positive if it was CT positive in the Abbott m2000 assay, but CT negative in the other two assays.

Results

25 specimens that were discordant for CT and 26 specimens that were discordant for NG between the two assays were resolved by Qiagen care CT & NG PCR assays. The sensitivity and specificity, respectively, for Abbott m2000 assay were 92.59% and 100% for CT and 95.45% and 99.90% for NG. The positive predictive value (PPV) and negative predictive value (NPV) of Abbott m2000 assay were100% and 98.52% for CT and 95.5% and 99.90% for NG, respectively. No candidate new-variant CT(nvCT)specimens were identified.

Conclusion

Abbott RealTime CT/NG assay were more specify for CT and NG detection, however, its sensitivity for CT and NG were a little bit lower than Roche Cobas Amplicor CT/NG assay. Abbott RealTime CT/NG assay had higher PPV for NG detection than Roche Cobas Amplicor CT/NG assay; it would be more suitable for screening for population with low-prevalence NG. There is currently no evidence that nvCT is present in FSWs in China.

Most but not all laboratories can detect the recently emerged Neisseria gonorrhoeae porA mutants - results from the QCMD 2013 N. gonorrhoeae external quality assessment programme

We describe the results of the Quality Control for Molecular Diagnostics 2013 Neisseria gonorrhoeae external quality assessment programme that included an N. gonorrhoeae strain harbouring an N. meningitidis porA gene which causes false-negative results in molecular diagnostic assays targeting the gonococcal porA pseudogene. Enhanced awareness of the international transmission of such gonococcal strains is needed to avoid false-negative results in both in-house and commercial molecular diagnostic assays used in laboratories worldwide, but particularly in Europe.

Expression and targeting of secreted proteins from Chlamydia trachomatis

Chlamydia trachomatis is an obligate intracellular pathogen that replicates in a vacuole termed the inclusion. Many of the interactions of chlamydiae with the host cell are dependent upon bacterial protein synthesis and presumably exposure of these proteins to the cytosol. Because of the dearth of genetic tools for chlamydiae, previous studies examining secreted proteins required the use of heterologous bacterial systems. Recent advances in genetic manipulation of chlamydia now allow for transformation of the bacteria with plasmids. We describe here a shuttle vector system, pBOMB4, that permits expression of recombinant proteins under constitutive or conditional promoter control. We show that the inclusion membrane protein IncD is secreted in a type III-dependent manner from Yersinia pseudotuberculosis and also secreted from C. trachomatis in infected cells where it localizes appropriately to the inclusion membrane. IncD truncated of the first 30 amino acids containing the secretion signal is no longer secreted and is retained by the bacteria. Cytosolic exposure of secreted proteins can be confirmed by using CyaA, GSK, or microinjection assays. A protein predicted to be retained within the bacteria, NrdB is indeed localized to the chlamydia. In addition, we have shown that the chlamydial effector protein, CPAF, which is secreted into the host cell cytosol by a Sec-dependent pathway, also accesses the cytosol when expressed from this system. These assays should prove useful to assess the secretion of other chlamydial proteins that are potentially exposed to the cytosol of the host cell.

Detection of Chlamydia trachomatis by immunological and genetic methods in female sex workers and the local female population of reproductive age in Mymensingh, Bangladesh

To investigate the accurate prevalence of genital Chlamydia trachomatis infection in Mymensingh, a local area in central-northern Bangladesh, 40 female sex workers (FSW) and 110 sexually active women (SAW, non-FSW) of reproductive age from a local community with clinical symptoms were examined by an immunochromatography test (ICT) and plasmid-based polymerase chain reaction (PCR) during a 1-year period from July 2011 to June 2012 using the endocervical swab as a specimen. By ICT and/or PCR, the C. trachomatis detection rate was 58% and 27% in FSW and SAW, respectively, showing a significant difference (P < 0.01). Two C. trachomatis strains from FSW were determined to be serovar D by ompA-based PCR and sequencing analysis. The highest prevalence was found among women aged 15 to 35 years. A lower socioeconomic status was considered to be an important risk factor for C. trachomatis infection in FSW but not in SAW. This is the first study to determine the prevalence of C. trachomatis infections in FSW and SAW in the same local area in Bangladesh.

