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

An eye on sexually transmitted diseases: sexually transmitted diseases and their ocular manifestations

Ocular examination should be a part of the routine assessment of the patients seen at sexually transmitted diseases (STD) clinics due to the importance of these organs in the general wellbeing of patients. It is essential to keep an open eye on ocular signs and symptoms of patients with a history of exposure to common STD pathogens, to ensure prompt investigation and management of ocular complications of the STDs, which, if left unnoticed, otherwise could subject the patients to a great deal of anxiety and distress.

Nucleotide sequence-based multitarget identification

MULTIGEN technology (T. Vinayagamoorthy, U.S. patent 6,197,510, March 2001) is a modification of conventional sequencing technology that generates a single electropherogram consisting of short nucleotide sequences from a mixture of known DNA targets. The target sequences may be present on the same or different nucleic acid molecules. For example, when two DNA targets are sequenced, the first and second sequencing primers are annealed to their respective target sequences, and then a polymerase causes chain extension by the addition of new deoxyribose nucleotides. Since the electrophoretic separation depends on the relative molecular weights of the truncated molecules, the molecular weight of the second sequencing primer was specifically designed to be higher than the combined molecular weight of the first sequencing primer plus the molecular weight of the largest truncated molecule generated from the first target sequence. Thus, the series of truncated molecules produced by the second sequencing primer will have higher molecular weights than those produced by the first sequencing primer. Hence, the truncated molecules produced by these two sequencing primers can be effectively separated in a single lane by standard gel electrophoresis in a single electropherogram without any overlapping of the nucleotide sequences. By using sequencing primers with progressively higher molecular weights, multiple short DNA sequences from a variety of targets can be determined simultaneously. We describe here the basic concept of MULTIGEN technology and three applications: detection of sexually transmitted pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, and Ureaplasma urealyticum), detection of contaminants in meat samples (coliforms, fecal coliforms, and Escherichia coli O157:H7), and detection of single-nucleotide polymorphisms in the human N-acetyltransferase (NAT1) gene (S. Fronhoffs et al., Carcinogenesis 22:1405-1412, 2001).

Evaluation of the specificities of five DNA amplification methods for the detection of Neisseria gonorrhoeae

The intragenus specificities of five molecular diagnostic methods for Neisseria gonorrhoeae were determined. Three assays were considered suboptimal. Molecular detection of N. gonorrhoeae from sites where other Neisseria spp. commonly occur or from any site in low-prevalence settings should be confirmed by a test targeting a different genetic locus.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Multiplex PCR: optimization and application in diagnostic virology

PCR has revolutionized the field of infectious disease diagnosis. To overcome the inherent disadvantage of cost and to improve the diagnostic capacity of the test, multiplex PCR, a variant of the test in which more than one target sequence is amplified using more than one pair of primers, has been developed. Multiplex PCRs to detect viral, bacterial, and/or other infectious agents in one reaction tube have been described. Early studies highlighted the obstacles that can jeopardize the production of sensitive and specific multiplex assays, but more recent studies have provided systematic protocols and technical improvements for simple test design. The most useful of these are the empirical choice of oligonucleotide primers and the use of hot start-based PCR methodology. These advances along with others to enhance sensitivity and specificity and to facilitate automation have resulted in the appearance of numerous publications regarding the application of multiplex PCR in the diagnosis of infectious agents, especially those which target viral nucleic acids. This article reviews the principles, optimization, and application of multiplex PCR for the detection of viruses of clinical and epidemiological importance.

Mycoplasma genitalium in males with nongonococcal urethritis: prevalence and clinical efficacy of eradication

BACKGROUND

Mycoplasma genitalium is regarded as a potential pathogen of the human urogenital tract based on prevalence findings of several European studies.

GOAL

To determine the prevalence of M genitalium in urethral specimens of symptomatic patients with nongonococcal urethritis and from asymptomatic patients attending a sexually transmitted disease clinic in Milan, and to verify the clinical efficacy of M genitalium eradication by antibiotic treatment.

