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Columbia CNA Agar with 5% Sheep Blood
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| I. INTRODUCTION |
| Columbia CNA Agar with 5% Sheep Blood is a selective and differential medium for the isolation and differentiation of gram-positive microorganisms from clinical and nonclinical specimens. |
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PRODUCT INFORMATION
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| II. INTENDED USE |
| Columbia CNA Agar with 5% Sheep Blood is a selective and differential medium used for the isolation and differentiation of gram-positive microorganisms from clinical and nonclinical materials. |
| III. SUMMARY AND EXPLANATION |
| Ellner et al., in 1966, reported the development of a blood agar formulation, which has been designated as Columbia Agar. The Columbia Agar base, which achieves rapid and luxuriant growth and sharply defined hemolytic reactions, is utilized as the bas for media containing blood and for selective formulations in which various combinations of antimicrobial agents are used as additives. |
| Ellner and his colleagues found that a medium consisting of 10 mg of colistin and 15 mg of nalidixic acid per liter in a Columbia agar base enriched with 5% sheep blood would support the growth of staphylococci, hemolytic streptococci and enterococci while inhibiting the growth of Proteus, Klebsiella and Pseudomonas species. |
| IV. PROCEDURE |
| Materials Required But Not Provided Ancillary culture media, reagents and laboratory equipment as required. |
| Instructions The agar surface should be smooth and moist, but without excessive moisture. Streak the specimen as soon as possible after it is received in the laboratory. The streak plate is used primarily to isolate pure cultures from specimens containing mixed flora. Alternatively, if material is being cultured directly from a swab, roll the swab over a small area of the surface at the edge; and streak from this inoculated area. Incubate plates for 24 to 48 h at 35 ± 2°C in an aerobic atmosphere supplemented with carbon dioxide. |
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Visual Results on This Medium Should
Be As Follows
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| After incubation most plates will show an area of confluent growth. Because
the streaking procedure is, in effect, a "dilution" technique,
diminishing numbers of microorganisms are deposited on the streaked areas.
Consequently, one or more of these areas should exhibit isolated colonies
of the organisms contained in the specimen. Better isolation is obtained
due to the inhibitory nature of the media.
Typical colonial morphology on Columbia CNA Agar with 5% Sheep Blood is as follows: |
| Streptococci (non-group D) . . . Small, white to grayish. Beta or alpha
Hemolysis.
Enterococci (Group D) . . . . . Small, but larger than group A streptococci, blue-gray. Beta or alpha hemolysis. Staphylococci . . . . . . . . Large, white to gray or cream to yellow, with or without hemolysis. Micrococci . . . . . . . . . Large, white to gray or yellow to orange, with or without hemolysis. Corynebacteria . . . . . . . . Small to large, white to gray or yellow, with or without hemolysis. Candida . . . . . . . . . . . Small, white Listeria monocytogenes . . . . . Small to large, blue-gray, with beta hemolysis Gram-negative bacteria . . . . . No growth to trace growth |