Mycoplasmas lectures 11

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Mycoplasmaslectures 11 12
Dr.Ihsan Edan Alsaimary
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Mycoplasma cell wall defective bacteria
two hoursAim
study the differentiation and clinical importance
of Mycoplasma with its infectionsTopics-
General Characteristics of M. pneumoniae,
Ureaplasma urealyticum and other
genera-structures and physiology-pathogenicity
and Mechanism of Pathogenesis- virulence
factors enzymes, toxins-laboratory diagnosis-
immunity-epidemiology and predisposing factors
of Mycoplasma-treatment , prevention and control
measures
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Mycoplasmas
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Morphology and Physiology

• The smallest free-living organisms
• Pass through some filters used to remove bacteria
  
• Lack of a cell wall
• Multiple shapes including round, pear shaped and
  even filamentous

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• Require complex media
• Require sterols for growth and for membrane
  synthesis
• Grow slowly (3 weeks) by binary fission and
  produce "fried egg" or T strain (tiny strain)
  colonies on agar plates

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Structure

• Three layer membranes
• Outer and inner proteins and saccharide
• Middle 1/3 cholesterol
• dsDNA, has ribosomes, no endoplasmic reticulum
  (ER)

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Pathogenesis

• Adherence factors
• Adherence proteins are one of the major virulence
  factors
• Adhesin localizes at tips of the cells and binds
  to sialic acid residues on host epithelial cells

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Specialized tip organelle
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Pathogenesis

• Toxic Metabolic Products
• The intimate association provides an environment
  in which toxic metabolic products accumulate and
  damage host tissues
• Products of metabolism hydrogen peroxide and
  superoxide -- oxidize host lipids
• Inhibit host cell catalase

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Pathogenesis

• Immunopathogenesis
• M. pneumoniae is a superantigen
• Activate macrophages and stimulate
  cytokine production and lymphocyte activation
• Host factors contribute to pathogenesis

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M. Pneumoniae

• Need 10-20 Serum to culture in pH 7.8-8.0
• Pathogenesis P1 protein, capsule and saccharide
• Spread  by close contact via aerosolized droplets
• Cause tracheobronchitis
• Cause primary atypical pneumonia
• long duration
• Antibodies play a role in controlling infection,
  particularly sIgA
• Delayed type hypersensitivity

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M. Pneumoniae Laboratory Diagnosis

• Organisms can be cultured from sputum before
  symptoms occur and throughout the course of the
  disease.
• Serology
• Complement fixation test A fourfold rise in
  titer is indicative of a recent infection.
• Cold agglutinins are IgM antibodies that
  agglutinate human O erythrocytes at 4? but not
  at 37? not specific/a presumptive diagnosis
• ELISA

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• U. urealyticum and M. genitalium
  cause nongonococcal urethritis
• M. hominis implicated as a cause of
  pyelonephritis, pelvic inflammatory disease,
  and postpartum fever

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Lab diagnosis

• Culture of mycoplasmas is not routinely
  attempted, and relatively insensitive
• M. pneumoniae can grow in special medium with
  animal serum (sterols), yeast extract, glucose,
  and penicillin. Colonies have a
  mulberry-shaped.
• M. hominis requires arginine for growth. Colonies
  have a fried-egg appearance.
• Ureaplasma requires urea for growth
• Microscope no cell well, stain poorly, no value

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Serology - M. pneumoniae

• Complement fixation test high false-positive
  rate
• ELISE for detection of IgM and IgG Abs
• Nonspecific reaction to outer membrane
  glycolipids cold agglutinins
• IgM Abs that bind the I antigen on human RBC at
  4C) develop in 65 of the patients - a test
  frequently used to confirm the diagnosis.
• False-positive seen in infections with
  Epstein-Barr virus, cytomegalovirus, and
  adenovirus.

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Treatment

• M. pneumoniae erythromycin, tetracycline (also
  good for chlamydia)
• Ureaplasma use erythromycin, resistant to
  tetracycline
• M. hominis resistant to erythromycin and
  tetracycline, use clindamycin

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M. pneumoniae Treatment and Prevention

• The antibiotics of choice are tetracycline
  (adults only) and erythromycin.
• Long duration of the disease, hard to isolate
  patients to avoid close contact for a long period
  of time.
• No vaccines are currently available

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U. Urealyticum

• Isolation pathogen cultured in pH 6.0 media
• Metabolism of urea in infectious site and damage
  cells
• Associated with urogenital infections, can cause
  NGU (Nongonococcl urethritis)

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• Thanks