123som

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MYCOPLASMA

• Smallest free-living micro organisms, lack cell
  wall.
• Size varies from spherical shape(125-250nm to
  longer branching filaments 500-1000 nm in size.
  Many can pass through a bacterial filter.
• 1st member of this group isolated by Nocard
  Roux (1898) caused bovine
• pleuropneumonia.
• Later, many similar isolates were obtained from
  animals, human beings, plants environmental
  sources called as pleuropneumonia like
  organisms(PPLO).

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MYCOPLASMA

• Eaton (1944) first isolated the causative agent
  of the disease in hamsters and cotton rates.
• Also known as Eaton agent.
• 1956- PPLO replaced by Mycoplasma.
• Myco fungus like branching filaments
• Plasma plasticity
• highly pleomorphic no fixed shape or size -
  Lack cell wall.

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General characteristics

• smallest known free-living organisms.
• Because of the absence of cell walls, they do not
  stain with the Gram stain, and they are more
  pleomorphic and plastic than eubacteria.
• No cell wall
• Susceptible to tetracyclines and erythromycin
• very small (0.2 x 0.8 um)
• pass through a 0.45 um filter

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Mycoplasmas of Humans

• Parasitic
• Established pathogens M. pneumoniae
• Presumed pathogens M. hominis
• Non pathogenic M. orale, M. buccale, M.
  genitalium, M. fermentans
• Saprophytic present mainly on skin in mouth.

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Pathogenicity

• Produce surface infections adhere to the mucosa
  of respiratory, gastrointestinal genitourinary
  tracts with the help of adhesin.
• Two types of diseases
• Atypical Pneumonia
• Genital infections

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Pathogenicity cont

• 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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Diseases Caused by Mycoplasma

• Organism Disease
• M. pneumoniae Upper respiratory
  tract disease,
  
• 
  tracheobronchitis,
• atypical pneumonia, (chronic
  asthma?)
• M. hominis Pyelonephritis, pelvic
  inflammatory
• 
  disease,
• postpartum
  fever
• M. genitalium Nongonococcal
  urethritis

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M.pneamonia

• Pathogenicity of m.pneamonia
• Upper respiratory tract disease
• tracheobronchitis
• atypical pneumonia, (chronic asthma?)

Incubation period 1-3 wks
Transmission airborne droplets of
nasopharyngeal secretions, close contacts
(families, military recruits
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Epidemiology - M. pneumoniae

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

• Incubation 1-3 weeks
• Fever, headache and malaise
• Persistent, dry, non-productive cough
• Respiratory symptoms
• Patchy bronchopneumonia
• acute pharyngitis may be present
• Organisms persist
• Slow resolution
• Rarely fatal

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Laboratory Diagnosis

• Specimens
• throat swabs, respiratory secretions ,sputum
  ,mucous membrane, urine ,swabbings or other
  specimens..
• Morphology
• Pleomorphic, spherical, short rod, filament Gram
  negative bacteria.
• Gram negative, but better stained with
  Giemsa,Dienes stain, crystal-fast violet, orcein
  or fluorochroming with nucleic acid stain as
  acredine orange

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Laboratory Diagnosis
culture

• Isolation of Mycoplasma (Culture)
• Semi solid enriched medium containing 20 horse
  or human serum, yeast extract DNA. Penicillium
  Thallium acetate are selective agents.
  
• (serum source of cholesterol other
  lipids)
• 2. Incubate aerobically for 7 -12 days with
  510 CO2 at 35-37C. (temp range 22- 41C,
  parasites 35- 37C, saprophytes lower temp)

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Laboratory Diagnosis

• 3. Typical fried egg appearance of colonies -
  Central opaque granular area of growth extending
  into the depth of the medium, surrounded by a
  flat, translucent peripheral zone.
• 4. Colonies best seen with a hand lens after
  staining with Dienes method.
• 5. Produce beta hemolytic colonies, can
  agglutinate guinea pig erythrocytes.

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Identification of Isolates

• Growth Inhibition Test inhibition of growth
  around discs impregnated with specific antisera.
• Immunofluorescence on colonies transferred to
  glass slides.
• 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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Identification of Isolates

• Serological diagnosis
• Specific tests IF, HAI
• 2. Non specific serological tests cold
  agglutination tests (Abs agglutinate human group
  O red cells at low temperature, 4?C).
• 132 titer or above is significant.

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Treatment and PreventionM. pneumoniae

• Treatment
• Tetracycline in adults (doxycycline) or
  erythromycin (children)
• Tetracycline, Erythromycin Clarithromycin
  drug of choice
• 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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Biochemical test

• Mycoplasma hominis
• Argenin lysis
• Carbomate kinase positive
• Mycoplasma pneamonia
• Argenin lysis and fermentation glucose
• Carbomate kinase and scetate kinase positive

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M.hominas

• Caused by gental infection
• Transmitted by sexual contact
• Men - Nonspecific urethritis, proctitis,
  balanoposthitis Reiters syndrome
• Women acute salpingitis, PID, cervicitis,
  vaginitis
• Also associated with infertility, abortion,
  postpartum fever, chorioamnionitis low birth
  weight infants

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M. hominis, M. genitalium

• Treatment
• Tetracycline or erythromycin
• M. hominis is resistant to erythromycin and
  sometimes to tetracyclin, Clindamycin for these
  resistant strains
• Prevention
• Abstinence or barrier protection
• No vaccine

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POINTS TO BE REMEMBER

• Cold agglutination test
• Cell culture contamination
• Ureaplasma hydrolysis of urea
• Primary atypical/ walking pneumonia
• Genital infections

• Mycoplasma
• No cell wall
• Pleomorphism
• Fried egg colonies
• Dienes stain