Download Mycoplasma and Ureaplasma

Mycoplasma and Ureaplasma
This class is called "Mollicutes" and is divided into five families.
Family “Mycoplasmatacae” contains two genera “Mycoplasma” and
“Ureaplasma” which cause disease in humans.
M.pneumoniae also known as “Eaton’s agent” or “pleuropneumonialike organism” most important species in terms of human infections.
Characteristics.
 Smallest free living bacteria. Pass through (0.45 µm) filters.
(Previously thought to be viruses).
 Variation in shape. Form pleomorphic filaments.
 Unique bacteria. No cell wall. Cell membrane contains sterols
(different from L-forms)
 Resistant to antibiotics acting on cell walls.
 Replication by binary fission (as bacteria).
 Grow on artificial cell free media with sterols (as bacteria).
 Slow growers.
 Contain both DNA and RNA (as bacteria)
 Colonies on solid media very small with characteristic “fried egg
appearance” .
Pathogenesis.
Produces “primary atypical pneumonia” or walking pneumonia.
Extra-cellular pathogen. Adheres to respiratory epithelium by
special protein.
• Virulence Factors:
1. Adhesion protein known as P1.
2. P1 interacts with receptors at base of cilia. Cilia & later ciliated
epithelial cells destroyed.
3. Produce hydrogen peroxide which leads to lysis of host cells.
• Normal clearance of airways affected & allows lower respiratory
tract to become contaminated & mechanically irritated.
• Leads to persistent cough in patients with disease which can last
for several weeks.
•
•
Mycoplasma/medlect/notes/1209/rz
1
Epidemiology.
 Occurs world wide. All through the year.
 Epidemics every few years.
 Most common in school children & those living in close
confines such as military recruits.
 Often affects young adults (5-15y).
 Transmission by nasal secretions.
 Affects close contacts. Class mates or family members.
 Attack rate higher in children than in adults.
 Older patients may have more severe attacks. May be result of
autoimmune reaction in patients who have repeated attacks with
M.pneumoniae.
Clinical Disease
1.
2.
3.
4.
5.
6.
7.
8.
Initially sore throat, malaise, myalgia, headache & low grade fever.
Dry, non-productive cough develops 2-3 days later.
Symptoms slowly worsen & persist for 2 wks or longer.
10% patients may have severe respiratory disease.
Tracheobronchitis or “Atypical” pneumonia.
Atypical pneumonias seen as patchy broncho-pneumonia on Xrays.
Relapse is common.
Complications: Otitis media,erythema multiforme (Stevens
Johnson syndrome), haemolytic anaemia, myocarditis, pericarditis
& neurologic abnormalities.
Secondary infections occur because immunity is incomplete.
Laboratory Diagnosis.
1. Clinical diagnosis.
2. Specimen: Sputum. To exclude other pathogens. Flourescent
staining (using flourescin labelled antibodies confirmatory).
3. Culture: Other specimens such as throat washings, bronchial
washings may be more reliable. Use special agar with supplement
such as serum (sterols), yeast extract, glucose, pH indicator and
penicillin.
Colonies small (Fried egg) & require confirmation.
4. Cold haemagglutinins: Antibodies that agglutinate type O human
erythrocytes at 4°C.
5. Serological tests: Using complement fixation test.
6. Agglutination: Using Streptococcus mg.
7. Nucleic acid hybridisation: PCR tests available reliable &
sensitive.
Mycoplasma/medlect/notes/1209/rz
2
Treatment
1. Erythromycin and Tetracycline equally effective. (Erythromycin
favoured because covers Legionella also).
Control
(Difficult to control as spread by close contact).
 Endemic world wide.
 Formalin inactivated vaccine. Efficacy only 50% used in high
risk individuals.
 Living attenuated vaccine. Patients may develop signs of disease.
 Mostly administer vaccines only to at risk individuals.
Mycoplasma hominis
Characteristics as other mycoplasmas.
Produces fried egg colony.
Normal habitat human genital tract.
Associated with pyelonephritis, pelvic inflamatory disease &
postpartum fever.
 Mostly considered non-pathogenic.




Treatment:
1. Azithromycin increasingly used because many strains are
Tetracycline resistant.
Mycoplasma genitalium





Characteristics as other mycoplasma.
Frequently found in genital tract.
More pathogenic than M.hominis has adhesions like M.pneumoniae.
Causes Non-gonococcal urethritis.
Associated with endometriosis and pelvic inflamatory disease.
Treatment:
 Tetracyclines (or Azithromycin for resistant strains).
Diagnosis:
 Culture methods difficult. Easier & more effective to use
Serology & PCR methods.
Mycoplasma/medlect/notes/1209/rz
3
Ureaplasma urealyticum





Very small (known as Tiny-strain mycoplasma).
Require both sterols and urea for growth.
Ureaplasma urealyticum mostly found in genital tract.
Produces non-gonococcal urethritis.
Transmission by sexual contact.
Treatment:

Some strains resistant to Tetracycline but Erythromycin is
effective.
Diagnosis:

Culture methods difficult it is more effective to use serology
or PCR methods (Like the genital tract mycolplasma).
Mycoplasma Infections.
Summary
Species
Site of Infection Disease
M.pneumoniae
Respiratory
tract
M.hominis
Genital tract
M.genitalium
Genital tract
Non-gonococcal
Urethritis.
U.urealyticum
Genital tract
Non-gonococcal
urethritis.
URT.
Tracheobronchitis.
Atypical
pneumonia
Post partum fever.
PID
********
Mycoplasma/medlect/notes/1209/rz
4