1b.Actinomycetes

8/11/2019 1b.Actinomycetes

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Actinomycetes


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Actinomycetes

Classification

OrderActinomycetales

Show fungus-like characteristics such as branching in tissues or in

culture (look like mycelia). The filaments frequently segment during

growth to produce pleomorphic, diphtheroidal, or club shaped cells.

The cell wall and the internal structures are typical of bacteria rather

than fungi.

Some are aerobic and others are anaerobic.

All are slow growing


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Actinomycetes

The anaerobic genera:Actinomyces, Arachnia, and Bifidobacterium

Morphology and cultural characteristics

G+ branching, or diphtheroid-like bacilli

Anaerobic and require CO2for growth

Non-sporing Will grow on anaerobic BA or PEA. A israelii, the most commonly

isolated species, produces rough, granular colonies that resemble molars.

Biochemistry

ID by gas liquid chromatography (GLC) of metabolic by-products or

fluorescent antibody studies


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Actinomycetes

Clinical significance

Are part of the NF found in the cavities of humans and other

animals.

All may cause actinomycosis or lumpy jaw. A cervicofacial

infection that used to occur following tooth extractions or dentalsurgery which provided traumatized tissue for growth of the

microorganism which may also invade the bone. This is rare

today because of prophylactic antibiotic therapy.

May cause thoracic or abdominal infections

May cause meningitis, endocarditis, or genital infections


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Actinomycetes

Every kind of infection is characterized by draining sinuses,

usually containing characteristic granules which are colonies of

bacteria that look like dense rosettes of club-shaped filaments in

radial arrangement

Treatment Penicillin


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Granules


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Actinomycetes

The aerobic genera:Nocardia, Actinomadura, and Streptomyces.There are three clinically important species ofNocardiaN.asteroides, N. brasilensis, and N. caviae Morphology and cultural characteristics

G+ branching bacillus that may fragment to bacillary or coccoid forms Aerobic

Specimens should be inoculated onto 7H10 agar or Lowenstein-Jensenagar and brain heart infusion agar. Colonies produced are typicallyorange, dry, crumbly, and adherent.

The organisms are weakly acid fast or non acid fast


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Nocardia acid fast stain


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Actinomycetes

Biochemistry

The organisms are identified based on sugar fermentations and

hydrolysis reactions (caseine, tyrosine, etc.)

Clinical significance

Mycetomaorganism enters the body through breaks in the skin

and causes a localized infection involving skin, cutaneous, and

subcutaneous tissue. The three most characteristic features seen

are swelling, draining sinuses and granules. This disease can also

be caused by fungi as well asNocardia, Actinomadura, and

Streptomyces.


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Actinomycetes

Nocardiosisis a localized or disseminated disease occurring

after inhalation of organisms. Pulmonary infections resemble

tuberculosis and can remain confined to the lungs or may

disseminate, with a predilection for the brain and meninges. The

disease is characterized by multiple confluent abscesses and

intense suppuration. It is usually a disease of compromised

hosts.

Antimicrobic susceptibility/treatment

Mycetomaaminoglycosides

Nocardiosissulfonamides or sxt

1b.Actinomycetes

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