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Sexually Transmitted Infections (STIs)

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This article provides an overview of sexually transmitted infections (STIs) including the organisms involved, symptoms, signs, investigations and management options. Due to changes in sexual behaviours, diagnostic investigations and demographics, the epidemiology of STIs continue to change, with chlamydia now being the most common STI in the UK.


Risk factors for STIs

  • Unprotected sexual intercourse
  • Multiple sexual partners
  • 15-24 year-olds
  • Illicit drug use and alcohol use
  • Men who have sex with men (MSM)
  • Sex workers
  • Urban areas

Just remember that if one STI is present the chances are there will be another one due to co-infection, so ALWAYS test for others!


Chlamydia

Causative organism

Chlamydia trachomatis

Transmission

These obligate intracellular bacteria are predominantly transmitted via sexual contact. However, perinatal transmission from an infected mother to her baby during vaginal delivery is possible which can lead to neonatal conjunctivitis (ophthalmia neonatorum) and pneumonia.

Presentation

Asymptomatic in more than 80% of cases.

Males: Mucopurulent urethral discharge, dysuria, scrotal pain, proctitis.

Females: Mucopurulent vaginal discharge, cervicitis, cervical bleeding upon contact, proctitis, post-coital bleeding, intermenstrual bleeding.

Diagnostic investigations

Nucleic Acid Amplification Test (NAAT)- First pass urine in males and vulvovaginal swabs in females are used for testing.

If applicable, oropharyngeal and rectal sites should also be swabbed for NAAT testing. It can take up to 14 days from exposure for infection with Chlamydia or Gonorrhoea to show up on a NAAT test, therefore screening should be repeated after this window.

Management

Doxycycline 100mg oral twice daily for 7 days (contraindicated in pregnancy)

or

Azithromycin 1g oral, followed by 500mg daily for 2 days

A full STI screen including blood tests should be performed if not already done. Contact tracing and partner notification need to be offered. Advise that all forms of sexual intercourse need to be avoided until all parties are tested and treated.

A test of cure at around 5 weeks should be offered in cases of rectal infection or pregnancy. For individuals under 25 years of age, repeat testing should be offered at 3 months.

Complications

  • Pelvic inflammatory disease (PID)- increases the risk of ectopic pregnancy and infertility
  • Epididymitis
  • Prostatitis
  • Reactive arthritis

Lymphogranuloma venereum (LGV) is caused by a more invasive serotype of chlamydia trachomatis which presents as a triad of inguinal lymphadenopathy, proctocolitis and fever. Patients with proctitis should have NAAT swabs sent to test for this. Patients with LGV, and HIV-positive individuals with proctitis, should be treated with 3 weeks of Doxycycline and be offered a test of cure at least 3 weeks after completion of treatment.


Gonorrhoea

Causative organism 

Neisseria gonorrhoeae

Transmission

This gram-negative diplococcus bacteria is predominantly transmitted via sexual contact. Mucosal epithelium lining the genital tract, oropharynx and the rectum are most commonly infected. Similar to chlamydia, vertical transmission of gonorrhoea during childbirth can cause ophthalmia neonatorum however the onset of gonococcal conjunctivitis is earlier then chlamydial conjunctivitis.

Presentation

Males: Mucopurulent urethral discharge, dysuria, orchitis.

Females: Mucopurulent cervical discharge with cervicitis, cervical bleeding upon contact, dyspareunia, pelvic pain.

Rectal infection can cause: rectal bleeding, rectal discharge, tenesmus, proctitis.

Oropharyngeal infection can cause: Pharyngitis, anterior cervical lymphadenopathy.

Diagnostic investigations

Nucleic Acid Amplification Test (NAAT)- First pass urine in males and vulvovaginal swabs in females are used for testing.

If applicable, oropharyngeal or rectal sites should also be swabbed for NAAT. It can take up to 14 days from exposure for infection with Chlamydia or Gonorrhoea to show up on a NAAT test, therefore screening should be repeated after this window.

In addition, cultures (urethral, cervical, anal and oropharyngeal) are taken prior to administering antibiotics to assess antibiotic susceptibility.

Where resources allow, Gonorrhea can be diagnosed at the time of assessment by identifying Gram-negative intracellular diplococci on microscopy.

