The Impact of Lateral Gene Transfer in Chlamydia

Lateral gene transfer (LGT) facilitates many processes in bacterial ecology and pathogenesis, especially regarding pathogen evolution and the spread of antibiotic resistance across species. The obligate intracellular chlamydiae, which cause a range of diseases in humans and animals, were historically thought to be highly deficient in this process. However, research over the past few decades has demonstrated that this was not the case. The first reports of homologous recombination in the Chlamydiaceae family were published in the early 1990s. Later, the advent of whole-genome sequencing uncovered clear evidence for LGT in the evolution of the Chlamydiaceae, although the acquisition of tetracycline resistance in Chlamydia (C.) suis is the only recent instance of interphylum LGT. In contrast, genome and in vitro studies have shown that intraspecies DNA exchange occurs frequently and can even cross species barriers between closely related chlamydiae, such as between C. trachomatis, C. muridarum, and C. suis. Additionally, whole-genome analysis led to the identification of various DNA repair and recombination systems in C. trachomatis, but the exact machinery of DNA uptake and homologous recombination in the chlamydiae has yet to be fully elucidated. Here, we reviewed the current state of knowledge concerning LGT in Chlamydia by focusing on the effect of homologous recombination on the chlamydial genome, the recombination machinery, and its potential as a genetic tool for Chlamydia.

The Chlamydia trachomatis Early Effector Tarp Outcompetes Fascin in Forming F-Actin Bundles In Vivo

The intracellular pathogen Chlamydia trachomatis secretes multiple early effectors into the host cell to promote invasion. A key early effector during host cell entry, Tarp (translocated actin-recruiting phosphoprotein) is comprised of multiple protein domains known to have roles in cell signaling, G-actin nucleation and F-actin bundle formation. In vitro, the actin bundles generated by Tarp are uncharacteristically flexible, however, in vivo, the biological significance of Tarp-mediated actin bundles remains unknown. We hypothesize that Tarp's ability to generate unique actin bundles, in part, facilitates chlamydial entry into epithelial cells. To study the in vivo interaction between Tarp and F-actin, we transgenically expressed Tarp in Drosophila melanogaster tissues. Tarp expressed in Drosophila is phosphorylated and forms F-actin-enriched aggregates in tissues. To gain insight into the significance of Tarp actin bundles in vivo, we utilized the well-characterized model system of mechanosensory bristle development in Drosophila melanogaster. Tarp expression in wild type flies produced curved bristles, indicating a perturbation in F-actin dynamics during bristle development. Two F-actin bundlers, Singed/Fascin and Forked/Espin, are important for normal bristle shape. Surprisingly, Tarp expression in the bristles displaced Singed/Fascin away from F-actin bundles. Tarp's competitive behavior against Fascin during F-actin bundling was confirmed in vitro. Loss of either singed or forked in flies leads to highly deformed bristles. Strikingly, Tarp partially rescued the loss of singed, reducing the severity of the bristle morphology defect. This work provides in vivo confirmation of Tarp's F-actin bundling activity and further uncovers a competitive behavior against the host bundler Singed/Fascin during bundle assembly. Also, we demonstrate the utility of Drosophila melanogaster as an in vivo cell biological platform to study bacterial effector function.

Translational gene expression control in Chlamydia trachomatis

The human pathogen Chlamydia trachomatis proceeds through a multi phenotypic developmental cycle with each cell form specialized for different roles in pathogenesis. Understanding the mechanisms regulating this complex cycle has historically been hampered by limited genetic tools. In an effort to address this issue, we developed a translational control system to regulate gene expression in Chlamydia using a synthetic riboswitch. Here we demonstrate that translational control via a riboswitch can be used in combination with a wide range of promoters in C. trachomatis. The synthetic riboswitch E, inducible with theophylline, was used to replace the ribosome binding site of the synthetic promoter T5-lac, the native chlamydial promoter of the pgp4 plasmid gene and an anhydrotetracycline responsive promoter. In all cases the riboswitch inhibited translation, and high levels of protein expression was induced with theophylline. Combining the Tet transcriptional inducible promoter with the translational control of the riboswitch resulted in strong repression and allowed for the cloning and expression of the potent chlamydial regulatory protein, HctB. The ability to control the timing and strength of gene expression independently from promoter specificity is a new and important tool for studying chlamydial regulatory and virulence genes.

