Doxycycline is a widely used antibiotic of tetracycline. It is prescribed adults for the treatment of severe microbal diseases on the west market. It has a strong action, and therefore it is not taken by children. Due to the strong action the effect starts within several days.


Chlamydia is a bacterial genus comprising of intracellular obligate bacteria. They portray virus-like characteristics. In humans, it causes sexually transmitted infection of the adult and the infant born from chlamydia-infected mothers. Chlamydia infection in humans is the leading cause of blindness, especially in infants.


Chlamydia is a ubiquitous infection occurring all around the world and affecting all age group. However, the prevalence increases.

In the global scale, 61million people were infected with chlamydia by 2015 with high prevalence in women at about 3.9% and in men at about 2.3% and 200 died of chlamydia in the same year.

In the US chlamydia tops in tally in the reported bacterial infections and also as the top cause of urethritis in men and cervical infection in women. The CDC also reported that in the year 2016 1.6million cases of chlamydia were reported in the USA and that about 2% of the young population was affected.

Chlamydia is also the most common bacterial STI in the UK as per the CDC report.

The incidence is high in men who have sex with men and in sexually active population, I.e. 15 years to 35 years.

Incidence increases in women at age above 25 and chlamydia is the highest cause of pelvic inflammatory disease (PID) in women


Chlamydia belongs to the bacterial domain of classification however scientifically it's classified into

  • Kingdom: monera
  • Phylum: chlamydiae
  • Class: chlamidiae
  • Oder: chlamidiae
  • Family: chlamydiceae and
  • Genus: chlamydia.

There are three main species of chlamydia namely Chlamydia suis which cause infection in swine Chlamydia muridam which causes infection in mice and hamsters and Chlamydia trachomatis which causes infection in humans. Our discussion will focus on Chlamydia trachomatis. Another human infection is by Chlamydia pneumonia which causes pneumonia in humans

Laboratory features and characteristics of chlamydia trachomatis

  • They are aerobic obligate intracellular parasites of humans in that they cannot exist as free-living in the environment.
  • They are gram-negative bacteria that measure about 1 micrometres in diameter which are typically coccoid or rod-shaped which can only be cultured in growing cells.
  • The cell wall of chlamydia lack peptidoglycan instead they contain cysteine amino acid which makes up the outer membrane which has the same properties as peptidoglycan making the bacteria to be gram-positive. It's pleomorphic often portraying a variety of shape but limited to rod-like to cocci.
  • They take up Giemsa stain and stain blue hence termed basophilic.
  • They have a predilection for the epithelial cells parasitizing the epithelial cell of the urethra cervix anal canal and that of the mouth and the throat.
  • Chlamydia portrays viral like characteristics hence are cultured and studied like viruses more than like bacteria. The main way of culturing chlamydia was originally passing through the egg yolk which is a living cell. They are hard to propagate in a living cell, therefore, their growth is aided by the use of chemical or mechanical means.

Pathogenesis of chlamydia

As mentioned before chlamydia is an intracellular parasite with a predilection to the epithelial cells. It replicates in the human cell rather than multiplying like other bacteria and has a life cycle. Infection and transmission are sexual; coitus, oral sex.

The incubation period of chlamydia vary from one individual to another and may vary from just a few days to months before the appearance of first symptoms may occur.

The life cycle of Chlamydia begins by the attachment of the bacteria on the endo-cervical cells and that of mouth and anus depending on the site of infection. Attachment occurs by the use of elementary bodies (EB) which adhere to the epithelial cell. After about 8 hours the elementary bodies will transform to reticulate bodies (RB). This enables the bacteria to invade the other cells in the tissues and they multiply in cytoplasmic bodies known as inclusion bodies. This process takes about 24 hours before some cell revert to forming of elementary bodies that enable them to infect new cell and individuals hence transmission when the infected person comes into contact with a healthy individual.

It should also be noted that if test positive for chlamydia one should ensure that his or her partner is tested too in the Oder to avoid reinfection. Also one should avoid sexual contact with others until confirmed free of chlamydia infection.

Clinical manifestation

Clinically chlamydia trachomatis is asymptomatic in about 80% of the infection and in the 20% it manifests as localized infection of the urinary tract, the anus and the mouth. Manifestation may vary a little in men, women and infants.

Manifestation in men

  • Inflammation of the testes and the anal canal in those who were involved in receptive anal intercourse
  • Systemically it manifests as fever.
  • Purulent urethral discharge.
  • Rectal discharge.
  • Oral lesions in those infected in the mouth
  • Asymptomatic in about 50% of men.
  • Dysuria and frequent urination

Manifestation in women

  • Mucopurulent vaginal discharge
  • Itching pain and vaginal burning sensation
  • Pain of the pelvic and abdominal region and fever (PID).
  • May also be asymptomatic.

