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PubMed1993

Detection of serum antibodies to Chlamydia trachomatis in patients with chlamydial and nonchlamydial pelvic inflammatory disease by the IPAzyme Chlamydia and enzyme immunoassay.

A novel serological test, IPAzyme Chlamydia (Savyon Diagnostics Ltd., Beer Sheva, Israel), was compared with an enzyme immunoassay (EIA) for the ability to detect serum immunoglobulin G and A antibodies in the diagnosis of acute chlamydial pelvic inflammatory disease. In comparison with cell culture, which is the "gold standard," IPAzyme Chlamydia and EIA exhibited sensitivities of 63 and 68% and specificities of 76 and 87%, respectively. Thus, IPAzyme Chlamydia offers no advantages over the EIA, and neither serological test can be recommended for the diagnosis of acute Chlamydia trachomatis infection. So far, conventional cell culture remains the most reliable diagnostic test for chlamydial pelvic inflammatory disease.

Antibodies, Bacterial↗
PubMed2003

Who has chlamydia? The prevalence of genital tract Chlamydia trachomatis within Portsmouth and South East Hampshire, UK.

OBJECTIVE: To determine the prevalence of genital tract Chlamydia trachomatis infection in women and men attending different health care settings in Portsmouth and South East Hampshire. DESIGN: Prospective, opportunistic screening. SETTING: Multiple health care sites. PARTICIPANTS: Consenting sexually active women and men. INTERVENTION: A urine sample was tested for Chlamydia trachomatis and positive patients were offered treatment and partner notification. MAIN OUTCOME MEASURES: The presence or absence of chlamydia infection according to age, gender, health care setting and reason for attendance. RESULTS: A total of 14,756 samples were tested giving an overall prevalence of 9.6%. The prevalence was significantly higher in women attending for a termination of pregnancy, antenatal care, women and men attending genitourinary medicine and in those with genital tract symptoms. The prevalence was different for men and women at different ages. CONCLUSION: The prevalence of genital Chlamydia trachomatis infection was high but differed at various health care settings and by reason for attendance.

Adolescent↗
PubMed1993

Evaluation of Pharmacia Chlamydia EIA for diagnosis of genital infections caused by Chlamydia trachomatis.

A new enzyme-immunoassay test (EIA), Pharmacia Chlamydia EIA, was evaluated in comparison with isolation in cell culture for the diagnosis of genital infections caused by Chlamydia trachomatis. Endocervical and endourethral specimens were collected from 913 patients (875 female and 38 male patients respectively). Sensitivity, specificity, positive predictive and negative predictive values for this test were 89.4%, 99.2%, 85.8% and 99.4% respectively. Where discrepancies between the 2 techniques occurred, the remainder of the EIA buffer was stained for chlamydial antigen by direct immunofluorescence using the Syva Microtrak Chlamydia trachomatis Direct Specimen Test. Laboratory strains of various micro-organisms that may be present in genital specimens did not cross react with the EIA test except for Staphylococcus aureus and Group B Streptococcus at very high concentrations. The Pharmacia Chlamydia EIA is suitable for a laboratory which handles a large number of chlamydial specimens daily. However, when interpreting EIA results, the prevalence of chlamydial infection in the patient population should be established. At present, EIA tests are unsuitable as the only test for chlamydial diagnosis in low risk populations.

Bacteriological Techniques↗
PubMed2005

Immunocomb Chlamydia bivalent assay to study Chlamydia species-specific antibodies in patients with coronary heart disease.

BACKGROUND & OBJECTIVE: Serological evidences suggested an association between Chlamydia pneumoniae infection and coronary heart disease (CHD). Efficacy of available serological tests for detection of C. pneumoniae antibody has been debated. The present study was carried-out to assess the efficacy of Immunocomb Chlamydia bivalent IgG assay vis-à-vis micro immunofluorescence (MIF) test in detecting C. pneumoniae and C. trachomatis--specific antibodies in patients with CHD. METHODS: Serum samples collected from clinically confirmed cases of CHD (n=114) were subjected to Immunocomb Chlamydia bivalent assay and the standard MIF test. Antibodies specific to C. pneumoniae and C. trachomatis were detected quantitatively. RESULTS: Though Immunocomb Chlamydia bivalent test yielded 73.7 per cent positivity for C. pneumoniae- specific IgG antibody (compared to 50.8% by MIF), the specificity of Immunocomb was found only 32.14 per cent. Positive and negative predictive values of Immunocomb assay were 54.8 and 60.0 per cent respectively. INTERPRETATION & CONCLUSION: The findings of the present study indicated that though Immunocomb assay was inferior to MIF, it can be used as a method for presumptive serology due to its rapidity and ease of performance. Wherever possible, one or more additional tests should also be performed to increase the specificity of such studies.

