Chlamydia trachomatis

The Biology of a Sexually Transmitted Bacterium

ChlamydiaChlamydia

Three species are human pathogensThree species are human pathogens

Chlamydia trachomatisChlamydia trachomatis

Chlamydia pneumoniaeChlamydia pneumoniae

Chlamydophila psittaciChlamydophila psittaci

• Reticulate body, obligately intracellular in eukaryotic cells

• Elementary body, metabolically inert, an extracellular spore-like state

• 48-72 hour cycle

Chlamydial Life Cycle

Chlamydial Biology

• Prokaryotes

• Gram negative with LPS

• Lack peptidoglycans?

• Obligate intracellular life cycle

Chlamydial Genome

• 1.043 million base pairs

• Missing genes for amino acid and purine-pyrimidine biosynthesis, anaerobic fermentation, and transformation competence proteins

• Contains genes for LPS, glycolysis, fatty acid and phospholipid synthesis, peptidoglycan synthesis

Chlamydia trachomatis: Disease Presentations

• Perinatal infections

• Genitourinary tract infections

• Trachoma

Chlamydia trachomatis and Sexually Transmitted Infections

• Urogenital infections: cervicitis, urethritis, PID, epididymitis/prostatitis

• 4-6 million cases/year, U.S.

• Prevalence highest in young women, 3-11% (age 15-24)

• Lymphogranuloma venereum

Serious Consequences of C. trachomatis STI's

• Tubal infertility

• Ectopic pregnancy

• Reactive arthritis (Reiter's syndrome)

C. trachomatis Perinatal Infections

• Neonatal inclusion conjunctivitis (20-45% of infants from infected mothers)

• Infant pneumonia (10-20% of infants from infected mothers)

C. trachomatis and Trachoma

• Blinding conjunctival infection

• 600 million cases worldwide

• Develops over years,

chronic inflammation

• Endemic in Middle East, Asia

C. trachomatis: Diagnosis

• Serology (MIF=microimmunofluorescence)

• Culture

• EIAs/DFA (direct fluorescent antibody)

• Direct hybridization

• Nucleic acid amplification (PCR, LCR, others)

C. trachomatis: NA Amplification

• Nucleic acid amplification can be used on urine, cervical/urethral specimens

• Vaginal specimens also have been used

• Sensitivity, 90%+, specificity >99%

• Identifying more male cases, providing easier specimen collections

C. trachomatis: Treatment

• Azithromycin,

(single 1000 mg dose acceptable)

• Tetracyclines (erythromycin in children)

Chlamydia pneumoniae

• 1983, described as a distinct chlamydial pathogen

• Less than 10% DNA homology with C. trachomatis

• Similar life cycle but different cell wall construction

C. pneumoniae: Disease Presentations

• Pharyngitis, bronchitis

• Pneumonia (7-10% of cases)

• Other syndromes

(otitis media, endocarditis)

C. pneumoniae and Chronic Diseases

• Atherosclerosis (seroepidemiologic studies, experimental disease)

• Asthma

• Neurological disease? (MS, Alzheimer’s)

C. pneumoniae: Diagnosis

• Serology

(MIF = microimmunofluorescence)

• Culture

• PCR

C. pneumoniae: Treatment

• Azithromycin/clarithromycin (macrolides)

• Erythromycin

• Tetracycline/doxycycline

Chlamydophila psittaci

• Recently distinguished as a separate genus using sequence phylogeny

• Zoonosis, typically from pet birds, occupational exposure

• 80 cases/year in the U.S

Chlamydophila psittaci: Clinical Disease/Dx/Tx

• Severe pneumonia

• Endocarditis, other systemic presentations

• Diagnosis by serology, culture

• Prolonged therapy with tetracycline