Actinomycetes

Actinomycetes

1. Actinomycetes

2. General properties Gram positive branching filaments Slow growers Gram + ,filamentous bacteria. Resemble Corynebacteria , mycobacteria and fungi Include: Actinomyces – anaerobe, normal flora, grows in narrow range of temp Nocardia – aerobe, saprophyte – PARTIALLY ACID FAST, grows in wide range of temp Streptomyces - aerobe, saprophyte

3. Actinomycetes Classification Order – Actinomycetales Show fungus-like characteristics such as branching in tissues or in culture (look like mycelia). 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

4. ACTINOMYCETES ECOLOGY Predominantly soil bacteria Good at degrading recalcitrant compounds such as chitin & cellulose Often active at higher pH (contrast to fungi who may dominate at lower pH) Give soil the “earthy” smell

5. Genus - Actinomyces Strict anaerobe Gram positive Non-motile Non-proteolytic

6. ACTINOMYCES Anaerobic, filamentous, gram positive bacillus Exhibit true branching “Mykes” – Greek for “fungus” Thought by early microbiologist to be fungi because of: Morphology Disease they cause

7. ACTINOMYCOSIS Not highly virulent (Opportunist) Component of Oral Flora Periodontal pockets Dental plaque Tonsilar crypts Take advantage of injury to penetrate mucosal barriers suppurative A chronic and granulomatous disease of the cervico -facial, thoracic or abdominal areas Three-quarters of human cases are caused by Actinomyces israelii .

8. ACTINOMYCOSIS Form indurated masses with fibrous walls and central loculations with pus Pus contains "Sulfur Granules" Gritty, yellow white Average diameter - 2mm Composed of mineralized “ mycelial ” mass   Chronic infection Form burrowing sinus tracts to skin or mucus membranes Discharge purulent material

9. Morphology of Nocardia The Nocardia are branched, strictly aerobic, Gram-positive bacteria that are closely related to the rapidly growing mycobacteria. They are environmental saprophytes with a broad temperature range of growth. 9

10. Nocardiosis Nocardiosis primarily presents as a pulmonary disease or brain abscess in the U.S. Subcutaneous infections, pulmonary infections, and brain abscesses N. asteroides ; N. brasiliensis 10

11. Over 500 distinct antibiotic substances have been shown to be produced by streptomycete . produce many important antibiotics, including Streptomycin - originally from S. griseus . Antibiotics Actinomycetes

12. The genus Streptomyces includes- aerobic, Gram-positive, filamentous bacteria that produce well-developed vegetative hyphae with branches. They form a complex substrate mycelium that aids in scavenging organic compounds from their substrates.

13. Other antibiotics produced by Streptomyces spp : Antibiotic: affects: Spectinomycin M. tuberculosis, N. gonorrhea Neomycin Broad spectrum, topical Tetracyclines Broad spectrum, Chlamydias , Rickettsias etc. Nystatin Fungi, esp. Candida Erythromycin Gram + Bacteria and Legionella Chloramphenicol Broad spectrum, typhoid fever ACTINOMYCETES ANTIBIOTICS Over 500 distinct antibiotic substances have been shown to be produced by streptomycete . produce many important antibiotics, including Streptomycin - originally from S. griseus .

14. Ecology and isolation of Streptomyces: Alkaline and neutral soils are more favorable Streptomyces require a lower water potential for growth than many other soil bacteria. Media often selective for Streptomyces contain the usual assortment of inorganic salts

15. Aerobic Actinomycetes : Natural Habitats Nocardia species and other aerobic Actinomycetes ubiquitous in soil and primarily responsible for decomposition of organic plant matter Rhodococcus species present in the intestinal bacterial flora of grazing herbivores especially horses Streptomyces species (>3,000) widely distributed in soil

16. Aerobic Actinomycetes : Modes of Infection Nocardia infection acquired by inhalation of or direct skin inoculation (traumatic) by environmental organisms Rhodococcus infection due primarily to inhalation of organisms by animal handlers (horses, pigs, cattle) Streptomyces are soil organisms that can infect traumatic wounds especially of the feet

17. Anaerobic Actinomyces : Natural Habitats Anaerobic Actinomyces species are normal inhabitants of the mucous membranes of humans and animals Anaerobic Actinomyces : Modes of Infection Actinomyces invades normally sterile tissue from endogenous mucous membrane sites of normal colonization