Detection of Chlamydia trachomatis by nucleic acid sandwich hybridization

Abstract Chromosomal DNA fragments from Chlamydia trachomatis serotype L2 were shotgun-cloned into pBR322. A C. trachomatis -specific clone was further subcloned to produce specific DNA reagents for the identification of C. trachomatis by nucleic acid sandwich hybridization. The chosen DNA reagents from serotype L2 also hybridized with all the other chlamydial serotypes tested, but not with the DNA from 41 unrelated organisms. The sensitivity of the sandwich hybridization test was 10⁶ DNA molecules. The applicability of the test for routine diagnostic use was demonstrated by a pilot study in which C. trachomatis was directly detected from genital specimens.     

Reliability of detecting rRNA sequences of Chlamydia trachomatis with fluorescence in situ hybridization without amplification

OBJECTIVE: To use fluorescence in situ hybridization (FISH) using ribosomal RNA (rRNA) oligonucleotide probes as the target nucleic acid for the detection of Chlamydia trachomatis. STUDY DESIGN: Suitable sequences selected from the rRNA sequence of C trachomatis were labeled with a fluorescent dye and used in FISH for detecting chlamydial inclusion bodies and/ or elementary bodies in paraformaldehyde-fixed urogenital swab samples. The sensitivity and specificity of the FISH assay were compared with those of the polymerase chain reaction (PCR) using plasmid primers. Positive known C trachomatis-infected McCoy cells were used as positive controls. Urogenital swab specimens that were C trachomatis negative on culture and PCR were used as negative controls. RESULT: Among the 128 samples included in the study, FISH was positive in 28 (21.8%) and PCR in 33 (25.7%). A significant correlation was found between the 2 detection methods. Results of PCR and FISH were consistent in 115 of the 128 samples (R = 0.89). Thirteen samples showed discordant results. Of these, 9 FISH negative samples were PCR positive and 4 FISH positive samples were PCR negative. CONCLUSION: FISH was a highly specific and fairly sensitive technique for detecting C trachomatis. Signal amplification techniques and use of different fluorophores may further increase the sensitivity of this technique.     

Detection and differentiation of chlamydiae by fluorescence in situ hybridization

Chlamydiae are important pathogens of humans and animals but diagnosis of chlamydial infections is still hampered by inadequate detection methods. Fluorescence in situ hybridization (FISH) using rRNA-targeted oligonucleotide probes is widely used for the investigation of uncultured bacteria in complex microbial communities and has recently also been shown to be a valuable tool for the rapid detection of various bacterial pathogens in clinical specimens. Here we report on the development and evaluation of a hierarchic probe set for the specific detection and differentiation of chlamydiae, particularly C. pneumoniae, C. trachomatis, C. psittaci, and the recently described chlamydia-like bacteria comprising the novel genera Neochlamydia and PARACHLAMYDIA: The specificity of the nine newly developed probes was successfully demonstrated by in situ hybridization of experimentally infected amoebae and HeLa 229 cells, including HeLa 229 cells coinfected with C. pneumoniae and C. trachomatis. FISH reliably stained chlamydial inclusions as early as 12 h postinfection. The sensitivity of FISH was further confirmed by combination with direct fluorescence antibody staining. In contrast to previously established detection methods for chlamydiae, FISH was not susceptible to false-positive results and allows the detection of all recognized chlamydiae in one single step.     

Detection by multiplex polymerase chain reaction and typing of Chlamydia trachomatis isolates

Abstract The multiplex polymerase chain reaction (PCR) was applied for the detection of the Chlamydia trachomatis chromosome and plasmid. The multiplex PCR demonstrated a sensitivity of 0.8 fg of chlamydial DNA, corresponding to the detection of about 5 copies of the plasmid. Analysis of 195 genital specimens collected randomly from a female population, showed that the multiplex PCR is more sensitive and rapid than culturing for detecting Chlamydia trachomatis . Moreover, sequencing of the II variable domain of the ompl gene, directly from DNA of the clinical specimens, appears to be a simple and rapid method for determining serovar isolates.     

