31.3.1  STIs caused by bacteria


Gonorhoeal urethral discharge.
Figure 31.1  Gonorhoeal urethral discharge.

Gonorhoea is one of the most common STIs and is caused by bacteria called Neisseria gonorrhoeae. Men with gonorrhoea may present with a burning sensation while urinating and a discharge from the urethra (Figure 31.1), whereas women may present with vaginal discharge and lower abdominal pain. A discharge is a yellowish or whitish substance released from the opening of the reproductive tract in both men and women. Most men infected with gonorrhoea have symptoms, but in women gonorrhoea is commonly asymptomatic (i.e. they do not have any symptoms). Women who have gonorrhoea (with or without symptoms) can transmit the bacteria to infants during birth. In newborn babies, gonorrhoea usually presents with eye disease (termed neonatal conjunctivitis) and can lead to blindness.

  • What can you see in Figure 31.1? What could be the possible cause?

  • A whitish discharge from the opening of the penis can be seen; the likely clinical diagnosis is gonorrhoea.


Chlamydia is also one of the most common (if not the commonest) STIs, and is caused by bacteria called Chlamydia trachomatis. In men it usually presents with discharge from the urethra and in women it presents with cervicitis (inflammation of the neck of the womb or cervix) and lower abdominal pain. The discharge is generally less ‘sticky’ and lighter in colour than for gonorrhoea. Chlamydia, like gonorrhoea, can also be asymptomatic, but in this case in both men and women. In addition, pregnant women with chlamydia can also transmit the STI to their babies during childbirth and cause neonatal conjunctivitis.


Syphilis is caused by bacteria called Treponema pallidum. Syphilis has four stages: primary, secondary, latent and tertiary syphilis, with different signs and presentations according to the time passed from the initial infection. The different stages can be described as follows:

  • Primary syphilis is characterised by a painless ulcer (known as chancre) in the genital or anal area resulting from direct sexual contact with a person with syphilis. The chancre has obvious edges, and the lymph nodes in the groin may also appear swollen. Primary syphilis takes 10 to 90 days to develop from initial exposure to the bacterium.
Primary syphilitic chancre.
Figure 3.2  Primary syphilitic chancre.
  • Describe what you see in Figure 31.2. What could be the most likely diagnosis?

  • A solitary ulcer with clear edges on the penis. The possible diagnosis is primary syphilis.

  • Secondary syphilis is characterised by a non-itchy rash over the trunk and the extremities, arising 1 to 6 months after primary syphilis.
  • Latent syphilis is the stage between secondary and tertiary syphilis in which an infected patient shows few or no symptoms.
  • Tertiary syphilis is a rare phenomenon characterised mainly by soft tumour-like balls of inflammation under the skin, or on bones, that may appear anywhere in the body. Some individuals with tertiary syphilis may show serious neurological (nervous system) or cardiovascular problems (heart and blood vessels). Tertiary syphilis takes 1 to 10 years to develop, but it can take up to 50 years.


Chancroid is caused by bacteria termed Haemophilus ducreyi and in the majority of cases it presents with painful ulcers and sores in the genital area (particularly in the foreskin of the penis). Many patients also develop a bubo, an enlargement of the lymph nodes on one side of the groin that exudes liquid. By contrast, most infected women do not show any symptoms.

Granuloma inguinale

Raised solid bumps on both sides of the groin caused by granuloma inguinale.
Figure 31.3  Raised solid bumps on both sides of the groin caused by granuloma inguinale.

Granuloma inguinale is caused by an infection with bacteria called Calymmatobacterium granulomatis. It presents initially with small lesions in areas surrounding the anus and/or genitals, which are difficult to differentiate from chancroid, but then turn into ulcerative lesions and lead to painless raised solid bumps in both sides of the groin area (Figure 31.3).

31.3  Presentation of common STIs

31.3.2  STIs caused by viruses