Trends in Chlamydia and Gonorrhea Testing and Positivity Rates in a Safety Net Hospital in Georgia: 2014 to 2017

BACKGROUND

Sexually transmitted infections (STIs) in the United States continue to increase at an alarming rate. Since 2015, reported cases of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC), the 2 most prevalent reportable STIs, have increased by 19% and 56%, respectively. Characterizing testing patterns could elucidate how CT/GC care and positivity have evolved over time in a high-risk urban setting and illustrate how patients use the health care system for their STI needs.

METHODS

Using electronic medical record data from a large safety net hospital in Georgia, patient demographics and clinical characteristics were extracted for all nucleic acid amplification tests ordered from 2014 to 2017 (n = 124,793). Descriptive statistics were performed to understand testing patterns and assess positivity rates.

RESULTS

Annual nucleic acid amplification test volume grew by 12.0% from 2014 to 2017. Obstetrics/gynecology consistently accounted for half of all tests ordered; volume in emergency medicine grew by 45.2% (n = 4108 in 2014 to n = 5963 in 2017), whereas primary care volume fell by -4.3% (n = 4186 in 2014 to n = 4005 in 2017). The largest number of positive results was detected among 15- to 24-year-olds. The positivity of CT was higher among females, and GC among males. The percent positivity of CT remained stable (range, 6.4%-7.0%). The percent positivity of GC increased from 2.7% to 4.3% over time.

CONCLUSIONS

Testing volume in emergency medicine has increased at a faster rate than other specialties; point-of-care testing could ensure more accurate treatment and improve antibiotic stewardship. The rates of CT/GC were high among adolescents and young adults. Tailored approaches are needed to lower barriers to care for this vulnerable population.

Detection of Lymphogranuloma Venereum-Associated Chlamydia trachomatis L2 Serovars in Remnant Rectal Specimens Collected from 7 US Public Health Laboratories

ABSTRACT

The frequency of lymphogranuloma venereum or invasive Chlamydia trachomatis infection with serovar L1, L2, or L3 is unknown in the United States. While no diagnostic test is commercially available, we used a laboratory-developed test and detected lymphogranuloma venereum-associated serovar L2 in 14% of 132 remnant C. trachomatis-positive rectal swabs.

A broad-spectrum cloning vector that exists as both an integrated element and a free plasmid in Chlamydia trachomatis

Plasmid transformation of chlamydiae has created new opportunities to investigate host-microbe interactions during chlamydial infections; however, there are still limitations. Plasmid transformation requires a replicon derived from the native Chlamydia plasmid, and these transformations are species-specific. We explored the utility of a broad host-range plasmid, pBBR1MCS-4, to transform chlamydiae, with a goal of simplifying the transformation process. The plasmid was modified to contain chromosomal DNA from C. trachomatis to facilitate homologous recombination. Sequences flanking incA were cloned into the pBBR1MCS-4 vector along with the GFP:CAT cassette from the pSW2-GFP chlamydial shuttle vector. The final plasmid construct, pBVR2, was successfully transformed into C. trachomatis strain L2-434. Chlamydial transformants were analyzed by immunofluorescence microscopy and positive clones were sequentially purified using limiting dilution. PCR and PacBio-based whole genome sequencing were used to determine if the plasmid was maintained within the chromosome or as an episome. PacBio sequencing of the cloned transformants revealed allelic exchange events between the chromosome and plasmid pBVR2 that replaced chromosomal incA with the plasmid GFP:CAT cassette. The data also showed evidence of full integration of the plasmid into the bacterial chromosome. While some plasmids were fully integrated, some were maintained as episomes and could be purified and retransformed into E. coli. Thus, the plasmid can be successfully transformed into chlamydia without a chlamydial origin of replication and can exist in multiple states within a transformed population.

Community-Based Prevalence Estimates of Chlamydia trachomatis and Neisseria gonorrhoeae Infections Among Gay, Bisexual, and Other Men Who Have Sex With Men in Montréal, Canada

BACKGROUND

Reported cases of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections are increasing among Canadian men. Estimates of community-based CT/NG prevalence are lacking among gay, bisexual, and other men who have sex with men (GBM).

METHODS

Respondent driven sampling was used to recruit GBM in Montréal, Canada between February 2017 and June 2018. Specimens provided from urogenital, rectal, and pharyngeal sites were analyzed using nucleic acid amplification test to detect CT/NG. Prevalence estimates of CT/NG, overall and by anatomical site were calculated. All estimates are respondent-driven sampling-adjusted.