Interaction of Chlamydia trachomatis with human genital epithelium in culture

Primary cultures of human endometrial and ectocervical epithelial cells were examined as a new model system to study genital infection by Chlamydia trachomatis. Initial studies demonstrated that these cells were indeed susceptible to chlamydial infection. Inocula, adjusted to produce inclusions in 50 to 80% of equivalent numbers of standard McCoy cells, resulted in infection rates of approximately 15 to 30% for the columnar cells of the endometrium and 5 to 10% for the squamous cells of the ectocervix. Exposure of cultures to DEAE-dextran and centrifugation-assisted inoculation, manipulations reported to enhance infection of HeLa and McCoy cells, did not alter the number of inclusion-positive genital cells. Addition of cycloheximide to the post-inoculation culture medium slightly increased numbers of inclusion-bearing cells while growth of genital cells in hormone-supplemented medium resulted in a variable effect on inclusion development and a significant reduction in the association of radiolabelled organisms with these cells. The basis for the different levels of infection in McCoy versus genital cell cultures was revealed by immunofluorescence analysis of chlamydial association with host cells immediately after inoculation. Chlamydiae failed to adhere to many cells in the genital cell cultures while adherence to McCoy cells was uniform. In addition, the association of radiolabelled C. trachomatis was significantly lower with genital cells than with McCoy cells. Finally, culture conditions were defined which markedly inhibited inclusion development without an immediate loss of chlamydial growth potential. This investigation indicates that primary genital cell cultures are susceptible to chlamydial infection and will be valuable for studies on the nature of C. trachomatis interactions with natural human target cells.     

Chlamydia trachomatis infections in infants.

In recent years considerable progress has been made in understanding chlamydial infections. The spectrum of pediatric Chlamydia trachomatis infection includes neonatal inclusion conjunctivitis, infantile pneumonia, occasional respiratory or genital tract infections in older children and sexually transmitted diseases in adolescents. The role of maternal chlamydial infection in prematurity and in perinatal death is currently an area of active study. We outline the current knowledge of the biologic characteristics of C. trachomatis, the epidemiologic features of chlamydial infection, and the clinical aspects, diagnosis and treatment of neonatal chlamydial infections.     

Detection of Chlamydia trachomatis in clinical specimens by nucleic acid spot hybridization

A nucleic acid spot hybridization assay was used to detect Chlamydia trachomatis DNA. The hybridization probes included DNA isolated from elementary bodies of lymphogranuloma venereum (LGV) strains and cloned fragments of both chromosomal and plasmid DNA. The sensitivity of the test was in the range 10 to 100 pg homologous DNA and 10 in vitro infected cells. Cross-reactivity with bacterial DNA was avoided when purified chlamydia-specific DNA fragments were used as probes. C. trachomatis was detectable in most of the clinical specimens with large amounts of infectious particles. Also some isolation-negative specimens gave a positive signal in the test.     

Detection of Chlamydia trachomatis in pregnant women by the Papanicolaou technique, enzyme immunoassay and polymerase chain reaction

OBJECTIVE: To compare Papanicolaou staining, enzyme immunoassay (EIA) and the polymerase chain reaction (PCR) techniques for detecting Chlamydia trachomatis in pregnant women. STUDY DESIGN: Endocervical specimens were taken randomly from 125 pregnant women with or without symptoms. These women attended their first medical consultation at the Regional General Ignacio Zaragoza Hospital. Samples were analyzed for detection of C trachomatis. When results differed between tests, specimens were evaluated by direct immunofluorescence staining. RESULTS: The prevalence of chlamydial infection was 2.4%. The characteristics of patients positive for Chlamydia were: average age, 24 years; first sexual encounter at age 21 years, one partner and six to nine months of gestation. The sensitivity, specificity, accuracy, positive predictive values and negative predictive values were 100%, 99.18%, 99.20%, 75% and 100%, respectively, for Papanicolaou staining; 100%, 92.62%, 92%, 25% and 100% for EIA; and 100%, 100%, 100% and 100% for PCR. CONCLUSION: Both Papanicolaou staining and PCR were adequate for diagnosis of C trachomatis infection. EIA was not reliable and therefore is not recommended for use as a diagnostic technique in a pregnant population with low risk and low prevalence.     

