Enzyme amplified immunoassay: a novel technique applied to direct detection of Chlamydia trachomatis in clinical specimens

Comparison of a polymer conjugate-enhanced enzyme immunoassay to ligase chain reaction for diagnosis of Chlamydia trachomatis in endocervical swabs

Two endocervical swabs from each of 1,123 women were collected into manufacturer-supplied transport tubes and tested for Chlamydia trachomatis by a polymer conjugate-enhanced (PCE) enzyme immunoassay (EIA) (IDEIA PCE Chlamydia; DAKO) and a ligase chain reaction assay (LCx Chlamydia; Abbott). After confirmation by the EIA blocking test, the sensitivity of the IDEIA PCE remained at 91.8% and the specificity increased from 98.2 to 99.8% compared to LCx.

Rapid screening method for identification of cholera toxin-producing Vibrio cholerae O1 and O139

A novel method of identifying cholera enterotoxin (CT)-producing Vibrio cholerae serogroups O1 and O139 was developed. The method uses degradation of NAD as a specific biochemical marker for the CT-producing strains. The substrate NAD at a concentration of 100 mumol/liter was markedly degraded when it was incubated at 37 degrees C for 2 h with the CT-producing stains at a final cell density equivalent to that of a twofold dilution of a McFarland no. 1 standard. NAD degradation was monitored by an enzyme-amplified color development assay. Subsequent tests conducted with a total of 119 strains of V. cholerae, including both clinical and environmental isolates, confirmed a significant correlation between NAD degradation and CT production for all V. cholerae strains belonging to serogroups O1 and O139. Since 2 of 11 non-O1, non-O139 V. cholerae strains not carrying the CT gene degraded NAD, serotyping of the strains prior to the test is recommended.

Tosulfoxacin Treatment of Chlamydia Trachomatis Infection of the Uterine Cervix

In vivo efficacy of tosufloxacin (TFLX) for treatment of Chlamydia trachomatis cervical infection in women was evaluated by enzyme immunoassay. The short term (within 31 days of treatment) response rates with a dosage of 150mg orally 3 times daily were 100% (54/54) with 14 days of treatment and 97% (38/39) with 7 days of treatment. Subjective symptoms such as lower abdominal pain, vaginal discharge, or atypical bleeding were observed in 76 (82%) of the 93 patients. After treatment, symptoms improved in 75 (99%) of 76 patients. Two of 34 patients (5.9%) showed positive results in the long interval tests (1 to 18 months after treatment). Three (2.3%) of 131 patients needed to be changed from TFLX to other drugs due to side effects (eczema, face edema, urticaria). TFLX was effective and patients showed high compliance for treatment of cervical C. trachomatis infection.

Establishment of a particle-counting method for purified elementary bodies of chlamydiae and evaluation of sensitivities of the IDEIA Chlamydia kit and DNA probe by using the purified elementary bodies

To evaluate the sensitivity of commercially available test kits for detection of chlamydiae, we established a method of purifying Chlamydia trachomatis and Chlamydia pneumoniae elementary bodies (EBs). We then subjected the purified EBs, together with the purified EBs of Chlamydia psittaci, to the IDEIA Chlamydia (IDEIA) and DNA probe test kits to determine the EB numbers at the detection limits. The sensitivities of the test kits were thus compared. The results can be summarized as follows. (i) Intact EBs in the purified preparations were present at 100, 96.3, and 97% for the C. psittaci Cal 10, C. trachomatis L2/434/Bu (L2), and C. pneumoniae TW-183 strains, respectively. The preparations of the L2 and TW-183 EBs contained a few EB envelopes, which reacted with antilipopolysaccharide monoclonal antibodies, as did the intact EBs, indicating that elimination of EB envelopes is not required for testing of the IDEIA kit's sensitivity. (ii) We established a method of counting intact EBs and EB envelopes under a scanning electron microscope after sedimentation of EBs on a coverslip by centrifugation. (iii) The EB numbers per assay at the cutoff level, which is set up in the IDEIA kit, were 9.6 x 10(2), 6.5 x 10(3), and 2.5 x 10(4) for the L2, TW-183, and Cal 10 strains, respectively. When the same EB preparations were applied to the DNA probe kit, the EB number at the cutoff level was 7.5 x 10(3) per assay for the L2 strain, but no reaction occurred for the Cal 10 and TW-183 strains at any EB number, indicating that the DNA probe kit is highly specific for C. trachomatis. Although the IDEIA kit designed for detection of C. trachomatis showed a sensitivity superior to that of the DNA probe, the chlamydial species was not determined by the IDEIA kit.