Towards multitarget testing in molecular microbiology

Advantages of PCR assays over more conventional culture-based diagnostics include significantly higher sensitivities and shorter turnaround times. They are particularly useful when patient treatment has already been initiated or for specimens that may contain microorganisms that are slow-growing, difficult to culture, or for which culture methods do not exist. However, due to genome variability, single target testing might lead to false-negative results. This paper focuses on examples from our own experiences and the literature to provide insight into the limitations of single target testing in molecular biology. Lessons learned from these experiences include the careful design of diagnostic assays, preferably multitargeted, the importance of investigating the incidence and epidemiology of infection in detail, the frequent participation in appropriate quality assurance schemes, and the importance of continuous attentiveness by investigators when confronted with inconsistent results. In conclusion, multitargeted testing in microbiological molecular assays should be a rule.

Plasmid-mediated transformation tropism of chlamydial biovars

Chlamydia trachomatis and C. muridarum are human and mouse pathogens, respectively, which show high conservation of gene order and content. Both species contain a common 7.5-kb plasmid that is an important virulence factor. Recently described transformation systems have been used to characterize C. trachomatis L2 plasmid gene functions; however, similar studies have not been reported for C. trachomatis ocular tropic serovar A or the mouse strain, C. muridarum. Here, we have conducted genetic experiments with C. trachomatis serovar A and C. muridarum and report the following: (1) successful transformation of C. muridarum and C. trachomatis serovar A is restricted to a shuttle vector with a C. muridarum or C. trachomatis serovar A plasmid backbone, respectively; (2) transformation of plasmid-deficient C. muridarum with the C. muridarum-based shuttle vector complement glycogen accumulation and inclusion morphology; and (3) C. muridarum plasmid-encoded Pgp4 is a regulator of chromosomal (glgA) and plasmid (pgp3) virulence genes. In summary, our findings show a previously unrecognized and unexpected role for the chlamydial plasmid in its transformation tropism and confirm the plasmids regulatory role of virulence genes in C. muridarum.

Plasmid deficiency in urogenital isolates of Chlamydia trachomatis reduces infectivity and virulence in a mouse model

We hypothesized that the plasmid of urogenital isolates of Chlamydia trachomatis would modulate infectivity and virulence in a mouse model. To test this hypothesis, we infected female mice in the respiratory or urogenital tract with graded doses of a human urogenital isolate of C. trachomatis, serovar F, possessing the cognate plasmid. For comparison, we inoculated mice with a plasmid‐free serovar F isolate. Following urogenital inoculation, the plasmid‐free isolate displayed significantly reduced infectivity compared with the wild‐type strain with the latter yielding a 17‐fold lower infectious dose to yield 50% infection. When inoculated via the respiratory tract, the plasmid‐free isolate exhibited reduced infectivity and virulence (as measured by weight change) when compared to the wild‐type isolate. Further, differences in infectivity, but not in virulence were observed in a C. trachomatis, serovar E isolate with a deletion within the plasmid coding sequence 1 when compared to a serovar E isolate with no mutations in the plasmid. We conclude that plasmid loss reduces virulence and infectivity in this mouse model. These findings further support a role for the chlamydial plasmid in infectivity and virulence in vivo.

Cobas® 4800: a fully automated system for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae

Chlamydia trachomatis and Neisseria gonorrhoeae (CT/NG) are the most common sexually transmitted bacterial infections globally and account for the majority of the infections monitored by public health surveillance systems. Therefore, access to diagnostic tools that facilitate identification of these infections is critical to sexually transmitted infection control efforts. The cobas(®) 4800 system is a fully automated system that incorporates nucleic acid extraction and real-time PCR. The cobas 4800 CT/NG assay is one component of the test menu available on this system. The cobas 4800 CT/NG assay has excellent sensitivity and specificity as a result of dual primer targets, it utilizes self-obtained sample types, and is only one assay in a larger menu of tests that are performed on a system that is easy to use and maintain.

