Mycoplasma And Ureaplasma

Mycoplasma and Ureaplasma

Family: Mycoplasmataceae • Genus: Mycoplasma – Species: M. pneumoniae – Species: M. hominis – Species: M. genitalium

• Genus: Ureaplasma – Species: U. urealyticum

Diseases Caused by Mycoplasma Organism

Disease

M. pneumoniae

Upper respiratory tract disease, tracheobronchitis, atypical pneumonia, (chronic asthma??)

M. hominis

Pyleonephritis, pelvic inflammatory disease, postpartum fever

M. genitalium

Nongonococcal urethritis

U. urealyticum

Nongonococcal urethritis, (pneumonia and chronic lung disease in premature infants??)

N.B. Other organisms infect humans but their disease association is not known.

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

“Fried Egg” Colonies of Mycoplasmas

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

Differentiation of Species • • • •

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

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)

Mycoplasma pneumoniae • Tracheobronchitis • Atypical pneumonia (walking pneumonia)

Epidemiology - M. pneumoniae • Occurs worldwide • No seasonal variation – Proportionally higher in summer and fall

• Epidemics occur every 4-8 year

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

Epidemiology - M. pneumoniae • Estimated pneumonia in USA per year – 2 million • Estimated respiratory disease in USA per year – 20 million • Non-reportable disease

Clinical Syndrome - M. pneumoniae • Tracheobronchitis – 70-80% of infections

• Pneumonia – Approximately 10% of infections • Mild disease but long duration • “Primary atypical pneumonia” • “Walking pneumonia”

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

Immunity - M. pneumoniae • Complement activation – Alternative pathway

• Phagocytic cells • Antibodies – IgA important

• Delayed type hypersensitivity – More severe disease (immunopathogenesis)

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

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

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.

Treatment and Prevention M. pneumoniae • Treatment – Tetracycline or erythromycin • Newer fluoroquinolones

– Can’t use cell wall synthesis inhibitors

• Prevention – Avoid close contact – No vaccine

M. hominis, M. genitalium and U. 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 - ??

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