Task 4. The differentiating properties of corynebacteria

TYPE OF DIFFERENTIATION OF DIPHTHERIA BACILLI

Properties	GRAVIS	INTERMEDIUS	MITIS
Morphology	Usually short rods, with uniform staining, few or no granules. Some degree of pleomorphism, with irregularly barred, snow-shoe and tear-drop forms	Long barred fixms witli clubbed ends; poor granulation, very pleomorphic	Long, curved, pleomorphic rods with prominent granules
Colony on tellurite blood agar	In 18 hours, colony is 1 -2 mm in size, with greyish black center, paler, semiranslucent peniphery and commencing crenation of edge. In 2-3 days, 3-5 mm in size, flat colony with raised dark center and crenated edge with radial striation -"daisy head" colony	18 hour colony small, 1 mm in size, misty. Does not enlarge in 48 hours, dull granular center with smoother, more glistening periphery and a lighter ring near the edge—"frog‘s egg” colony	Size variable, black. In 2-3 days, colonies become flat, with a central elevation "poached egg” colony
Consistency of colonies	Like "cold margarine", britle, moves as a whole on the plate, not easily picked out or emulsifiable	Intemiediate between gravis and mitis	Soft buttery, easily emulsifiable
Hemolysis	Variable	Nonhemolytic	Usually hemolytic
Grow th in broth	Surface pellicle, granular deposit, little or no lurbidity	Turbidity in 24 hours, clearing in 48 hours, with fine granular sediment	Diffuse turbidity with soft pellicle later
Glycogen aid starch fermentation	Positive	Negative	Negative

Task 5. Test at cistinase (Pizy test)

In the column of gelose with cistin by a prick sow the studied culture and put a test tube in a thermostat. In 1 day a medium is blaking on motion a prick, on the depth of 1 cm view a brown «cloud» appears from a surface. Difteroidy does not form a «cloud».

Task 6. Test at urease (Zaksa test)

Determination of urease is made sowing on media with urea. As an indicator in a nutrient media, bring in phenolic red. A nutrient medium with culture Corynebacterium spp. put on 30 minutes in a thermostat (37°C). For this time an urea fissions with formation of ammonia and an medium becomes red (a test is positive, because рН changes).

Task 7. The indirect hemagglutination test determine the antitoxin antibodies concentration in blood serum. It is made according to the formula: X=10*A/B, where X is content of diphtheria antitoxin in assayed serum (IU), 10- titer of control serum (IU/ml), A - maximal dilution of assayed serum with positive result, B - maximal dilution of control serum with positive result.

Task 8.

B. pertussis is small, coccoid, nonmotile, Gram-negative rods.

Date: 2016-01-14; view: 1926

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