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a widespread genus of gram-negative, nonmotile bacteria. They are obligate intracellular parasites that are totally dependent on the host cell for energy in the form of adenosine triphosphate (ATP), which they cannot synthesize. Outside a host they exist as elementary bodies that have a rigid cell wall and are unable to grow and divide. The elementary bodies attach to the host cells and are taken in by phagocytosis. Inside the phagosome they become reticulate bodies that have flexible cell walls and are able to grow and divide. Subsequent release of elementary bodies and lysis of the host cell permit infection of surrounding cells.

The genus Chlamydia contains two species, C. tracho´matis and C. psit´taci. C. trachomatis can cause trachoma, inclusion conjunctivitis, lymphogranuloma venereum, nongonococcal urethritis, and a number of other genital infections. C. psittaci causes psittacosis.

The symptoms of sexually transmitted chlamydial infections may be mild; hence this is sometimes called “the silent STD.” Victims may not be aware they have the disease and may not seek treatment until serious complications and unwitting transmission to other persons have occurred. Males who have symptoms usually have painful urination and a watery discharge from the penis. Women may suffer itching and burning in the genital area, an odorless, thick, yellow-white vaginal discharge, dull abdominal pain, and bleeding between menstrual periods. C. trachomatis causes about half of all pelvic inflammatory disease. Symptoms can appear from a week to five weeks after exposure to the bacteria, during which time almost all sexual contacts become infected.

Chlamydial infection during pregnancy can increase the risk of stillbirth or premature birth. The newborn is at risk for infection from its mother and may suffer from inclusion conjunctivitis. Chlamydial infection can also lead to pneumonia some weeks after birth, probably because of infectious material from the eye draining through the nasolacrimal ducts and being aspirated into the lungs.

Chlamydial infection is usually treated with an antibiotic; effective single antibiotic therapy is available. It is essential that condoms be used during sexual intercourse throughout the treatment period to prevent reinfection, and condom use is usually recommended for 3 to 6 months after treatment. As with all sexually transmitted diseases, both partners should be treated at the same time to prevent reinfection. If left untreated, chlamydial infection can cause scarring in the fallopian tubes and lead to infertility and tubal pregnancies. In the male, nongonococcal urethritis due to chlamydiae may lead to epididymitis and sterility.

The U.S. Preventive Services Task Force has drawn up guidelines that strongly recommend routine screening for Chlamydia infections for all sexually active women ages 25 and younger in order to insure detection. Printed copies of the Guidelines are available online through the National Guideline Clearinghouse at They can also be obtained from the AHRQ Publications Clearinghouse by calling 1-800-358-9295.


any member of the genus Chlamydia.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


One of three genera in the family Chlamydiaceae, Chlamydia muridarum, the cause of pneumonitis; Chlamydia suis; and Chlamydia trachomatis. Chlamydia are obligatory intracellular spheric or ovoid bacteria with a complex intracellular life cycle; the infective form is the elementary body, which penetrates the host cell, replicating as the rediculate body by binary fission; replication occurs in a vacuole called the inclusion body; lack peptidoglycan in cell walls; type species in Chlamydia trachomitis. Formerly called Betsonia.
Synonym(s): Chlamydozoon
[G. chlamys, cloak]


, pl.


(kla-mid'ē-ă, -mid'ē-ē),
A vernacular term used to refer to any member of the genus Chlamydia.
Farlex Partner Medical Dictionary © Farlex 2012


n. pl. chlamyd·iae (-ē-ē′)
1. Any of various gram-negative, coccoid bacteria of the genus Chlamydia, especially C. psittaci and C. trachomatis, that are pathogenic to humans and other animals, causing infections such as conjunctivitis in cattle and sheep and trachoma, urethritis, and pneumonia in humans.
2. Any of several common, often asymptomatic, sexually transmitted diseases caused by the bacterium Chlamydia trachomatis.

chla·myd′i·al adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


One of three genera in the family Chlamydiaceae; includes Chlamydia muridarum, the cause of pneumonitis in mice, C. suis, and C. trachomatis, the type species. Chlamydiae are obligatory intracellular spheric or ovoid bacteria with a complex intracellular life cycle; the infective form is the elementary body, which penetrates the host cell, replicating as the reticulate body by binary fission. Replication occurs in a vacuole called the inclusion body. Chlamydiae lack peptidoglycan in their cell walls. Formerly called Bedsonia.