Management

Ceftriaxone 1g intramuscular injection as a single dose

or

Ciprofloxacin 500mg orally as a single dose (only where antimicrobial sensitivities are known prior to treatment)

or

Cefixime 400mg orally as a single dose with Azithromycin 2g orally as a single dose (if IM injection is contraindicated)

A full STI screen including blood tests should be performed if not already done. Contact tracing and partner notification need to be offered. Advise that all forms of sexual intercourse need to be avoided until both parties are tested and treated.

Test of cure following two weeks after treatment using NAAT is recommended.

Complications

  • Pelvic inflammatory disease (PID)- increases the risk of ectopic pregnancy and infertility
  • Fitz-Hugh-Curtis syndrome- secondary to PID there is inflammation of the hepatic capsule leading to perihepatic adhesions
  • Chronic pelvic pain in females
  • Infertility in males secondary to epididymitis
  • Prostatitis
  • Bartholinitis

Syphilis

Causative organism

Treponema pallidum

Transmission

This spirochete bacterium can be transmitted via direct sexual contact with an infected individual who has a lesion on the skin or mucosa. Congenital syphilis in infants occurs as a result of trans-placental transmission which increases the risk of stillbirth and miscarriage.

Presentation

There are 5 stages of syphilis each with its characteristic features. An individual is most infectious during the primary and secondary stages.

  1. Primary: Development of an indurated painless ulcer called a chancre forms most often on the genitals. This can form from 9-90 days.
  2. Secondary: 6 weeks to 6 months following the primary infection a widespread non-pruritic maculopapular rash involving the palms and soles develops accompanied by alopecia, condylomata lata, generalised lymphadenopathy, oral snail-track lesions and constitutional symptoms (pyrexia, fatigue, malaise).
  3. Early latent: Asymptomatic infection plus positive diagnostic serology obtained within two years of infection.
  4. Late latent: Asymptomatic infection plus positive diagnostic serology obtained after two years of infection.
  5. Tertiary: Untreated syphilis over many years can develop into:
  • Neurosyphilis Tabes dorsalis, general paresis, strokes
  • Cardiovascular syphilis Aortitis, aortic aneurysms
  • Gummatous syphilis Formation of granulomas on bone, skin and mucosa

Diagnostic investigations

Dark ground microscopy of the chancre fluid – shows motile spring-shaped bacteria in primary syphilis.

Syphilis PCR from a swab taken from an ulcerated lesion.

Treponemal-specific serology remains positive throughout life:

  • Treponemal enzyme immunoassay (EIA)
  • T.pallidum haemagglutination test (TPHA)
  • T. pallidum particle agglutination test (TPPA)

Cardiolipin serology tests are used as an indicator to measure disease activity, disease staging and treatment efficacy. These include:

  • Rapid Plasma Reagin (RPR)
  • Venereal Disease Research Laboratory (VDRL)

It can take up to 12 weeks from exposure for laboratory tests to show a positive Syphilis result. Tests should, therefore, be repeated at 12 weeks post-exposure, and if considered high-risk at 6 weeks as well.

Management

Treatment is with Benzathene benzylpenicillin IM injection, however, the dose depends on the nature of the infection, whether the infection is congenitally acquired, and whether the individual is pregnant. Prednisolone is given alongside antibiotics in cases of neurosyphilis.

Primary, secondary and early latent syphilis: Benzathine benzylpenicillin 2.4 million units IM injection as a single dose

Late latent, cardiovascular and gummatous syphilis: Benzathine benzylpenicillin 2.4 million units IM injection weekly for three weeks (three doses)

A full STI screen including blood tests should be performed if not already done. Contact tracing and partner notification need to be offered. Patients should be followed up with a clinical review and repeat serology testing at 3, 6 and 12 months.

Complications

  • Jarisch-Herxheimer reaction- antibiotic treatment of syphilis causes a sepsis-like picture due to the release of toxins from treponemal bacterium breakdown, therefore steroids are administered beforehand to prevent this.
  • HIV co-infection

Herpes simplex virus (HSV)

Causative organism

HSV-1 and HSV-2

Transmission

HSV are double-stranded DNA viruses which are transmitted through mucosal surfaces or broken skin. Infection with HSV can be primary or secondary, episodes symptomatic or asymptomatic, and clinical manifestations may represent initial or recurrent infection. The incubation period for infection is usually under 2 weeks, but most individuals will not display any symptoms. Infection with HSV is lifelong as the virus lies dormant within local sensory ganglia. Intermittent reactivation can be symptomatic with lesions to the skin, or asymptomatic with unnoticed active viral shedding.

