Enzyme immunoassay for diagnosis of gonorrhea

Molecular genetic methods for diagnosis and characterisation of Chlamydia trachomatis and Neisseria gonorrhoeae: impact on epidemiological surveillance and interventions

One of the mainstays in the prevention of Chlamydia trachomatis and Neisseria gonorrhoeae infections is the availability of laboratory diagnostics with high sensitivity and specificity. Assays for diagnosis of C. trachomatis include cell culture and nucleic acid amplification tests (NAATs). The major target sequences for C. trachomatis diagnosis by NAATs are located at the cryptic plasmid and the major target used for characterisation is the omp1 gene. The gold standard for diagnosis of N. gonorrhoeae is culture. However, numerous NAATs for identification of N. gonorrhoeae and a number of molecular genetic methods for characterisation of N. gonorrhoeae have been developed. Probably no routine laboratory can attain as high sensitivity by culturing C. trachomatis or N. gonorrhoeae as by using NAATs. For that reason NAATs can be recommended for diagnosing C. trachomatis, but not as the only diagnostic assay for N. gonorrhoeae, due to lack of antibiotic susceptibility testing and specificity problems, most pronounced for pharyngeal and rectal samples. Genotyping of C. trachomatis or N. gonorrhoeae provides additional information for contact tracing. It is recommended for N. gonorrhoeae, at least in low prevalence geographic areas, but cannot today be recommended for C. trachomatis. This is due to the low genetic variability and hence the limited benefits for partner notification. However, genotyping of C. trachomatis may play an important role under special circumstances.

Multiplexed immunoassays by flow cytometry for diagnosis and surveillance of infectious diseases in resource-poor settings

An accurate, rapid and cost-effective diagnosis is the cornerstone of efficient clinical and epidemiological management of infections. Here we discuss the relevance of an emerging technology, multiplexed immunoassays read by flow cytometry, for the diagnosis of infectious diseases. In these assays, multiple fluorescent microspheres, conjugated to different antigens or antibodies, constitute the solid phase for detecting antibodies or antigens in biological samples. These assays seem to be more sensitive than traditional immunoassays, have a high throughput capacity, and provide a wide analytical dynamic range. Additionally, they have multiplexing ability-ie, they are capable of measuring multiple antibodies or antigens simultaneously. We discuss four different areas where this technology could make an impact in resource-poor settings: (i) infections causing rash and fever in children; (ii) sero-epidemiological studies on vaccine-preventable diseases; (iii) management of genital ulcers and vaginal discharge; and (iv) screening of infections in blood banking. We predict a widespread use for a new breed of small, affordable, practical flow cytometers as field instruments for replacing ELISA and RIA tests, which will also be capable of doing cellular immunological tests such as CD4+ T-cell enumeration and Plasmodium falciparum detection in whole blood.

Evaluation of an in-house polymerase chain reaction for detection of Neisseria gonorrhoeae in urogenital samples

AIM

To develop and evaluate a one day in-house polymerase chain reaction (PCR) assay for the detection of Neisseria gonorrhoeae DNA in urogenital samples.

METHODS

429 urogenital specimens were tested for the presence of N gonorrhoeae by in-house PCR and by Gen-Probe. The PCR assay amplifies target sequences within the N gonorrhoeae cppB gene on the 4.2 kb cryptic plasmid, after which amplicons are detected by a streptavidinbiotin based enzyme immunoassay using an internal probe. Discordant specimens were further evaluated by repeating the PCR and the Gen-Probe assay, and by an additional PCR using another set of 16S primers followed by radioactive detection of amplicons on a Southern blot.

RESULTS

Of the 429 samples tested, 15 were found positive by in-house PCR, eight of which were confirmed by Gen-Probe. Of the seven discrepant samples, five were confirmed by 16S PCR and are also considered true positive. The remaining two samples were positive in the in-house PCR only, and are considered false positive. After resolution of discrepant samples, the sensitivities of the N gonorrhoeae assays were 100% and 61.5% for the in-house PCR and Gen-Probe, respectively, while specificities were comparable at 99.5% and 100%.

CONCLUSIONS

The in-house PCR for the detection of N gonorrhoeae DNA is at least comparable to Gen-Probe in performance. An extended evaluation period should elucidate if the additional five GO-PCR positive specimens, confirmed by 16S PCR, are caused by persistence of DNA or whether the method is indeed more sensitive.