[Microbiological diagnosis of infections due to Chlamydia spp. and related species]

Until recently the number of completed genomes belonging to Chlamydia trachomatis was very low, despite its importance in Public Health. Now, there are currently sixty-six completed genomes of C.trachomatis sequenced in different parts of the world. This genomic revolution has helped in understanding its biology, as well as improved the sensitivity and specificity in the diagnosis, and the development of epidemiological tools, not only for in C.trachomatis, but also for related species such as C.pneumoniae and C.psittaci. The diagnosis based on cell culture, serology and microimmunofluorescence is gradually being replaced by molecular techniques based on PCR or real-time PCR. This is because these molecular tests do not have cross-reactions problems and the procedures are easily standardised between laboratories. Moreover, molecular epidemiology tools described recently, such as Multi-Locus Sequence Typing (MLST) and Variable Number Tandem Repeat (VNTR), have increased our knowledge on local and global epidemiology. This article focuses on the impact of the genomics advances achieved over the last few years as applied to the diagnosis, epidemiology and biology of the family Chlamydiaceae family and related species.

Developmental stage-specific metabolic and transcriptional activity of Chlamydia trachomatis in an axenic medium

Chlamydia trachomatis is among the most clinically significant human pathogens, yet their obligate intracellular nature places severe restrictions upon research. Chlamydiae undergo a biphasic developmental cycle characterized by an infectious cell type known as an elementary body (EB) and an intracellular replicative form called a reticulate body (RB). EBs have historically been described as metabolically dormant. A cell-free (axenic) culture system was developed, which showed high levels of metabolic and biosynthetic activity from both EBs and RBs, although the requirements differed for each. EBs preferentially used glucose-6-phosphate as an energy source, whereas RBs required ATP. Both developmental forms showed increased activity when incubated under microaerobic conditions. Incorporation of isotopically labeled amino acids into proteins from both developmental forms indicated unique expression profiles, which were confirmed by genome-wide transcriptional analysis. The described axenic culture system will greatly enhance biochemical and physiological analyses of chlamydiae.

Whole-genome analysis of diverse Chlamydia trachomatis strains identifies phylogenetic relationships masked by current clinical typing

Chlamydia trachomatis is responsible for both trachoma and sexually transmitted infections causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed whole genome phylogeny from representative strains of both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis demonstrates that predicting phylogenetic structure using the ompA gene, traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks true relationships. We show that in many instances ompA is a chimera that can be exchanged in part or whole, both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, another important diagnostic target. We have used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b.

Evolution of Chlamydia trachomatis

We know surprisingly little about the evolutionary origins of Chlamydia trachomatis. It causes both ocular (trachoma) and sexually transmitted infections in humans, it is an obligate intracellular pathogen, and there are only a few "isolates" that have been well characterized. From the first few genomes analyzed, it seems that the C. trachomatis genome is highly conserved. The genomes possess high synteny and, in some cases, the sequence variation between genomes is as little as 20 SNPs. Recent indications from partial genome analyses suggest that recombination is the mechanism for generating diversity. There is no accurate molecular clock by which to measure the evolution of C. trachomatis. The origins of both sexually transmitted and ocular C. trachomatis are unclear, but it seems likely that they evolved with humans and shared a common ancestor with environmental chlamydiae some 700 million years ago. Subsequently, evolution within mammalian cells has been accompanied by radical reduction in the C. trachomatis genome.

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.

Unraveling the basic biology and clinical significance of the chlamydial plasmid

Chlamydial plasmids are small, highly conserved, nonconjugative, and nonintegrative DNA molecules that are nearly ubiquitous in many chlamydial species, including Chlamydia trachomatis. There has been significant recent progress in understanding chlamydial plasmid participation in host-microbe interactions, disease, and immune responses. Work in mouse model systems and, very recently, in nonhuman primates demonstrates that plasmid-deficient chlamydial strains function as live attenuated vaccines against genital and ocular infections. Collectively, these studies open new avenues of research into developing vaccines against trachoma and sexually transmitted chlamydial infections.