High-sensitivity quantitative PCR platform

Real-time PCR methods have become widely used within the past few years. However, real-time PCR is rarely used to study chronic diseases with low pathogen loads, presumably because of insufficient sensitivity. In this report, we developed an integrated nucleic acid isolation and real-time PCR platform that vastly improved the sensitivity of the quantitative detection of the intracellular bacterium, Chlamydia spp., by fluorescence resonance energy transfer real-time PCR. Determinants of the overall detection sensitivity were analyzed by extracting nucleic acids from bovine milk specimens spiked with low amounts of chlamydial organisms. Nucleic acids were optimally preserved and recovered by collection in guanidinium stabilization buffer, binding to a matrix of glass fiber fleece, and elution in low volume. Step-down thermal cycling and an excess of hot-start Taq polymerase vastly improved the robustness and sensitivity of the real-time PCR while essentially maintaining 100% specificity. The amplification of Chlamydia 23S rRNA allowed for the differentiation of chlamydial species and was more robust at low target numbers than amplification of the omp1 gene. The best combined method detected single targets per a 100-microL specimen equivalent in a 5-microL real-time PCR input. In an initial application, this high-sensitivity real-time PCR platform demonstrated a high prevalence of chlamydial infection in cattle.     

The first performance report for the Bio-Rad Dx CT/NG/MG assay for simultaneous detection of Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium in urogenital samples

We evaluated the clinical performance of the Bio-Rad Dx CT/NG/MG assay for the detection of Chlamydia trachomatis, Mycoplasma genitalium and Neisseria gonorrhoeae in urogenital samples in comparison with the Roche COBAS? TaqMan? CT assay for C. trachomatis and an in-house TaqMan PCR assay for M. genitalium. Swab specimens were cultured for N. gonorrhoeae. In this prospective study, urogenital samples were obtained from symptomatic and asymptomatic patients attending the sexually transmitted disease clinic of Bordeaux, France, from January to April 2010. A total of 658 clinical specimens (259 male and 180 female urines, 191 vaginal, 21 endocervical and 7 urethral swabs) from 453 patients were analyzed. The prevalence of C. trachomatis and M. genitalium infections was 8.1% (21/260) and 1.9% (5/260) in men and 10.4% (20/193) and 2.1% (4/193) in women, respectively. The Bio-Rad Dx CT/NG/MG clinical sensitivity was 100% for C. trachomatis and M. genitalium in men and women. In male urine, the clinical specificity was 99.6% for C. trachomatis and 100% for M. genitalium. In women, the specificity was 99.5% for swabs and 100% for urines for detecting C. trachomatis and M. genitalium. All seven N. gonorrhoeae PCR-positive samples were also positive by culture. Patients were co-infected in 5/57 cases (8.8%), with C. trachomatis and M. genitalium in three cases, and C. trachomatis and N. gonorrhoeae in two cases. In conclusion, the Bio-Rad Dx CT/NG/MG assay can be recommended for the simultaneous detection of C. trachomatis, M. genitalium and N. gonorrhoeae in urogenital specimens of symptomatic and asymptomatic individuals.     