Multiplex AMPLICOR PCR screening for Chlamydia trachomatis and Neisseria gonorrhoeae in women attenting non-sexually transmitted disease clinics. The European Chlamydia Epidemiology Group

A new PCR kit (AMPLICOR CT/NG; Roche Diagnostic Systems, Inc., Branchburg, N.J.) was used as a screening tool for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in first-void urine (FVU) specimens from 3,340 asymptomatic women attending European health care units for contraceptive advice or pregnancy termination. All samples were kept frozen (-20 degrees C) prior to testing. Chlamydia-positive samples were retested once by the plasmid-based PCR kit and also by a major outer membrane protein (MOMP) primer-based PCR. Discrepancies were resolved by using the direct immunofluorescence test (DIF) with the centrifuged sediment of the FVU specimens. Samples positive for N. gonorrhoeae were retested by chromosomal primer-based PCR and verified by a 16S RNA PCR. Of the samples tested, 1.8% were considered inhibitory by using the internal amplification control. Of 81 samples positive for C. trachomatis, 74 samples were positive by both plasmid- and MOMP-based PCRs, 6 samples were positive by plasmid-based PCR and DIF, and one sample was positive by both MOMP-based PCR and DIF. Nine samples (0.3%) were positive for N. gonorrhoeae by the chromosomal primer-based PCR; however, none of the results could be confirmed. The test offers the unique ability to identify inhibition of amplification with the optional internal control.

Ligase chain reaction for detection of Neisseria gonorrhoeae in urogenital swabs

The ligase chain reaction (LCR) is an in vitro nucleic acid amplification technique that exponentially amplifies targeted DNA sequences. In a multicenter study, we evaluated the use of a 4-h LCR-based assay for the diagnosis of Neisseria gonorrhoeae infection of the cervix and male urethra. The LCR results were compared with those of culture for N. gonorrhoeae by using selective media. This assay amplifies target sequences within the N. gonorrhoeae opacity gene. Discordant LCR-positive and culture-negative specimens were further evaluated by testing by another LCR assay which used N. gonorrhoeae-specific pilin probe sets. A total of 1,539 female endocervical specimens and 808 male urethral swab specimens were evaluated in the study. An expanded "gold standard" was defined to include all culture-positive as well as culture-negative, confirmed LCR-positive specimens. After resolution of discrepant samples, the sensitivities of the N. gonorrhoeae LCR assays for the female and male specimens were 97.3 and 98.5%, respectively, with specificities of 99.6 and 99.8%, respectively. Resolved culture sensitivities were 83.9 and 96.5% for the female and male specimens, respectively. The LCR assay for gonorrhea is a rapid, highly sensitive nonculture method for detecting gonococcal infection of the cervix and male urethra.

Duplex PCR system for simultaneous detection of Neisseria gonorrhoeae and Chlamydia trachomatis in clinical specimens

AIMS

To evaluate the use of a duplex polymerase chain reaction (PCR) assay for the simultaneous detection of Neisseria gonorrhoeae and Chlamydia trachomatis in clinical samples.

METHODS

Genital swab specimens were obtained from both China (203 swabs) and Hong Kong (202 swabs). N gonorrhoeae and C trachomatis were detected in each specimen with a number of tests including enzyme immunoassays (IDEIA) and PCR assays using both single and double primer pairs. The primer pair for N gonorrhoeae was derived from the cppB gene on its cryptic plasmid and the PCR product was 390 base pairs long. For C trachomatis, the PCR product was 473 base pairs long, resulting from amplification of a sequence in the common 7.4 kilobase plasmid present in all serovars. For N gonorrhoeae, PCR results were also compared with those obtained by culture and Gram's smear of the discharges.

RESULTS

For the 203 specimens collected in China, similar numbers of positive results (177) were obtained by both Gonozyme and duplex PCR for the detection of N gonorrhoeae. No discrepant results were found among the cultured specimens when Gonozyme and duplex PCR were compared. C trachomatis was detected in 47 specimens by duplex PCR, but was detected in only 28 by IDEIA. Of the 202 Hong Kong specimens, 46 were positive for N gonorrhoeae, detected by both Gonozyme and duplex PCR; 34 were positive for C trachomatis, 25 of which were detected by IDEIA and the remainder by duplex PCR.