The differentiation of Chlamydia species by antigen detection in sputum specimens from patients with community-acquired acute respiratory infections

An amplified enzyme immunoassay (IDEIA III: Dako Diagnostics Ltd) for detecting genus-specific chlamydia antigen was evaluated prospectively on 286 respiratory specimens from 275 patients presenting with community-acquired pneumonia or persistent chest infection. Nineteen patients had evidence of recent chlamydial infection, having two or more positive sputum or serological markers. Sputa from two other patients were ELISA-positive in the absence of other positive criteria and were regarded as false-positive results. When compared with a direct immunofluorescence test for chlamydial elementary bodies (EBs) using a genus-specific monoclonal antibody, the ELISA gave a positive predictive value of 91% and a negative predictive value of 99%. Non-specific problems with a wide variety of other micro-organisms isolated from the sputa were not encountered. Attempts to differentiate between Chlamydia psittaci, Chlamydia pneumoniae and Chlamydia trachomatis using genus-specific lipopolysaccharide reactive--and species-specific major outer membrane protein--monoclonal antibodies were encouraging and results were substantiated, in most patients, by the species-specific serological assays of the whole-cell-inclusion immunofluorescence or micro-immunofluorescence assays. The study demonstrated that antigen detection techniques offer scope for routine laboratories to diagnose chlamydial respiratory infections rapidly and reliably and may enable differentiation to species level. Although immunofluorescence offers marginally greater sensitivity and specificity when compared with ELISA, the latter is less subjective and less demanding. Sixty-eight per cent of these infections would have remained undiagnosed despite the general availability of ELISA tests.

Diagnosis of avian chlamydiosis: specificity of the modified Giménez staining on smears and comparison of the sensitivity of isolation in eggs and three different cell cultures

For the diagnosis of chlamydiosis in dead and live birds different methods were compared for their sensitivity and specificity. The specificity of the modified Giménez staining and the direct immunofluorescence (DIF) test for direct demonstration of Chlamydia psittaci in organ, cloacal and/or conjunctival smears was examined. The sensitivity of the isolation of Chlamydia psittaci in 6 days embryonated specific pathogen free (SPF) chicken eggs, Buffalo Green Monkey (BGM) cell line, McCoy cell line and Vero cell line was compared. On smears, the direct immunofluorescence test was more specific than the modified Giménez staining. The concordance between the results of both detection methods was 80%. The BGM cell culture was the most sensitive artificial host for isolation of Chlamydia psittaci, followed by the embryonated eggs, the Vero cell line and the McCoy cell line. The concordance between the results of isolation in BGM cell culture and eggs was 96.5%, while it was 86% between the results of isolation in BGM cell culture and Vero cell culture and only 65.5% between the results of isolation in BGM cell culture and McCoy cell culture. For dead bird species, chlamydiosis could be diagnosed more often using DIF on smears than with isolation. The concordance between the results of the DIF on smears and isolation followed by DIF was 91%.

Combined effect of infection and heavy wrapping on the risk of sudden unexpected infant death

Three methods were used to investigate the role of infection in sudden unexpected infant death (SUD): (i) microbiological comparison of SUD victims and matched, live, community controls; (ii) postmortem classification of the contribution of infection to death; and (iii) case-control analysis of the relative risk associated with both infection and heavy wrapping. Limited sampling from the upper respiratory tract and gut in SUD victims and controls showed no significant excess of viral infection in the SUD victims (odds ratio = 1.98, 95% confidence interval (CI) 0.9 to 4.5). At postmortem examination, infection explained death in 3/95 babies and may have contributed to death in 37/95. Over 70 days of age, the combined presence of viral infection and wrapping in excess of 10 togs produced an odds ratio of SUD of 51.5 (95% CI 5.64 to 471.48) compared with wrapping of less than 6 togs. Viral infection was not a major risk factor as long as babies were lightly wrapped. In heavily wrapped babies the presence of a viral infection greatly increased the risk of SUD.

