(redirected from chlamydial)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to chlamydial: chlamydial conjunctivitis


(kləmĭd`ēə), genus of microorganisms that cause a variety of diseases in humans and other animals. Psittacosis, or parrot fever, caused by the species Chlamydia psittaci, is transmitted to people by birds, particularly parrots, parakeets, and lovebirds. In birds the disease takes the form of an intestinal infection, but in people it runs the course of a viral pneumonia. Different forms of Chlamydia trachomatis cause trachomatrachoma
, infection of the mucous membrane of the eyelids caused by the bacterium Chlamydia trachomatis. Trachoma affects at least 86 million people worldwide. An estimated 1.
..... Click the link for more information.
, an infection of the mucous membrane of the eyelids, and the sexually transmitted diseasesexually transmitted disease
(STD) or venereal disease,
term for infections acquired mainly through sexual contact. Five diseases were traditionally known as venereal diseases: gonorrhea, syphilis, and the less common granuloma inguinale, lymphogranuloma venereum, and
..... Click the link for more information.
 lymphogranuloma venereum. This same species also causes the sexually transmitted disease called chlamydia, the most common such disease in the United States. In women, chlamydia is a common cause of pelvic inflammatory diseasepelvic inflammatory disease
(PID), infection of the female reproductive organs, usually resulting from infection with the bacteria that cause chlamydia or gonorrhea. The infection typically first affects the cervical area, then spreads to the uterus, fallopian tubes, ovaries,
..... Click the link for more information.
, which can result in infertility and an increased risk of tubal pregnancy. Men are the primary carriers, but painful urination and discharge often prompt men to get treatment before the testes can be infected and male infertility can result. Chlamydial infections can be treated with antibiotics such as tetracycline.


A genus of bacteria with a growth cycle differing from that of all other microorganisms. Chlamydiae grow only in living cells and cannot be cultured on artificial media. Although capable of synthesizing macromolecules, they have no system for generating energy; the host cell's energy system fuels the chlamydial metabolic processes. The genome is relatively small; the genomes of C. pneumoniae and C. trachomatis have been completely sequenced.

The chlamydial infectious particle, called the elementary body, is round and about 350–450 nanometers in diameter. It enters a susceptible host cell and changes to a metabolically active and larger (approximately 800–1000 nm in diameter) reticulate body that divides by binary fission. The entire growth cycle occurs within a vacuole that segregates the chlamydia from the cytoplasm of the host cell. The reticulate bodies change back to elementary bodies, and then the cell lyses and the infectious particles are released. The growth cycle takes about 48 h.

Human diseases are caused by three species of Chlamydia. Chlamydia trachomatis is almost exclusively a human pathogen, and one of the most common. Infections occur in two distinct epidemiologic patterns. In many developing countries, C. trachomatis causes trachoma, a chronic follicular keratoconjunctivitis. It is the world's leading cause of preventable blindness, affecting approximately 500 million people. In areas where this condition is highly endemic, virtually the entire population is infected within the first few years of life. Most active infections are found in childhood. By age 60, more than 20% of a population can be blinded as a result of trachoma. See Eye disorders

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen; an estimated 3–4 million cases occur each year in the United States, and there are close to 90 million worldwide. The most common manifestation is nongonococcal urethritis in males. The cervix is the most commonly infected site in women. Ascending infections can occur in either sex, resulting in epididymitis in males or endometritis and salpingitis in females. Chlamydial infection of the fallopian tube can cause late consequences such as infertility and ectopic pregnancy, even though the earlier infection is asymptomatic. The infant passing through the infected birth canal can acquire the infection and may develop either conjunctivitis or pneumonia. A more invasive form of C. trachomatis causes a systemic sexually transmitted disease called lymphogranuloma venereum. See Sexually transmitted diseases

Chlamydia psittaci is virtually ubiquitous among avian species and is a common pathogen among lower mammals. It is economically important in many countries as a cause of abortion in sheep, cattle, and goats. It causes considerable morbidity and mortality in poultry. Chlamydia psittaci can infect humans, causing the disease psittacosis. Psittacosis can occur as pneumonia or a febrile toxic disease without respiratory symptoms.

Chlamydia pneumoniae appears to be a human pathogen with no animal reservoir. It is of worldwide distribution and may be the most common human chlamydial infection. It appears to be an important cause of respiratory disease.

Azithromycin is the drug of choice for uncomplicated chlamydial infection of the genital tract. Two therapeutic agents require longer treatment regimens: doxycycline, a tetracycline antibiotic, is the first alternate treatment; erythromycin may be used for those who are tetracycline-intolerant, as well as for pregnant women or young children. See Medical bacteriology


The single genus of the family Chlamydiaceae.
References in periodicals archive ?
Baseline and Follow-up Characteristics of Cases with [greater than or equal to] 1 Chlamydial Infection Reported to the Regional Public Health Department (n = 44,580), by Residential Location Status (Available vs.
Covariates to detect differences in chlamydial infection prevalence included socio-demographics, reported symptoms, and other factors.
The Centers for Disease Control and Prevention (CDC) recommends screening with nucleic acid amplification tests (NAATs), which have high specificity (> 95%) and sensitivity (80% to 93%) for chlamydial infections.
Our case suggests that oropharyngeal chlamydial infection might be more common than realized and emphasizes the need to consider the possibility of LGV in patients with unexplained cervical lymphadenopathy or tonsillitis.
The apoptotic effect during Chlamydial infection of epithelial cells has been observed previously.
They were able to show in their rat model, that progesterone increases and oestradiol decreases the susceptibility to intrauterine chlamydial infection.
The UMA vaccine technology would be expected to cover all chlamydial infections, including those caused by Chlamydia psittaci, which often results in pneumonia and endocarditis in humans, and Chlamydia pneumoniae, which is responsible for some pneumonia, bronchitis, pharyngitis, laryngitis, and sinusitis.
Treatments for the under-20s covered syphilis, uncomplicated gonorrhoea, chlamydial herpes and genital warts.
Pelvic inflammatory disease develops in 10 percent to 40 percent of women with untreated or inadequately treated Chlamydial disease (Hillis and Wassweheit, 1996).
LaFrance quotes World Health Organization statistics as saying "that in 1998, there were 62 million cases of gonorrhea, 89 million cases of chlamydial infection, and 170 million cases of trichomoniasis.