RESULTS

Among 1177 GBM, the prevalence of rectal, urogenital, pharyngeal and overall were respectively 2.4%, 0.4%, 0.4%, and 2.8% for CT infections, and 3.1%, 0.4%, 3.5%, and 5.6% for NG infections. If testing had been limited to the urogenital site, 80% and 94% of CT and NG infections, respectively, would have been missed.

CONCLUSIONS

This community-based study among GBM shows that the CT prevalence was about half of that observed for NG. A large part of CT/NG infections involves only the extragenital sites, highlighting the need for systematic multisite screening regardless of symptoms. In the mist of the COVID-19 pandemic and the limited CT/NG screening capacity due to test kits shortage, it might be considered to prioritize rectal and pharyngeal CT/NG testing over urogenital testing in asymptomatic GBM.

Inter-species lateral gene transfer focused on the Chlamydia plasticity zone identifies loci associated with immediate cytotoxicity and inclusion stability

Chlamydia muridarum actively grows in murine mucosae and is a representative model of human chlamydial genital tract disease. In contrast, C. trachomatis infections in mice are limited and rarely cause disease. The factors that contribute to these differences in host adaptation and specificity remain elusive. Overall genomic similarity leads to challenges in the understanding of these significant differences in tropism. A region of major genetic divergence termed the plasticity zone (PZ) has been hypothesized to contribute to the host specificity. To evaluate this hypothesis, lateral gene transfer was used to generate multiple hetero-genomic strains that are predominately C. trachomatis but have replaced regions of the PZ with those from C. muridarum. In vitro analysis of these chimeras revealed C. trachomatis-like growth as well as poor mouse infection capabilities. Growth-independent cytotoxicity phenotypes have been ascribed to three large putative cytotoxins (LCT) encoded in the C. muridarum PZ. However, analysis of PZ chimeras supported that gene products other than the LCTs are responsible for cytopathic and cytotoxic phenotypes. Growth analysis of associated chimeras also led to the discovery of an inclusion protein, CTL0402 (CT147), and homolog TC0424, which was critical for the integrity of the inclusion and preventing apoptosis.

[Mycoplasma genitalium probably as common in Sweden as Chlamydia trachomatis]

Mycoplasma genitalium is a common sexually transmitted infection, probably as common in Swedish STI clinics as Chlamydia trachomatis. M. genitalium may cause urethritis in men and and urethritis, cervicitis, pelvic inflammatory disease (PID) and infertility in women. The proportion of PID and its implications need further studies. The prevalence of M. genitalium infection in a general population and in asymptomatic patients is estimated to be low and general screening is not recommended. Antimicrobial resistance is a growing problem. Nucleic acid amplification tests (NAATs) including resistance testing for macrolides are available in Sweden. The first-line treatment in the absence of macrolide resistance is with azithromycin, but not as a single dose. Pretreatment with doxycycline to lower bacterial load and reduce risk of macrolide resistance during treatment is under discussion.

Is an Antenatal Screening for Chlamydia trachomatis Necessary in the Current Society?

A screening of Chlamydia trachomatis infection in young pregnant women (≤25 years old) and their newborns was conducted. A total of 136 women were tested with urine samples in the immediate postpartum period. The prevalence was 18.4% (95% confidence interval [CI]: 11.9-24.9%) (25/136) and the rate of perinatal transmission was 35% (7/20). These results support the need for antenatal screening programs in high-risk women in Madrid (Spain).

Spread of clonal genovar E Chlamydia trachomatis among men who have sex with men

In a previous study, we developed a Multi-Locus VNTRs Analysis (MLVA) typing system, called MLVA-5, for the discrimination of Chlamydia trachomatis genovar E strain. The results suggested the clonal spread of a MLVA-5 type 21 strain among men who have sex with men (MSM). We applied the MLVA-5 typing method on 157 French anorectal genovar E specimens and 19 Swedish specimens collected between 2010 and 2015. A total of 29 MLVA-5 types was obtained, with three predominant types among French samples: 78 specimens belonged to MLVA-5 type 21, two other types, 11 and 13, included 9 and 14 specimens, respectively. In 15 cases, one unique MLVA-5 type was observed for a single patient, 7 of which were new types not previously described. The distribution of MLVA-5 types according to sexual orientation showed that the 7 anorectal specimens from heterosexual patients belonged to 6 genotypes, and the 12 anorectal specimens from bisexual patients comprised eight types. The 95 anorectal specimens from MSM were distributed into 22 types, but 55 (57.9%) of them belonged to MLVA-5 type 21. Among the Swedish specimens from MSM, eight were from MLVA-type 21 (4 urines and 4 anorectal specimens). The results support the hypothesis of the spread of clonal genovar E strain among MSM.