Prevalence of chlamydial genital infection and associated risk factors in adolescent females at an urban reproductive health care center in Croatia

The study was undertaken to determine the prevalence of chlamydial genital infection in sexually active, urban adolescent females 15-19 years; to identify behavioral, demographic, and clinical factors associated with chlamydial infections; and to develop criteria for potential screening strategies. 500 adolescent women, median age 17.7 years, who visited gynecological outpatient clinic in Children's Hospital Zagreb for different reasons were enrolled in this study. Gynecological exam, colposcopy, detection of chlamydial infection by the rapid direct immunoassay of endocervical swab (Clearview Chlamydia-Unipath), endocervical cytological examination--Papanicolaou smear, and questionnaire to obtain demographic, social, behavioral and presence of symptoms data were performed. Positive Chlamydia trachomatis test were found in 16.4% of participants, cytologic cervical abnormalities--cervical intraepithelial neoplasia (CIN I-CIN III) were found in 25.2% and cytological signs of Human papilloma virus were found in 11.4%. Stepwise multivariate logistic regression analysis identified five factors associated with infection: the age of menarche < or =13 years, > or =4 lifetime sexual partners, non-use of contraception (rare or never), cervical friability, and abnormal Papanicolaou test. Urban adolescent sexually active women are at high risk for chlamydial infection and other sexually transmitted diseases including HIV infection. Association between chlamydial genital infection and risk-taking sexual and contraceptive behavior was found. Routine Chlamydia trachomatis testing for this population is recommended as well as implementation of school based sexual health education because of their risk-taking sexual behavior.     

Sensitivity and specificity of the Papanicolaou-stained cervical smear in the diagnosis of Chlamydia trachomatis infection

Two hundred young women had simultaneously prepared cultures for Chlamydia trachomatis and cervical smears; they also completed a questionnaire. Twelve of the chlamydial cultures were positive. There was poor correlation between the culture results and the cytologic morphology or symptoms. On initial blind reading, only 10% of the smears cytologically interpreted as positive were actually positive by culture. Under the most favorable (non-blind) interpretation, only 23% of the smears cytologically interpreted as positive for chlamydial infection were also culture positive. Because of the high incidence of false positives, we conclude that routine cytologic examination of Papanicolaou-stained smears is not an acceptable method for the diagnosis of chlamydial infections of the cervix. Immunoperoxidase staining of duplicate smears did not appear to be a successful replacement for culture.     

Blockade of epithelial membrane protein 2 (EMP2) abrogates infection of Chlamydia muridarum murine genital infection model

New methods are needed to eradicate or prevent Chlamydia trachomatis infections. Blockade of epithelial membrane protein 2 (EMP2) by genetic silencing or neutralizing polyclonal antibody reduced chlamydial infectivity in vitro . This study tests the prediction that recombinant anti-EMP2 diabody could reduce early chlamydial infection of the genital tract in vivo . In a murine infection model, pretreatment with anti-EMP2 diabody, as compared with control diabody, significantly reduced bacterial load, tissue production of inflammatory cytokines, recruitment of polymorphonuclear leukocytes, and local tissue inflammation. These findings support EMP2 as a potential preventative and therapeutic target for genital chlamydial infection.     

Vaccines for Chlamydia infections of the female genital tract.

Genital infection with Chlamydia trachomatis is an escalating global public health concern causing considerable morbidity and socioeconomic burden worldwide. Although antibiotics are used to treat symptomatic urogenital infections, chlamydial infection remains asymptomatic in approximately 50% of infected men and 70% of infected women. The major clinical manifestations of genital chlamydial infection in women include mucopurulent cervicitis, endometritis and pelvic inflammatory disease. Genital infection with C. trachomatis markedly enhances the risk for reproductive tract sequelae in women, including tubal factor infertility, chronic pain and ectopic pregnancy. Definitive infection control of chlamydial infections will likely be achievable through a safe and efficacious vaccine. This will require identifying protective chlamydial antigens in animal models as well as identifying effective adjuvants and delivery systems that target subunit vaccines to immune inductive sites or secondary lymphoid tissues, and will be safe for use in humans.     

Chlamydia trachomatis infections in women with urogenital symptoms.

