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18 Cards in this Set
- Front
- Back
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Describe the common characteristics of the genus Corynebacterium |
Gram positive rods that tend to be pleomorphic Non-spore forming "snapping" when cells divide aerobic or facultative catalase positive motility negative |
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describe the cellular morphology of Corynebacterium diphtheriae |
Gram positive rods, tend to over decolourize "chinese letters" from cell snapping Volutin granules are usually present (deeply stained granules) |
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list two other stains used to visualize Corynebacterium diphtheriae' volutin granules |
Loeffler's alkaline methylene blue (volutin granules stain deep purplish blue, rest of cell stains blue) Albert's stain (volutin granules stain deep blue-black, rest of the cell stains pale green) |
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Describe the Growth Requirements for Corynebacterium diphtheriae |
facultative anaerobes, but scant growth without O2 needs greater than 24hrs incubation Increased CO2 not required Optimum growth at 35C will grow on nutrient media but enrichment with blood or serum enhances growth |
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Describe Potassium Tellurite Agar as a selective medium for Corynebacterium diphtheriae |
potassium tellurite added to blood, serum or choc agar bacterial growth appears gun metal gray to black Corynebacterium species will grow, occasionally staphylococci, yeast will also grow inhibits the growth of most other bacteria
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Describe Cystine-Tellurite Agar as a selective medium for Corynebacterium diphtheriae |
Sheep BAP with L-cystine and potassium tellurite added. inhibitory to most organisms other than Corynebacterium. colonial morphology may be used to establish the biotype of C. diphtheriae |
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Describe Modified Tinsdale Medium as a selective and differential medium for C. diphtheriae |
agar enriched with L-cystine and bovine serum other ingredients include potassium tellurite and sodium thiosulfate all colonies will be shade of black, but C. diphtheriae produces a brown halo around colonies halo formation enhanced by stabbing inoculum into the agar. unstable medium, needs constant quality control |
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describe the colonial morphology of C. diphtheriae |
BAP: 1-4mm White, gray dull, raised and opaque, may look granular usually gamma hemolytic, may be beta
colonies on Tinsdale media are gray to black with brown halos. colonies growing on tellurite have strong garlic odor. |
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describe genus tests for Corynebacterium |
Gram positive rods opaque, dull colonies on BAP, growth on tellurite media presence of volutin granules Catalase positive non motile |
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what tests differentiate C. diphtheriae from other Corynebacterium species? |
C. diphtheriae is Urease negative, and produces acid from glucose, maltose, and sometimes sucrose. It does not produce acid from mannitol or xylose |
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what causes some strains of Corynebacterium diphtheriae to produce toxins? |
infection with a bacteriophage |
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Describe diphtheria |
infection of the pharynx, or less commonly cutaneous infections bacteria multiply quickly and produce toxin inflammation and exudate may cause pseudomembrane of diphtheria, a grayish membrane composed of fibrin, epithelial cells, blood cells, and bacteria swollen lymph nodes gives bull neck appearance toxin causes myocardial degeneration, cranial and peripheral nervous dysfunction. |
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describe the antimicrobial susceptibility of Corynebacterium diphtheriae |
no resistance to penicillin or erythromycin. Antibiotics have no effect on toxins produced. |
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describe the cellular morphology of diphtheroids |
short, club shaped Gram positive rods cells slide together to form pallisades and V shapes volutin granules may be present |
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Describe the cultural characteristics of diphtheroids |
BAP: dull opaque, raised, gray or white, usually non-hemolytic, dry Tellurite medium: gray to black halos not usually formed on tinsdale
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describe the clinical significance of Diphtheroids |
normal flora of upper respiratory tract, skin, genital mucosa, and feces endocarditis most common infection |
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Describe Corynebacterium jeikeium |
normal skin flora, more common on the skin of hospitalized patients Gram positive coccoid rods that may look like streptococcus but in classic diphtheroid arrangements slow growing gray-white glistening colonies resistant to most antimicrobials other than vancomycin |
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Describe Rhodococcus equi |
gram positive cells that are coccoid in young cultures but filamentous and branching as cells age colonies on BAP and CHOC are tiny at 24 hours but large, mucoid and pink on 48h cultures non-motile, catalase positive, fails to ferment carbs well known animal pathogen, may infect immunosuppressed patients with respiratory infections similar to tuberculosis |