Chlamydia abortus OmcB protein is essential for adhesion to host cells

Chlamydia abortus (C. abortus) is one of the most important zoonotic pathogens, causing a number of serious diseases. The adhesion of C. abortus to host cells is the first and crucial step in the process of infection. Outer membrane protein 2 (OmcB) is the second most abundant outer membrane protein. It has been shown to be an important adhesin of Chlamydia trachomatis and Chlamydia pneumoniae. In the present study, the OmcB gene of C. abortus was cloned and expressed in Escherichia coli, and the recombinant OmcB protein with His-tag was used to prepare polyclonal antibodies. Infectivity inhibition assays carried out with C. abortus in the presence of recombinant OmcB showed a considerable reduction (∼50%) in infectivity. Using anti-OmcB serum in infectivity inhibition assays resulted in a 30% reduction in infectivity. Anti-OmcB serum and recombinant OmcB protein in infection inhibition assays showed that OmcB is a surface-exposed protein that functions as an adhesin. The constructed deletion variant of the OmcB motif for infection inhibition assays showed that the first XBBXBX motif of the C. abortus OmcB protein is essential for binding to host cells.

Human genital antibody-mediated inhibition of Chlamydia trachomatis infection and evidence for ompA genotype-specific neutralization

The endocervix, the primary site of Chlamydia trachomatis (Ct) infection in women, has a unique repertoire of locally synthesized IgG and secretory IgA (SIgA) with contributions from serum IgG. Here, we assessed the ability of genital and serum-derived IgG and IgA from women with a recent positive Ct test to neutralize Ct elementary bodies (EBs) and inhibit inclusion formation in vitro in human endocervical epithelial cells. We also determined if neutralization was influenced by the major outer membrane protein (MOMP) of the infecting strain, as indicated by ompA gene sequencing and genotyping. At equivalent low concentrations of Ct EB (D/UW-3/Cx + E/UW-5/Cx)-specific antibody, genital-derived IgG and IgA and serum IgA, but not serum IgG, significantly inhibited inclusion formation, with genital IgA being most effective, followed by genital IgG, then serum IgA. The well-characterized Ct genotype D strain, D/UW-3/Cx, was neutralized by serum-derived IgG from patients infected with genotype D strains, genital IgG from patients infected with genotype D or E strains, and by genital IgA from patients infected with genotype D, E, or F strains. Additionally, inhibition of D/UW-3/Cx infection by whole serum, rather than purified immunoglobulin, was associated with levels of serum EB-specific IgG rather than the genotype of infecting strain. In contrast, a Ct genotype Ia clinical isolate, Ia/LSU-56/Cx, was neutralized by whole serum in a genotype and genogroup-specific manner, and inhibition also correlated with EB-specific IgG concentrations in serum. Taken together, these data suggest that (i) genital IgA most effectively inhibits Ct infection in vitro, (ii) human antibody-mediated inhibition of Ct infection is significantly influenced by the ompA genotype of the infecting strain, (iii) the genital antibody repertoire develops or matures differently compared to systemic antibody, and (iv) ompA genotype-specificity of inhibition of infection by whole serum can be overcome by high concentrations of Ct-specific IgG.

Extragenital Screening of Chlamydia trachomatis and Neisseria gonorrhoeae Among Women in the College Health Setting

BACKGROUND

Despite high frequencies of oral and receptive anal intercourse among young women, the Centers for Disease Control and Prevention does not recommend routine oropharyngeal or anorectal screening for CT and GC. Risk-based extragenital screening of women has not been adopted at the majority of college health centers, and existing research has not focused on the female or college population.

METHODS

We examined health records of women at a college health center in a large urban university for 3 years to evaluate the effectiveness of CT and GC screening. We also evaluated the proportion of CT and GC infections that would have been missed if risk-based extragenital screening was not performed. Decisions to screen at extragenital sites were based on patient-reported risk behavior.

