A patient presents with signs of pneumonia. The bacterium obtained from sputum was a gram-positive cocci which showed alpha hemolysis on sheep agar. Which of the following test will help to confirm the diagnosis?
Correct Answer: Bile solubility
Description: S. pneumoniae, however, differs from streptococci in its morphology (by having a specific polysaccharide capsule), bile solubility, and optochin sensitivity.
S. pneumoniae produces an autolytic enzyme amidase, which solubilizes the peptidoglycan of the cell wall; hence in old cultures, typical draughtsman colonies are formed. This autolytic activity can be augmented by surface active agents, such as bile and bile salts.
Bile solubility is a constant feature of pneumococci, and is positive in all the capsulated and some noncapsulated variants.
Pneumococci are catalase and oxidase negative.
Parija SC. Textbook of Microbiology & Immunology. Elsevier Health Sciences; 2014. Page:194-95
Category:
Microbiology
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