Comparison of enzyme immunoassay and culture for diagnosis of chlamydial conjunctivitis and respiratory infections in infants.

The efficacy of Chlamydiazyme (Abbott Laboratories, North Chicago, Ill.) in detecting neonatal conjunctival and respiratory infections caused by Chlamydia trachomatis was determined by comparison of this enzyme immunoassay (EIA) with the method of isolation of chlamydiae in tissue culture. The sensitivity and specificity of Chlamydiazyme for detecting C. trachomatis in conjunctival specimens from infants with conjunctivitis were 98 and 94%, respectively. For nasopharyngeal infection in infants with conjunctivitis, the sensitivity and specificity were 87 and 92%, respectively. There were nine nasopharyngeal specimens that were Chlamydiazyme positive and culture negative. All of these specimens demonstrated the presence of typical fluorescing chlamydial elementary bodies when pellets of the original specimens were examined with a fluorescein-conjugated monoclonal antibody. When the EIA was performed on nasopharyngeal specimens from infants with suspected chlamydial pneumonia, 6 culture-positive and 10 culture-negative specimens were correctly identified.     

Comparison of two enzyme immunoassays to culture for the diagnosis of chlamydial conjunctivitis and respiratory infections in infants.

Data are limited for the performance of enzyme immunoassays for the detection of Chlamydia trachomatis in conjunctival and nasopharyngeal specimens from infants. The only available data are for one assay, Chlamydiazyme (Abbott Diagnostics). The purpose of this study was to compare a new enzyme immunoassay, Pathfinder (Kallestad Diagnostics), with Chlamydiazyme and culture for the diagnosis of chlamydial conjunctivitis and pneumonia in infants. Pathfinder differs from Chlamydiazyme in that it uses a monoclonal antibody directed against the chlamydial lipopolysaccharide in addition to a polyclonal antichlamydial antibody. Triplicate conjunctival and nasopharyngeal specimens were obtained from 97 infants with conjunctivitis, and additional nasopharyngeal specimens were obtained from 14 infants with suspected chlamydial pneumonia (total, 111 nasopharyngeal specimens). Twenty-nine (30%) of the conjunctival specimens from infants with conjunctivitis and four (28.6%) of the nasopharyngeal specimens from the infants with pneumonia were positive for C. trachomatis by cell culture. The sensitivities, specificities, and positive and negative predictive values for Pathfinder for conjunctival specimens were 96.6, 98.5, 96.6, and 98.5%, respectively. The results for Chlamydiazyme were 96.6, 100, 100, and 98.6%, respectively. For nasopharyngeal specimens, the results for Pathfinder were 77.8, 94.6, 73.7, and 95.7%, respectively. The results for Chlamydiazyme were 66.7, 95.7, 75, and 93%, respectively. Pathfinder and Chlamydiazyme appeared to perform equivalently for the detection of C. trachomatis in both eye and nasopharyngeal specimens from infants with chlamydial conjunctivitis and pneumonia.     

Comparison of a chemiluminometric immunoassay with culture for diagnosis of chlamydial infections in infants.

The performance of Magic Lite (CIBA-Corning), a chemiluminescent immunoassay (CIA), was compared with that of culture for the diagnosis of neonatal chlamydial conjunctivitis and respiratory infection. We performed a retrospective evaluation of 51 ocular and 96 nasopharyngeal specimens previously collected for culture testing with the CIA. The sensitivities for the ocular and the nasopharyngeal specimens were 91 and 91.7%, respectively. The specificities for both sites were 100%. A subsequent prospective study evaluating 71 ocular and 38 nasopharyngeal specimens revealed sensitivities of 83.3 and 20%, respectively. The specificities for both sites were 100%. The CIA performed favorably, compared with culture, for the diagnosis of chlamydial conjunctivitis; however, the CIA appeared less sensitive for the diagnosis of respiratory infection, including pneumonia.     

Evaluation of a new optical immunoassay for diagnosis of neonatal chlamydial conjunctivitis.

The BioStar OIA Chlamydia test (BioStar, Inc., Boulder, Colo.) is a novel immunoassay system that uses changes in reflection of light to directly detect chlamydial antigen in clinical specimens. We compared the optical immunoassay (OIA) with culture for detecting Chlamydia trachomatis in ocular specimens from infants with suspected chlamydial conjunctivitis. We initially performed a retrospective evaluation, testing 152 ocular specimens previously collected for culture with the OIA. The sensitivity and specificity were 94.2 and 97%, respectively. A subsequent prospective study evaluating 37 ocular specimens from infants with suspected C. trachomatis conjunctivitis revealed a sensitivity and specificity of 100 and 92.6%, respectively.     