Aged↗
PubMedDate not supplied

Evaluation of a new chemiluminometric immunoassay, Magic Lite Chlamydia, for detecting Chlamydia trachomatis antigen from urogenital specimens.

The chemiluminometric sandwich immunoassay, Magic Lite Chlamydia by Ciba Corning (Medfield, MA), using one Chlamydia trachomatis-specific monoclonal antibody conjugated with acridinium ester and one polyclonal immobilized to magnetic particles, was compared to cell culture in 291 urogenital specimens from 92 men and 102 women tested both in the cervix and urethra. The proportion of patients with positive culture results ranged from 11.8% among the women to 15% among the men, using microculture plates and peroxidase-antiperoxidase staining procedure with genus-specific monoclonal antibody (Orthodiagnostics, Raritan, NJ). The chemiluminometric method for detecting Chlamydia trachomatis antigen showed an overall sensitivity of 72.4%, specificity of 97.7%, positive predictive value of 77.7%, and negative predictive value of 96.9%. A higher sensitivity of Magic Lite was found in clinical specimens yielding more than 10 inclusions by well in cell culture. The newly developed chemiluminometric test, easy to perform, had the same limits in terms of sensitivity and positive predictive value than the other widely-used existing tests for detecting Chlamydia trachomatis antigen from urogenital specimens.

Adult↗
PubMed1991

[Recovery of Chlamydia pneumoniae and Chlamydia trachomatis in a patient with recurrent tonsillitis, bronchitis and otitis media with effusion].

We report a case of recurrent tonsillitis and otitis media with effusion (OME) from which Chlamydia trachomatis was isolated. Chlamydia pneumoniae, a newly recognized species of Chlamydia, was also recovered from the tonsillar and bronchial swabs. A 8-year-old girl was seen on February 23, 1988, because of a running nose, a productive cough and bilateral hearing difficulty. She had a history of recurrent tonsillitis. The diagnosis was acute sinusitis with tubal obstruction, then cefixime was prescribed. Her symptoms were once resolved, for the time being but she came back to the hospital a week later with a bilateral ear-ache. The tympanic membranes were injected and characteristically retracted. Her left ear showed type B tympanogram (effusion). Tympanocentesis was performed to remove middle-ear effusion, from which C. trachomatis but no ordinary bacterium was isolated. Therefore rokitamycin 300 mg/day was administered for a week. Her condition improved, however, a rhinorrhea, a plugged ear sensation and a hacking cough returned in a month. She was admitted to the hospital on May 10, for tympanostomy and grommet insertion, but from the day before admission, she had a sore throat with fever (39.2 degrees C). The surgery was withheld until May 26. When adenotonsillectomy and grommets insertion were undertaken, C. trachomatis had disappeared from the middle-ear effusion, but C. pneumoniae was recovered from both tonsillar and bronchial swabs. Readministration of rokitamycin was performed and to date (June, 1990) she remains well.

Bronchitis↗
PubMed2001

Non-detection of Chlamydia species in carotid atheroma using generic primers by nested PCR in a population with a high prevalence of Chlamydia pneumoniae antibody.

BACKGROUND: The association of Chlamydia pneumoniae with atherosclerosis is controversial. We investigated the presence of C. pneumoniae and other Chlamydia spp. in atheromatous carotid artery tissue. METHODS: Forty elective carotid endarterectomy patients were recruited (27 males, mean age 65 and 13 females mean age 68), 4 had bilateral carotid endarterectomies (n= 44 endarterectomy specimens). Control specimens were taken from macroscopically normal carotid artery adjacent to the atheromatous lesions (internal controls), except in 8 cases where normal carotid arteries from post mortem (external controls) were used. Three case-control pairs were excluded when the HLA DRB gene failed to amplify from the DNA. Genus specific primers to the major outer membrane protein (MOMP) gene were used in a nested polymerase chain reaction (nPCR) in 41 atheromatous carotid specimens and paired controls. PCR inhibition was monitored by spiking with target C. trachomatis. Atheroma severity was graded histologically. Plasma samples were tested by microimmunofluorescence (MIF) for antibodies to C. pneumoniae, C. trachomatis and C. psittaci and the corresponding white cells were tested for Chlamydia spp. by nPCR. RESULTS: C. pneumoniae was not detected in any carotid specimen. Twenty-five of 38 (66%) plasma specimens were positive for C. pneumoniae IgG, 2/38 (5%) for C. trachomatis IgG and 1/38 (3%) for C. psittaci IgG. CONCLUSIONS: We were unable to show an association between the presence of Chlamydia spp. and atheroma in carotid arteries in the presence of a high seroprevalence of C. pneumoniae antibodies in Northern Ireland.

