Chlamydia infection

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Chlamydia
Classification and external resources
Pap smear showing C. trachomatis (H&E stain)
ICD-10 A55.-A56.8, A70.-A74.9
ICD-9 099.41, 483.1
DiseasesDB 2384
eMedicine med/340 
MeSH D002690

Chlamydia (from the Greek, χλαμύδος meaning "cloak") is a common sexually transmitted infection (STI) caused by the bacterium Chlamydia trachomatis. The term Chlamydia refers to an infection by any one of the species in the bacterial genus Chlamydia—Chlamydia trachomatis, Chlamydia suis or Chlamydia muridarum—, but of these, only C. trachomatis is found in humans.[1] Chlamydia is a major infectious cause of human genital and eye disease.

Chlamydia infection is one of the most common sexually transmitted infections in people worldwide — about 2.8 million cases of chlamydia infection occur in the United States each year.[2] It is the most common bacterial STI in humans.[3]

C. trachomatis is naturally found living only inside human cells. Chlamydia can be transmitted during vaginal, anal, or oral sex, and can be passed from an infected mother to her baby during vaginal childbirth. Many people with Chlamydia exhibit no symptoms of infection. Between half and three-quarters of all women who have chlamydia have no symptoms and do not know that they are infected. If untreated, chlamydial infections can cause serious reproductive and other health problems with both short-term and long-term consequences. Chlamydia is easily treated with antibiotics.

Chlamydia conjunctivitis or trachoma is a common cause of blindness worldwide. The World Health Organization estimates that it accounted for 15% of blindness cases in 1995, but only 3.6% in 2002.[4][5][6]

Contents

[edit] Related conditions

[edit] Genital disease

Chlamydial cervicitis in a female patient characterized by mucopurulent cervical discharge, erythema, and inflammation.
Chlamydial cervicitis in a female patient characterized by mucopurulent cervical discharge, erythema, and inflammation.

Chlamydial infection of the neck of the womb (cervicitis) is an asymptomatic sexually transmitted illness for about 50-70% of the female population. Of those who have an asymptomatic infection that is not detected by their doctor, approximately half will develop pelvic inflammatory disease (PID), a generic term for infection of the uterus, fallopian tubes, and/or ovaries. PID can cause scarring inside the reproductive organs, which can later cause serious complications, including chronic pelvic pain, difficulty becoming pregnant, ectopic (tubal) pregnancy, and other dangerous complications of pregnancy. Chlamydia causes 250,000 to 500,000 cases of PID every year in the United States. Women infected with chlamydia are up to five times more likely to become infected with HIV, if exposed.[7]

Chlamydia is known as the "Silent Epidemic" because in women, it may not cause any symptoms and will linger for months or years before being discovered. Symptoms that may occur include: unusual vaginal bleeding or discharge, pain in the abdomen, painful sexual intercourse (dyspareunia), fever, painful urination or the urge to urinate more frequently than usual (urinary urgency).

Male patients may develop a white, cloudy or watery discharge (shown) from the tip of the penis.
Male patients may develop a white, cloudy or watery discharge (shown) from the tip of the penis.

In men, Chlamydia shows symptoms of infectious urethritis (inflammation of the urethra) in about 50% of cases. Symptoms that may occur include: a painful or burning sensation when urinating, an unusual discharge from the penis, swollen or tender testicles, or fever. Discharge, or the purulent exudate, is generally less viscous and lighter in color than for gonorrhea. If left untreated, it is possible for Chlamydia in men to spread to the testicles causing epididymitis, which in rare cases can cause sterility if not treated within 6 to 8 weeks. Chlamydia causes more than 250,000 cases of epididymitis in the U.S. each year. Chlamydia is also a potential cause of prostatitis in men, although the exact relevance in prostatitis is difficult to ascertain due to possible contamination from urethritis.[8]

[edit] Eye disease

Conjunctivitis due to chlamydia.
Conjunctivitis due to chlamydia.

Chlamydia conjunctivitis or trachoma was once the second most important cause of blindness worldwide, but its role diminished from 15% of blindness cases by trachoma in 1995 to 3.6% in 2002, according to WHO estimates.[6][4][5] The infection can be spread from eye to eye by fingers, shared towels or cloths, coughing and sneezing and eye-seeking flies.[9] Newborns can also develop chlamydia eye infection through childbirth (see below). Using the SAFE strategy (acronym for surgery for in-growing or in-turned lashes, antibiotics, facial cleanliness, and environmental improvements), the World Health Organisation aims for the global elimination of trachoma by 2020 (GET 2020 initiative).[10][11]

[edit] Rheumatological conditions

Chlamydia may also cause reactive arthritis, especially in young men. About 15,000 men develop reactive arthritis due to chlamydia infection each year in the U.S., and about 5,000 are permanently affected by it. The triad of reactive arthritis, conjunctivitis and urethritis (inflammation of the urethra) is known as Reiter's syndrome. It can occur in both men and women, though is more common in men.