STUDY DESIGN

From May 1998 to late April 1999, a routine analysis for M genitalium by DNA amplification (polymerase chain reaction) was performed in patients attending the Institute of Dermatological Science in Milan. The authors examined urethral swabs from 178 symptomatic and 23 asymptomatic males. M genitalium-positive patients were clinically and microbiologically tested after treatment with either doxycycline or azithromycin.

RESULTS

Among males with nongonococcal urethritis, M genitalium was detected in 14.0% of patients as the only agent; in 15.1% of patients in association with Chlamydia trachomatis and/or Ureaplasma urealyticum; and in 1 asymptomatic patient. In all symptomatic M genitalium-positive patients, antibiotic treatment eradicated the infection and cured clinical symptoms.

CONCLUSION

These data reveal the high prevalence of M genitalium in symptomatic patients, the rarity of asymptomatic carriers, the high susceptibility to antibiotic treatment, and the clinical efficacy of M genitalium eradication. Moreover, data confirm the etiologic role of M genitalium in inflammatory processes of the human urogenital tract in the Mediterranean area.

Detection of male genital infection with Chlamydia trachomatis and Neisseria gonorrhoeae using an automated multiplex PCR system (Cobas Amplicor)

We evaluated Cobas Amplicor, a highly automated polymerase chain reaction (PCR) system, to test first-void urine (FVU) and urethral swab specimens for Chlamydia trachomatis and Neisseria gonorrhoeae in men attending a sexually transmitted infection (STI) clinic. Results were compared against an in-house radioimmune dot blot (DB) test for C. trachomatis and selective culture for N. gonorrhoeae. Three hundred and ninety sets of specimens were obtained from 378 consecutive new and returned-new patients. Gonorrhoea prevalence was 9.49%, with no significant difference in sensitivity or specificity between culture and PCR. Chlamydia prevalence was 15.4%, with sensitivities of: DB 55%, PCR of FVU 86.7%, urethral swab PCR 90%. The specificity of PCR on FVU and urethral swabs was 100%. We have shown that Cobas Amplicor PCR is highly sensitive and specific in the diagnosis of chlamydia and gonorrhoea in men attending an STI clinic. Further economic and scientific studies are needed to determine the cost-effectiveness of this technique for screening in primary care settings.

A community-based approach to the control of sexually transmitted diseases in the Northern Territory

A program to control sexually transmitted diseases (STDs) was undertaken during a Men's Health Week in a remote Aboriginal community in Western Arnhem Land, Northern Territory. A total of 151 men aged 13 years and over who attended over a five-day period underwent a full physical examination, and first-void urine specimens were tested for the presence of leukocytes, chlamydia (by enzyme immunoassay antigen detection) and gonorrhoea (by culture and antigen detection). Blood was taken for syphilis serology from all patients and for human immunodeficiency virus (HIV) from patients with a proven STD or at the patient's request. Consent for testing was obtained from all participants. Patients with a positive urinary leukocyte test or symptoms were offered urethral swab investigations and treated empirically according to a set protocol. Patients with STDs detected by subsequent laboratory investigations were followed up and treated. The overall prevalence of one or more of syphilis, gonorrhoea or chlamydia was 17.4 per cent. No men presented with genitourinary symptoms and none was HIV-infected. In this population, STDs were an important cause of morbidity, and a community-based approach was adopted to identify infected persons. The use of urine for the detection of gonorrhoea and chlamydia was highly acceptable. Although not used in this study, polymerase chain reaction and ligase chain reaction technology will facilitate similar activities in the future.

Pattern of sexually transmitted diseases among pregnant women in Burkina Faso, west Africa: potential for a clinical management based on simple approaches

OBJECTIVES

(1) To determine the prevalence of sexually transmitted diseases (STDs) in pregnant women in Burkina Faso. (2) To evaluate the potential of clinical management of STDs based on screening with clinical data and urine leucocyte esterase test (LET).

METHODS

Cross sectional study among antenatal clinic attendees was conducted in 1994 in Ouagadougou and Bobo-Dioulasso, the two largest urban centres in Burkina Faso, where more than 94% of the pregnant women benefit from antenatal care at least twice during their pregnancy. Each woman selected underwent an interview, general and gynaecological examination. Genital samples were collected to confirm the presence of STD pathogens. Logistic regression analysis was done to identify models that predict (a) gonorrhoea and/or chlamydia, (b) trichomoniasis and/or bacterial vaginosis, (c) candidiasis. Sensitivity, specificity and positive and negative predictive values of these models were assessed using standard methods.