Comparison of the ligase chain reaction with cell culture for the diagnosis of Chlamydia trachomatis infection in women.

OBJECTIVE: To determine the sensitivity and specificity of ligase chain reaction (LCR) analysis of cervical and urine specimens from women compared with cell culture of cervical and urethral specimens for the diagnosis of genitourinary chlamydial infection. METHODS: Women (n = 624) attending the Genitourinary Medicine Clinic at University College London Hospitals, were enrolled. Patients who had received antibiotics within the previous two weeks were excluded. Specimens were obtained from the urethra and cervix for chlamydial culture, and from the cervix for LCR. A specimen of first void urine was also obtained for LCR. Discrepancies were resolved by direct immunofluorescence or a major outer membrane protein targeted LCR, or both. RESULTS: The prevalence of Chlamydia trachomatis in 600 patients, using an expanded standard of a positive cell culture or two confirmed positive non-culture tests, was 13.2% (79/600). Cervical culture detected 68.4% and urethral culture 62% of all positive results compared with 81% detected by cervical LCR and 69% by urine LCR. Cervical and urethral culture combined detected 87.3% whereas cervical and urine LCR combined detected 91.1% of positive cases. Specificity of LCR was 100% in the cervix and 99.8% in urine. CONCLUSION: This study demonstrates that LCR analysis of cervical and urine specimens is a reliable method for the diagnosis of chlamydial genital infection in women. However, the study also demonstrates that no single test will detect all chlamydial infections. Conventional non-culture tests and cell culture may grossly underestimate the prevalence of chlamydial infection. LCR analysis of a cervical specimen was superior to conventional cell culture without blind passage as a single test for diagnosing chlamydial infection in women, followed by LCR of a urine specimen.     

Tear and serum antibody response to Chlamydia trachomatis antigens during acute chlamydial conjunctivitis in monkeys as determined by immunoblotting.

In this study, we examined the temporal antibody response by immunoblotting analysis in tears and sera of three cynomolgus monkeys (Macaca fasicularis) with primary acute Chlamydia trachomatis serovar B conjunctivitis. The objective was to identify chlamydial antigens stimulating antibody during the host responses in the course of this self-limiting infection with the rationale that they may be protective antigens. The major outer membrane protein (MOMP), lipopolysaccharide (LPS), and polypeptides of 60 and 68 kilodaltons (kDa) were the predominant antigens recognized by immunoglobulin A (IgA) in monkey tears. Tear IgA antibody specific for the MOMP was first detected 14 days postinfection, whereas tear IgA reactive with LPS or the 68- and 60-kDa polypeptides was first detectable on day 21. Tear IgA antibodies specific for each of these antigens persisted in tears through day 56, 4 weeks after both peak clinical disease and recovery of the organism from the conjunctivae. In contrast, tear IgG antibodies peaked at approximately 28 days postinfection, the time of maximal inflammatory response. The IgG response in monkey sera was similar to that observed for tear antibodies, in that the MOMP, 60-, and 68-kDa polypeptides were the primary immunogens. The exception was that IgG antibody against these antigens was detected 1 week later than that observed for tear IgA antibodies. Of three monkeys that responded with tear IgA antibody against LPS, one did not have detectable serum IgG LPS antibody. The specificity of the tear IgA antibody response of monkeys was determined by immunoblotting nine other C. trachomatis serovars in addition to the homologous B serovar. The tear IgA response to the MOMP was predominantly B complex subspecies-specific (serovars B, Ba, D, and E), whereas the response to chlamydial LPS was found to be species-specific. The significance of these observations in relation to previous vaccine studies in nonhuman primates is discussed.     

Comparison of two rapid microscopic methods and culture for detection of Chlamydia trachomatis in ocular and nasopharyngeal specimens from infants.

The data available for the diagnosis of chlamydial infections in infants which compare direct fluorescent-monoclonal-antibody stains (DFAs) with culture are limited to one reagent, MicroTrak (Syva Inc., Palo Alto, Calif.). We therefore performed a comparison of Pathfinder (Kallestad Diagnostics, Chaska, Minn.) and MicroTrak with chlamydia culture. Paired conjunctival and nasopharyngeal specimens for DFAs and cultures were obtained from 56 infants less than 1 month of age with conjunctivitis. The sensitivities for detecting C. trachomatis in conjunctival specimens with MicroTrak and Pathfinder were 93.8 and 88.2%, respectively, and the specificities were 87.5 and 94.9%, respectively. The DFA tests on nasopharyngeal specimens from infants with conjunctivitis did not perform as well. The sensitivities for Pathfinder and MicroTrak were 33 and 50%, respectively. There were a total of six patients with culture-positive chlamydial conjunctivitis whose nasopharyngeal specimens were DFA positive and culture negative; four of the specimens were positive by both DFAs. These six discordant specimens were further evaluated by preparing pellets and smears of the original culture specimens. All six contained typical fluorescing elementary bodies when stained with the Syva DFA reagent.     