HSV-1 is the usual cause of labial (oral) herpes infections and is now also the most common cause of anogenital herpes. Anogenital infections caused by HSV-2 are around four times more likely than HSV-1 to cause recurrent symptoms.

Presentation

As discussed above, infection can be asymptomatic. Symptoms of infection include blisters which progress to painful ulcers around the anogenital area. This can be accompanied by dysuria, discharge and inguinal lymphadenopathy. In primary infection, systemic symptoms such as pyrexia and myalgia are not uncommon.

Symptoms from primary initial infection tend to be more severe than those of recurrent infection.

Diagnostic investigations

HSV PCR from swabs taken from lesions- when taking the sample, remember to burst the lesion and swab the base of the ulcer. NAAT testing is also used in some centres.

Testing for HSV does not form part of routine STI screening in the UK.

Management

Primary episode: Aciclovir 400mg oral three times a day for 5 days (commenced within 5 days of symptom onset)

Recurrent episodes: Aciclovir 800mg oral three times a day for 2 days

Prophylaxis in patients with >5 episodes per year: Aciclovir 400mg twice daily

Saltwater baths, topical petroleum jelly, oral analgesia and topical lidocaine gel can be used for pain control. Again, a full STI screen should be offered to individuals. There is no requirement for contact tracing, however, patients should be advised to refrain from intercourse when they have lesions and disclosure in relationships should be advised. Condoms can reduce the rate of spread and should be encouraged.

Complications

  • Urinary retention
  • HSV keratitis- dendritic lesion on the cornea
  • Aseptic meningitis
  • Herpes proctitis
  • Neonatal HSV- an increased risk if the mother becomes infected in the third trimester
  • Herpetic whitlow

Genital warts

Causative organism

Human papillomavirus (HPV) 6 and 11

Transmission

This double-stranded DNA virus is mainly transmitted via direct skin to skin contact, and more rarely can be transmitted perinatally. Infection with HPV is very common in sexually active individuals and most will not develop visible warts. The incubation period from exposure to infection can be up to 8 months.

In 2008 a vaccination programme against HPV was introduced in the UK, initially protecting against HPV types 16 and 18 (commonly implicated in anogenital cancers) and offered to girls aged 12-13. As it stands, the Gardasil® 4-valent recombinant human papillomavirus vaccine is now offered to all 12 and 13-year-olds in the UK and protects against HPV types 6, 11, 16 and 18. This vaccine is also offered to all MSMs (men who have sex with men) who attend a sexual health clinic in the UK and are up to and including 45 years old.

Presentation

Anogenital warts can vary in size, number, colour and texture but mostly appear as textured, soft growths around the vaginal opening and penis. The anus, cervix and urethral meatus can also be affected. On first presentation, a speculum examination should be performed to visualise the cervix. Predominantly genital warts are asymptomatic however itching, bleeding and pain can occur.

Diagnostic investigations

Diagnosis is clinical however biopsies should be obtained if the lesion bleeds, is ulcerated or indurated.

Testing for HPV does not form a part of routine STI screening in the UK.

Management

A shared decision should be made about treating anogenital warts. In a third of patients, warts will resolve with no intervention. Warts can re-occur after initial resolution, and several treatment courses are often required. Smoking is known to increase the risk of recurrence.

Topical:

  • Topical podophyllotoxin (Warticon® and Condyline®)
  • Topical imiquimod (patients should be made aware that this damages condoms)

Physical ablation:

  • Cryotherapy
  • Surgical excision

A full STI screen including blood tests should be offered. Contact tracing is not required. The use of condoms should be encouraged. Note that the HPV vaccine has not been shown to be effective in treating existing anogenital warts.

Complications

  • Ano-genital cancer
  • Scarring following treatment

Trichomoniasis

Causative organism

Trichomonas vaginalis

Transmission

This flagellated protozoan is transmitted via sexual intercourse.

Presentation

Asymptomatic in up to 50% of cases.

Females: Vaginal discharge (thin, frothy yellow coloured with a ‘fishy’ smell), vulval pruritus, vulvovaginitis, dysuria, dyspareunia

Males: urethral discharge, dysuria, balanitis

Diagnostic investigations

Testing for trichomoniasis does not form a part of a routine STI screen in the UK.

