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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: 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