Comparison of monoclonal antibody staining and culture in diagnosing cervical chlamydial infection.

We compared a fluorescein-conjugated monoclonal antibody (FA) direct specimen test (MicroTrak; Syva Co., Palo Alto, Calif.) with culture (TC) in McCoy cells (vials, with blind passage and iodine staining of inclusions) for diagnosis of Chlamydia trachomatis infection in the cervix. Duplicate specimens were collected from 1,230 women, but for 262 of these subjects, both results were unavailable (150 FA smears were inadequate, indicating a need for clinical training in specimen collection), leaving 968 comparisons. Prevalence of chlamydiae by culture was 13% (126/968). Compared with TC results, the sensitivity of FA was 70% (88/126) and the specificity was 94% (795/842). There was a 91% agreement (883/968). The predictive value of a positive FA test was 65% (88/135), and that of a negative FA was 95% (795/833). We reexamined 38 smears for which paired results were discrepant, and the reread would have changed the result in only 5 of these. TC is less than 100% sensitive and some FA-positive, TC-negative specimens represent positive specimens not detected by TC. Unfortunately, it is not possible to identify which results in this group are truly false-positive. Clearly, the FA procedure has a performance profile which would make it a useful tool in screening high-risk populations (particularly when TC is not available) but it is less suited to screening low-risk populations, for which false-positive results are more important. The greater utility of the FA procedure in a venereal disease clinic was confirmed by testing 172 evaluable specimen pairs, of which 34 (20%) were Chlamydia isolate positive. The FA sensitivity was 76% (26/34) and specificity was 96% (133/138), giving a predictive value of 84% (26/31) for a positive test.     

Localization of chlamydial group Antigen in McCoy cell monolayers infected with Chlamydia trachomatis or Chlamydia psittaci.

Chlamydial inclusions were demonstrated by indirect immunofluorescence (IF) with antiserum to the chlamydial group antigen when McCoy cell monolayers infected with either Chlamydia trachomatis or Chlamydia psittaci were fixed in formaldehyde or paraformaldehyde, provided the monolayer was not allowed to dry. If these monolayers were then air dried and restained by IF with the same antiserum but with a different fluorescence conjugate, group antigen associated with inclusion-containing McCoy cells but independent of the inclusions was revealed. This antigen was not restricted to infected cells but appeared to radiate out from them, suggesting that group antigen was released from infected cells. Similar host cell-associated antigen could be shown by IF of glutaraldehyde-fixed, air-dried monolayers, but inclusions could not be stained by IF before these preparations were dried, presumably because antibody could not penetrate glutaraldehyde-fixed cells. Electron microscopic immunoperoxidase studies of paraformaldehyde-fixed, wet monolayers located group antigen within inclusions on the outer membrane of chlamydial organisms and on single-membrane vesicles. However, when dried monolayers were labeled with the same immunoperoxidase technique, no intracellular labeling occurred, but dense staining was seen at the surface of infected cells and on adjacent membranous material. These observations are compatible with the postulate that replicating chlamydiae produce outer membrane blebs containing group antigen, which are excreted by the host cells during the chlamydial developmental cycle.     

Accuracy of immunoglobulin M immunoassay for diagnosis of chlamydial infections in infants and adults

An improved solid-phase enzyme immunoassay (EIA) with Chlamydia trachomatis L2 434/Bu elementary bodies was developed for the measurement of immunoglobulin M (IgM) antibody to C. trachomatis in serum. Comparison of EIA and microimmunofluorescence IgM antibody titers of 156 serum samples revealed an EIA sensitivity and specificity of 100% for infants, but reduced sensitivity (85%) and specificity (76%) for sera from adults. Sera containing IgM class rheumatoid factor produced false-positive IgM results which could easily be eliminated by pretreatment of the sera with anti-human IgG. Analysis of sera from infants with chlamydial infections revealed that 17 of 17 infants with C. trachomatis pneumonia had high IgM antibody titers (geometric mean titer, 1:64,812), whereas two infants with conjunctivitis only lacked detectable IgM antibody. EIA detected IgM antibody to several serovar groups in serum, including serovars B, BDE, FG, and J. IgM antibody to C. trachomatis in serum was detected as early as 5 days after the infection that was acquired at delivery and persisted for 3 months. The availability of an EIA possessing good sensitivity and specificity for the detection of IgM antibody to C. trachomatis may permit more laboratories to diagnose perinatal chlamydial infections.     

