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Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is called a hemolysin.
Chocolate agar is a type of blood agar plate in which the blood cells have been lysed by heating the cells to 80 °C. It is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae. Chocolate agar is named for its color, and no chocolate is contained in the plate.
Chocolate agar (CHOC) or chocolate blood agar (CBA) is a nonselective, enriched growth medium used for isolation of pathogenic bacteria. [ 1 ] [ 2 ] [ 3 ] It is a variant of the blood agar plate , containing red blood cells that have been lysed by slowly heating to 80°C.
DNA hydrolysis is tested by growing an organism on a DNase Test Agar plate (providing nutrients and DNA) and then checking the plate for hydrolysis. The agar plate has DNA-methyl green complex, and if the organism on the agar does hydrolyze DNA then the green color fades and the colony is surrounded by a colorless zone. [25]
Streptococcus pneumoniae: small colonies with raised edges displaying alpha-hemolysis on blood agar [8]: 223 Proteus sp. : swarming behaviour on blood agar [ 1 ] : 167 Serratia marcescens : red pigmentation: although considered characteristic of the species, only about 10% of specimens produce this pigment [ 8 ] : 236
The increase in pH then causes color change in the bromothymol blue indicator, turning it blue. Under neutral conditions the medium remains a green color. The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change.
If the area of inoculation turns dark-blue to maroon to almost black, then the result is positive. If a color change does not occur within three minutes, the result is negative. In alternative manner, live bacteria cultivated on trypticase soy agar plates may be prepared using sterile technique with a single-line streak inoculation. The ...
However, once the agar has solidified, the pH does not appear to change with temperature but remains at 6.9. For preparation of BCYE + antibiotics, add membrane-filtered antibiotics and mix. For BCYE + albumin agar, dissolve the albumin in distilled water and filter sterilize before addition to the medium. Dispense 20 mL per 15 X 100-mm Petri dish.