Mycoplasma and Ureaplasma

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Mycoplasma and Ureaplasma
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Family Mycoplasmataceae

• Genus Mycoplasma
• Species M. pneumoniae
• Species M. hominis
• Species M. genitalium
• Genus Ureaplasma
• Species U. urealyticum

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Diseases Caused by Mycoplasma
N.B. Other organisms infect humans but their
disease association is not known.
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Morphology and Physiology

• Smallest free-living bacteria (0.2 - 0.8 m)
• Small genome size
• Require complex media for growth
• Facultative anaerobes
• Except M. pneumoniae - strict aerobe
• Lack a cell wall

• Grow slowly by binary fission
• Fried egg colonies
• M. pneumoniae colonies have a granular appearance

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Fried Egg Colonies of Mycoplasmas
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Morphology and Physiology

• Smallest free-living bacteria
• Small genome size
• Require complex media for growth
• Facultative anaerobes
• Except M.. pneumoniae - strict aerobe
• Lack a cell wall
• Grow slowly by binary fission
• Fried egg colonies

• Ureaplasma - T strains
• Require sterols for growth

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Differentiation of Species

• M. pneumoniae - glucose
• M. hominis - arginine
• U. urealyticum - urea
• M. genitalium - difficult to culture

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Pathogenesis - Mycoplasma

• Adherence
• P1 pili (M. pneumoniae)
• Movement of cilia ceases
• Clearance mechanism stops resulting in cough
• Toxic metabolic products
• Peroxide and superoxide
• Inhibition of catalase
• Immunopathogenesis
• Activate macrophages
• Stimulate cytokine production
• Suprerantigen (M. pneumoniae)

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Mycoplasma pneumoniae

• Tracheobronchitis
• Atypical pneumonia (walking pneumonia)

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Epidemiology - M. pneumoniae

• Occurs worldwide
• No seasonal variation
• Proportionally higher in summer and fall
• Epidemics occur every 4-8 year

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Epidemiology - M. pneumoniae

• Spread by aerosol route (Confined populations)
• Disease of the young (5-20 years), although all
  ages are at risk

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Epidemiology - M. pneumoniae

• Estimated pneumonia in USA per year 2
  million
• Estimated respiratory disease in USA per year
  20 million
• Non-reportable disease

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Clinical Syndrome - M. pneumoniae

• Tracheobronchitis
• 70-80 of infections
• Pneumonia
• Approximately 10 of infections
• Mild disease but long duration
• Primary atypical pneumonia
• Walking pneumonia

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Clinical Syndrome - M. pneumoniae

• Incubation - 2-3 weeks
• Fever, headache and malaise
• Persistent non-productive cough
• Respiratory symptoms
• Radiological signs precede symptoms
• Organisms persist
• Slow resolution
• Rarely fatal

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Immunity - M. pneumoniae

• Complement activation
• Alternative pathway
• Phagocytic cells
• Antibodies
• IgA important
• Delayed type hypersensitivity
• More severe disease (immunopathogenesis)

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Laboratory Diagnosis - M. pneumoniae

• Microscopy
• Difficult to stain
• Can help eliminate other organisms
• Culture (definitive diagnosis)
• Sputum (usually scant) or throat washings
• Special transport medium needed
• Must suspect M. pneumoniae
• May take 2-3 weeks

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Laboratory Diagnosis - M. pneumoniae

• Serology
• Complement fixation
• May take 4-6 weeks
• Fourfold rise in titer
• Cold agglutinins
• 1/3 - 2/3 of patients
• I antigen
• Appear first
• Non-specific
• Presumptive diagnosis
• ELISA
• Not commercially available

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Laboratory Diagnosis - M. pneumoniae

• Molecular diagnosis
• PCR-based tests are being developed and these are
  expected to be the diagnostic test of choice in
  the future.

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Treatment and PreventionM. pneumoniae

• Treatment
• Tetracycline or erythromycin
• Newer fluoroquinolones
• Cant use cell wall synthesis inhibitors
• Prevention
• Avoid close contact
• No vaccine

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M. hominis, M. genitalium andU. urealyticum

• Clinical syndromes
• M. hominis - pyleonephritis, pelvic inflammatory
  disease and postpartum fever
• M. genitalium - nongonococcal urethritis
• U. urealyticum - nongonococcal urethritis
• Epidemiology
• Colonization at birth - usually cleared
• Colonization with M. hominis - 15
• Colonization with U. urealyticum - 45 -75
• Colonization with M. genitalium - ??

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M. hominis, M. genitalium and U. urealyticum

• Laboratory diagnosis
• Culture (except M. genitalium)
• Treatment and prevention
• Treatment
• Tetracycline or erythromycin
• Prevention
• Abstinence or barrier protection
• No vaccine