Adult↗
PubMedDate not supplied

Chlamydia trachomatis species specific serology: ImmunoComb Chlamydia bivalent versus microimmunofluorescence (MIF).

The ImmunoComb Chlamydia Bivalent IgG/IgA (Orgenics, Israel) is a new quantitative serologic test that employs LPS extracted Chlamydia trachomatis L2 and LPS extracted Chlamydia pneumoniae elementary bodies on two separate antigenic spots. The Bivalent C. trachomatis specific test results were compared with microimmunofluorescence (MIF), the gold standard of chlamydial species specific serology. For C. trachomatis IgG the Bivalent was highly concordant with the MIF: the rate of positive titres (IgG > or = 1:8) was 10% vs. 11% in 100 blood donors, 18% vs. 16% in 111 obstetric patients (6% antigen prevalence), 26% vs. 22% in sterile women with open (n = 54) and 86% vs. 84% with occluded (n = 51) tubes, and 88% vs. 85% in 103 women with C. trachomatis positive cervical smears. Surprisingly, the Bivalent differed considerably from the MIF in IgA prevalence: in obstetric patients (8% vs. 4%), sterile women with open (13% vs. 6%) and occluded (71% vs. 20%) tubes, and women with positive cervical smears (78% vs. 24%). Bivalent IgA appeared to be more sensitive than MIF IgA and showed a stronger correlation with positive cervical smears in obstetric patients (sensitivity 67% vs. 0%, specificity 95% vs. 96%, positive prediction 44% vs. 0%, negative prediction 98% vs. 94%) and with tubal occlusion in sterile women (sensitivity 71% vs. 20%, specificity 87% vs. 94%, positive prediction 84% vs. 77%, negative prediction 76% vs. 55%). MIF IgM was of little diagnostic help. Supplemental to the often difficult C. trachomatis antigen detection, the easily performed Bivalent IgG/IgA appears to be of great value in routine diagnosis of genital chlamydial infections.

Adult↗
PubMed1998

Induction of apoptosis by Chlamydia psittaci and Chlamydia trachomatis infection in tissue culture cells.

The role of programmed cell death (apoptosis) in LLC-MK2 cells infected with Chlamydia trachomatis LGV2 serotype and Chlamydia psittaci 6BC strain was investigated using flow cytometry and TUNEL procedures. The number of apoptotic cells was significantly higher at 72 and 96 hours post infection in the Chlamydia infected cell cultures in comparison with mock-infected cells. We postulate the apoptotic process to be a mechanism induced by C. trachomatis and C. psittaci infection in LLC-MK2 cells.

Animals↗
PubMed1997

Association of positive Chlamydia trachomatis and Chlamydia pneumoniae immunoglobulin-gamma titers with increasing age.

STUDY OBJECTIVES: To use Chlamydia trachomatis immunoglobulin-gamma (IgG) titers to investigate the possibility of their association with ovarian cancer, and to evaluate the effectiveness of this titer in algorithmic protocols in infertility. DESIGN: Prospective, age-matched, pilot study (Canadian Task Force classification II-2). SETTING: University and university-affiliated office practice. PATIENTS: The original 30 patients were seen for follow-up of ovarian cancer (19) and at yearly examination for nonmalignant disease (10). An additional group of 21 women seen for pelvic pain and infertility was added to clarify questions that arose during the study. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Chlamydia trachomatis IgG titers were positive in 15 (79%) of 19 of women with ovarian cancer, 9 (90%) of 10 age-matched controls, and 14 (67%) of 21 patients with infertility and pain. When analyzed by age, 4 (40%) of 10 patients under 30 years and 34 (85%) of 40 patients 30 years of age or older had positive titers (p = 0.007). Of 21 women with positive Chlamydia pneumoniae titers, 17 (81 %) had positive C. trachomatis titers, and 17 (85%) of 20 with positive C. trachomatis titers had positive C. pneumoniae titers. CONCLUSION: The test kit used in this study may not be adequate in older patients due to cross-reaction with C. pneumoniae titers. Further evaluation of C. trachomatis IgG titers as a marker in the study of ovarian cancer will require titers that are more specific than those we used. Although these titers may be useful as an immunologic screening marker in infertile patients, results should be interpreted with caution. A positive test may not be evidence of C. trachomatis infection and is not an indication for specific therapy. Successful use of some currently available C. trachomatis IgG titers in algorithms for infertility may be related to a patient's age.

