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Actinomyces israelii

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Arod-shaped non-spore formingbacterium recognized as commensal and opportunistic pathogen in humans exists as strict filamentous anaerobes.


Actinomyces israelii is an organism typically present in soil and decaying organic matter as well as in oral cavities, dental plaques and intestinal tract though it is not a disease causing organism but it is a main causative agent of actinomycosis a long term infection that usually affect neck and face.

Actinomyces israelii is covered by thick wall and surrounded by an outer coat of hair-like fimbriae covering the surface. In growth medium it requires nicotinic acid, riboflavin, biotin and pyridoxal as growth factor which synthesize coenzyme-A for metabolic function where L-cysteine amino acid is essential for its nutrition. It is sensitive to ampicillin, penicillin, chloramphenicol and tetracyclines.

Actinomyces israelii is a normal colonizer in vagina, mouth and colon wherein infection is established by breaching the mucosal barrier during particular procedures which is typified by slow, contiguous growth that ignores tissue planes into tract formation which spontaneously heal and recur leading to a densely fibrotic lesion. It is implicated in abscess and empyema a rare infection which manifest tissue fibrosis, abscess formation and sulfur granules in lesions.

Scientific classification:

Domain: Bacteria
Phylum: Actinobacteria
Order: Actinomycetales
Family: Actinomycetaceae
Genus: Actinomyces
Species: Actinomyces israelii

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