BIOL 3052 Lecture Notes - Lecture 17: Evaporation, Reagent, Surface Tension
28 Jan 2017
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Document Summary
Differentiate streptococcus pneumoniae (positive- soluble) from alpha-hemolytic streptococci (negative- insoluble). Streptococcus pneumoniae is bile soluble whereas all other alpha-hemolytic streptococci are bile resistant. S. pneumoniae has an autolytic enzyme which can be demonstrated by allowing a broth culture to age in the incubator; at 24 hours the broth is turbid; after a few days the medium will become clear. Bile or a solution of a bile salt (e. g. , sodium desoxycholate) rapidly lyses pneumococcal colonies. Bile salts lower the surface tension between the bacterial cell membrane and the medium, thus. Lysis depends on the presence of an intracellular autolytic enzyme, amidase. accelerating the orga(cid:374)is(cid:373)"s (cid:374)atural autolytic process. Bile salts activate the autolytic enzyme which induces clearing of the culture. The rapid identification of microorganisms recovered in blood can provide information about the source of the infectious process and guide the specific therapeutic management of the septic patient. Positive result: suspension clears in tube labelled test and remains turbid in control tube.
