The Use of Molecular Techniques for the Diagnosis and Epidemiologic Study of Sexually Transmitted Infections

Delivery of Chlamydia vaccines

The plethora of ocular, genital and respiratory diseases of Chlamydia, including nongonococcal urethritis, cervicitis pelvic inflammatory disease, ectopic pregnancy, tubal factor infertility, conjunctivitis, blinding trachoma and interstitial pneumonia, and chronic diseases that may include atherosclerosis, multiple sclerosis, adult onset asthma and Alzheimer's disease, still pose a considerable public health challenge to many nations. Although antibiotics are effective against Chlamydia when effectively diagnosed, asymptomatic infections are rampart, making clinical presentation of complications often the first evidence of an infection. Consequently, the current medical opinion is that an effective prophylactic vaccine would constitute the best approach to protect the human population from the most severe consequences of these infections. Clinical and experimental studies have demonstration that Chlamydia immunity in animals and humans is mediated by T cells and a complementary antibody response, and the completion of the genome sequencing of several isolates of Chlamydia is broadening our knowledge of the immunogenic antigens with potential vaccine value. Thus, major advances have been made in defining the essential elements of a potentially effective subunit vaccine design and parameters for evaluation. However, the challenge to develop effective delivery systems and human compatible adjuvants that would boost the immune response to achieve long-lasting protective immunity remains an elusive objective in chlamydial vaccine research. In response to evolving molecular and cellular technologies and novel vaccinology approaches, considerable progress is being made in the construction of novel delivery systems, such as DNA and plasmid expression systems, viral vectors, living and nonliving bacterial delivery systems, the use of chemical adjuvants, lipoprotein constructs and the codelivery of vaccines and specific immuno-modulatory biological agonists targeting receptors for chemokines, Toll-like receptors, and costimulatory molecules. The application of these novel delivery strategies to Chlamydia vaccine design could culminate in timely achievement of an efficacious vaccine.

Prevalence ofChlamydia TrachomatisInfections in Symptomatic Patients in Bulgaria

The aim of the study was to investigate the prevalence of C. trachomatis infection in symptomatic patients and to compare our data with similar studies made in Bulgaria. 822 patients were included in the study with a diagnosis suggestive of Chlamydial infection: urethritis, prostatitis, Reiter syndrome, cervicitis, salpingitis, pelvic inflammatory disease, ectopic pregnancy, infertility, etc. The samples were cell cultured on McCoy and detected by immunofluorescence with anti-lipopolysaccharide monoclonal antibody. The prevalence of C. trachomatis infection in symptomatic patients was about 37% in the investigated 822 urogenital samples (568 women and 254 men). Active infection with C. trachomatis was detected in 39% of the women and in 33% of the men. Our study shows a relatively high prevalence of C. trachomatis infection in symptomatic patients; a lower prevalence of the infection in comparison with other Bulgarian studies, using different methods for detection. The results prove the high sensitivity and specificity of the cell-culture method for the detection of Chlamydial infections and the need for screening of the symptomatic patients and their sexual partners for Chlamydial infection.

Surveillance and modelling of HIV, STI, and risk behaviours in concentrated HIV epidemics

BACKGROUND

HIV epidemics in most countries are highly concentrated among population subgroups such as female sex workers, injecting drug users, men who have sex with men, mobile populations, and their sexual partners. The perception that they are important only when they cause epidemic expansion to general populations has obscured a critical lack of coverage of preventive interventions in these groups, as well as appropriate methods for monitoring epidemic and behavioural risk trends. The difficulties in accessing such groups have likewise often cast doubt on the representativeness of observed disease and behavioural risk estimates and their validity and reliability, particularly those related to sampling and the measurement of risk behaviours.

OBJECTIVES

To review methodological obstacles in conducting surveillance with population subgroups in concentrated HIV epidemics, elaborate on recent advancements that partially overcome these obstacles, and illustrate the importance of modelling integrated HIV, STI, and behavioural surveillance data.

METHODS

Review of published HIV, STI, and behavioural surveillance data, research on epidemic dynamics, and case studies from selected countries.