In some centres, diagnosis can be made at the time of assessment by detecting motile trichomonads on wet mount microscopy. There is also rapid point of care tests such as OSOM Trichomonas Rapid Test (Genzyme Diagnostics®) which can give results from a high vaginal swab.

Alternatively, a NAAT test can be performed on vulvovaginal swabs or first-pass urine in men.

Trichomonas vaginalis can also be detected from a culture of vaginal or urethral discharge, or of first-pass urine in men.

Traditionally vaginal pH was measured (alkaline >5 in trichomoniasis; normal 3.5-4.5) but this is less reliable than other methods.

Management

Metronidazole 2g oral as a single dose or 400-500mg twice daily for 5-7 days (note alcohol should be avoided during treatment and for 72 hours afterwards)

A full STI screen including blood tests should be performed. Contact tracing and partner notification need to be offered.

Advise that all forms of sexual intercourse need to be avoided until both parties are tested and treated. Test of cure is not routinely required.

Complications

  • Pelvic inflammatory disease – increases the risk of ectopic pregnancy and infertility
  • Altered vaginal flora
  • Prostatitis
  • In pregnancy, there is an increased risk of premature rupture of membranes and preterm birth.

Mycoplasma genitalium (M. gen)

Causative organism

Mycoplasma genitalium is a tiny self-replicating bacterium.

Transmission

M. genitalium is a sexually transmitted infection which is in the majority of cases asymptomatic. The bacteria invade epithelial cells and can remain there for many years if left untreated.

Presentation

In the vast majority of cases, infection with M. genitalium is asymptomatic. Symptoms are non-specific.

Males: urethral discharge, dysuria, in some cases epididymitis. Rarely proctitis. Infection is mainly implicated in non-gonococcal urethritis (NGU) and non-chlamydial non-gonococcal urethritis (NCNGU).

Females: Dysuria, post-coital bleeding, lower abdominal pain, pelvic inflammatory disease (PID). Rarely proctitis. Infection is mainly implicated in cervicitis and PID.

Diagnostic investigations

Testing for M. genitalium does not form a part of a routine STI screen in the UK. Testing should be done in cases of NGU/NCNGU, PID, cervicitis, epididymitis and proctitis; or as part of contact screening.

NAATs are the gold-standard for diagnosis. First void urine in men and vaginal swabs in women should be sent.

Management

In cervicitis/urethritis: Doxycycline 100mg twice daily for 7 days followed by Azithromycin 1g as a single dose then 500mg daily for 2 days (total 10 days of antibiotic treatment)

In PID/epididymo-orchitis: Moxifloxacin 400mg daily for 14 days

Different regimens apply in pregnancy.

A full STI screen including blood tests should be performed. Current partners should be informed and treated.

Advise that all forms of sexual intercourse need to be avoided until for at least 14 days after initiation of treatment and until symptoms have resolved. Test of cure should be performed 5 weeks post-initiation of treatment.

Complications

  • Sexually acquired reactive arthritis (SARA)
  • Pelvic inflammatory disease – increases the risk of ectopic pregnancy and infertility
  • Pre-term delivery

Reviewer

Dr Grace Farrington

GP Trainee


References

  1. BMJ Publishing Group (2018) Overview of sexually transmitted diseases, Available at: [LINK]
  2. British Association for Sexual Health and HIV (2015; Updated 2018) 2015 UK national guideline for the management of infection with Chlamydia trachomatis, Available at: [LINK]
  3. British Association for Sexual Health and HIV (2018) 2018 UK national guideline for the management of infection with Neisseria gonorrhoeae, Available at:[LINK]
  4. British Association for Sexual Health and HIV (2015; Updated 2019) UK national guidelines on the management of syphilis 2015, Available at:[LINK]
  5. British Association for Sexual Health and HIV (2014) 2014 UK national guideline for the management of anogenital herpesAvailable at: [LINK]
  6. British Association for Sexual Health and HIV (2015) UK National Guidelines on the Management of Anogenital Warts 2015. Available at:[LINK]
  7. National Health Service UK (2019) HPV vaccine overview. Available at: [LINK]
  8. British Association for Sexual Health and HIV (2014). United Kingdom National Guideline on the Management of Trichomonas vaginalis 2014Available at: [LINK]
  9. British Association for Sexual Health and HIV (2018). British Association for Sexual Health and HIV national guideline for the management of infection with Mycoplasma genitalium (2018). Available at: [LINK]

 

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