[edit] Perinatal infections

As many as half of all infants born to mothers with chlamydia will be born with the disease. Chlamydia can affect infants by causing spontaneous abortion; premature birth; conjunctivitis, which may lead to blindness; and pneumonia. Conjunctivitis due to chlamydia typically occurs one week after birth (compare with chemical causes (within hours) or gonorrhea (2-5 days)).

[edit] Other conditions

Chlamydia trachomatis is also the cause of lymphogranuloma venereum, an infection of the lymph nodes and lymphatics. It usually presents with genital ulceration and swollen lymph nodes in the groin, but it may also manifest as proctitis (inflammation of the rectum), fever or swollen lymph nodes in other regions of the body.[12]

[edit] Diagnosis

[edit] Screening

For sexually active women who are not pregnant, screening is recommended in those under 25 and others at risk of infection.[13] Risk factors include a history of chlamydial or other sexually transmitted infection, new or multiple sexual partners, inconsistent condom use, and exchanging sex for money or drugs.[14] For pregnant women, guidelines vary: screening women with age or other risk factors is recommended by the U.S. Preventive Services Task Force (USPSTF) (which recommends screening women under 25) and the American Academy of Family Physicians (which recommends screening women aged 25 or younger). The American College of Obstetricians and Gynecologists recommends screening all at risk, while the Centers for Disease Control and Prevention recommend universal screening of pregnant women.[13] The USPSTF acknowledges than in some communities there may be other risk factors for infection, such as ethnicity.[13] Evidence-based recommendations for screening initiation, intervals and termination are currently not possible.[13] There is no universal agreement on screening men for chlamydia.

[edit] Laboratory detection

The diagnosis of genital chlamydial infections evolved rapidly from the 1990s through 2006. Nucleic acid amplification tests (NAAT), such as polymerase chain reaction (PCR), transcription mediated amplification (TMA), and the DNA strand displacement assay (SDA) now are the mainstays. NAAT for chlamydia may be performed on swab specimens collected from the cervix (women) or urethra (men), on self-collected vaginal swabs, or on voided urine. Urine and self-collected swab testing facilitates the performance of screening tests in settings where genital examination is impractical. At present, the NAATs have regulatory approval only for testing urogenital specimens, although rapidly evolving research indicates that they may give reliable results on rectal specimens.

Because of improved test accuracy, ease of specimen management, convenience in specimen management, and ease of screening sexually active men and women, the NAATs have largely replaced culture, the historic gold standard for chlamydia diagnosis, and the non-amplified probe tests. The latter test is relatively insensitive, successfully detecting only 60-80% of infections in asymptomatic women, and often giving falsely positive results. Culture remains useful in selected circumstances and is currently the only assay approved for testing non-genital specimens.

[edit] Treatment

Chlamydia trachomatis inclusion bodies (brown) in a McCoy cell culture.
Chlamydia trachomatis inclusion bodies (brown) in a McCoy cell culture.

C. trachomatis infection can be effectively cured with antibiotics once it is detected. Current Centers for Disease Control guidelines provide for the following treatments:

Untested Treatments

  • Ciprofloxacin 500 milligrams twice daily for 3 days. (Although this is not an approved method of treatment, as it is shown to be ineffective and may simply delay symptoms.)

β-lactams are not suitable drugs for the treatment of chlamydia. While they have the ability to halt growth of the organism (i.e. are microbistatic), these antibiotics do not eliminate the bacteria. Once treatment is stopped, the bacteria will begin to grow once more. (See below for Persistence.)

[edit] Areas of research

Recent phylogenetic studies have revealed that chlamydia shares a common ancestor with modern plants, and retains unusual plant-like traits (both genetically and physiologically). In particular, the enzyme L,L-diaminopimelate aminotransferase, which is related to lysine production in plants, is also linked with the construction of chlamydia's cell wall. The genetic encoding for the enzymes is remarkably similar in plants and chlamydia, demonstrating a close common ancestry.[15] This unexpected discovery may help scientists develop new treatment avenues: if scientists could find a safe and effective inhibitor of L,L-diaminopimelate aminotransferase, they might have a highly effective and extremely specific new antibiotic against chlamydia.