Adolescent↗
PubMed2005

Immunology of Chlamydia infection: implications for a Chlamydia trachomatis vaccine.

Sexually transmitted Chlamydia trachomatis infections are a serious public-health problem. With more than 90 million new cases occurring annually, C. trachomatis is the most common cause of bacterial sexually transmitted disease worldwide. Recent progress in elucidating the immunobiology of Chlamydia muridarum infection of mice has helped to guide the interpretation of immunological findings in studies of human C. trachomatis infection and has led to the development of a common model of immunity. In this review, we describe our current understanding of the immune response to infection with Chlamydia spp. and how this information is improving the prospects for development of a vaccine against infection with C. trachomatis.

Animals↗
PubMed2000

Genome sequences of Chlamydia trachomatis MoPn and Chlamydia pneumoniae AR39.

The genome sequences of Chlamydia trachomatis mouse pneumonitis (MoPn) strain Nigg (1 069 412 nt) and Chlamydia pneumoniae strain AR39 (1 229 853 nt) were determined using a random shotgun strategy. The MoPn genome exhibited a general conservation of gene order and content with the previously sequenced C.trachomatis serovar D. Differences between C.trachomatis strains were focused on an approximately 50 kb 'plasticity zone' near the termination origins. In this region MoPn contained three copies of a novel gene encoding a >3000 amino acid toxin homologous to a predicted toxin from Escherichia coli O157:H7 but had apparently lost the tryptophan biosyntheis genes found in serovar D in this region. The C. pneumoniae AR39 chromosome was >99.9% identical to the previously sequenced C.pneumoniae CWL029 genome, however, comparative analysis identified an invertible DNA segment upstream of the uridine kinase gene which was in different orientations in the two genomes. AR39 also contained a novel 4524 nt circular single-stranded (ss)DNA bacteriophage, the first time a virus has been reported infecting C. pneumoniae. Although the chlamydial genomes were highly conserved, there were intriguing differences in key nucleotide salvage pathways: C.pneumoniae has a uridine kinase gene for dUTP production, MoPn has a uracil phosphororibosyl transferase, while C.trachomatis serovar D contains neither gene. Chromosomal comparison revealed that there had been multiple large inversion events since the species divergence of C.trachomatis and C.pneumoniae, apparently oriented around the axis of the origin of replication and the termination region. The striking synteny of the Chlamydia genomes and prevalence of tandemly duplicated genes are evidence of minimal chromosome rearrangement and foreign gene uptake, presumably owing to the ecological isolation of the obligate intracellular parasites. In the absence of genetic analysis, comparative genomics will continue to provide insight into the virulence mechanisms of these important human pathogens.

Animals↗
PubMedDate not supplied

Evaluation of Abbott Testpack Chlamydia for detection of Chlamydia trachomatis in patients attending sexually transmitted diseases clinics.

This work compares a rapid solid-phase EIA (Abbott TestPack Chlamydia) to tissue culture and a direct fluorescent antibody test (Syva Microtrak) for detection of C. trachomatis in 436 patients attending two inner-city sexually transmitted diseases (STD) clinics. The prevalence of C. trachomatis by culture was 12% (5% in men, 15% in women). Overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TestPack compared to culture were 70%, 98%, 80%, and 96% respectively. In men, 12 specimens were positive by TestPack, while only eight specimens were positive by culture. Six TestPack-positive, culture-negative specimens were further evaluated by centrifugation of culture transport media and examination of the sediment for chlamydia elementary bodies (EBs) using fluorescent monoclonal antibodies to C. trachomatis. Using this procedure, five of six culture negative specimens contained EBs (revised sensitivity 85%, specificity 99%, PPV 92%, NPV 99%). In 285 women evaluable in culture and TestPack, 44 (15%) specimens were culture positive; TestPack was positive in 29 (sensitivity 66%) culture positive women. Of 241 culture negative patients, 238 had negative TestPack results (specificity 99%) and no EBs were detected in the culture-negative, TestPack-positive specimens. Twenty-three (8%) Microtrak specimens were unsatisfactory for testing; two of these were culture and TestPack positive. Therefore, of 263 specimens evaluable using Microtrak, 42 (16%) specimens were culture positive; Microtrak was positive in 32 (sensitivity 76%) culture-positive women. Abbott TestPack Chlamydia is a rapid (25 minute), visually read format requiring no specialized equipment for detection of chalmydia infections with a sensitivity comparable to that of Microtrak.