Comparison of three enzyme immunoassays to tissue culture for the diagnosis of rotavirus gastroenteritis in infants and young children.

Three enzyme immunoassays (EIAs), Rotazyme II, IDL, and Pathfinder, were evaluated for rotavirus detection in stool and rectal swab specimens from children with symptomatic gastroenteritis and compared with virus isolation in primary African green monkey kidney cells. Of 125 specimens tested, 49 were rotavirus positive by tissue culture isolation; of these 49, 40 were positive by Rotazyme II, 43 were positive by IDL, and 46 were positive by Pathfinder EIAs. As compared with tissue culture isolation, the Rotazyme II, IDL, and Pathfinder EIAs had sensitivities of 82, 88, and 94%, specificities of 90, 99, and 95%, and overall agreements of 86, 94, and 94%, respectively.     

Comparison of a DNA probe assay with culture for the detection of Chlamydia trachomatis

A new DNA probe assay (PACE 2, Gen-probe) was compared with cell culture for the detection of Chlamydia trachomatis in 909 women attending the Royal Women's Hospital, Melbourne, Victoria. The DNA probe assay had a sensitivity of 86.2%, a specificity of 99.9% and a positive predictive value of 96.2% in a population with 3.2% prevalence, indicating that it may be a suitable alternative to culture for the detection of C. trachomatis in specimens from the genital tract.     

Immunoelectron-microscopic quantitation of differential levels of chlamydial proteins in a cell culture model of persistent Chlamydia trachomatis infection.

Electron immunolabeling techniques were used for quantitative evaluation of alterations in the steady-state levels of chlamydial antigens in persistent Chlamydia trachomatis cultures. Gamma interferon-mediated persistent chlamydial development correlated with an increase in the levels of the chlamydial heat shock protein (hsp60) and with a significant reduction in the levels of the major outer membrane protein.     

Efficacy of neonatal ocular prophylaxis for the prevention of chlamydial and gonococcal conjunctivitis

Opinions differ concerning the efficacy of prophylaxis against neonatal chlamydial and gonococcal conjunctivitis. From January 1986 through June 1988, we gave all infants born at Kings County Hospital Medical Center one of three prophylactic agents -- silver nitrate drops, erythromycin ophthalmic ointment, or tetracycline ophthalmic ointment. The treatments were rotated monthly. Gonococcal ophthalmia occurred in 8 of the 12,431 infants born during the study (0.06 percent), 1 in the silver nitrate group, 4 in the erythromycin group, and 3 in the tetracycline group (P not significant). Seven of these infants were born to women who had received no prenatal care. From September 1985 through December 1987, we screened 4357 pregnant women for cervical chlamydial infection, of whom 341 (8 percent) had positive cultures. Of their offspring, 230 were evaluated for neonatal chlamydial conjunctivitis; the incidence was 20 percent in the silver nitrate group, 14 percent in the erythromycin group, and 11 percent in the tetracycline group (P not significant). We conclude that neonatal ocular prophylaxis with either erythromycin or tetracycline ophthalmic ointment does not significantly reduce the incidence of chlamydial conjunctivitis in the offspring of mothers with chlamydial infection as compared with silver nitrate, and that better management of maternal chlamydial infection is therefore required. We also conclude that there is a small but appreciable incidence of neonatal gonococcal ophthalmia that could be prevented by better prenatal screening and treatment of maternal gonococcal infection.     

Diagnosis of Chlamydia trachomatis genital infections by cell culture and two enzyme immunoassays detecting different chlamydial antigens.

The enzyme-amplified immunoassay IDEIA (CellTech Diagnostics), which measures lipopolysaccharide antigen, and Chlamydiazyme (Abbott Laboratories, North Chicago, Ill.), which measures several antigenic components of Chlamydia trachomatis, were compared for specimens from urethral swabs from 235 men attending a clinic for sexually transmitted diseases (culture prevalence of 14.9%) and 458 endocervical swabs from women attending planned parenthood and obstetrics-gynecology clinics (culture prevalences of 5.9 and 7.7%, respectively). Compared with cell culture, the percent sensitivites, specificities, and positive and negative predictive values for IDEIA were 62.5, 99.5, 95.2, and 94.3%, respectively, for specimens from men and 96.3, 97.9, 74.3, and 99.8%, respectively, for specimens from women; results for Chlamydiazyme for specimens from men were 81.8, 99.5, 96.4, and 97.1%, respectively, and for specimens from women, results were 85.2, 99.3, 88.5, and 99.1%, respectively. Although the specificities of IDEIA and Chlamydiazyme were comparable, the sensitivity of IDEIA appeared higher for women (96.3%) than for men (67.5%), while the sensitivities of Chlamydiazyme were similar for men (81.8%) and women (85.2%). Western blot (immunoblot) analysis of the detector reagents from the two immunoassays indicated that the differences in performance observed for the two immunoassays may be due to measurement of different antigens.     