CONCLUSIONS

The duplex PCR assay is a satisfactory diagnostic tool for the simultaneous detection of N gonorrhoeae and C trachomatis in clinical swab samples. Further evaluation is suggested.

Detection of cervical Chlamydia trachomatis and Neisseria gonorrhoeae with deoxyribonucleic acid probe assays in obstetric patients

OBJECTIVE

The Gen-Probe PACE 2 deoxyribonucleic acid probe assays for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae are targeted against the ribosomal ribonucleic acid of each pathogen. Our study compared the performance of the probe assays with culture for Chlamydia trachomatis (246 patients) and Neisseria gonorrhoeae (310 patients) while screening obstetric patients.

STUDY DESIGN

Using culture as a gold standard, we assessed the sensitivity, specificity, positive predictive value, and negative predictive value of the chlamydia and gonorrhea probes.

RESULTS

The prevalence of chlamydia by culture was 13.4% and gonorrhea 4.8%. Against culture, the chlamydia probe assay performed as follows: sensitivity 93.9%, specificity 99.1%, positive predictive value 93.9%, and negative predictive value 99.1%. Values for the gonorrhea probe assay were 93.3%, 99.0%, 82.4%, and 99.7%, respectively. Additional molecular analysis of probe-positive-culture-negative specimens suggests that the gonorrhea probe-positive predictive value may be even higher.

CONCLUSION

The Gen-Probe PACE 2 deoxyribonucleic acid probe assays for chlamydia and gonorrhea appear to be promising as convenient, reliable, and cost-effective alternatives to conventional cultures in screening obstetric patients.

Urethritis caused by neisseria meningitidis: a case report

Isolation of N. meningitidis from the male urethra has become more common in recent years and this has been attributed to sexual activities and changes in social attitudes. We describe a further case of acute urethritis caused by transmission of N. meningitidis occurring after a single sexual contact (fellatio) in a heterosexual man. The urethritis was initially diagnosed as being caused by N. gonorrhoeae on a presumptive basis, then attributed to N. meningitidis serogroup Y. This case shows the need of accurate diagnostic procedures in all cases resembling gonococcal urethritis.

Laboratory methods in genitourinary medicine. Methods of diagnosing gonorrhoea

Gonorrhoea is normally diagnosed presumptively by the presence of intracellular Gram-negative cocci on a Gram stain and confirmed by culture of the causative organism, Neisseria gonorrhoeae. Alternative methods have been evaluated extensively for the detection of gonococci in clinical specimens including immunological techniques such as ELISA and immunofluorescence, DNA probes, genetic transformation and the limulus lysate assay. Some of these tests have proved as sensitive and specific for the detection of gonorrhoea in symptomatic men as the Gram stain but offer no advantage in time or cost. In women, no test has been found that shows a sensitivity and specificity sufficiently adequate for clinical use. Culture in men and women remains the method of choice for diagnosis. In addition the need to obtain the infecting organism for antibiotic susceptibility testing has not been overcome. In contrast, the rapid identification of N gonorrhoeae can be achieved within four hours using either monoclonal antibodies or by the detection of preformed enzymes. New methods for both the detection and identification of N gonorrhoeae should be carefully evaluated particularly for use in cases of child and sexual abuse where medico-legal problems may arise.

Rapid diagnosis of common sexually transmitted diseases in adolescents: a review

Sexually transmitted diseases (STDs) represent a significant health problem for adolescents in the United States. As a result, clinicians from a number of disciplines, among them pediatrics and dermatology, may be called on to evaluate teenage patients with these infections. Traditionally, the diagnosis of many STDs has relied on isolation of the causative organisms in culture. While such procedures typically offer optimal diagnostic accuracy, they are often time consuming and expensive, and may not be widely available. In an attempt to remedy this, culture-independent techniques have been developed to permit more rapid and economical diagnosis of these important pathogens. The strengths and limitations of these methods must be understood, however, for the tests to be used effectively.