Adult↗
PubMed2001

Male sex predominance in Chlamydia trachomatis sexually acquired reactive arthritis: are women more protected by anti-chlamydia antibodies?

OBJECTIVE: To determine whether the humoral anti-chlamydia antibody response might be related to the ineffective bacterial elimination seen in patients with Chlamydia trachomatis reactive arthritis, particularly in men, who have a higher prevalence of the disease than women. METHODS: The number and specificity of the antibody responses to 27 different C trachomatis antigens were determined by western blots in serum samples from patients with C trachomatis urogenital infection, with and without reactive arthritis, with a special regard to the sex of the patients. RESULTS: Patients with reactive arthritis had antibodies to significantly fewer chlamydia antigens than those with urethritis only. Antibodies from men recognised significantly fewer antigens than antibodies from women. The IgA class antibodies were slightly more relevant than those of the IgG class for differentiation of patients with reactive arthritis from those with uncomplicated genitourinary infection. CONCLUSIONS: In patients with acute C trachomatis infection the development of reactive arthritis may be related, particularly in men, to a deficient humoral response, to antigens which perhaps play a part in the clearance of the bacteria. Men who cannot generate antibodies to a large number of antigens may be less able to contain the local infection, allowing a wide systemic dissemination of the organisms to the joints.

Adolescent↗
PubMed2003

Measurement of IgG antibodies to Chlamydia trachomatis by commercial enzyme immunoassays and immunofluorescence in sera from pregnant women and patients with infertility, pelvic inflammatory disease, ectopic pregnancy, and laboratory diagnosed Chlamydia psittaci/Chlamydia pneumoniae infection.

BACKGROUND: Screening for Chlamydia trachomatis specific antibodies is valuable in diagnosing asymptomatic pelvic inflammatory disease (PID) and tubal damage following repeated episodes of PID. The assays in current use are unsuitable for screening large numbers of samples so there is a need to develop more suitable assays. AIMS: To compare the performance of several commercial C trachomatis enzyme immunoassays (EIAs) (SeroCT, C tracho(pep), Medac p-EIA, Vircell and Labsystems C trachomatis IgG EIAs) using major outer membrane protein (MOMP), an inactivated organism EIA (Genzyme Virotech EIA), and a genus specific EIA (Platelia Chlamydia IgG) with the whole cell inclusion immunofluorescence (WIF) assay. In addition, to adapt, using time resolved fluorescence technology, the assay showing the highest correlation with WIF. METHODS: Ninety sera from patients presenting with ectopic pregnancies, 187 sera from those with a variety of types of infertility, 33 sera from cases of PID where a fourfold rise in WIF titre occurred, and 90 sera from antenatal clinic attenders were tested. A panel of 36 sera from laboratory diagnosed cases of Chlamydia psittaci/Chlamydia pneumoniae infection was also tested. RESULTS: The Genzyme Virotech EIA showed the highest rank correlation coefficient (0.82) with WIF, particularly at high WIF titres. The MOMP specific assays varied in their correlation with WIF, with rank correlation coefficients ranging from 0.70 (Medac p-EIA) to 0.80 (Vircell EIA). The Genzyme Virotech assay showed poor specificity (5.6%; 95% confidence interval (CI), 0.68% to 18.7%)--it was reactive with 34 of the panel of 36 C psittaci/C pneumoniae positive sera. The MOMP based EIAs showed high specificity, particularly the Medac p-ELISA (97.2%; 95% CI, 85.5% to 99.9%)--only one serum was reactive. In view of the good correlation between WIF and the Genzyme Virotech EIA, a time resolved fluorescence immunoassay (TRFIA) was developed using the Genzyme Virotech antigen. Using an appropriate cut off the TRFIA assay showed excellent correlation with WIF. CONCLUSIONS: The TRFIA assay may be useful as a screening assay, possibly in conjunction with one of the highly specific EIAs studied (for example, Medac p-EIA) to confirm the antibody specificity of sera selected by the screening assay.