Chlamydia trachomatis was isolated from 30 to 100 women attending a family physician''s office with dysuria, frequency or vaginal discharge, compared with 2 of 30 asymptomatic women. Multiple infections were common: C. trachomatis coexisted with Gardnerella vaginalis, Candida albicans, Trichomonas vaginalis or a bacterial cause of urinary tract infection in 15 patients. C. trachomatis was isolated alone from 15 symptomatic women. The source of the positive culture was not always the site of symptoms. C. trachomatis was isolated from both the cervix and the urine of 9 patients, either simultaneously or sequentially. The probability of finding a chlamydial infection was 30% in young women with vaginal discharge alone, 33% in those with dysuria and frequency alone and 53% in those with abdominal or pelvic pain in addition to lower urogenital tract symptoms.     

Detection and Differentiation of Chlamydiae by Fluorescence In Situ Hybridization

Chlamydiae are important pathogens of humans and animals but diagnosis of chlamydial infections is still hampered by inadequate detection methods. Fluorescence in situ hybridization (FISH) using rRNA-targeted oligonucleotide probes is widely used for the investigation of uncultured bacteria in complex microbial communities and has recently also been shown to be a valuable tool for the rapid detection of various bacterial pathogens in clinical specimens. Here we report on the development and evaluation of a hierarchic probe set for the specific detection and differentiation of chlamydiae, particularly C. pneumoniae, C. trachomatis, C. psittaci, and the recently described chlamydia-like bacteria comprising the novel genera Neochlamydia and Parachlamydia. The specificity of the nine newly developed probes was successfully demonstrated by in situ hybridization of experimentally infected amoebae and HeLa 229 cells, including HeLa 229 cells coinfected with C. pneumoniae and C. trachomatis. FISH reliably stained chlamydial inclusions as early as 12 h postinfection. The sensitivity of FISH was further confirmed by combination with direct fluorescence antibody staining. In contrast to previously established detection methods for chlamydiae, FISH was not susceptible to false-positive results and allows the detection of all recognized chlamydiae in one single step.     

儿童呼吸道肺炎支原体感染的实验室诊断

目的同时用目前常用的几种诊断肺炎支原体（MP）感染的实验方法检测MP,相互比较,得出适于常规诊断MP感染的方法或组合。方法搜集我院于2006年10月至2007年5月间以呼吸道感染入院儿童病例75例,采集其咽拭子和双份血清标本,以多种方法检测有无MP感染：培养法、EIA法测抗原、PCR法测MP-DNA,ELISA法测MP特异性IgG、IgA型抗体以及捕获法ELISA测MP特异性IgM型抗体。结果上述75例儿童中,共计有12例感染MP。以此为基础,上述各方法的敏感度分别是：培养法（25％）、EIA法测抗原（8．3％）、PCR法测MP-DNA（75．0％）、ELISA法测MP特异性IgA型抗体（单份血清为0,双份血清为33．3％）、捕获法ELISA测MP特异性IgM型抗体（单份血清为66．7％,双份血清为100％）。特异度分别是：100％、96．8％、93．7％（93．7％）、98．4％（98．4％）。PCR法和捕获法ELISA测MP特异性IgM型抗体结合后敏感度和特异度分别达到100％和95．2％。结论PCR法测MP-DNA和捕获法ELISA测MP特异性IgM型抗体的组合可高效地诊断MP感染,因而可作为临床诊断MP感染的一个常规组合。     

A predominant role for antibody in acquired immunity to chlamydial genital tract reinfection