RESULTS

For 8027 unique chlamydia screens and 7907 unique gonorrhea screens, approximately 20% of the visits used extragenital screening in response to self-reported risk behaviors. More than 44% of patients were non-Hispanic White, and approximately 48% fell within the 20- to 24-year age group. The case positivity rates for CT were 2.85% with urogenital-only screening and 1.30% with risk-prompted extragenital screening (1.1% throat, 4.3% rectal). The case positivity rates for GC were 0.11% with urogenital-only screening and 0.37% with risk-prompted extragenital screening (0.37% throat, 0% rectal). If the college health center had relied solely on urogenital screening rather than adding risk-based extragenital screening, 4.41% of CT infections would have been missed and 28.57% of GC infections would have been missed.

CONCLUSIONS

Nearly 1 of 22 CT infections and nearly 1 of 3 GC infections would have been missed without extragenital screening in this analysis of college women. Inclusion of risk-prompted extragenital screening in asymptomatic STD screening protocols can help clinicians diagnose CT and GC infections that would be have been missed with urogenital-only screening. Although rectal GC infections among women seem to be less common, oropharyngeal testing, in particular, for GC is suggested for women based on sexual risk. However, clinicians might only identify these risks if they ask patients directly about these potential exposures. Because guidelines exist only for men, future studies should focus on extragenital screening in college women to build the evidence that this particular population of patients may benefit from this practice, given the high risk of STDs in young adults.

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.

[Comparison of two methods for detection of Chlamydia trachomatis and Ureaplasma urealyticum in male reproductive tract]

OBJECTIVE

To investigate the value of clinical application of simultaneous amplification and testing of RNA (SAT-RNA) for detecting Chlamydia trachomatis (CT) and Ureaplasma urealyticum (UU) by comparing with the polymerase chain reaction testing of DNA (PCR-DNA) method.

METHODS

Specimens from both urethra swab and the first avoid urine which should be at least one hour after the previous urination were collected from 163 men who were scheduled for in vitro fertilization and embryo transfer (IVF-ET) treatment due to female factors at Center for Reproductive Medicine, Shengjing Hospital of China Medical University during the period of April 2016 to April 2017. Among the 163 men, 109 simultaneously provided semen that was collected after 3-7 days of sexual abstinence for the testing. Urine and semen specimens were detected for CT and UU with SAT-RNA, while urethra swab specimens were detected for CT and UU with standard PCR-DNA. Detection results of the SAT-RNA were compared with those of the PCR-DNA method.

RESULTS

The positive rate of UU in the urethra swab detected with PCR-DNA and that of UU in the urine with SAT-RNA were 47.24% and 47.85%, respectively, and the coincidence rate was 93.25%. In addition, the positive and negative coincidence rates were 93.51% and 93.02%, respectively, and the concordance between the two methods was very good (Kappa=0.865). On the other hand, the positive rate of CT in the swab specimen tested with PCR-DNA was 3.07% and that of CT in urine with SAT-RNA was 4.29%, and the coincidence rate was 97.55%. Moreover, the positive and negative coincidence rates were 80.00% and 98.10%, respectively, and the concordance between the two methods was good (Kappa=0.654). Regarding SAT-RNA detection of UU in the urine and semen specimen of the 109 patients, the positive rates of UU in the urine and semen specimens were 50.46% and 44.95%, respectively; and the coincidence rate between the two specimens was 88.99%. In addition, the positive coincidence rate and the negative coincidence rate was 93.88% and 85.00%, respectively, and the concordance between the two specimens was good (Kappa=0.780). Similarly, SAT-RNA detection of CT in the urine and semen specimens showed the positive rate was 5.50% and 3.67%, respectively; and the two specimens showed 98.17% coincidence rate. The positive and negative coincidence rates were 100.00% and 98.10%, respectively, and the concordance was also good (Kappa=0.791).

CONCLUSION

SAT-RNA detection of CT and UU in the urine specimen showed good concordance with the PCR-DNA detection of CT and UU in the urethra swab specimen. In addition, the concordance was also good between the urine and semen specimens detected with SAT-RNA. These results indicate that, as a less invasive and equally accurate procedure, SAT-RNA may be more suitable for clinical application.

