Sexually Transmitted Infections

Sexually transmitted infections are infections transmitted from person to person through sexual contact. Other routes of transmission include mother-to-child transmission (during pregnancy and childbirth) and intravenous transmission.

Most Common Causative Agents

There are several sexually transmitted bacteria, viruses, and parasites:

• Chlamydia trachomatis
• Neisseria gonorrhoeae
• Treponema pallidum
• Haemophilus ducreyi
• Mycoplasma genitalium
• Human Immunodeficiency Virus (HIV 1 and 2)
• Herpes Simplex Virus (HSV 1 and 2)
• Human Papillomavirus
• Hepatitis B and C viruses
• Trichomonas vaginalis
• Phthirus pubis (causative agent of pubic lice)
• Sarcoptes scabiei (the causative agent of scabies).
• Chlamydia trachomatis and Neisseria gonorrhoeae
  These are the most common bacterial agents in STIs, with an increasing prevalence among young adults.
• Trichomonas vaginalis and Mycoplasma genitalium
  These are agents with a well-established role in genital disease.

Other microorganisms that can also cause genital infections, although they are not STIs, include: Mycoplasmas and Ureaplasmas, Candida sp., and Gardnerella vaginalis.

What are the consequences?

The consequences of STIs have a profound impact on sexual and reproductive health.

Untreated infections with Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma genitalium are associated with serious complications such as pelvic inflammatory disease (PID) and infertility.

Other consequences include ectopic pregnancy, preterm birth, chronic pelvic pain, and systemic disease. Infection with Trichomonas vaginalis increases the risk of acquiring and transmitting the human immunodeficiency virus (HIV).

What are the most common symptoms?

Why is diagnosis important?

Sexually transmitted infections are a major public health problem.

The diagnosis and management of STIs are based on the onset of the disease or specific symptoms (1). Many patients are asymptomatic, which increases the risk of complications and transmission. Screening of asymptomatic target populations is essential. Partners should also be screened and treated to prevent reinfection and break the chain of transmission

LABORATORY DIAGNOSIS - New Technologies in the Diagnosis of STIs

Many STI-causing microorganisms are not detected by standard methods (serology and culture). New molecular biology techniques applied to samples of genital secretions and urine have led to significant advances in diagnosis.

At the laboratories of the Prof. Germano de Sousa Center for Laboratory Medicine, it is possible to perform laboratory testing on asymptomatic individuals or those suspected of having an infection with:

Chlamydia trachomatis

• Lymphogranuloma venereum (LGV)-causing organisms
• Non-lymphogranuloma venereum (NLGV)-producing

Neisseria gonorrhoeae Mycoplasma genitalium Trichomonas vaginalis

Detection is performed by PCR (polymerase chain reaction), with amplification of the DNA of each microorganism in the sample. Visualization of the amplified product is made possible by a new technological platform based on low-density arrays: CLART® (Clinical Array Technology).

The test performed in our laboratory allows for the simultaneous detection of these organisms (co-infection) in the same sample.

Indirect immunological methods (detection of antibodies against the infectious agent) or direct methods (detection of the infectious agent using specific antibodies against it) are less sensitive and specific when compared to molecular biology methods; therefore, the latter should always be preferred for the diagnosis of STIs.

What is the added value of performing a molecular biology test that detects multiple microorganisms?

These tests allow for the simultaneous detection of the most common causative agents of STIs, leading to a faster diagnosis and more targeted clinical decisions.

Several STI-causing agents can be transmitted during a single sexual encounter, and it is common for patients to have two or more STIs at the same time.

Bibliography

• www.who.int/reproductivehealth
• www.cdc.gov/std/Treatment/
• Jalal H., Delaney A., Bentley N., Sonnex C., Carne C. Molecular epidemiology of selected sexually transmitted infections. Int J Mol Epidemiol Genet 2013;4(3):167-174
• J D C Ross, J S Jensen. Mycoplasma genitalium as a sexually transmitted infection: implications for screening, testing, and treatment. Sex Transm Infect 2006;82:269-271.
• Barreiros H., Azevedo J., Santo I. Gonococcal infection at the STD clinic of the Lapa Community Health Center (2007–2011). Revista SPDV 71(1) 2013
• Screening for sexually transmitted infections. www.uptodate.com
• Diagnosis of gonococcal infections. www.uptodate.com 2013
• Genital Chlamydia trachomatis infections in women. www.uptodate.com
• Baseline report on global sexually transmitted infection surveillance 2012. WHO
• STIs in Europe 2011. Surveillance report. ECDC.

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