Chlamydia trachomatis antigen can be detected in the urine sample of men with non-gonococcal urethritis

We tested the first portion of voided urine (FVU) and urethral swab from 80 patients with non-gonococcal urethritis (NGU) using a novel enzyme-amplified immunoassay (IDEIA) for the detection of Chlamydia trachomatis antigen. Urine specimens were positive in all patients with positive urethral swabs (positive coincidence ratio, 100%) and in 6 of 54 patients with negative swabs (negative coincidence ratio, 88.9%). Our data suggest that FVU is suitable for the detection of Chlamydia trachomatis antigen using the IDEIA test in patients with NGU.

Laboratory techniques for the diagnosis of chlamydial infections

Yolk-sac inoculation of embryonated eggs was superseded 25 years ago by the use of cell cultures (often McCoy) for the isolation of Chlamydia trachomatis. Centrifugation of specimens onto the cell monolayers was shown to increase sensitivity, but little of late has further improved sensitivity which is at least ten-fold greater than that of eggs. However, culture is slow and labour intensive so that non-cultural techniques without these drawbacks have come to dominate. Direct fluorescent antibody (DFA) tests are rapid and have sensitivities that range from 70% to 100% for men and 68% to 100% for women, and specificities that range from 87% to 99% for men and 82% to 100% for women; if the tests are read by competent observers the values are at the top end of the ranges. The detection rate may be enhanced even further by relatively low-speed centrifugation of specimens before staining. Skilled reading is not a feature of enzyme immunoassays (EIAs) which according to the literature have sensitivities that range from 62% to 97% for men and 64% to 100% for women, and specificities that range from 92% to 100% for men and 89% to 100% for women. However, comparison against poor reference tests is responsible for most of the higher values and the clinician should not be misled into believing that EIAs have excellent sensitivity; the lower values in the ranges are closer to reality. Furthermore, EIAs that are being designed for use by general practitioners should be regarded with the greatest caution since lack of sensitivity means that chlamydia-positive patients will go undetected. The polymerase chain reaction (PCR) is not bedevilled by insensitivity but it is no more sensitive than the most sensitive cell culture or DFA tests. PCR is unsuitable for routine diagnosis but has a place as a research tool. For men, examination of "first-catch" urine samples by the best of the non-cultural procedures provides an acceptable non-invasive approach to diagnosis; for women, the value of examining urine may be less, but needs to be thoroughly tested. However, there is little doubt that a Cytobrush used to obtain cervical specimens holds no practical advantage over a swab. Serological tests are reliant on the provision of paired sera for making a diagnosis; high antibody titres in single sera may be suggestive of an aetiological association in deep-seated chlamydial infections (epididymitis, arthritis, salpingitis, etc), but unequivocal interpretation is unusual, particularly in an individual case, since the distinction between a current and past infection is problematical.

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.

Syphilis, gonorrhoea and genital chlamydial infection in a Somali village

A total of 767 sera were collected from 187 men, 200 women and 380 children in a Somali village, Jambaluul. All sera were tested for syphilis serological markers by Venereal Diseases Research Laboratory (VDRL) and Treponema pallidum Haemagglutination Assay (TPHA). Sera positive for both or either of these tests were further analysed for the presence of specific IgM antibodies by Solid Phase Haemadsorption Assay (SPHA). A high and almost equal prevalence of TPHA positivity was found in men and women; 24% and 22.5%, respectively, and IgM antibodies were found in 3% and 4%, respectively. TPHA positivity significantly increased with age. Thus more than half of the villagers at the age of 45 years or more were TPHA positive. One percent of the children were TPHA positive. From all adults aged 15 years and above urogenital specimens were also taken for Chlamydia trachomatis antigen detection with an enzyme-amplified immunoassay (IDEIA) and Neisseria gonorrhoeae culture. Chlamydial genital infection was found in 6% of the men and 18% of the women. All gonococcal cultures were negative.

Age and sex correlation of Chlamydia trachomatis infections evaluated by the culture technique and by an enzyme immunosorbent assay, IDEIA

A total number of 1358 patients were examined for genital infections with Chlamydia trachomatis. 252 urethral smears from men and 1106 cervical smears from women were obtained. The average age of infected patients was 24.8 years (females 24.1, males 27.7). The overall prevalence was 10.6% (females 10.0%, males 13.1%). At the age below 20 years, the prevalence was 21% for both women and men, and 25% when data were restricted to patients consulting general practitioners. Above that age the overall prevalence was lower in all age intervals, and higher among males than females. All samples were tested by the tissue-culture technique, and the results were confirmed by the IDEIA (Boots-Celltech) enzyme-linked immunosorbent assay kit (EIA) for detection of C. trachomatis. The original smear was used for both culture and EIA. The EIA test was evaluated to have a sensitivity of 90.8% and a specificity of 95.4% when using a cut-off level of 0.05 mean extinction values (MEV), as described by the manufacturer.

