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Microbiology 12 |
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Microbiology 12 |
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NOTE: INFORMATION ON THIS PAGE IS INTENDED FOR EDUCATIONAL USE ONLY. FOR MEDICAL ADVICE YOU SHOULD CONSULT WITH A PHYSICIAN
Chlamydia (Greek=cloaked) trachoma ( Greek =pebbled or stony appearance)
Cultural and morphological characteristics
Chlamydiae are small gram negative, coccoid bacteria measuring about 0.2 x 1 um. They have a unique life intracellular life cycle and depend on the host cell for ATP. Chlamydiae take two forms; the rigid-walled, extracellular elementary body enters the host cell by phagocytosis and multiplies by binary fission in the form of a thin-walled, reticulate body. Daughter cells condense and reorganize as elementary bodies which go on to infect new cells.
Chlamydiae can not be detected by standard culture methods. Samples can be inoculated into tissue culture and growth can be detected by using monoclonal antibodies tagged to a fluorescent stain. Enzyme immunoassays are also being used to detect infections.
Diseases caused by strains of C. trachomatis
Newer diagnostic tests and active screening for the organism has revealed what has been termed a "silent epidemic" of C.trachomatis infection. This is the most common sexually-transmitted disease agent in the U.S.A. but many people are unaware of its existence as most people are asymptomatic. An estimated 4 million new infections will occur in 2001. Most cases occur in sexually-active young women under age 20. If a woman is untreated Chlamydia can lead to problems such as pelvic inflammatory disease, infertility and ectopic pregnancy. Infected pregnant women can also transmit Chlamydia to their infants during delivery which may cause eye infections and pneumonia. A small 1-2 % percent of infected men will develop epididymitis (inflammation of the testicles).
A more aggressive, ulcerative STD called lymphogranuloma venereum occurs in tropical regions. It is usally identified by iodine-stained inclusion bodies in pus taken from infected lymph nodes.
Other strains of C. trachomatis are the cause of a disease called trachoma, the world's leading cause of preventable blindness.
Nongonococcal urethritis (NGU) and pelvic inflammatory
disease Sexually-transmitted NGU is a gonorrhea-like STD most
often caused by C. trachomatis. Up to 70-80% of infected
women are asymptomatic. About 1/3 of infected men are
asymptomatic. Symptomatic males may exhibit a
thin, white urethral discharge. Women may experience a thin vaginal
discharge, lower abdominal pain, pain during sex, and
abnormal periods. Click here to learn more about
symptoms in women and children: http://www.aomc.org/chlamydia.html Inclusion conjunctivitis (inclusion blennorrhea) In adults can result from autoinoculation from genitals
via fingers Congenital transmission (mother-to-child during
delivery) C. trachomatis pneumonia (Congenital transmission (mother-to-child during
delivery) Symptoms usually appear 2-3 weeks after delivery) See an X-ray of chlamydial pneumonia infection at: http://www.vh.org/Providers/TeachingFiles/PAP/NeonatalChestCapt/PneumChlam01.html Trachoma Flies feed on infectious lacrimal secretions Mothers contract from infected infants The leading cause of preventable
blindness. The conjuntiva swells and beomes pebbled.
Eyelashes invert and scar the cornea. Secondary infections
contribute to much of the actual blindness. Learn more about trachoma:
http://www.trachoma.org Lymphogranuloma venereum Sexually-transmitted This ulcerative STD is common in
the tropics and subtropics and is caused by a highly
invasive strain of C. trachomatis Organisms cause lesions on genitals
which rupture & heal. Invasion of the lymphatics can
cause buboes to form which may burst and drain.
Elephantiasis of genitalia can occur as well as rectal
blockage & perforation
Treatment of C. trachomatis infections
Sexually-transmitted infections can be treated with a (large!) single dose of azithromycin or week long course of doxycycline. Treatment with these antibiotics is highly effective in curing the infection but will not prevent reinfections. Erythromycin is used as an alternative antibiotic in treating pregnent women. Penicillin is ineffective in treating Chlamydia. All infected sex partners should be treated regardless of symptoms and sex should be avoided until treatment is completed.
Erythromycin is effective in preventing and treating eye infections caused by C. trachomatis. Silver nitrate solutions are ineffective against this organism.
Prevention
The CDC currently recommends that all sexually active women under 20, and those who have inflammation of the cervix be tested for chlamydia during regular gynaecologic exams. Sex partners should also be tested and treated. Many physisicans are routinely testing pregnant women for STDs caused by chlamydia and gonorrhea.
As for all STDs, the risk of contracting chlamydia can be minimized by avoiding sex with multiple partners or avoiding sex with a person who has multiple partners. The use of barrier contraceptives such as condoms will also prevent transmission.