Acquired immunity to murine Chlamydia trachomatis genital tract reinfection has long been assumed to be solely dependent on cell-mediated immunity. However, in this study, we identify a previously unrecognized protective role for Ab. Immunity develops in Ab-deficient mice following the resolution of primary chlamydial genital infection. Subsequent depletion of CD4+ T cells, but not CD8+ T cells, in those immune Ab-deficient mice before secondary infectious challenge, resulted in an infection that did not resolve. Passive immunization with immune (convalescent) serum conferred a marked level of protective immunity to reinfection, which was characterized by a striking decrease in bacterial shedding, from >100,000 inclusion forming units to fewer than 10 inclusion forming units, and a shortened duration of infection. Furthermore, mAbs to the chlamydial major outer membrane protein and LPS conferred significant levels of immunity to reinfection and reduced chlamydial shedding by >100-fold. Anti-heat shock protein 60 mAb had no protective effect. In contrast to the marked protective efficacy of immune serum on reinfection, the course of primary infection was essentially unaltered by the passive transfer of immune serum. Our results convincingly demonstrate that Abs contribute importantly to immunity to chlamydial genital tract reinfection, and that Ab-mediated protection is highly dependent on CD4+ T cell-mediated adaptive changes that occur in the local genital tract tissues during primary infection. These results impact our understanding of immunity to chlamydial genital infection and may provide important insight into vaccine development.     

Prévalence de l'infection cervicale à Chlamydia trachomatis dans une population féminine consultant pour contraception.

OBJECTIVES: To determine the prevalence and risk indicators of cervical infection due to Chlamydia trachomatis among female patients consulting for contraception and to evaluate an enzyme immunoassay for the detection of C. trachomatis in this setting. DESIGN: Prevalence study. Endocervical specimens were analysed by means of culture and enzyme immunoassay. C. trachomatis infection was diagnosed through culture. SETTING: A hospital family planning clinic in Trois-Rivières, Que. SUBJECTS: All 533 female patients who consulted for contraception between November 1986 and March 1988. Results of culture were available for 495 patients. MAIN OUTCOME MEASURE: Demographic, epidemiologic and clinical information was collected by means of a standard questionnaire and a gynecologic examination. MAIN RESULTS: The prevalence rate of chlamydial infection was 9% (45/495). Enzyme immunoassay detected 37 (82%) of the infections. The mean age of the patients was 19.8 years, and 98% of the infections were diagnosed in those aged 25 years or less. The variables significantly associated with C. trachomatis infection were having more than one sexual partner in the preceding year (odds ratio [OR] 2.9; 95% confidence limits [CL] 1.7 and 5.0) and having more than one partner in the preceding 3 months (OR 2.3; 95% CL 1.2 and 4.3). These two indicators would have detected 58% and 22% of the infections respectively. CONCLUSIONS: Screening for C. trachomatis infection by means of enzyme immunoassay should be proposed to all female patients aged 25 years or less consulting for contraception in our clinic. Such screening may prove to be an effective preventive measure in other similar clinical settings.     

Induction of HLA class I-restricted CD8+ CTLs specific for the major outer membrane protein of Chlamydia trachomatis in human genital tract infections.

HLA class I-restricted CD8+ CTLs specific for the major outer membrane protein (MOMP) of Chlamydia trachomatis are present in the peripheral blood of humans who acquired genital tract infections with the organism. Three HLA-A2-restricted epitopes and two HLA-B51-restricted epitopes were identified in serovar E-MOMP. One of the five epitopes spans a variable segment of MOMP and is likely a serovar E-specific epitope. The other four epitopes are localized in constant segments and are C. trachomatis species specific. CTL populations specific for one or more of the four constant segment epitopes were isolated from all 10 infected subjects tested, regardless of infecting serovars, but from only one of seven uninfected subjects tested. The CTLs failed to recognize corresponding peptides derived from Chlamydia pneumoniae MOMP, further suggesting that they indeed resulted from genital tract infections with C. trachomatis. Significantly, ME180 human cervical epithelial cells productively infected with C. trachomatis were killed by the MOMP peptide-specific CTLs. Further investigations of the ability of such CTLs to lyse normal infected epithelial cells and their presence at inflamed sites in the genital tract will help understand the protective or pathological role of CTLs in chlamydial infections. The MOMP CTL epitopes may be explored as potential components of a subunit vaccine against sexually transmitted diseases caused by C. trachomatis. Moreover, the knowledge provided here will facilitate studies of HLA class I pathways of chlamydial Ag processing and presentation in physiologically relevant human APCs.