Evaluation of three Chlamydia trachomatis immunoassays with an unbiased, noninvasive clinical sample

First-catch early morning urine samples from patients attending a genitourinary medicine clinic were tested by three different enzyme immunoassays. The results suggest significant differences in the sensitivities and specificities of the different assays. The direct visualization of elementary bodies in urine deposits by direct immunofluorescence was used as the "gold standard," using a monoclonal antibody with a different epitope specificity from those of antibodies used in the enzyme-linked immunosorbent assays. We report for the first time that urine specimens represent an unbiased sample, free of the inherent sampling errors associated with other genital specimens. We feel that urine is a valid specimen for use in any evaluation study of new assays directed towards the detection of Chlamydia trachomatis.

Favourable effect of detergent on antigen detection and comparison of enzyme linked detection systems in an ELISA for Chlamydia trachomatis

The influence of addition of detergents to the antigen on sensitivity of an ELISA for the detection of Chlamydia trachomatis was investigated. Of the detergents tested, only octyl-beta-d-glucopyranoside and sodiumdesoxycholate gave respectively a two- to fourfold and an eightfold increase in sensitivity. The effect was only present within a narrow range of detergent concentrations. The optimal detergent concentration was strongly dependent on the protein concentration in the antigen preparation. For optimal detection of the bound chlamydial antigen, enzyme and biotin labeled secondary antibodies were compared. The biotin labeled antibodies were combined with enzyme labeled streptavidin-biotin complex (SBC). Color development was obtained with both types of conjugates by using either o-phenylenediamine (OPD) or an enzyme amplification system. The best results were obtained with the SBC method and OPD.

A polymerase chain reaction (PCR) protocol for the specific detection of Chlamydia spp

The polymerase chain reaction is an in vitro procedure for primer-directed enzymatic amplification of specific template nucleic acid sequences. This technique was used to detect and differentiate Chlamydia trachomatis and Chlamydia psittaci in laboratory samples of infected McCoy cells. The polymerase chain reaction was shown to be both sensitive, detecting in the order of one chlamydial DNA molecule in 10(5) cells, and specific. No cross reaction (amplified product) was detected when a variety of mammalian cell and bacterial DNAs were used as template with the Chlamydia-specific oligonucleotide primers.

Comparison of three non-culture techniques for detection of Chlamydia trachomatis in genital tract specimens

A direct immunofluorescence (DIF) technique (Imagen) and two enzyme immunoassay (EIA) techniques (Chlamydiazyme and IDEIA) were compared for the detection of Chlamydia trachomatis in genital specimens from 502 attenders at a genitourinary medicine clinic. Eighty-two attenders were regarded as infected: 67 with positive results by at least two of the three techniques and 15 by virtue of elementary bodies detected in stored EIA buffer samples. With a positivity criterion of greater than or equal to 6 bodies Imagen was 76% sensitive for men and 61% sensitive for women. The sensitivity of Chlamydiazyme was 73% for men and 90% for women; comparative values for IDEIA were 80% and 71%, respectively. All three techniques were over 98% specific. Sampling order appeared to influence the sensitivity of IDEIA for specimens from men. All three techniques were less sensitive in the absence of cervicitis. The performances of the EIA techniques compared favourably with that of the more established technique of DIF.

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.

