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Chlamydia trachomatis
The Biology of a Sexually
Transmitted Bacterium
Chlamydia
¨Three species are human pathogens
¨Chlamydia trachomatis
¨Chlamydia pneumoniae
¨Chlamydophila psittaci
Chlamydial Life Cycle
• Reticulate body, obligately intracellular in
eukaryotic cells
• Elementary body, metabolically inert, an
extracellular spore-like state
• 48-72 hour 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 purinepyrimidine 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
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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