Mycoplasma and Ureaplasma

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Mycoplasma and Ureaplasma
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(No Transcript)
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Family Mycoplasmataceae

• Genus Mycoplasma
• Species M. pneumoniae
• Species M. hominis
• Species M. genitalium
• Genus Ureaplasma
• Species U. urealyticum
• 16 species colonize humans, the above have been
  associated with disease.

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Diseases Caused by Mycoplasma
Organism Disease M. pneumoniae Upper
respiratory tract disease, tracheobronchitis, a
typical pneumonia, (chronic asthma?) M.
hominis Pyelonephritis, pelvic inflammatory
disease, postpartum fever M.
genitalium Nongonococcal urethritis U.
urealyticum Nongonococcal urethritis,
(pneumonia and chronic lung disease in
premature infants?)
Note that Other organisms in the family of
Mycoplasmataceae infect humans but a disease
association is not known.
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Morphology and Physiology

• Smallest free-living bacteria (0.2 - 0.8 mm) many
  can pass through a 0.45 µm filter, mistaken for
  viruses
• Small genome size (M. pneumoniae is 800 Kbp)
• Require complex media for growth
• Facultative anaerobes
• Except M. pneumoniae - strict aerobe
• Lack a cell wall, membrane contains sterols
• no cell wall means these are resistant to
  penicillins, cephalosporins, vancomycin, etc.

• Grow slowly by binary fission
• Doubling time can be as long as 16 hours,
  extended incubation needed

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Fried Egg Colonies of some Mycoplasmas
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Colony morphology, contd
Except for M. pneumoniae colonies which have a
granular appearance, described as being mulberry
shaped
mulberry
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Morphology and Physiology, contd

• Require complex media for growth, including
  sterols
• Major antigenic determinants are glycolipids and
  proteins, some cross reaction with human tissues
• Requirements for growth allow one to
  differentiate between species

• M. pneumoniae - glucose
• M. hominis - arginine
• U. urealyticum - urea (buffered media due to
  growth inhibition by alkaline media)
• M. genitalium - difficult to culture

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Pathogenesis

• Adherence
• P1 pili (M. pneumoniae)
• Movement of cilia ceases (ciliostasis)
• Clearance mechanism stops resulting in cough
• Toxic metabolic products
• Peroxide and superoxide
• Inhibition of catalase
• Immunopathogenesis
• Activate macrophages
• Stimulate cytokine production
• Superantigen (M. pneumoniae)
• Inflammatory cells migrate to infection and
  release TNF-a then IL-1 and IL-6

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Transmission electron photomicrograph of a
hamster trachea ring infected with M. pneumoniae.
Note the orientation of the M. pneumoniae through
their specialized tip-like organelle, which
permits close association with the respiratory
epithelium. M, mycoplasma m, microvillus C,
cilia. Image used with permission. From Baseman
and Tully, Emerging Infectious Diseases 3
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Mycoplasma pneumoniae

• Tracheobronchitis
• Atypical pneumonia (walking pneumonia)
• More common in school-age children and young
  adults but everyone is susceptible (theory that
  adults might be partially immune due to previous
  exposure)
• Estimate of 2,000,000 cases in USA annually,
  possibly resulting in 100,000 hospitalizations
• Not a reportable disease, so true incidence is
  not known

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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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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, dry, non-productive cough
• Respiratory symptoms
• Patchy bronchopneumonia, may precede symptoms
• acute pharyngitis may be present
• Organisms persist
• Slow resolution
• Rarely fatal
• Note Muscle pain and GI symptoms usually not
  present

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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
• This process 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 or longer, 6 hour doubling
  time with glucose and pH indicator included
• Incubation with antisera to look for inhibition,
  not a typical test

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Laboratory Diagnosis - M. pneumoniae

• Serology
• Complement fixation
• May take 4-6 weeks
• Fourfold rise in titer (requires collection two
  samples 3-4 weeks apart)
• Relatively insensitive
• Cold agglutinins
• 1/3 - 2/3 of patients
• I antigen
• Appear first
• Non-specific and insensitive
• 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.
• These should have good sensitivity and be specific

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Treatment and PreventionM. pneumoniae

• Treatment
• Tetracycline in adults (doxycycline) or
  erythromycin (children)
• Newer fluoroquinolones (in adults)
• Resistant to cell wall synthesis inhibitors
• Prevention
• Avoid close contact
• Isolation is not practical due to length of
  illness
• No vaccine, although attempted

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M. hominis, M. genitalium andU. urealyticum

• Clinical syndromes
• M. hominis - pyelonephritis, pelvic inflammatory
  disease and postpartum fever
• M. genitalium - nongonococcal urethritis
• U. urealyticum - nongonococcal urethritis
• Epidemiology
• Colonization at birth - usually cleared but could
  persist
• sexually active adults with M. hominis - 15
• 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
• U. urealyticum is resistant to tetracycline
• M. hominis is resistant to erythromycin and
  sometimes to tet, Clindamycin for these resistant
  strains
• Prevention
• Abstinence or barrier protection
• No vaccine