Chlamydia trachomatis

What is Chlamydia trachomatis?

Chlamydia trachomatis is a small bacterium that cannot grow outside a living cell. In this respect

it resembles a virus, but it is actually a very sophisticated organism. There are two other related

organisms: Chlamydia psittaci is widespread in animals and can be transmitted to humans. This

organism in humans is an uncommon cause of severe pneumonia particularly when acquired from

infected birds of the parrot (Psittacine) family, and occasionally of abortion following contact with

infected sheep. The more recently described Chlamydia pneumoniae (also known as the TWAR

agent - Taiwan Acute Respiratory, after the designations of the first two isolates), may prove to be

a frequent cause of upper and lower respiratory infection transmitted from person to person by

infected droplets.

Which diseases does it cause?

Worldwide, the most important disease caused by Chlamydia trachomatis is trachoma, one of

the commonest infectious causes of blindness. In some parts of the developing world, over 90% of

the population becomes infected. However, the specific strains of Chlamydia trachomatis which

cause trachoma and the epidemiological conditions for its spread, are not found in the UK. In

Britain, the organism often causes genital tract infection. In men, Chlamydia trachomatis is the

commonest cause of non-gonococcal or (less correctly) non-specific urethritis. In women, the

organism may infect both the cervix and the urethra. Epididymitis may complicate infection in men,

whilst in women infection in the upper genital tract - the endometrium and the fallopian tubes, may

lead to acute pelvic inflammatory disease (PID). Chlamydia trachomatis is the most frequent

cause of PID and its long term consequences include chronic pain, ectopic pregnancy and

infertility. In both sexes, conjunctivitis (that does not progress to blindness) and joint inflammation

may occur.

Babies born to mothers with infection of their genital tract frequently present with chlamydial eye

infection within a week of birth (chlamydial ophthalmia neonatorum), and may subsequently

develop pneumonia.

What are the symptoms and signs?

Symptoms and signs are non-specific, and variable. In men, a mucopurulent urethral discharge,

with or without pain on passing urine appears between one and three weeks after exposure. In

women, cervical infection may produce vaginal discharge. It is impossible to exclude other genital

infections such as gonorrhoea or bacterial vaginosis on clinical examination alone and laboratory

examination of the discharge is essential to make the diagnosis. Mixed infections are common.

In both men and women, asymptomatic infection is not uncommon.

Abdominal pain and raised temperature may indicate PID in women. This condition may be difficult

to distinguish from other causes of abdominal pain.

How is it spread?

The organism is transmitted from one partner to another during sexual intercourse. Contamination

of the hands with genital discharge may lead to a conjunctival infection following contact with the

eyes.

How is it diagnosed?

The organism cannot be grown outside living cells. Culture of Chlamydia trachomatis is therefore

restricted to laboratories with special facilities. However, using new techniques of direct antigen

detection, the organism can be identified in clinical material with a high degree of accuracy without

the need to culture. These facilities are now becoming widely available.

Samples of discharge from the urethra or cervix, or an early morning urine specimen from men, can

be tested for the presence of the organism. These tests are not perfect, and any positive result

should be confirmed by further tests either on the original specimen, or on a further sample. Blood

tests for specific antibody against Chlamydia trachomatis are unhelpful for diagnosing acute

infection, and should not be used.

How is it treated?

Infection with Chlamydia trachomatis is treated with a course of antibiotics. The most commonly

used are doxycycline or erythromycin. Newer antibiotics include azithromycin (related to

erythromycin, but effective in a single dose against uncomplicated chlamydial genital infection), and

ofloxacin (a new fluoroquinolone). Side effects (nausea, vomiting and diarrhoea) are less frequent

with newer agents, but older therapies are cheaper.

Bibliography

Black, Jacquelyn. Microbiology Principles and Explorations. Prentice Hall;

Upper Saddler River, New Jersey. 1999.

http://www.amm.co.uk/html/publications.htm Copyright © Association of Medical Microbiologists, 1993

Lederberg, Joshua. Encyclopedia of microbiology. Academic Press; San Diego,

Calafornia. 2000.

Bibliography

Bibliography

Black, Jacquelyn. Microbiology Principles and Explorations. Prentice Hall;

Upper Saddler River, New Jersey. 1999.

http://www.amm.co.uk/html/publications.htm Copyright © Association of Medical Microbiologists, 1993

Lederberg, Joshua. Encyclopedia of microbiology. Academic Press; San Diego,

Calafornia. 2000.

Word Count: 687