[Comparison of two methods for detection of Chlamydia trachomatis and Ureaplasma urealyticum in male reproductive tract]

OBJECTIVE

To investigate the value of clinical application of simultaneous amplification and testing of RNA (SAT-RNA) for detecting Chlamydia trachomatis (CT) and Ureaplasma urealyticum (UU) by comparing with the polymerase chain reaction testing of DNA (PCR-DNA) method.

METHODS

Specimens from both urethra swab and the first avoid urine which should be at least one hour after the previous urination were collected from 163 men who were scheduled for in vitro fertilization and embryo transfer (IVF-ET) treatment due to female factors at Center for Reproductive Medicine, Shengjing Hospital of China Medical University during the period of April 2016 to April 2017. Among the 163 men, 109 simultaneously provided semen that was collected after 3-7 days of sexual abstinence for the testing. Urine and semen specimens were detected for CT and UU with SAT-RNA, while urethra swab specimens were detected for CT and UU with standard PCR-DNA. Detection results of the SAT-RNA were compared with those of the PCR-DNA method.

RESULTS

The positive rate of UU in the urethra swab detected with PCR-DNA and that of UU in the urine with SAT-RNA were 47.24% and 47.85%, respectively, and the coincidence rate was 93.25%. In addition, the positive and negative coincidence rates were 93.51% and 93.02%, respectively, and the concordance between the two methods was very good (Kappa=0.865). On the other hand, the positive rate of CT in the swab specimen tested with PCR-DNA was 3.07% and that of CT in urine with SAT-RNA was 4.29%, and the coincidence rate was 97.55%. Moreover, the positive and negative coincidence rates were 80.00% and 98.10%, respectively, and the concordance between the two methods was good (Kappa=0.654). Regarding SAT-RNA detection of UU in the urine and semen specimen of the 109 patients, the positive rates of UU in the urine and semen specimens were 50.46% and 44.95%, respectively; and the coincidence rate between the two specimens was 88.99%. In addition, the positive coincidence rate and the negative coincidence rate was 93.88% and 85.00%, respectively, and the concordance between the two specimens was good (Kappa=0.780). Similarly, SAT-RNA detection of CT in the urine and semen specimens showed the positive rate was 5.50% and 3.67%, respectively; and the two specimens showed 98.17% coincidence rate. The positive and negative coincidence rates were 100.00% and 98.10%, respectively, and the concordance was also good (Kappa=0.791).

CONCLUSION

SAT-RNA detection of CT and UU in the urine specimen showed good concordance with the PCR-DNA detection of CT and UU in the urethra swab specimen. In addition, the concordance was also good between the urine and semen specimens detected with SAT-RNA. These results indicate that, as a less invasive and equally accurate procedure, SAT-RNA may be more suitable for clinical application.

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.

[Chlamydia trachomatis prevalence in women from the Hospital General de Zona No. 29]

BACKGROUND

Chlamydia trachomatis is the main cause of sexually transmitted bacterial infections worldwide. An estimated of 131 million cases occur each year. It is asymptomatic, but ascending infection in women can lead to pelvic inflammatory disease, ectopic pregnancy, and infertility.

OBJECTIVE

To determine the prevalence of C. trachomatis in open population women who attend the Hospital General de Zona No. 29.

MATERIAL AND METHODS

Identification of C. trachomatis was carried out by PCR testing of 200 vaginal exudate samples and its genotype was determined. In parallel, a routine microbiological diagnosis was carried out.

RESULTS

The prevalence of C. trachomatis was 8.5% (17/200) with a significant concomitance of p = 0.006 with Gardnerella vaginalis (relative risk of 2.871, 95%CI: 1.574-5.236). Likewise, C. trachomatis was identified in 5 samples as the only etiological agent. Sixteen strains of C. trachomatis belong to genotype F. An identified strain of C. trachomatis presented genetic motifs similar to the Mexican variant reported in 2019.

CONCLUSIONS

The prevalence of C. trachomatis in the studied population indicates the need to implement diagnostic techniques for this bacterium. The use of PCR allows a rapid genotypic determination that would explain the epidemiological behavior of C. trachomatis and would represent a significant improvement in the quality of life of the patient.

Performance of Sexually Transmitted Disease Laboratories for Chlamydia trachomatis Detection in Guangdong, China

BACKGROUND

Chlamydia trachomatis detection plays a crucial role in early diagnosis and treatment of C. trachomatis infection. In the current study, the capability of sexually transmitted disease (STD) laboratories to detect C. trachomatis was investigated in Guangdong, China.

