Streptococcus and Enterococcus Flashcards
Characteristics of organisms:
1) Morphology
2) Gram stain
3) Identifying traits
4) Motility
1) Heterogenous, spherical or ovoid in shape
2) Positive
3) Coagulase negative, hemolytic patterns, and Lancefield groupings
4) Non-motile
Know groups:
1) What bacteria component is used to differentiate them?
2) What is the hemolytic reaction for each group?
3) What are the representative organisms for each group?
4) What diseases does each group cause? Where does each group normally colonize? Does each group cause a common disease, if so which one?
1, 2, 3 and 4) Group A Streptococcus (GAS): S. pyogenes; bacitracin susceptible; beta-hemolytic reaction; many important human diseases ranging from mild skin infections to life-threatening systemic diseases; numerous bodily tissues
1, 2, 3 and 4) Group B Streptococcus (GBS): S. agalactiae; beta-hemolytic or nonhemolytic; sepsis, infant meningitis, pneumonia; gastrointestinal normal flora
1, 2, 3 and 4) Group D Streptococcus: Enterococcus faecalis, Streptococcus bovis; gamma-hemolytic reaction; wound infections, UTIs, bacteremia; commensal bacterium inhabiting GI tract
1, 2, 3, and 4) No Group Streptococcus: S. pneumoniae and S. mutans abiotrophia; alpha-hemolytic reaction; S. pneumoniae causes lobar pneumonia and respiratory tract infections, S. mutans abiotrophia causes dental caries
What type of media is chocolate agar? Why do we use it to identify streptococcus and which streptococcus?
Chocolate agar is an enrichment media. We use it because fastidious bacteria like S. pneumoniae like it because using heat inactivates many enzymes that could degrade these growth factors
Why and what did we use the Optochin Test for? What does it differentiate?
We used it to determine the sensitivity of the bacteria to Optochin. It differentiates no group streptococcus (S. pneumoniae is highly sensitive)
Why and what did we use the Bacitracin Test for? What does it differentiate?
We used it to determine the sensitivity of the bacteria to Bacitracin. It differentiates GAS (S. pyogenes) because it is highly sensitive bacitracin
What does NaCl Broth test for? What component of the media is important/allows us to test for this?
NaCl broth tests for organisms’ ability to grow in a high salinity environment. The salt in the media allows to test for this
IMPORTANT: THIS MEDIA SELECTS FOR E. FAECALIS ONLY
What does Bile Esculin Test test for? What component in the media allows it to do this? How does this media work (what biochemical process/reaction occurs within the media)?
Bile Esculin Test is used for the detection of esculin hydrolysis to esculetin (black/brown color). The bile in the media allows to do this. It works because esculetin reacts with Fe3+ and forms a dark brown to black precipitate
What does Sodium Hippurate test test for? How does this media work (what biochemical process/reaction occurs within the media)?
Sodium Hippurate tests an organisms’ ability to hydrolyze sodium hippurate to benzoic acid. It works because when bezoic acid is added, feric chloride will precipitate out due to the presence of the enzyme hippuricase which hydrolyzes sodium hippurate to benzoic acid and glycine
What does the Bile Solubility Test test for? What does it differentiate? How does this media work (what biochemical process/reaction occurs within the media)?
The Bile Solubility Test tests for the activity of bile which activates an enzyme that leads to a rapid autolysis of S. pneumoniae. It differentiates S. pneumoniae. It works because bile salts lower the surface tension between the bacterial cell membrane and the medium, thus accelerating the organism’s natural autolytic process (lysis depends on the presence of an intracellular autolytic enzyme, amidase)
