actinomyces. lecture slides
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Actinomycetes
Prof M.I.N. MateeDepartment of Microbiology and
ImmunologySchool of Medicine
MUCHS
Tuesday, November 8, 2005
General propertiesGram positive branching filamentsSlow growers
Resemble Corynebacteria, mycobacteria and fungiInclude:
Actinomyces – anaerobe, normal floraNorcadia – aerobe, saprophyte – PARTIALLY ACID FASTStreptomyces- aerobe, saprophyte
Actinomyces
• Strict anaerobe
• Gram positive
• Non-motile
• Non-proteolytic
• Catalase negative
Motility
From left to right:+ – +
Actinomyces
C diptheriae: Gram stain
CytoplasmCytoplasm
Lipoteichoic acid Peptidoglycan-teichoic acid
Cytoplasmic membrane
GRAM POSITIVE CELL GRAM POSITIVE CELL ENVELOPEENVELOPE
Degradative enzyme
ACTINOMYCESAnaerobic, filamentous, gram positive
bacillus – Exhibit true branching
• “Mykes” – Greek for “fungus”
• Thought by early microbiologist to be fungi because of:– Morphology– Disease they cause
Actinomycosis
• Chronic suppurative disease
• Spread by direct extension - sinuses
• A israelii
• A bovis – lumpy jaw in cattles
ACTINOMYCOSISForm indurated masses with fibrous walls
and central loculations with pus– Pus contains "Sulfur Granules"
• Gritty, yellow white• Average diameter - 2mm• Composed of “mycelial” mass
Chronic infection
– Form burrowing sinus tracts to skin or mucus membranes
• Discharge purulent material
Actinomycosis - sulfur granule
III. Epidemiology
-part of normal mouth and gut flora
-cervicofacial infection from tooth extraction or poor oral hygiene
-thoracic infection from aspiration
-abdominal infection from perforated gut or ruptured appendix
-foot infection from bacteria in soil
-infection mainly in immunocompromised patients
-not a communicable disease
Pulmonary Actinomycosis
• 15% of cases• Aspiration of organism
from the oropaharynx• Slowly progressive
process involving lung and pleura– May be mistaken for
malignancy
• Chest pain, fever, wgt loss and hemoptysis
Laboratory diagnosis
• Specimens – pus, sputum, tissue biopsy
• Microscopic examination – sulphur granules
• Culture – thioglycolate medium and BHI
• Incubation: anaerobic for 2 weeks
• Gas liquid chromtography (GLC) of metabolic by-products
Anaerobic jar
Figure 6.5
IV. Control
-surgical drainage of abscess,
-parenteral penicillin for a few weeks, followed by oral for 6-12 months (very long term treatment)-cephalosporins, erythromycin, clindamycin if pt allergic to pen
-prophylactic penicillin if pt has recurring infection, esp. before oral surgery
Nocardia asteroides
I. Organism
-also actinomycete morphology
-produces shorter mycolic acids, hence partially acid fast
-aerobe, with both aerial and subsurface mycelia
Norcadiosis
Nocardiosis – is a localized or disseminated disease occurring after inhalation of organisms.
Pulmonary infections resemble tuberculosis
may disseminate, with a predilection for the brain and meninges.
It is usually a disease of compromised hosts
II. Clinical(nocardiosis)
-usually presents as lobar pneumonia in alcoholics or immunocompromised patients
-abscess formation in lung lobe
(nocardiosis)-usually presents as lobar pneumonia in alcoholics or
immunocompromised patients
-abscess formation in lung lobe
-may spread to brain and CNS and cause meningitis or brain abscess
II. Clinical(nocardiosis)
-usually presents as lobar pneumonia in alcoholics or immunocompromised patients
-abscess formation in lung lobe
-may spread to brain and CNS and cause meningitis or brain abscess
-can also on the foot from soil-based infections
III. Epidemiology-soil bacterium
-opportunistic pathogen
-lung infection from aspiration, dissemination to CNS, kidneys
Laboratory diagnosis
• Specimens – sputum, pus, spinal fluid, biopsy
• Microscopy – coccoid, bacillary, tangled mass
• Culture – on most ordinary media
• Tissue section – methenamine-silver stain
IV. Treatment
Mycetoma – aminoglycosidesNocardiosis – sulfonamides or sxt
–Surgical debridement
–Underlying cause
• Actinomycetes such as Streptomyces have a world-wide distribution in soils.
• They are important in aerobic decomposition of organic compounds and have an important role in biodegradation and the carbon cycle.
• Actinomycetes are the main producers of antibiotics in industrial settings, being the source of most tetracyclines, macrolides (e.g. erythromycin), and aminoglycosides (e.g. streptomycin, gentamicin, etc.).
•Thank you for listening