METHODS

An external quality assessment panel, including 5 positive samples with different C. trachomatis loads and 2 negative samples was distributed to 654 participating laboratories in October 2019, and the test results were analyzed by Guangdong Central STD Laboratory. The use of various C. trachomatis detection methods in Guangdong from 2015 to 2019 was also retrospectively investigated.

RESULTS

Of the 654 participating STD laboratories, 559 (85.47%) used immune chromatographic-rapid diagnostic tests (IC-RDTs) to detect C. trachomatis in 2019, and 95 (14.53%) used nucleic acid amplification tests (NAATs). The rate of NAATs use increased approximately 4-fold from 2015 to 2019. The sensitivity of IC-RDTs decreased markedly from 97.32% to 30.89% with decreasing C. trachomatis load, whereas that of NAATs was 97.62% to 100% in all positive samples. With respect to negative samples the specificity of IC-RDTs was 97.13% to 97.30% and that of NAATs was 98.95% to 100%. Laboratories using IC-RDTs were less likely to detect C. trachomatis than those using NAATs in samples with C. trachomatis loads of 20000 copies/mL or less (P < 0.0001). Further analysis indicated no significant difference (P > 0.05) in detection rate among the 4 IC-RDT assays commonly used by the participating laboratories.

CONCLUSIONS

Immune chromatographic-rapid diagnostic tests are commonly used for C. trachomatis detection by many laboratories in Guangdong, but their low sensitivity may lead to missed diagnoses. Nucleic acid amplification tests exhibit high sensitivity and specificity and should be recommended for C. trachomatis detection in STD laboratories.

Association of Chlamydia and Mycoplasma infections with susceptibility to ovarian cancer: A systematic review and meta-analysis

BACKGROUND

Ovarian cancer is one of the most prevalent cancers with a high mortality rate in women. Published studies indicate that inflammation, DNA damage, and pelvic inflammatory disease (PID) are the most important risk factors for ovarian cancer and this could be induced and exacerbated by infectious agents such as Chlamydia trachomatis and Mycoplasma genitalium. The aim of this study was to determine the association between Chlamydia and Mycoplasma infections and the risk of ovarian cancer.

METHODS

We carried out a comprehensive search of PubMed, Scopus, Web of Science, Embase, and Google Scholar without limitation on publication date. All relevant studies which investigatived probable potential connection between Chlamydia and Mycoplasma infection and development of ovarian cancer were included.

RESULTS

Eighteen studies comprising a total of 8207 patients were evaluated in the study and this showed that the frequency of infection with Chlamydia and Mycoplasma among ovarian cancer patients was 32.6 % and 23 %, respectively. The results suggested that Chlamydia trachomatis infection increased the overall risk for ovarian cancer by 1.344 fold (OR: 1.344; 95 %CI: 1.19-1.50). Moreover, infection with Mycoplasma infections showed a week but not significant increased risk of ovarian cancer (OR: 1.12; 95 %CI: 0.86-1.44). However, the test for heterogeneity was significant among these studies.

CONCLUSION

This study confirmed the clinical relevance of Chlamydia and Mycoplasma infection and development of the ovarian cancer risk, although the significance was marginal and study heterogeneity was significant. This highlights the need for further studies in this area.

The sRNA Regulated Protein DdbA Is Involved in Development and Maintenance of the Chlamydia trachomatis EB Cell Form

The chlamydial small non coding RNA, IhtA, regulates the expression of both HctA and DdbA, the uncharacterized product of the C. trachomatis L2 CTL0322 gene. HctA is a small, highly basic, DNA binding protein that is expressed late in development and mediates the condensation of the genome during RB to EB differentiation. DdbA is conserved throughout the chlamydial lineage, and is predicted to express a small, basic, cytoplasmic protein. As it is common for sRNAs to regulate multiple mRNAs within the same physiological pathway, we hypothesize that DdbA, like HctA, is involved in RB to EB differentiation. Here, we show that DdbA is a DNA binding protein, however unlike HctA, DdbA does not contribute to genome condensation but instead likely has nuclease activity. Using a DdbA temperature sensitive mutant, we show that DdbAts creates inclusions indistinguishable from WT L2 in size and that early RB replication is likewise similar at the nonpermissive temperature. However, the number of DdbAts infectious progeny is dramatically lower than WT L2 overall, although production of EBs is initiated at a similar time. The expression of a late gene reporter construct followed live at 40°C indicates that late gene expression is severely compromised in the DdbAts strain. Viability assays, both in host cells and in axenic media indicate that the DdbAts strain is defective in the maintenance of EB infectivity. Additionally, using Whole Genome Sequencing we demonstrate that chromosome condensation is temporally separated from DNA replication during the RB to EB transition. Although DdbA does not appear to be directly involved in this process, our data suggest it is a DNA binding protein that is important in the production and maintenance of infectivity of the EB, perhaps by contributing to the remodeling of the EB chromosome.