Improved sensitivity of an enzyme immunoassay IDEIA for detecting Chlamydia trachomatis

In tests on 375 genital tract specimens a commercially available enzyme immunoassay for Chlamydia trachomatis (IDEIA; Boots-Celltech) was found to have sensitivity values of 62% for men and 74% for women, and a specificity of 97% for both groups, relative to the results obtained by a fluorescence assay (Micro Trak; Syva). The positive predictive value and the negative predictive value of the immunoassay were 91% and 87%, respectively. Collection of samples for IDEIA in transport medium in plastic phials, as opposed to glass phials recommended by the manufacturer, had no effect on these values. Tests of the sensitivity of IDEIA using laboratory strains of C trachomatis showed that the assay detected chlamydial elementary bodies only at dilutions at least 10-fold lower than those at which they could be detected by Micro Trak. Tests of the specificity of the assay with microorganisms found in the genital tract, other than chlamydiae, showed that reactions occurred with a number of these. Testing three cervical swabs from the same patient, with the material taken into a single phial of transport medium, increased the sensitivity of IDEIA from 74% to 96%, without reducing the specificity which remained at 97%. It is concluded that this approach enchances the value of the test in a sexually transmitted disease clinic population and may do so in a population with a low prevalence of chlamydiae.

Comparison of DNA probe, monoclonal antibody enzyme immunoassay, and cell culture for the detection of Chlamydia trachomatis

A total of 201 endocervical specimens were obtained from patients with a clinical or epidemiological history suggestive of chlamydial infection. These specimens were tested by DNA probe (Gen-Probe, San Diego, Calif.) and the IDEIA III (Boots-Celltech, Berkshire, United Kingdom) monoclonal antibody enzyme immunoassay and compared with cell culture for detection of Chlamydia trachomatis. Discrepancies between cell culture and antigen detection methods were resolved by direct fluorescent-antibody testing. In a population with a 17.4% prevalence, the sensitivities and specificities of these assays were 82.8 and 99.4%, respectively, for the DNA probe assay and 97.1 and 98.1%, respectively, for the IDEIA III.

Laboratory diagnosis of human chlamydial infections

Chlamydia trachomatis is a human pathogen that causes ocular disease (trachoma and inclusion conjunctivitis), genital disease (cervicitis, urethritis, salpingitis, and lymphogranuloma venereum), and respiratory disease (infant pneumonitis). Respiratory chlamydioses also occur with infection by avian strains of C. psittaci or infection by the newly described TWAR agent. Diagnosis of most acute C. trachomatis infections relies on detection of the infecting agent by cell culture, fluorescent antibody, immunoassay, cytopathologic, or nucleic acid hybridization methods. Individual non-culture tests for C. trachomatis are less sensitive and specific than the best chlamydial cell culture system but offer the advantages of reduced technology and simple transport of clinical specimens. Currently available nonculture tests for C. trachomatis perform adequately as screening tests in populations in which the prevalence of infection is greater than 10%. A negative culture or nonculture test for C. trachomatis does not, however, exclude infection. The predictive value of a positive nonculture test may be unsatisfactory when populations of low infection prevalence are tested. Tests that detect antibody responses to chlamydial infection have limited utility in diagnosis of acute chlamydial infection because of the high prevalence of persistent antibody in healthy adults and the cross-reactivity due to infection by the highly prevalent C. trachomatis and TWAR agents. Assays for changes in antibody titer to the chlamydial genus antigen are used for the diagnosis of respiratory chlamydioses. A single serum sample that is negative for chlamydial antibody excludes the diagnosis of lymphogranuloma venereum.

The Hawaii Chlamydia Network Project: a successful program incorporating close intra-agency cooperation

The Hawaii State Department of Health's Chlamydia Network Project screened 272 asymptomatic females for chlamydia; 20 (7.4 per cent) were found to be positive. When interviewed, 75 per cent (15/20) of the cases gave information such that their sexual partner(s) could be located. Ninety per cent (14/16) of the locatable partners were brought to examination within seven days. Keys to success were the training of family planning clinic staff in STD (sexually transmitted disease) control methods, and close intra-agency cooperation.

Detection of Chlamydia trachomatis by isolation in cell culture and enzyme amplified immunoassay

188 (139 female; 49 male) genital swabs from patients with urogenital complaints (greater than 6 weeks), 69 (33 female; 36 male) conjunctival swabs from patients with chronic conjunctivitis and 14 swabs from newborns with acute conjunctivitis were tested for the presence of Chlamydia trachomatis (Ct) by inoculation in cell culture and visualisation by indirect immunofluorescence (IFT) with a monoclonal antibody and enzyme immunoassay (ELISA). Of the 271 specimens 20 (7.4%) were Ct positive by cell culture (IFT) and 18 (6.6%) were positive by ELISA. In 184 (97.9%) urogenital specimens results between cell culture (IFT) and ELISA agreed. With ELISA 4 further genital specimens were found to be Ct positive. In 59 (85.5%) conjunctival swabs of patients with chronic conjunctivitis results between cell culture (IFT) and ELISA agreed. By inoculation of cell culture (IFT) 6 (8.7%) more Ct positive specimens could be identified which were negative in ELISA. There was complete agreement between positive and negative Ct detection with cell culture (IFT) and ELISA in the cases of acute conjunctivitis.

