Actinomyces

Lab Twelve:- ________________ Medical Microbiology
Prepared by: Luma J. Witwit


Actinomyces

Actinomyces spp. are members of a large group of pleomorphic gram-positive bacteria, many of which have some tendency toward mycelial growth, Both are members of the oral flora of humans or animals. Actinomyces species are major components of dental plaque. A. israellii, (previously A. israelli serotype II), other species of Actinomyces can be involved in mixed anaerobic and other infections.

Actinomycosis

Actinomycosis is a chronic disease characterized by the production of suppurative abscesses that eventually develop draining sinuses.

These lesions discharge or pus containing the organisms. These are found in yellowish granules called sulfur granules. The etiologic agents are several closely related members of normal flora of mouth and gastrointestinal tract. Most cases are due to Actinomyces israelii, A. naeslundii, and other related anaerobic or facultative bacteria. Based on the form of involvement, the three common forms are cervicofacial, thoracic, and abdominal actinomycosis.

Diagnosis

1- Direct Gram stain of pus or suppurative exudates shows Gram positive, non-acid-fast rods in diphtheroidal arrangement with or with out branching.

2- Granules are crushed Gram stain
Cultured in rich media
3- Media blood agar
brain heart infusion

incubated an aerobically and aerobically with added carbon dioxide, plates are examined after 24 hours and after 5 to 7 days for the characteristic colonies of A. israellii, A.gerencseriae.

Colonies of other Actinomyces spp. Can take a variety of forms including smooth domed or flat colonies of various sizes.

Characteristic colonies of A.israellii micro colony at 24 hr on :
Brain heart infusion agar shows branching filaments with no distinct center, spider colony.

Mature colony at 14 days on brain heart infusion agar, heaped colony with central depression.