CONCLUSIONS

The population subgroups that merit regular and systematic surveillance in concentrated epidemics are best determined through extensive assessment and careful definition. Adherence to recently refined chain referral and time location sampling methods can help to ensure more representative samples. Finally, because of the inherent limitations of cross sectional surveys in understanding associations between complex sexual behaviours and HIV and STI transmission, mathematical models using multiple year data offer opportunities for integrated analysis of behavioural change and HIV/STI trends.

[Up to date in sexually transmitted infections: epidemiology, diagnostic approaches and treatments]

In the last years, there have been important advances in sexually transmitted infections such as genome sequencing of Treponema pallidum, Chlamydia trachomatis or Mycoplasma genitalium; the new taxonomic position of Calymmatobacterium granulomatis; commercial diagnostic systems based on nucleic acid amplification; the emergence of quinolone resistance in Neisseria gonorrhoeae; new therapeutic approaches in vulvovaginal candidiasis that include boric acid; the demonstration that valacyclovir reduces the risk of transmission of genital herpes or the availability of immune-response modifier in the treatment of genital warts, and that are questions in the goal of this review. Viral hepatitis and HIV were no reviewed by space reasons.

Principles of molecular microbiology testing methods

Molecular testing methods have the potential to replace many conventional microbiology laboratory assays. Recent refinements in technology have resulted in more user-friendly testing platforms. These platforms are automated and have lowered risks for contamination, decreased costs, and are faster than older platforms. The success of these technologies depends on their successful application to patient care. Quality issues include appropriate specimens for analysis, performance characteristics of different analytical methods, optimal specimen processing, the effects of PCR inhibitors, and false-positive results caused by contaminating nucleic acids. Quality control guidelines for molecular microbiologic diagnostic assays are in their infancy and require further development. Additionally, the problem of "too much" sensitivity (brought on by the extreme sensitivity of these techniques coupled with the potential presence of small numbers of pathogenic organisms in asymptomatic individuals) should be considered. Potential problems when monitoring therapy (because molecular detection techniques do not generally have the ability to determine whether an organism is dead or alive) can also occur. Cost-effective test use, pathogen- or disease-targeted algorithms, and standardized methods will be necessary for the true value of these technologies to be realized. This is especially important, because, unlike traditional culture methods, most molecular microbiology methods are pathogen-specific. Clinicians familiar with the reasons why "pan-culture" (i.e., requesting all culture possibilities at once) is inadvisable should not use the same irrational approach when requesting molecular tests. The clinical usefulness of molecular testing will be maximized as targeted algorithms are developed and an understanding of molecular test ordering patterns is realized. Laboratory technicians and physicians must continue to apply and combine theories of traditional microbiology, clinical chemistry, and general medicine to the understanding and application of molecular diagnostics.

Impact of New Sexually Transmitted Disease Diagnostics on Clinical Practice and Public Health Policy

Nucleic acid amplification tests (NAAT) offer enhanced sensitivity and excellent specificity for many sexually transmitted diseases. For some pathogens for which a practical diagnostic test does not exist, such as human papillomavirus (HPV), NAAT are also useful. Further, most NAAT can be applied to less "invasive" patient specimens, including urine and vaginal fluid. This dramatically increases opportunities to test persons outside of traditional clinic settings. Use of NAAT has resulted in revisions of the proportion of sexually transmitted diseases (STDs) that are asymptomatic, and has increased measured prevalence of some STDs, notably Chlamydia trachomatis. NAAT have helped to clarify the eitiologies of genital ulcer disease and urethritis, and have provided a more complete picture of the natural history of genital herpes and HPV. The ability of polymerase chain reaction to detect HPV may change the management of patients who have abnormal Pap smears. Efforts to bear the relatively high cost of NAAT, such as pooling urine, are under study. NAAT for bacterial STD should be in populations at high risk for asymptomatic STD, especially those who might not access routine STD screening at traditional settings. Working through the cost to health care systems, including the public health arena, and implementation at the laboratory level are challenges to overcome before NAAT become the standard of care in most settings.

New tests for bacterial sexually transmitted diseases

Recent advances in diagnostic tests for sexually transmitted diseases include the development of a synthetic Venereal Disease Research Laboratory reagent that will improve the sensitivity and stability of nontreponemal serologic tests for syphilis. A second generation user friendly and high throughput nucleic acid amplification test for Chlamydia trachomatis and Neisseria gonorrhoeae has also been developed.