Amperometric enzyme-amplified immunoassays

Enzyme-amplified immunoassays have been adapted for electrochemical measurement, using an NAD+/NADH redox cycle coupled to an electrode via the active site of diaphorase. Two amperometric methods are described, the first employs an organic conducting salt electrode, NMP+/TCNQ-; the second a platinum wire with ferricyanide as electron transfer mediator. In an immunoenzymometric assay for human prostatic acid phosphatase the sensitivities of the electrochemical methods were comparable to that achieved with the existing optical technique, but the dynamic range of the electrochemical assays was increased by at least two orders of magnitude. It is proposed that electrochemical enzyme-amplified immunoassays may eventually replace their optical counterparts.

Chlamydia: its influence in chronic secretory otitis media

Since Chlamydia trachomatis was isolated from middle ear effusions of neonates with natally acquired chlamydial infection (Tipple et al., 1979), there have been several studies to detect chlamydia in older children with chronic secretory otitis media, mainly by tissue culture. In this study, the aspirates of 106 middle ear effusions of 60 children with chronic secretory otitis media were investigated for the presence of C. trachomatis, other bacteria and viruses. An amplified enzyme-linked immunoassay was used to detect the presence of chlamydia. The bacteriological and virological results mirrored previous studies in the United Kingdom and no chlamydia were found. Chlamydia do not appear to be related to the aetiology of this disease in the population examined.

Clinical laboratory applications of monoclonal antibodies

Monoclonal antibody (MAb) technology is well recognized as a significant development for producing specific serologic reagents to a wide variety of antigens in unlimited amounts. These reagents have provided the means for developing a number of highly specific and reproducible immunological assays for rapid and accurate diagnosis of an extensive list of diseases, including infectious diseases. The impact that MAbs have had in characterizing infectious disease pathogens, as well as their current and future applications for use in clinical microbiology laboratories, is reviewed. In addition, the advantages (and disadvantages) of the use of MAbs in a number of immunoassays, such as particle agglutination, radioimmunoassays, enzyme-linked immunosorbent assays, immunofluorescent-antibody assays, and immunohistology, are explored, including the use of these reagents in novel test system assays. Also, nucleic acid probe technology is compared with the use of MAbs from the perspective of their respective applications in the diagnosis of infectious disease agents. There is no question that hybridoma technology has the potential to alter significantly the methods currently used in most clinical microbiology laboratories.

Testing for Chlamydia trachomatis

Chlamydia trachomatis is a highly prevalent and damaging sexually transmitted disease. Since it may occur in an asymptomatic state, it is important for family physicians to know when screening or testing for this infection is indicated. The value of screening may be increased by correct collection, storage and transport of specimens. The techniques currently used in the laboratory to test specimens for chlamydia include cell culture, ELISA and immunofluorescent antibody (IFA) assay. Cell culture remains the 'gold standard'. The IFA and ELISA are simpler and quicker to perform than is culture and have sufficiently comparable measurements of accuracy.

Clinical acute cholecystitis and the Curtis-Fitz-Hugh syndrome

When patients are admitted with clinically diagnosed acute cholecystitis, no cause will be found for their pain in 9-13% (4.5). Our retrospective study shows that women between 15-35 years are most likely to be in this group. Our prospective study of all patients in the 15-35 year age group admitted with clinical 'acute cholecystitis', showed that in 6 out of 7 patients with 'undiagnosed' pain, the Curtis-Fitz-Hugh syndrome was the cause. We suggest that screening for the Curtis-Fitz-Hugh syndrome is performed in all patients with right upper quadrant pain who have a normal ultrasound scan.