CRISPR Interference To Inducibly Repress Gene Expression in Chlamydia trachomatis

The ability to inducibly repress gene expression is critical to the study of organisms, like Chlamydia, with reduced genomes in which the majority of genes are likely to be essential. We recently described the feasibility of a CRISPR interference (CRISPRi) system to inducibly repress gene expression in Chlamydia trachomatis. However, the initial system suffered from some drawbacks, primarily leaky expression of the anhydrotetracycline (aTc)-inducible dCas9 ortholog and plasmid instability, which prevented population-wide studies (e.g., transcript analyses) of the effects of knockdown. Here, we describe various modifications to the original system that have allowed us to measure gene expression changes within a transformed population of C. trachomatis serovar L2. These modifications include (i) a change in the vector backbone, (ii) the introduction of a weaker ribosome binding site driving dCas9 translation, and (iii) the addition of a degradation tag to dCas9 itself. With these changes, we demonstrate the ability to inducibly repress a target gene sequence, as measured by the absence of protein by immunofluorescence analysis and by decreased transcript levels. Importantly, the expression of dCas9 alone (i.e., without a guide RNA [gRNA]) had minimal impact on chlamydial growth or development. We also describe complementation of the knockdown effect by introducing a transcriptional fusion of the target gene 3' to dCas9. Finally, we demonstrate the functionality of a second CRISPRi system based on a dCas12 system that expands the number of potential chromosomal targets. These tools should provide the ability to study essential gene function in Chlamydia.

A Comparison of US Clinical Laboratory Chlamydia and Gonorrhea Testing Practices Before and After the 2014 Centers for Disease Control and Prevention Testing Recommendations

BACKGROUND

Adherence to recommended laboratory testing practices is crucial for sexually transmitted infection prevention and control. The objective of this article is to compare Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) testing practices of US clinical laboratories in 2013 before the updated 2014 Centers for Disease Control and Prevention recommendations and in 2015 after the updated recommendations.

METHODS

A total of 236 clinical laboratories participated in surveys about their 2013 and 2015 CT and NG testing practices, including questions on specimen types collected and assays used.

RESULTS

There was an increase of 5 laboratories offering CT nucleic acid amplification testing (NAAT) from 2013 to 2015 and an increase of 5 laboratories offering NG NAAT. There was a net increase of 3 laboratories accepting urine for CT and NG NAAT, the preferred specimen type for male individuals. There was not a net increase in the total number of laboratories accepting vaginal swabs for CT NAAT (n = 89 in 2013 and 2015), the preferred specimen type for female individuals, but there was an increase of 3 laboratories accepting vaginal swabs for NG NAAT. The number of laboratories performing NG susceptibility testing decreased from 100 in 2013 to 89 in 2015 (χ2 = 1.07, P > 0.10).

CONCLUSIONS

There were no major changes in testing practices in the 2-year period from 2013 to 2015. However, there were some small shifts, including increases in the use of NAATs, acceptance of Centers for Disease Control and Prevention-preferred specimen types for CT/NG, and changes in usage of assays by manufacturer.

The growing repertoire of genetic tools for dissecting chlamydial pathogenesis

Multiple species of obligate intracellular bacteria in the genus Chlamydia are important veterinary and/or human pathogens. These pathogens all share similar biphasic developmental cycles and transition between intracellular vegetative reticulate bodies and infectious elementary forms, but vary substantially in their host preferences and pathogenic potential. A lack of tools for genetic engineering of these organisms has long been an impediment to the study of their biology and pathogenesis. However, the refinement of approaches developed in C. trachomatis over the last 10 years, and adaptation of some of these approaches to other Chlamydia spp. in just the last few years, has opened exciting new possibilities for studying this ubiquitous group of important pathogens.