RESULTS

All 645 consecutive pregnant women were enrolled in the two sites. Among these women 32.4% presented at least one STD. The major STDs were: trichomoniasis (14%), bacterial vaginosis (13%), recent syphilis (3.6%), chlamydial infection (3.1%), genital warts (3%), gonococcal infection (1.6%) and genital ulcer (0.8%). Prevalence of vaginal candidiasis was 14%. The use of a risk marker (length of relationship with regular sexual partner < 3 years), and the positivity +3 of the urine LET provided a sensitivity of 80% and a positive predictive value of 7% for the screening of gonococcal and/or chlamydial infection. If clinical signs and positivity of the urine LET were taken into account sensitivity and positive predictive value of trichomoniasis and/or bacterial vaginosis screening were 77% and 37%, respectively. Clinical signs and positivity of the urine LET showed a low sensitivity (23%) for screening vaginal candidiasis.

CONCLUSIONS

The prevalence of STDs in pregnant women is high in urban Burkina Faso. Systematic screening combined with effective treatment should be included in antenatal care in the future. Urine LET, if associated with interview and clinical examination offers a simple, rapid and affordable tool for systematic screening of STDs in pregnant women. However, the proportion of overtreatments with proposed strategies will be high. Further studies are needed to develop and validate better algorithms with probably cheap laboratory tests.

Evaluation of a screening algorithm for the diagnosis of genital infections with Neisseria gonorrhoeae and Chlamydia trachomatis among female sexworkers in Bénin

BACKGROUND AND OBJECTIVES

In developing countries, simple and cheap procedures for the diagnosis of sexually transmitted diseases (STDs) are urgently needed, especially for screening purposes in high risk groups.

GOALS

To evaluate the sensitivity and specificity of a screening algorithm for STDs among 364 female sex workers in Bénin, in comparison with reference laboratory tests.

STUDY DESIGN

The algorithm relied on the following criteria, which were evaluated in sequence: the presence of endocervical mucopus on visual inspection of the cervix, a positive swab test, or a microscopic examination of vaginal fluid showing more than 10 polymorphonuclear cells per field. The algorithm diagnosed an infection if any one of these criteria was fulfilled. True infectious status was determined by the combined results of culture for Neisseria gonorrhoeae, enzyme immunoassay for Chlamydia trachomatis, and polymerase chain reaction assays for both infections.

RESULTS

Gonococcal or chlamydial infection was diagnosed in 39.8% of the study population according to the reference tests. The algorithm had a sensitivity of 57.9% and a specificity of 61.2%. In the presence of Candida sp or Trichomonas vaginalis, specificity decreased to 39.1%, but sensitivity increased to 67.5%.

CONCLUSIONS

These results underscore the limitations of simple, nonlaboratory diagnostic tools for screening STDs in high-risk groups in developing countries. Further research is needed to increase the validity--especially the sensitivity--of these algorithms.

Detection of Burkholderia pseudomallei in blood samples using polymerase chain reaction

A highly sensitive, specific, rapid and simple method to detect Burkholderia pseudomallei in blood samples was developed. Two 22-base oligonucleotide primers, based on sequences from a specific DNA probe, were used for amplification of bacterial DNA by the polymerase chain reaction (PCR). Amplification with these primers yielded a 178-base pair product in 100 clinical isolates of B. pseudomallei. As little as 0.5 fg of B. pseudomallei DNA was detectable by this method. Experiments involving inoculation of the organism into uninfected blood samples showed that the method could be used to detect as few as 1 bacterial cell ml-1 of whole blood. Non-specific amplification of other bacterial DNAs from 18 samples of bacteria was not observed. Blood samples from seven patients proven to have melioidosis by haemoculture were positive using these primers. The total time required for sample processing, amplification and visualization was approximately 3.5 h. The high sensitivity, rapidity and simplicity of this method should make it valuable for diagnosis, monitoring of drug treatment and for epidemiological studies of the melioidosis.