Mycobacterial Organisms

Bacteriology ACTINOMYCETES (NON-MYCOBACTERIAL ORGANISMS) BERGEY'S CLASSIFICATION-order Actinomycetales 1. All organisms tend to form filaments to varying degree, gram-positive rods 2. Includes Mycobacteria, Nocardia, Actinomyces, Actinomadura, and Streptomyces 3. Classified according to cell wall differences, by presence or absence of certain amino acids and sugars STREPTOMYCETES 1. Aerobic, filamentous, may produce spores a. Substrate filaments long, branching b. Aerial filaments may be extensively branched 2. Decompose organic material in soil 3. Responsible for production of approximately 85% of known antibiotics ACTINOMYCOSIS 1. Three etiologic agents of medical importance in humans, causing actinomycosis a. Actinomyces israelii-most common isolate b. Arachnia propionica c. Actinomyces naeslundii 2. Three genera-Actinomyces, Arachnia, and Bifidobacterium, morphologically and physiologically similar a. No aerial filaments b. No spores c. Non acid-fast d. Bifidobacterium-strict anaerobes; Arachnia and Actinomyces facultative anaerobes. 3. Etiologic agents part of normal flora of mouth and gastrointestinal tract Clinical infection a. Cervicofacial actinomycosis i. Lower jaw involvement following dental caries ii. Pyogenic abscesses may develop iii. Interconnecting sinus tracts with "sulfur granule" formation in late infections or gram positive filaments in early infections iv. Osteomyelitis frequent b. Thoracic actinomycosis i. By extension from cervicofacial or aspiration ii. Sinus tracts form iii. Subacute to chronic pulmonary infection iv. May invade ribs, vertebrae c. Abdominal actinomycosis i. Traumatic perforation of intestinal mucosa (a) Ruptured appendix (b) Perforated ulcer ii. May extend to liver, bladder, vertebrae, abdominal wall d. Genital actinomycosis i. In women with intrauterine devices ii. May either colonize or produce infection Diagnosis a. Examine secretions or tissue for granules b. Crushed "sulfur granules" contain gram-positive, non acid-fast diphtheroids c. Catalase negative

d. Cultures anaerobically on thioglycolate broth Treatment a. Penicillin for several weeks b. May require surgical drainage NOCARDIOSIS Morphology and physiology a. Aerobic, gram-positive, partially acid-fast b. Non-sporeforming c. Highly developed filamentation d. Cell walls contain mycolic acid e. Cell walls enhance macrophage antitumor and antimicrobial activity f. Decomposes and utilizes paraffin as source for carbon and energy g. Produces catalase, urease h. Three species, found in soil and aquatic environments i. N. ASTEROIDES-most common isolate ii. N. BRASILIENSIS Clinical infection a. Half of patients have underlying disease b. 75% cases occur in males c. Begins as chronic lobar pneumonia following inhalation i. 80-90% cases caused by N. asteroides ii. May mimic tuberculosis iii. Granuloma formation, caseation are rare d. Central nervous system most common site of metastatic infection e. Kidneys, skin may also become involved f. Abscess formation most common pathologic finding g. Treatment usually with sulfonamides ACTINOMYCETOMA 1. 2. 3. 4. 5. 6.

Chronic suppurative and granulomatous infection of subcutaneous tissue, called "Madura foot" May be caused by Actinomadura, Nocardia, Streptomyces, Actinomyces israelii, and fungi Infection more common in tropical and subtropical regions caused by ubiquitous soil saprophytes Infection results from traumatized subcutaneous surface contaminated with organisms Exposed areas of extremities are most commonly involved Therapy includes long-term antibiotics