Antibodies, Bacterial↗
PubMed2006

Clinic-based evaluation of Clearview Chlamydia MF for detection of Chlamydia trachomatis in vaginal and cervical specimens from women at high risk in China.

OBJECTIVES: To determine the performance of a rapid Chlamydia trachomatis (CT) test (Clearview Chlamydia MF) compared to the current "gold standard" (Roche Amplicor CT assay) test, and to assess acceptability of the tests to patients. METHODS: A total of 1497 women at sexually transmitted diseases (STD) clinics or re-education centres in six urban cities (Shanghai, Nanjing, Shenzhen, Guangzhou, Chengdu and Fuzhou) in China participated in the study. Three vaginal and three cervical swabs were collected from each participant. Rapid CT tests were performed locally on the first vaginal and cervical swabs and the results were read independently by two staff members. The second and third swabs were randomised for performing the Roche CT assay at the National STD Reference Laboratory. Acceptability of the rapid tests to patients was determined by asking patients in clinics about their willingness to wait for the results. RESULTS: The prevalence of CT was 13.2% (197/1497), as determined by the Roche assay with cervical specimens. CT was detected in 78 vaginal and 127 cervical specimens by the rapid test and the positive rates determined with cervical specimens were significantly higher than those with vaginal specimens (p<0.001). There was good agreement between the results read by two independent staff for either vaginal or cervical specimens (both kappa = 0.98, p<0.001). Sensitivities for vaginal and cervical specimens were 32.8% and 49.7%, respectively, and specificities were 99.2% and 97.9%, respectively. The positive predictive value was 85.7% for vaginal and 78.4% for cervical specimens. The vast majority of the patients (99.1%) were willing to wait up to two hours for the results. CONCLUSION: Clearview Chlamydia MF, while yielding a rapid result and requiring minimal laboratory facilities, had unacceptably low sensitivity compared to a nucleic acid amplification test. Rapid tests yielding results within one hour are generally accepted by the clients.

Adult↗
PubMedDate not supplied

Use of the Cytobrush for concurrent cytology and chlamydia sampling: a comparison of immunofluorescence and culture for detection of chlamydia.

Five hundred and thirty-three women attending a genitourinary medicine clinic underwent concurrent cytology and Chlamydia trachomatis screening using a Cytobrush (Medscand AB). In each case, the same Cytobrush was used to give a sample for direct immunofluorescence and culture. 11.1% of samples were positive by immunofluorescence, while 10.6% were positive by culture. This was a close agreement (Kappa = 0.875). The ability of the same instrument to be used for both cytology and chlamydial screening, where direct immunofluorescence is used for detection of chlamydiae, may allow more widespread screening for chlamydia to be practical.

Adult↗
PubMedDate not supplied

Chlamydia trachomatis antigen detection by Chlamydiazyme combined with Chlamydia Blocking Reagent verification.

Several options exist for the detection of chlamydial infection in a routine laboratory setting. Enzyme immuno assay (EIA) technology offers rapid turn around of results and is less technically demanding than chlamydial cell culture. In addition, recently introduced EIA confirmatory reagents have the potential to improve the accuracy of EIA detection. We have evaluated one such confirmatory reagent (Chlamydia Blocking Reagent, Abbott Laboratories) to determine the accuracy of the Chlamydiazyme EIA with special regard to interpretation of low absorbance values. An initial series of 192 male urethral specimens showed that use of a lowered cut off level (absorbance value 0.05) compared with that recommended by the manufacturer increased sensitivity of the EIA from 0.73 to 0.83, thus motivating studies on this interpretative modification. Of 1101 EIA reactive specimens, 65% were determined to be chlamydia positive by the Chlamydia Blocking Reagent. The proportion of female cervical specimens that did not confirm positive was elevated compared with male urethral specimens, 43% vs. 5.7% respectively. In samples yielding absorbance from the recommended cut off level to 0.05 (approximately 50% below), the corresponding figures were 78% and 14% respectively. In 85 selected EIA reactive samples, examination by a direct immunofluorescence staining assay (DFA) (MicroTrak, Syva Inc.) revealed elementary bodies in 85% of 67 blocking test positive and in 24% of 18 blocking test negative samples. The possibility that Gram-negative bacteria were responsible for unconfirmed EIA reactive specimens was investigated using bacterial suspensions. While EIA reactivity was noted with several strains for Gram-negative bacteria, both the blocking reagent and DFA correctly verified the absence of chlamydial antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Bacterial↗