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Overview

Snapshot
Chlamydia trachomatis
  • A two-week-old neonate is brought to your office by his concerned mother who explains that her child is wheezing. Upon examination, you note an afebrile infant with a wheeze, stacatto cough, and increased anterior-posterior diameter of the chest. The lungs are tympanitic to percussion and the eyes appear crusty bilaterally.
Introduction
  • Classification
    • obligate intracellular bacteria
      • C. trachomatis
  • Pathogenesis
    • transmission
      • sex
      • birth (passage through birth canal)
      • trachoma transmitted by hand-to-eye contact and flies
    • reservoir
      • genital tract
      • eyes
    • molecular biology
      • obligate intracellular
        • cannot make ATP
        • requires live cells for growth in laboratory   
      • 2 forms
        • reticulate body
          • intracellular, metabolically active, replicating form
          • "Reticulate Replicates"
          • collections of reticulate bodies can be seen in the cytoplasm under light microscopy and are called "inclusion bodies"
        • elementary body
          • infectious, inactive, extracellular form
          • small, dense
          • "Elementary is Enfectious and Enters cell via Endocytosis"
      • infection of mucosal surfaces leads to granulomatous response and damage
      • multiple serotypes, each with a characteristic assocated disease
      • cell wall does not contain peptidoglycan
        • beta-lactam antibiotics are ineffective
Diseases
  • Chlamydia (sexually transmitted disease)
    • the most common bacterial STD in the U.S.
      • herpes and HPV are more common overall
    • serotypes D-K 
    • initial presentation
      • subacute (often undiagnosed)
      • cervical motion tenderness ("chandelier sign")
      • purulent cervical discharge
    • sequelae
      • nongonococcal urethritis
      • reactive arthritis (Reiter's syndrome)
      • cervicitis
      • PID
      • infertility
      • conjunctivitis (adults and neonates)
        • transmitted to neonates during birth
        • most common cause of conjunctivitis in the 2nd week of life
      • pneumonia in neonates (staccato cough)
        • transmitted to neonates during birth
      • ectopic pregnancy
  • Lymphogranuloma venereum 
    • serotypes L1, L2, L3 ("L for lymphogranuloma")
    • STD prevalent in Africa, Asia, and South America
      • begins as small papule on genital mucosa
      • rectal strictures
      • painful lymphadenopathy
        • can progress to genital elephantiasis
      • diagnosis with serology (complement fixation, enzyme immunoassay, PCR). Positive Frei test (obsolete), 
      • granulomatous and neutrophilic inflammation
    • do not confuse with granuloma inguinale (donovanosis)
      • caused by Calymmatobacterium granulomatis
      • papule becomes painless, exophytic mass
  • Trachoma
    • most common cause of preventable blindness
    • associated with Africa
    • serotypes A, B, Ba, C
    • follicular conjunctivitis and in-turned eyelashes
Laboratory
  • Characteristics
    • no muramic acid in cell wall
      • therefore not seen on Gram stain
  • Diagnosis
    • cytoplasmic inclusions seen on Giemsa stain or fluorescent antibody-stain
Treatment
  • Azithromycin (one-time treatment) or doxycycline
    • not sensitive to beta-lactams (cell wall does not contain peptidoglycan)
      • treatment of N. gonorrhoeae with ceftriaxone monotherapy is often inadequate, as it does not cover for possible coinfection with Chlamydia
  • Erythromycin prophylaxis in neonates
    • erythromycin eyedrops given at birth protect against Chlamydia and N. gonorrhoeae
    • topical and oral erythromycin used to treat neonatal chlamydial conjunctivitis 
      • oral erythromycin is used to prevent or treat systemic chlamydial infection
 

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