Detection of Chlamydia trachomatis by enzyme immunoassay in patients with trachoma

Trachoma control necessitates identification of individuals shedding ocular chlamydiae. Conventional techniques of chlamydial culture are unsuitable for large field surveys in developing countries. In this study an enzyme immunoassay (EIA) developed for the detection of chlamydial antigen in genital-tract infection was used in trachoma. Conjunctival swabs were taken for chlamydial antigen detection from 1225 subjects in a Gambian village with endemic trachoma. Of these, 997 had insignificant or no disease and 172 had mild, 30 moderate, and 26 severe disease. Chlamydial antigen was detected in 5.0%, 20.3%, 46.7%, and 26.9% of subjects in these four categories, respectively. Samples for chlamydial isolation were obtained from 259 subjects. The corresponding rates of detection obtained by chlamydial isolation were 3/90 (3.3%), 16/129 (12.4%), 7/21 (33.3%), and 7/19 (36.8%). If isolation is taken as the "gold standard", the EIA technique had a sensitivity of 70.6% and a specificity of 90%. A substantial proportion of subjects with severe conjunctival scarring, from whom chlamydiae cannot generally be isolated, were antigen positive by EIA, implying that persistent chlamydial antigen plays a part in the pathogenesis of the late sequelae of trachoma.

A simple method for the detection of Chlamydia trachomatis infections in general practice

Chlamydial infection is an important cause of genital tract disease in women and is often silent. Collection, storage and transportation of specimens required for culture pose problems which have made studies difficult and diagnosis impractical outside hospitals or sexually transmitted disease clinics.The direct monoclonal antibody test (MicroTrak, Syva) for detecting chlamydiae is comparable with the traditional culture method in sensitivity and specificity. The test requires only the preparation of a smear on a slide, making it convenient for use in general practice. The feasibility of using this procedure in an inner city practice was demonstrated in tests on 188 women who required pelvic examination. Of 169 women from whom valid specimens were obtained 18 (10.7%) were found to have a chlamydial infection. Only three of the infected women were asymptomatic and the organisms were associated particularly with dysuria. The value of the test in comparison with other procedures currently available for detecting chlamydiae is emphasized.

Evaluation of enzyme immunoassay (Chlamydiazyme) for detecting Chlamydia trachomatis in genital tract specimens

An enzyme immunoassay (Chlamydiazyme) for detecting Chlamydia trachomatis was evaluated on genital specimens from 96 men and 272 women attending a clinic for sexually transmitted diseases (STD clinic). Compared with a direct immunofluorescence test for chlamydial elementary bodies, the enzyme immunoassay had a sensitivity of 58% on specimens from men, a specificity of 90%, a positive predictive value of 93%, and a negative predictive value of 88%; the assay had a sensitivity of 67% on specimens from women, a specificity of 89%, a positive predictive value of 63% and a negative predictive value of 90%. Immunofluorescence provided the most stringent test for the performance of the enzyme immunoassay as values were improved a little when a cell culture procedure was used for comparison. Further evidence for the lack of sensitivity was the detection of elementary bodies, sometimes in large numbers, in the enzyme immunoassay buffer of 13 of 19 specimens that had given a negative enzyme immunoassay result and the finding in comparative titrations of four laboratory strains that the enzyme immunoassay was at least 100-fold less able to detect chlamydiae than either immunofluorescence or the cell culture procedure. Lack of specificity may be associated with the finding that the enzyme immunoassay antibody reacted with strains of Acinetobacter calcoaceticus, Escherichia coli, Gardnerella vaginalis, Neisseria gonorrhoeae and group B streptococci. The enzyme immunoassay was not considered to be sufficiently sensitive, specific, or reproducible for routine use.

Herpes simplex virus detection by ELISA: effect of enzyme amplification, nature of lesion sampled and specimen treatment

The relative sensitivity of two enzyme detection procedures was investigated in a simultaneous "monoclonal" ELISA for herpes simplex virus (HSV). A cyclical enzyme amplified detection system with alkaline phosphatase, rather than horse-radish peroxidase and a conventional chromogenic substrate, gave an increase in absolute sensitivity and a 20 to 30% increase in the detection of HSV in routine isolation-positive genital specimens collected in transport medium. The HSV detection rate, with both procedures, was shown to vary with the site and clinical stage of lesion sampled; it was highest with penile vesicular lesions. Direct extraction of the swab specimen in a small volume of diluent further increased the sensitivity of antigen detection giving positive and negative predictive values of 100 and 96% respectively. The overall sensitivity of HSV detection was equivalent to that obtained by isolation in cell culture. The amplified ELISA offers an alternative, rapid, simple, non-culture technique for routine HSV diagnosis that does not rely upon retention of virus viability.