Chlamydia trachomatis 
What is Chlamydia trachomatis?
Chlamydia trachomatis is a small bacterium that cannot grow outside a living cell. In this regard 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 pneumonia (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 sinXACINgle dose against uncomplicated chlamydial genital infection), and ofloxacin (a new fluoroquinolone).
MY REMARK : NEVER ,NEVER USE OFLOLOXACIN -A fluoroquinolone [search on my wordpress]
Side effects (nausea, vomiting and diarrhoea) are less frequent with newer agents, but older therapies are cheaper.