, pl. chlamydiae (klă-mid'ē-ă, -ē)
A vernacular term used to refer to any member of the bacterial genus Chlamydia.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


A genus of small, non-motile, GRAM NEGATIVE bacteria that occupy cells and were thus once thought to be viruses. They carry both DNA and RNA and multiply by binary fission. They can be destroyed by tetracycline antibiotics.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


Gram-negative BACTERIA (see GRAM'S STAIN) that are OBLIGATE INTRACELLULAR PARASITES of man and other animals. They can only reproduce (see REPRODUCTION) within a host CELL. They are smaller than some of the largest VIRUSES. They are COCCOID, about 0.2–1.5 μm in size and can be transmitted by interpersonal contact or by respiratory routes. Chlamydia trachomatis causes trachoma, a common cause of blindness in humans.
expected ratioobserved nos (o values)expected nos (E values)(o-e)(o-e)2(o-e)2/e
red 3 82 75 7 49 0.65
white 1 18 25 7 49 1.96
100 100 χ2=2.61
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005


One of the most common sexually transmitted diseases in the United States. It causes discharge, inflammation and burning during urination. About half of the cases of nongonococcal urethritis are due to chlamydia.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


Obligatory intracellular spheric or ovoid pathogenic bacteria with a complex intracellular life cycle; infective form is the elementary body, which penetrates the host cell, replicating as the rediculate body by binary fission.
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about Chlamydia

Q. How do I know if I'm infected by chlamydia?

A. i had this a long time ago,i got it when i was stationed over seas,i had painful urinations,had a puss like discharge,and sores on the penis.i always had discharge stains in my underwear.

Q. after takeing a 1g. dose of zithromax how long do u have to wait to have sex for clamydia i havent been diagnosed yet but to be on the safe side they gave me a 1g. z-pack just in case getting tested in two days but i wanted to see a girl this weekend and sleep with a girl should i wait

A. you need to wait till the doctor says its ok,i would wait 30 days just too be safe.

More discussions about Chlamydia
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References in periodicals archive ?
Entre as doencas de maior importancia clinica estao a gonorreia, a sifilis, a tricomoniase, o cancroide, o herpes genital, as verrugas genitais, as infeccoes por clamidia, pelo virus da hepatite B e pelo virus da imunodeficiencia humana, o HIV (11).
trachomatis (4), y en el mismo pais se encontro una prevalencia global de 8.90% (IC 95% 6.50-11.90) entre 464 mujeres de 15 a 19 anos de edad usando reaccion en cadena de la ligasa para la deteccion de clamidia (5).
En las ultimas tres decadas la reproduccion asistida (induccion de la ovulacion, fertilizacion invitro) ha incrementado la incidencia de embarazo ectopico de 1,3% a 4,5%; y algunos autores han resaltado como factores importantes en el aumento de la incidencia la infeccion por Clamidia, la enfermedad inflamatoria pelvica, el uso del dispositivo intrauterino, la endometriosis, la cirugia de las trompas, el tabaquismo, el uso de anticonceptivos con solo progestagenos, la esterilizacion quirurgica y el antecedente de embarazo ectopico (12,13,14,15,16).
Se elaboraron arboles de decision para las estrategias analizadas con las probabilidades y los costos de cada nodo, segun los datos primarios --publicados o no publicados-- de la infeccion por clamidia en Massachusetts, Estados Unidos, y los datos de salud de los participantes en los programas de entrenamiento laboral.
Puede que el riesgo de EIP sea mils alto en lugares con un alto indice de gonorrea y clamidia, donde es dificil garantizar condiciones asdpticas para la insercion del DIU.
Entretanto, a ocorrencia de praticas sexuais inseguras contribui para que essa populacao se torne mais vulneravel as infeccoes pelo Virus da Imunodeficiencia Humana (HIV) e outras doencas sexualmente transmissiveis (DST), como a sifilis, clamidia e gonorreia (6).
(1) Desde el ano 2.000 se ha descrito que los casos de Sindrome de Inmunodeficiencia Adquirida (SIDA) han crecido alrededor del mundo, (2) similar tendencia tienen otras ITS, tales como Clamidia, Herpes Genital, Virus de Papiloma Humano, Tricomoniasis, entre otras; describiendose que el grupo poblacional mas afectado, se encuentra entre los 13 y 24 anos.