Evaluation of a prototype DNA probe test for the noncultural diagnosis of gonorrhea

A prototype, nonisotopic, chemiluminescent DNA probe test called the Gen-Probe PACE (Probe Assay-Chemiluminescence Enhanced) system for Neisseria gonorrhoeae (Gen-Probe, San Diego, Calif.) was compared with conventional Martin-Lewis culture medium in JEMBEC plates for the laboratory diagnosis of gonorrhea. This 2-h noncultural assay is based upon the use of an acridinium ester-labeled DNA probe. The rRNA-directed DNA probe hybridizes with the target rRNA, and the hybridized probe is separated from the unhybridized probe through the use of magnetic microparticles. The esterified acridinium is hydrolyzed from the hybridized probe by the addition of an alkaline hydrogen peroxide solution, resulting in the production of visible light which is measured in a luminometer. The amount of light generated is directly proportional to the amount of gonococcal target rRNA present in the sample. A total of 407 clinical specimens (203 urethral and 204 endocervical) were collected from high-risk walk-in patients attending a sexually transmitted disease clinic. Separate patient specimens were collected for culture on Martin-Lewis medium in JEMBEC plates and for DNA probe assay. Statistical analysis of the overall comparative results showed that the DNA probe assay had a sensitivity, specificity, and positive and negative predictive values of 93, 99, 97, and 99%, respectively, in a patient population with a gonococcal disease prevalence of 21%. The results of this comparative study showed that the prototype chemiluminescent DNA probe assay is a rapid and reliable noncultural alternative for the laboratory diagnosis of gonorrhea.

Identification of Neisseria gonorrhoeae with the ORTHOProbe DNA probe test

We evaluated and compared the ORTHOProbe DNA hybridization test (Ortho Diagnostic Systems, Inc., Raritan, NJ) with conventional carbohydrate fermentation and commercial rapid tests for identifying gonococci (GC). The ORTHOProbe system employs a biotinylated DNA probe that hybridizes specifically with chromosomal target sequences of GC. Hybridization is detectable visually following the addition of a streptavidin-peroxidase conjugate in a rapid 10-min. assay. A total of 200 clinical isolates resembling Neisseria (gram-negative, oxidase-positive diplococci) cultured from various sites were tested. The ORTHOProbe test reacted strongly with all GC (94) and not with nongonococcal organisms (106), yielding a sensitivity and specificity of 100%. The ORTHOProbe system provides a convenient and reliable test for identifying Neisseria gonorrhoeae.

Historical perspectives and identification of Neisseria and related species

The pathogenic Neisseria spp., N. gonorrhoeae and N. meningitidis, have been studied extensively and rapid identification procedures have been designed to distinguish these species from the commensal Neisseria and related species that are normal flora of the oro- and nasopharynx. The commensal Neisseria spp. have been largely ignored except for isolated studies. It is important that we know about these species, however, because not only may some be misidentified as pathogenic species if identified with inappropriate procedures, but also they may occasionally be isolated from unusual sites and must be correctly identified to the species level for clinical purposes.

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.

Neisseria gonorrhoeae: a versatile pathogen

Neisseria gonorrhoeae is one of the most important causes of sexually transmitted disease. We do not fully understand the pathogenesis of infection with this organism, although recent improvements in immunological and molecular techniques have brought us closer to an answer. These techniques are now also being used to detect and identify N gonorrhoeae and to analyse the epidemiology of gonorrhoea. Plasmid and chromosomal mediated antibiotic resistance increases the difficulty of controlling gonorrhoea. Resistant strains occur all over the world and new patterns of resistance are still emerging. A better understanding of gonococcal pathogenicity is necessary for the development of an effective vaccine. Despite work on pili and outer membrane proteins no vaccine yet exists. The control of gonorrhoea still depends on diagnosis, treatment, and epidemiological control, facilities that are not widely available in many of those parts of the world where gonorrhoea is a major problem.

Rapid detection methods in microbiology: are they right for your office?

This article discusses some of the direct test methods for diagnosing Group A streptococcal pharyngitis, urinary tract infection, and the three most common sexually transmitted diseases: gonorrhea, Chlamydia, and Herpes simplex virus infection. Emphasis is placed on their practicality for the office setting as well as the limitations of the test methods in various patient populations.

