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