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.
  • 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
  • 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) 
      • 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
  • Characteristics
    • no muramic acid in cell wall
      • therefore not seen on Gram stain
  • Diagnosis
    • cytoplasmic inclusions seen on Giemsa stain or fluorescent antibody-stain
  • 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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(M1.MC.17) A sample is taken of an ulcer in the inguinal region of a 29-year-old Malaysian male who has had unprotected sex in the past few months. Intracytoplasmic inclusions are seen in the Giemsa staining in Image A. On which of the following can the organism in the staining be grown? Review Topic

QID: 101476

Bordet-Gengou agar




Löwenstein-Jensen agar




Charcoal yeast extract agar with cysteine and iron




Eaton's agar




Yolk sac of a chick embryo



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