Manifestation in infants

  • The main manifestation in infants is conjunctivitis and inflammation of the eye or conjunctiva, characterized by pain, redness and inflammation of the eye.
  • Infection occurs by inoculation of the pathogen during birth when the baby passes down the birth canal.
  • It begins with the watery discharge of the eye which turns to become more purulent and may be bloody.
  • May eventually lead to blindness if not treated a condition known as ophthalmia neonatorum.
  • Pneumonia in infants may occur 1-3 months after birth and is subacute pneumonia characterized by eosinophilia and hyperinflation of the chest.


The main specimen for diagnosis of chlamydia is the purulent discharge of the urethra and the vagina, cervical swabs, anal swabs the swabs are subjected to routine Pap smear test. Eye discharge from the infected infants. These samples are then gram stained or stained with Giemsa stain and its morphology is studied.

Presence of gram-negative coccoid cells is diagnostic of chlamydia.

Can also be also done on urine in men.

Urethral swabs should also be obtained in men.

Predisposed individuals

Due to high prevalence and occurrence of chlamydia in adolescent and women, the Centre for Disease Control (CDC) provided a protocol for diagnosis of chlamydia;

  1. Screening should be done to sexually active men and women who are of 25 years and bellow at least once a year.
  2. Older women should also be screened as chances of infection increases with age.
  3. Those who have multiple sex partners, for example, commercial sex workers or one with a new sex partner.
  4. One should also screen for chlamydia if his or her partner has any sexually transmitted infection
  5. A test should also be done on pregnant women to prevent transmission to the new-born.
  6. One should test in case he or she sees symptoms of STI such as dysuria pain and itching of the vagina and vaginal discharge.
  7. New-borns born from mothers with chlamydia at time of birth or those with conjunctivitis.

Serological techniques have been devised though they are not very effective as there is less systemic infection of the blood thus no antibody production against chlamydia.

Nucleic acid amplification test (NAAT) is used to detect the nucleic acid of the bacteria in the swabs obtained in men and women and in oropharyngeal trichomonas test. It's the most sensitive and specific test for chlamydia trachomatis.

In neonates, the diagnosis should include NAAT, Direct Fluorescence Antibody (DFA) test to diagnose ophthalmia neonatorum from eye swabs.

Specimen in neonates should be obtained in the inside of the eyelid and can be used for culturing and antigenic detection. They must contain the epithelial cells of the conjunctiva and these specimens should also be tested for N. gonorrhoea to rule out conjunctivitis due to gonococcus.

Treatment and management

Treatment of chlamydia is basically by use of antibiotics therapy. It's done in the infected people to avoid and prevent the development of complications and transmission to others. The main regimens for treatment of chlamydia as recommended by the Centre for Disease Control and Prevention (CDC) are;

  1. A single dose of Azithromycin 1 gram orally
  2. 100mg of Doxycycline orally twice a day for a week

The two doses are mainly used for the treatment of chlamydia. Alternatively one can use; Erythromycin 500mg orally four times a day for 7 days or Erythromycin ethylsuccinate 800mg four times a day for a week.

The most effective drug for treatment of urogenital trichomatis is azithromycin and doxycycline as they produce high percentage of clearance of 97% and 98% respectively. For treatment of oropharyngeal trichomatis one should also use azithromycin and doxycycline.

However, consideration in application of doxycycline during pregnancy should be made especially at 4-9 months of pregnancy because the drug contains ofloxacin and levofloxacin which is toxic to the infants during breast feeding and may affect cartilage formation in foetus thus alternative drugs should be used.

Neonates born to mothers who have chlamydia should be monitored for of the symptoms infection and treated if necessary. There is no prophylaxis. Treatment of ophthalmic neonatorum is done based on the weight of the baby in kilograms and include administration of erythromycin base or ethyl succinate in a dose of 50mg/kg/days in 4 doses in 14 days.

Azithromycin suspension can also be used the dose is given at 20mg/kg/ day orally single dose for three days.

However, there should be a follow up on infants treated with erythromycin and azithromycin due to association of hyper trophic pyloric stenosis in infants aged less than 6 weeks.

HIV patients receive the same treatment as non-HIV patients.

Follow up

This is the subsequent monitoring of the treatment in order to detect treatment failure. Testing is done three weeks after the final regimen of the drugs when the patient still shows symptoms of infection even after the treatment. One should not be treated with alternative drugs unless in a situation where there was failure to adhere to the regimen of treatment. Nucleic Acid Amplification Test (NAAT) should not be used for follow up testing due to false positive results at periods less than 3 weeks after treatment.

One should also monitor for post-treatment infections which occur due to failure of the sexual partner to treat of chlamydia or sex with another infected individual. PID in women occurring after treatment should raise an alarm of reinfection repeatedly.

Also, anyone treated for chlamydia should retest 3 months after end of treatment regimen regardless of the status of their partner. If not possible then test should be done the next time the patient seeks medical service within 12 months.


alertTo prevent new infection each and every one of us should consider use of protection during sex. Civil education should also be conducted among the predisposed population and all partners tested if one is found to have chlamydia.

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