Properties

Pathogenesis

Clinical findings

Laboratory diagnosis

Treatment & Prevention

Chlamydiae Trachomatis

Obligate intracellular bacteria: can grow only inside host cells.

Have a rigid cell wall but no peptidoglycan layer.

Share a group-specific lipopolysaccharide antigen, detected by complement fixation tests.

Transmission:

- infects only humans.

- transmitted by close personal contact: sexually or passage through birth canal.

- trachoma: finger, flies & fomites.

Life-cycle:

- inert elementary body enters cell & reorganizes into larger, active reticulate body.

- latter undergoes binary fissions to form daughter elementary bodies which are released from cells.

- appear as an inclusion body.

Infect primarily epithelial cells of the mucous membrane of the lungs; rarely cause invasive, disseminated infections.

Protective immunity does not develop:

- repeated infections occur.

- organisms are not eliminated.

Trachoma:

- caused by C.trachomatis A, B, Ba, C.

- an eye infection common in developing countries.

- cornea becomes clouded.

- chronic inflammation leads to scarring of eyelids & cornea with eventual blindness.

- no systemic illness.

Lymphogranuloma venereum:

- caused by C.trachomatis L1, L2, L3.

- most cases occur in tropics & subtropics.

- sexually transmitted.

- primary lesion is on genitalia – a small papule or vesicle.

- infection spreads to regional lymph nodes which enlarge, suppurate & discharge through sinuses.

- males: inguinal glands.

- females & homosexuals: perirectal glands suppurate leading to proctitis & bloody anal discharge.

- chronic inflammation can lead to rectal stricture, or elephantiasis of the genitals.

Genital tract infections:

- often caused by C.trachomatis D-K.

- occasionally transmitted to the eyes or the respiratory tract.

- man: common cause of nongonococcal urethritis, which may progress to epididymitis, prostatitis, or procitis.

- female: cervicitis develops, & may progress to salphingitis & pelvic inflammatory disease.

- infants born to affected mothers: develop mucopurulent eye infections 7-12 days after delivery & may develop chlamydial pneumonia 2-12 weeks after birth.

Form cytoplasmic inclusions seen by Giemsa’s stain or by immunofluorescence.

In exudates, organisms can be identified within epithelial cells by:

- fluorescent antibody staining.

- ELISA

- hybridization with a DNA probe.

Difficult to culture:

- C.trachomatis form inclusions containing glycogen.

Serologic tests are rarely helpful due to high frequency of infection.

Gram stain is not useful.

Antibiotics:

- erythromycin

- tetracyclin

- azithromycin

Prophylaxis:

- erythromycin given to newborn infants of infected mothers can prevent inclusion conjunctivitis & pneumonitis.

No vaccine.

Chlamydiae psittaci

Transmission:

- infects birds & many mammals.

- infected by inhaling organisms in dry bird feces.

Flu-like initial illness leading to pneumonia:

- infects lungs primariy.

- infection may be asymptomatic.

- produce high fever & pneumonia.

Dissemination of infection may lead to clinical infections of many body sites including brain, heart, joints, etc.

Rare cause of bacterial endocarditis.

Form inclusions that do not contain glycogen.

Glycogen-filled inclusions are visualized by staining with iodine.

Serologic tests are used.

Antibiotics:

- erythromycin

- tetracyclin

- azithromycin

Prevention:

- restrict importation of psittacine birds.

- destroying sick birds.

- adding tetracycline to bird feed.

- survey domestic flocks of turkeys & ducks for organism.

Chlamydiae pneumoniae

Transmission:

- infects only humans.

- person-to-person by aerosol.

Common cause of mild pneumonia in young adults: epidemics occur in military conscripts.

Both upper & lower respiratory tract symptoms may occur.

More severe infections in young children in developing countries.

Reinfection and/or chronic infection in older patients may occur.

May be associated with development of atherosclerosis & coronary heart disease.

Form inclusions that do not contain glycogen.

Glycogen-filled inclusions are visualized by staining with iodine.

Serologic tests are used.

Antibiotics:

- erythromycin

- tetracyclin

- azithromycin