Diagnosis of Neisseria gonorrhoeae and Chlamydia trachomatis infections using antigen detection methods

Rapid antigen detection methods have great potential value in managing sexually transmitted gonococcal and chlamydial infections. Ideally, such tests should be rapid, technically simple, inexpensive, accurate, and applicable to all sites of infection commonly sampled (cervix, urethra, pharynx). For gonorrhea, the Gram stain fulfills these criteria in men with symptomatic urethritis, but lacks sensitivity when used at other sites or in asymptomatic patients. Antigen detection for gonorrhea would thus be of greatest value in 1) the diagnosis of gonococcal cervical infections in women with mucopurulent cervicitis or pelvic inflammatory disease, 2) the diagnosis of gonococcal proctitis in homosexual men, and 3) in situations requiring lengthy specimen transport. Because culture confirmation of Chlamydia trachomatis infections is not widely available, antigen detection tests could be of great value in management of these infections. Major uses include 1) confirming infection in women with cervicitis, endometritis, and pelvic inflammatory disease; 2) screening for asymptomatic infections in high risk groups of women; and 3) confirmation of Chlamydia trachomatis infections in infants and in adult males. The currently available methods for diagnosis of gonococcal and chlamydial infection by antigen detection are reviewed herein. Continued experience with antigen detection tests in well defined populations having high and low risk of gonococcal and chlamydial infection is needed to more fully determine how best to utilize these assays.

Validity and cost-effectiveness of the Gonozyme test in the diagnosis of gonorrhea

Although bacterial culture is considered to provide the most definitive diagnosis of gonorrhea, it has limitations when specimens must be transported long distances. A study was carried out to evaluate the validity and cost-effectiveness of an alternative method of diagnosing gonorrhea, the Gonozyme test, a commercially available enzyme immunoassay. Urogenital specimens from 100 men and 100 women with symptoms suggestive of or a history of exposure to gonorrhea were tested for the presence of Neisseria gonorrhoeae by means of bacterial culture and for gonococcal antigen with the Gonozyme test. The specimens from the men were also examined by means of microscopy of Gram-stained smears. The sensitivity and specificity of the Gonozyme test with reference to culture results were 95.6% and 97.4% respectively in the men and 84.2% and 98.7% in the women. The predictive value of a positive result was 91.6% in the men and 94.1% in the women, and the predictive value of a negative result 98.6% in the men and 96.3% in the women. The cost-effectiveness of the Gonozyme test was higher than that of bacterial culture in this population, which had a high prevalence rate of gonorrhea (23% in the men and 19% in the women). The Gonozyme test would be an adequate alternative to culture for the diagnosis of gonorrhea and contact tracing in areas far from diagnostic laboratories.

Use of gonozyme on urine sediment for diagnosis of gonorrhea in males

We compared enzyme immunoassay (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of gonococcal antigen in urine sediments with urethral swab culture for diagnosis of gonorrhea in men attending a venereal disease clinic. The prevalence of infection was 14% by culture (27/196). The sensitivity of enzyme immunoassay was 93% (25/27) compared with the culture method, and the specificity was 99% (167/169). The ability to detect gonococcal antigen in urine sediment may provide the basis for a noninvasive method of screening for gonococcal infection.

Evaluation of a direct immunofluorescence test for diagnosing gonorrhoea

A new direct immunofluorescence reagent (Syva and Genetic Systems Inc) was evaluated for its ability to detect Neisseria gonorrhoeae in specimens from populations with a high prevalence of the infection. Gonorrhoea was diagnosed by culture in 45 of 105 (43%) urethral specimens from men and 17 of 90 (28%) urethral and 25 of 60 (42%) cervical specimens from women. In men the immunofluorescence test had a sensitivity of 84.4% and a specificity of 100%; Gram staining gave values of 94% and 100%, respectively. The sensitivity of the immunofluorescence test could be increased to 89% by testing duplicate smears. In women the immunofluorescence test had a sensitivity of 65% and a specificity of 98% for urethral samples and values of 72% and 94%, respectively for cervical samples. At both sites the sensitivity of the Gram stain was 40% and the specificity 100%. The testing of duplicate immunofluorescence smears increased the sensitivity to 76% for urethral and 88% for cervical samples.

