Question
The phenomenon marked by a “white arrow” in the picture below is seen in culture of which of the following organism?
A. Haemophilus.
B. Streptococcus.
C. Klebsiella.
D. Proteus.
Show Answer
|
Correct Answer » A
Explanation
|
|
The phenomenon marked by a white arrow in the picture above represents satellitism,
Satellitism refers to the phenomenon in which certain bacterial species like Haemophilus influenzae grows more vigorously in the immediate vicinity of the colonies of other unrelated species like Staphylococcus aureus which synthesize factor V.
It demonstrates the dependence of H influenzae on the V factor, which is available in high concentrations near the staphylococcal growth and only in smaller quantities away from it.
H influenzae can be isolated on chocolate agar enriched with factor X and V.
The blood used in chocolate agar is heated to inactivate nonspecific inhibitors of H. influenzae growth.
Definitive identification is made by Quellung reaction.
Additional means of identifying encapsulated strains include fluorescent-antibody staining of the organism and counter immunoelectrophoresis or latex agglutination tests, which detect the capsular polysaccharide
