Mycoplasmas and Actinomycetes

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Mycoplasmas and Actinomycetes

• Presented by
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• Dr Asif Jiman-Fatani, MB ChB, MSc, PhD (UK)
• Assistant Professor in Medical Microbiology,
• Faculty of Medicine, King Abdulaziz University
• Consultant Microbiologist
• Head, Clinical Microbiology Laboratories
• King Abdulaziz University Hospital

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MYCOPLASMASCharacteristics

• Lacking cell wall
• Resistant to antibacterials that inhibit cell
  wall synthesis
• Grams stain Not useful
• Pleomorphic
• Cannot be classified as either cocci or bacilli
• Enclosed in a plasma membrane
• Lipid bilayer membrane containing sterols
• Smallest free-living organisms
• Pass through bacteriologic filters
• Can be cultured in vitro.

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MYCOPLASMAS

• Mycoplasma pneumoniae ? Atypical Pneumonia
• Mycoplasma hominis ? STI Non-gonococcal
  Urethritis, Cervicitis, PID
• Ureaplasma urealyticum ? STI Non-gonococcal
  Urethritis, Cervicitis, PID

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Mycoplasma pneumoniae (Eatons reagent)Habitat
and Transmission

• Habitat is the human respiratory tract.
• Transmission Respiratory droplets.

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Mycoplasma pneumoniaePathogenesis

• P1 adhesion protein
• M. pneumoniae binds to respiratory ciliated
  epithelium
• Adherence results in ciliostasis cell
  destruction ? reduced ciliated clearance
• Bacteria then gain access to the lower
  respiratory tract
• Produces hydrogen peroxide may damage the
  respiratory tract.
• No exotoxins produced.
• No endotoxin because there is no cell wall.

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Mycoplasma pneumoniaeDiseases

• Atypical pneumonia
• Clinical Features Fever Dry cough or scantily
  productive cough
• Walking pneumonia
• Complications Mild hemolytic anaemia
• Upper Respiratory Diseases
• Otitis Media
• Pharyngitis
• Tracheobronchitis

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Mycoplasma pneumoniaeLaboratory Diagnosis

• Specimens but scanty sputum
• Gram stain not useful.
• Culture on special bacteriologic media. Takes at
  least 10 days to grow (too long to be clinically
  useful).
• Colonie Fried egg appearance
• Serology
• A cold-agglutinin titer of 1128 or higher is
  indicative of recent infection
• Cold agglutinin IgM autoantibodies against red
  blood cells that agglutinate these cells at 4 C
  but not at 37 C
• Complement fixation test for antibodies to
  Mycoplasma pneumoniae is more specific.
• PCR
• Note Diagnosis relies on clinical findings

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Mycoplasma pneumoniaeTreatment

• Erythromycin or
• Tetracycline.
• Prevention
• No vaccine or drug is available

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Genital Mycoplasmas

• Mycoplasma hominis ? STD Non-gonococcal
  Urethritis, Cervicitis, PID
• Ureaplasma urealyticum ? STD Non-gonococcal
  Urethritis, Cervicitis, PID

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Actinomycetes
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Actinomycetes

• Gram positive bacteria
• Filamentous branching bacilli
• Superficially resemble fungi on morphologic
  grounds
• They are prokaryotes
• Has bacterial size

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Actinomycetes

• Few are pathogenic to human, the most important
  are
• Actinomyces israelii
• Nocardia astroides

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ACTINOMYCETES Actinomyces israelii

• Gram-positive filamentous branching bacilli
• Anaerobic
• Grows slowly

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Actinomyces israelii Habitat and Transmission

• Habitat Found as scanty normal commensal in
  the
• Mouth, especially anaerobic crevices around the
  teeth
• Colon
• Vagina
• Disease begins when these normal flora enter
  adjacent sterile tissue e.g, by trauma, surgery
• Transmission into tissues occurs during
• Dental extraction - Poor dental hygiene
• Trauma (mouth uterus)
• Organism also aspirated into lungs, causing
  thoracic actinomycosis.

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Actinomyces israeliiPathogenesis

• Infections occur in both
• Normal hosts
• Immunocompromised patients
• No toxins or virulence factors known.
• Organism forms sinus tracts that open onto skin
  and contain yellow sulfur granules
• Sulfur granules are made up of large masses of
• organisms microcolonies of filamentous bacteria

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Actinomyces israelii Disease

• Actinomycosis (abscesses with draining sinus
  tracts)
• Chronic suppurative abscess
• The lesion (Mycetoma)
• Begins as a hard red swelling
• Ddevelops slowly, becomes filled with pus
• Draining with sinus formation
• Sites
• Oral-facial abscesses (gt 50 of cases)
• Often associated with trauma or dental extraction
• Abdominal infections
• Abscess. Many after appendicitis
• Uterine infection
• Associated with intrauterine contraceptive
  devices
• Chest infection
• Invasive infections in immunocompromised patients

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Actinomyces israelii Laboratory Diagnosis

• Specimen Pus
• Filaments may aggregate to form visible granules
  Sulphur granules in pus Yellowish particles
• No sulphur
• Microscopy
• Sulfur Granules Gram-positive filamentous,
  branching rods
• Culture
• Anaerobic culture on blood agar plate (10 days)
• Molar teeth colonies
• No serologic tests.

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Actinomyces israeliiTreatment

• Penicillin
• For up to 3-12 months
• Tetracyclin or Clindamycin
• For penicillin-allergic patients
• Surgical drainage
• Prevention
• Good oral hygiene
• Prophylactic antibiotics in association with GIT
  or oral trauma or surgery
• No vaccine is available.

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ACTINOMYCETES

• Nocardia asteroides

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Nocardia asteroidesDisease

• Nocardiosis (especially lung and brain abscesses).

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Nocardia asteroidesCharacteristics

• Gram positive filamentous, branching rods.
• Aerobic
• Acid-fast (weakly)

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Nocardia asteroides Habitat and Transmission

• Habitat is the soil.
• Transmission
• Airborne particles, which are inhaled into the
  lungs
• Implantation by contamination of skin wounds

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Nocardia asteroidesPathogenesis

• Predisposing Factors
• Immunosuppression
• HIV
• Cancer
• No toxins or virulence factors known.

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Nocardia asteroidesDiseases

• Diseases Abscesses in
• Lung
• Brain
• Kidney

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Nocardia asteroidesLaboratory Diagnosis

• Specimen Pus
• Microscopy
• Gram-stained smear Gram positive filamentous,
  branching rods
• Ziehl-Neelsen stain (modified) weakly AFB
  (branching)
• Culture
• Aerobic culture on blood agar plate.
• No serologic tests.

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Nocardia asteroidesTreatment

• Sulfonamides
• Long duration
• Nocardia is resistant to penicillin
• Prevention
• No vaccine is available.

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Differences between Actinomyces israelii
Nocardia astroides
Nocardia astroides Actinomyces israelii
Aerobic Anaerobic Growth Atmosphere
Soil Mouth, Colon, Vagina Habitat
Inhalation or implantation Trauma (Tooth extraction, Jaw fracture, Intrauterine Contr. Dev.) Transmission
No Yes Sulfur granules
Yes (weakly acid-fast( No Acid-Fastness
Nocardiosis (abscess in brain kidneys in immunodeficient patients Pneumonia) Actinomycosis (abscess with draining sinuses) Cervicofacial, Thorasic, Abd, Pelvic Disease
Sulfonamides Penicillin Treatment