[edit] Pathophysiology

For Chlamydia's life cycle, see Chlamydia (bacterium)

Chlamydiae have the ability to establish long-term associations with host cells. When an infected host cell is starved for various nutrients such as amino acids (e.g. tryptophan),[16] iron, or vitamins, this has a negative consequence for Chlamydiae since the organism is dependent on the host cell for these nutrients.

The starved chlamydiae enter a persistent growth state wherein they stop cell division and become morphologically aberrant by increasing in size.[17] Persistent organisms remain viable as they are capable of returning to a normal growth state once conditions in the host cell improve.

There is much debate as to whether persistence has in vivo relevance. Many believe that persistent chlamydiae are the cause of chronic chlamydial diseases. Some antibiotics such as β-lactams can also induce a persistent-like growth state, which can contribute to the chronicity of chlamydial diseases.

[edit] Footnotes

  1. ^ www.chlamydiae.com (professional) - Taxonomy diagram. Retrieved on 2007-10-27.
  2. ^ Chlamydia fact sheet from the Centers for Disease Control and Prevention
  3. ^ Gerbase AC, Rowley JT, Mertens TE (1998). "Global epidemiology of sexually transmitted diseases". Lancet 351 Suppl 3: 2-4. PMID 9652711. 
  4. ^ a b Thylefors B, Négrel AD, Pararajasegaram R, Dadzie KY (1995). "Global data on blindness". Bull World Health Organ 73 (1): 115-21. PMID 7704921. 
  5. ^ a b Resnikoff S, Pascolini D, Etya'ale D et al (2004). "Global data on visual impairment in the year 2002". Bull World Health Organ 82 (11): 844-851. PMID 15640920. 
  6. ^ a b Belland R, Ojcius D, Byrne G (2004). "Chlamydia". Nat Rev Microbiol 2 (7): 530 – 1. PMID 15248311. 
  7. ^ STD Facts - Chlamydia. Retrieved on 2007-10-26.
  8. ^ Wagenlehner FM, Naber KG, Weidner W (2006). "Chlamydial infections and prostatitis in men". BJU Int. 97 (4): 687-90. doi:10.1111/j.1464-410X.2006.06007.x. PMID 16536754. 
  9. ^ Mabey DC, Solomon AW, Foster A (2003). "Trachoma". Lancet 362 (9379): 223-9. doi:10.1016/S0140-6736(03)13914-1. PMID 12885486. 
  10. ^ World Health Organisation. Trachoma. Accessed March 17, 2008.
  11. ^ Ngondi J, Onsarigo A, Matthews F, et al (2006). "Effect of 3 years of SAFE (surgery, antibiotics, facial cleanliness, and environmental change) strategy for trachoma control in southern Sudan: a cross-sectional study". Lancet 368 (9535): 589-95. doi:10.1016/S0140-6736(06)69202-7. PMID 16905023. 
  12. ^ Williams D, Churchill D (2006). "Ulcerative proctitis in men who have sex with men: an emerging outbreak". BMJ 332 (7533): 99-100. doi:10.1136/bmj.332.7533.99. PMID 16410585. 
  13. ^ a b c d Meyers D, Wolff T, Gregory K. et al. USPSTF Recommendations for STI Screening. Am Fam Physician. 2008;77(6):819-824.
  14. ^ U.S. Preventive Services Task Force (2007). "Screening for chlamydial infection: U.S. Preventive Services Task Force recommendation statement". Ann Intern Med 147 (2): 128-34. PMID 17576996. 
  15. ^ McCoy AJ, Adams NE, Hudson AO, Gilvarg C, Leustek T, Maurelli AT (2006). "L,L-diaminopimelate aminotransferase, a trans-kingdom enzyme shared by Chlamydia and plants for synthesis of diaminopimelate/lysine". Proc. Natl. Acad. Sci. U.S.A. 103 (47): 17909–14. doi:10.1073/pnas.0608643103. PMID 17093042. 
  16. ^ Leonhardt RM, Lee SJ, Kavathas PB, Cresswell P (2007). "Severe Tryptophan Starvation Blocks Onset of Conventional Persistence and Reduces Reactivation of Chlamydia trachomatis". Infect. Immun. 75 (11): 5105–17. doi:10.1128/IAI.00668-07. PMID 17724071. 
  17. ^ Mpiga P, Ravaoarinoro M (2006). "Chlamydia trachomatis persistence: an update". Microbiol. Res. 161 (1): 9–19. doi:10.1016/j.micres.2005.04.004. PMID 16338585. 

[edit] External links

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Sexually transmitted diseases and infections (STD/STI) (primarily A50-A64, 090-099)
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Bacterial diseases (primarily A00-A79, 001-041,080-109)
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G-/α Proteobacteria
G-/β&γ Proteobacteria