Chapter 25 Chlamydia, Mycoplasma,

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Chapter 25 Chlamydia, Mycoplasma, Ureaplasma
Species

• MLAB 2434 Clinical Microbiology
• Keri Brophy-Martinez

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Chlamydia Characteristics

• Unique growth cycle because they are deficient in
  independent energy metabolism therefore they are
  obligate intracellular parasites
• Replication involves elementary body (EB) and
  reticulate body (RB)
• EBs are infectious, whereas RBs are
  noninfectious

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Life Cycle of Chlamydia

• EB infects host cell by inducing energy-requiring
  active phagocytosis
• Host cells are nonciliated columnar
  epithethelial cells found in tracts of
  urogenital, respiratory, rectum and conjunctiva
• EB organize into large, reticulating initial
  bodies, which divert the cells synthesizing
  functions to their own needs and begin to
  multiply by binary fission
• Organisms begin reorganizing into infective EBs.
• Disrupted host cell dies, releasing new EBs

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Life Cycle of Chlamydia
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Chlamydia pneumoniae

• Most recognized species of Chlamydia
• Important respiratory pathogen (acute respiratory
  disease, pneumonia, and pharyngitis)
• Implicated in asthma
• Risk factor for Guillain-Barre syndrome

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Chlamydia pneumoniae (contd)

• Common (50 of adults have antibodies)
• College age students most susceptible
• Reinfection common
• Prolonged sore throat and hoarseness, followed by
  flu-like lower respiratory symptoms
• Can be following by pneumonia and bronchitis
• Third most common respiratory infection

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Chlamydia pneumoniae (contd)

• If cultured, must be in cells (obligate
  intracellular pathogen) and then visualized with
  fluorescein-conjugated antibodies
• Serologic tests are method of choice for
  detection (Four-fold rise in titer)

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Chlamydia trachomatis

• Most commonly sexually transmitted bacterial
  pathogen in U.S.
• Only HPV is a more commonly sexually transmitted
  disease
• Adult males
• Non-gonococcal urethritis (NGU)
• Epididymitis and prostatitis

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Chlamydia trachomatis (contd)

• Adult females
• Urethritis, follicular cervicitis, endometritis,
  proctitis, salpingitis, PID and perihepatitis
  (Fitz-Hugh-Curtis syndrome)
• Major cause of sterility in U.S.
• May be transmitted to newborns during delivery

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Chlamydia trachomatis (contd)

• Other sites of infection
• Trachoma infection of the conjunctiva,
  resulting in scarring and blindness (Mostly in
  India and Egypt)
• Lymphogranuloma verereum infects lymph nodes
• STD found in immigrants from the tropics

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Chlamydia trachomatis (contd)

• Laboratory Diagnosis
• Direct microscopic examination to find EBs
• Cell culture
• Enzyme immunoassay
• Nucleic acid probes with and without
  amplification (PCR)
• Serologic (antibody) assay

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Chlamydia psittaci

• Causes psittacosis (parrot fever)
• Identification based on history of close contact
  with birds and serologic evaluation

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Mycoplasma and Ureaplasma Species

• General Characteristics
• Once thought to be viruses because of size
• Mycoplasmas are the smallest free-living organism
  in nature
• Four human pathogens
• Mycoplasma pneumoniae - respiratory
• Mycoplasma hominis - urogenital
• Ureaplasma urealyticum urogenital
• Ureaplasma parvum- urogenital

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Mycoplasma and Ureaplasma Species (contd)

• Pleomorphic organisms do not have a cell wall
  (resistant to cell-wall-active antibiotics)
• Slow growing, highly fastidious, facultative
  anaerobes
• Require complex media for growth
• Susceptible to heat and drying
• Transmitted via direct sexual contact,
  mother-child exposure during delivery or
  respiratory secretions

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Clinical Infections

• Mycoplasma pneumoniae
• Causes bronchitis, pharyngitis, or primary
  atypical pneumonia (a.k.a. walking pneumonia)
• Usually infects school-age children and young
  adults in close quarters (dorms, military
  barracks, etc.)
• 50 of infections produce cold agglutinins
• Most often diagnosed by serologic evaluation

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M. hominis Ureaplasma species

• Most often associated with urogenital tract
  infections
• May be isolated from asymptomatic individuals
• Can be transmitted to the fetus at delivery
• Opportunistic pathogens

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Laboratory Diagnosis

• Cultures must be delivered immediately to the
  lab, because the organisms are very susceptible
  to drying
• Should be placed in transport media
• Swabs should be of Dacron, polyester or calcium
  alginate with a plastic or aluminum shaft
• If not plated immediately, should be frozen at
  -70C
• Most infections detected via serologic evaluation