Solid-phase enzyme immunoassay for detection of Chlamydia trachomatis

The prototype of a solid-phase enzyme immunoassay for the detection of Chlamydia trachomatis antigen was tested in 403 men and 135 women attending a venereal disease clinic. Culture on HeLa 229 cells was used as reference method. In men the overall sensitivity and specificity of the enzyme immunoassay was 70% and 98.5% respectively. In the 158 men with non-gonococcal urethritis the sensitivity and specificity was 73% and 96.5% respectively, in the 31 men with post-gonococcal urethritis 82% and 100%, in the 48 men with gonococcal urethritis 67% and 100%, in the 125 men with discharge but normal urinary sediment 54% and 99.1% and in the 41 men with no signs or symptoms 50% and 100%. In women the sensitivity and specificity of the assay was 70% and 92% respectively. On account of the low degree of sensitivity in both men and women and the low degree of specificity in women the prototype of the enzyme immunoassay is not yet considered suitable for clinical use. An improved model is being developed.

Evaluation of Gonodecten for the presumptive diagnosis of gonococcal urethritis in men

Gonodecten (Gd; U.S. Packaging Corp., LaPorte, Ind.) is a commercially available test for the presumptive diagnosis of gonococcal urethritis in men. With this test, urethral discharge is collected on a swab, placed in a plastic tube, and moistened with oxidase reagent. Development of a purple color on the swab within 3 min indicates the presence of gonococci. This system was compared with culture and Gram-stained smear for the diagnosis of gonorrhea. Of 240 specimens tested, 174 were positive with culture, Gram stain, and the Gd test and 48 were negative with all tests. For eight specimens, cultures and smears were positive, but the Gd test was negative. Nine specimens produced positive Gd tests with negative smears and cultures. Only one specimen was positive on culture and with the Gd test and negative on Gram-stained smear. Haemophilus species were isolated from 14 specimens; 5 produced positive Gd test reactions, with gonococci being coisolated from 4. The sensitivity and specificity of the Gd test compared with culture were 95.6 and 84.2%, respectively, whereas the Gram stain was 99.5% sensitive and 100% specific compared with culture. The Gd test may be a useful screening test for the diagnosis of gonorrhea in men with urethral discharge, particularly in settings where a microscope, Gram stain reagents, or technological expertise is not readily available.

Immunodiagnosis of sexually transmitted disease

Methods for detecting microbial antigens in clinical specimens offer an alternative to culture in the diagnosis of some sexually transmitted diseases. Developers of the immunologic methods are faced with a number of problems in evaluating the new tests. Traditionally, these tests are compared to culture as the "gold standard." Unfortunately, culture for Neisseria gonorrhoeae or Chlamydia trachomatis--the two agents most commonly sought--is considerably less sensitive than 100 percent. Immunologic methods may appear to produce false positives when the paired specimens are actually false-negative cultures. Another source of discordant results is sampling variation. These considerations, however, will not account for all false-positive results. Even the best non-culture methods have a low rate of false-positive results. If a new test has a specificity of 97 percent, it, by definition, yields approximately 3 percent false-positive reactions. In low-prevalence settings this false-positive rate will create problems in interpreting the results. For example, in a population with 3 percent prevalence of infection, a positive result in a 97 percent specificity test could only have a predictive value of 50 percent. Most testing for STD agents is performed in low-prevalence settings. None of the currently available immunodiagnostic procedures has a performance profile that suggests it will be satisfactory for diagnostic use in the low-prevalence setting.

Evaluation of Gonozyme, an enzyme immunoassay for the rapid diagnosis of gonorrhea

A new indirect enzyme immunoassay (EIA), Gonozyme (Abbott Laboratories), was assessed for rapid detection of gonococcal antigens. A correlation of optic density (OD) readings by EIA with colony counts of serial dilutions of Neisseria gonorrhoeae ATCC 19424 disclosed that EIA detected 10(3) CFU/ml at OD readings of 0.1 to 0.3, that EIA consistently detected greater than or equal to 10(4) CFU/ml at OD readings of 0.6 to 1.3, and that concentrations of greater than or equal to 10(5) CFU/ml were associated with OD readings of greater than or equal to 2.0. The clinical usefulness of Gonozyme was evaluated by comparing results of EIA with those of Gram stain (GS) and culture for N. gonorrhoeae from urethral and endocervical swabs obtained prospectively in 886 randomly selected patients attending a clinic for sexually transmitted diseases. The patients evaluated included 83 female contacts of men with gonorrhea and 56 patients seen at the clinic for test of cure. In tests with 295 males, the sensitivities of GS and EIA were 91.3 and 97.1%, respectively, and both tests had specificities of greater than 96%. In tests with 591 females, the sensitivities of GS and EIA were 51.4 and 96.4%, respectively (P less than 0.0001, Z proportionality test), and the specificities were 98.7 and 86.5%, respectively (P less than 0.0001). In tests with 61 females and 3 males, EIA was positive, whereas GS and cultures were negative for N. gonorrhoeae. Gonozyme is a highly sensitive method for rapid detection of gonococcal antigens. EIA is comparable to GS for males and more sensitive though less specific than GS for females. Possible reasons for the lower specificity of EIA for females are discussed. Due to its high negative predictive value for female contacts, EIA offers an alternative to epidemiological treatment of contacts before culture results.

