Chlamydia trachomatis

Chlamydia trachomatis

Organism

Chlamydia trachomatis is a very small bacterium having a cytoplasmic membrane and outer membrane similar to gram-negative bacteria but lacking a peptidoglycan cell wall.
Exist in two morphological forms: small infectious elementary bodies 300nm - 400nm in diameter and larger replicating reticulate bodies 800nm - 900nm in size.
Chlamydias are obligate intracellular parasites of vertebrates unable to make their own ATP but rather getting it from their host cell. They have a unique intracellular pattern of replication. The infectious form or elementary body. The elementary body attaches to a susceptible host cell. The host cell subsequently phagocytoses the elementary body and places it in a vacuole where it develops into a larger reticulate body. The reticulate body then divides successively by binary fission and condenses to form more elementary bodies that are then released as the host cell ruptures.
C. trachomatis infects nonciliated columnar, cuboidal, or transitional epithelial cells.
There are two biovars of C. trachomatis: trachoma and LGV (lymphogranuloma venereum).

Habitat

Humans are the only natural host.

Source

Transmitted sexually by contact with an infected individual; may be transmitted from mother to baby during birth.

Epidemiology

In 2002, 834,555 chlamydial infections were reported to CDC from 50 states and the District of Columbia. Under-reporting is substantial because most people with chlamydia are not aware of their infections and do not seek testing. Also, testing is not often done if patients are treated for their symptoms. An estimated 2.8 million Americans are infected with chlamydia each year. Women are frequently re-infected if their sex partners are not treated.
C. trachomatis is the most common sexually transmitted bacterium in the U.S.
C. trachomatis is one of the leading causes of pelvic inflammatory disease (PID) (def) and infertility in women.
C. trachomatis is the most common cause of epididymitis (def) in males.

Clinical Disease

The trachoma biovar of C. trachomatis prevalent in the U.S. causes:
- urogenital infections
- ocular trachoma (def)
- adult and neonatal conjunctivitis (def)
- infant pneumonia
As many as 80% of women are asymptomatic. When symptoms appear, they include urethritis (def), dysuria (def), cervicitis (def), endometritis (def), salpingitis (def), pelvic inflammatory disease (def), and perihepatitis (def).
As many as 25% of males with chlamydial infection are asymptomatic. Whe symptoms appear, they include urethritis (def), urethral discharge, urinary frequency and/or urgency, dysuria (def), and scrotal pain or tenderness.
Congenital chlamydial infection appears as neonatal (def) conjunctivitis (def) and neonatal pneumonia. The newborn becomes infected as it passes through the birth canal. Antibiotic drops are put in the eyes of newborns to prevent congenital gonorrhea and congenital Chlamydia infection.
The LGV biovar of C. trachomatis causes lymphogranuloma venereum (LGV) LGV and is very prevalent in Asia, Africa, and South America. LGV typicall begins with a small, painless lesion at the site of infection that heals rapidly. Secondary LGV appears as marked inflammation and swelling of the lymph nodes draining the site of initial infection.

Pathogenicity

C. tracomatis replicates within epithelial cells evenyually causing those cells to lyse.
The bacterium blocks the fusion of phagosomes with cellular lysosomes to resist phagocytosis.
Cell wall adhesins (def) enable elementary bodies to adhere to host cell surfaces and subsequently enter those cells by phagocytosis.

Treatment

Ocular and urogenital infections can be treated with azrithromycin, ofloxacin or doxycycline. Neonatal conjunctivitis and pneumonia can be treated with erythromycin (see antibiotic table).

*Drugs may change with time.

For a more detailed article on Chlamydia trachomatis infections, see Chlamydial Genitourinary Infections, by Larry I Lutwick, MD, Director, Division of Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Professor, Department of Internal Medicine, State University of New York at Downstate; Renuka Heddurshetti, MD, Fellow in Infectious Diseases, Department of Internal Medicine, State University of New York at Brooklyn; and Jeffrey Blitstein, MD, Staff Physician, Department of Internal Medicine, Division of Infectious Disease, VA New York Harbor Health Care System at Brooklyn. Also see Lymphogranuloma venereum (LGV) by Gregory Shipkey, MD, Staff Physician, Department of Emergency Medicine, William Beaumont Army Medical Center; Alexandre F Migala, DO, FAAEM, Aerospace Medicine Service, Assistant Clinical Professor, Department of Family Care Medicine, Darnall Army Community Hospital; Gary P Holmes, MD, Division of Infectious Disease, Associate Professor, Departments of Epidemiology/Biostatistics and Medicine, Texas A&M University Schools of Rural Public Health and Medicine.