Comparison of IDEIA III and cell culture for the detection of Chlamydia trachomatis in endocervical specimens.

A total of 803 endocervical samples were obtained from females with clinical or epidemiological histories suggesting chlamydia infection. These specimens were tested by IDEIA III and cell culture for the presence of Chlamydia trachomatis. After resolution of discrepant results by direct fluorescent-antibody staining of pelleted cell culture transport materials, IDEIA III demonstrated sensitivity, specificity, and positive and negative predictive values of 93.8, 99, 92.9, and 99.1%, respectively.     

Comparison of the Syva MicroTrak enzyme immunoassay and Gen-Probe PACE 2 with cell culture for diagnosis of cervical Chlamydia trachomatis infection in a high-prevalence female population.

Culture is currently considered the "gold standard" for detecting Chlamydia trachomatis infections. We evaluated the Syva MicroTrak enzyme immunoassay (EIA) and Gen-Probe PACE 2 tests, which detect chlamydial antigens and rRNA, respectively. These assays were compared with each other and with culture for the detection of C. trachomatis in cervical specimens obtained from 217 women attending a clinic for sexually transmitted diseases. The prevalence of infection was 22.1% by culture. The sensitivity, specificity, and positive and negative predictive values were 79.2, 98.2, 92.6, and 94.3%, respectively, for EIA. For PACE 2, the respective values were 77.1, 97.6, 90.1, and 93.7%. After corrections for two false-negative cultures, the sensitivities and specificities were 80 and 99.4%, respectively, for the EIA and 78 and 98.8%, respectively, for the probe assay. Quantitative evaluation of the results showed that false-negative results with either assay were associated with cultures that had low inclusion counts or were negative without subpassage. Analysis of nonculture results revealed that 2.3% of the EIA results and 4.6% of the probe assay results were within +/- 30% of the respective assay cutoff values. These included four false-negative (one EIA and three probe) and two false-positive (one EIA and one probe) results. The Syva MicroTrak EIA and the Gen-Probe PACE 2 assay are comparable to but significantly less sensitive than culture. Use of a grey zone may help identify the need for repeat or confirmatory testing.     

Comparison of the Clearview Chlamydia test, Chlamydiazyme, and cell culture for detection of Chlamydia trachomatis in women with a low prevalence of infection.

Two antigen detection systems, Clearview Chlamydia (Unipath Ltd., Bedford, United Kingdom) and Chlamydiazyme (Abbott Laboratories, North Chicago, Ill.), were compared with culture for the diagnosis of chlamydia infection in women attending gynecological clinics. Chlamydia trachomatis was isolated from 43 (4.5%) of the 965 women tested. In comparison with tissue culture, the Clearview Chlamydia and Chlamydiazyme tests had sensitivities of 79.0 and 74.4%, respectively, and both had a specificity of 99.6%. The results show that the Clearview Chlamydia test is comparable to Chlamydiazyme for the detection of C. trachomatis from endocervical specimens in a population with a low prevalence of infection.     

Comparison between cell culture and serology for detecting Chlamydia trachomatis in women seeking abortion.

The efficiency of an immunoperoxidase serological assay and culture of Chlamydia trachomatis were compared in 127 women seeking first trimester abortion. Serum IgG and IgA antibodies specific for C trachomatis were detected by a single serovar (L2) inclusion immunoperoxidase assay (IPA). Eighty (63%) women were seropositive for chlamydial IgG and 31 (24%) for IgA antibodies. C trachomatis was isolated from 21 of 127 (17%) women. Twenty of the 80 women (25%) seropositive for specific IgG antibodies and one of 47 (2%) patients without these antibodies were culture positive (p less than 0.001). Compared with isolation, chlamydial antibodies at a titre of greater than or equal to 16 showed high sensitivity and negative predictive value (95% and 98%, respectively), but low specificity and efficiency (43% and 52%, respectively). Chlamydial IgA antibodies at a titre of greater than or equal to 8 showed low sensitivity (52%), but a higher specificity, negative predictive value, and efficiency of 81%, 90%, and 76%, respectively. C trachomatis IgG antibodies at a titre of 16 as determined by IPA can be used as an efficient negative exclusion marker for active chlamydial infection in screening women seeking abortion.