Modified enzyme immunoassay for detecting Neisseria gonorrhoeae antigens

A commercial modification of an enzyme immunoassay (EIA) (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of Neisseria gonorrhoeae antigens was compared with conventional culturing. Specimens from males and females were collected at a sexually transmitted disease clinic; additional female specimens were collected at an obstetrics and gynecology clinic. EIA sensitivity and specificity for males were 100 and 98.6%, respectively (68 negative, 34 positive, 1 false-positive, and 0 false-negative). EIA sensitivity and specificity for female sexually transmitted disease clinic patients were 74.4 and 95.7%, respectively (66 negative, 29 positive, 3 false-positive, and 10 false-negative) EIA sensitivity and specificity for obstetrics and gynecology clinic patients were 100 and 99.2%, respectively (6 positive, 119 negative, 1 false-positive, and 0 false-negative). In female patients from whom multiple swab specimens were collected, the sequence of specimen collection and subsequent EIA analysis affected sensitivity.

Sensitivity and specificity of monoclonal antibodies directed against antigenic determinants of Treponema pallidum Nichols in the diagnosis of syphilis

Murine anti-Treponema pallidum monoclonal antibodies were employed in studies on sensitivity and specificity of binding to examine their potential for use in the detection of low numbers of pathogenic treponemes present in various body fluids. Monoclonal antibodies were used as a primary antibody source in a solid-phase immunoblot assay system. All monoclonal antibodies assayed were capable of detecting ca. 1.0 X 10(3) to 2.5 X 10(3) treponemes. Of 13 monoclonal antibodies examined, 3 were able to detect 10(3) virulent treponemes, and 1 of these antibodies was able to reveal the presence of as few as 500 organisms. Western blot analyses showed that all anti-T. pallidum monoclonal antibodies exhibiting high sensitivities for the detection of T. pallidum cells were directed against an abundant, 47,000-dalton surface-exposed antigen of the organism (S. A. Jones, K. S. Marchitto, J. N. Miller, and M. V. Norgard, Abstr. Annu. Meet. Am. Soc. Microbiol. 1984, B173, p. 46; K. S. Marchitto, S. A. Jones, and M. V. Norgard, Abstr. Annu. Meet. Am. Soc. Microbiol. 1984, B182, p. 48). Differences in binding properties of the various monoclonal antibodies were most likely a reflection of differential binding affinities or their specificities for different epitopes on the 47,000-dalton surface antigen. With two possible exceptions, the monoclonal antibodies tested reacted specifically with T. pallidum, either purified or found within a high-contaminating tissue background, and not with Treponema phagedenis biotype Reiter, Haemophilus ducreyi, Neisseria gonorrhoeae, herpes simplex virus type 2, or normal rabbit testicular tissue. The high sensitivity and specificity exhibited by these anti-T. pallidum monoclonal antibodies make them excellent candidates for employment in new syphilis or other treponemal diagnostic tests designed to detect very low numbers of pathogenic treponemes in lesion exudates or other body fluids.

Efficacy of an enzyme immunoassay with uncentrifuged first-voided urine for detection of gonorrhea in males

An enzyme immunoassay (Gonozyme; Abbott Laboratories, North Chicago, Ill.) for detection of Neisseria gonorrhoeae antigens was used to screen 184 urethral or uncentrifuged first-voided urine or both specimens from males and 78 cervical specimens. When compared with culture, the sensitivity and specificity of Gonozyme for cervical and urethral specimens were comparable to those in published reports. The sensitivity and specificity for urine specimens were 91.6 and 97.9%, respectively.