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MICROBIO Ex21
Staphylococcus Species Identification
Question | Answer |
---|---|
Staphylococcus genus are Gram positive or negative? | Gram positive coccus |
Where do Staphylococcus live | Mucous membrane, skin of warm-blooded animals. Found in food, dust, water. |
What is osmotolerant? | They can tolerate salt upto 10% (some even beyond) |
What is the most pathogenic species in Staphylococcus genus? and where is it most located? | Staphylococcus aureus. 10% - 40% of the population harbors in their nose |
MSA? | Mannitol Salt Agar. Selective + differential medium. --> identify members of Staphylococcus genus. Medium mau` RED |
Selective Media? | contains ingredients that prevent the growth of some orgs while selecting for the growth of others. |
Differential media? | contains ingredients that will cause a color change or reaction that allows for the differentiation of the selected types of orgs. |
Positive for mannitol salt agar? | Growth, yellowing of medium around growth. ---> Org is not inhibited by the salt. mannitol is fermented to acid--> Staphylococcus species. |
Negative for mannitol salt agar? | Growth, no color change of medium. ---> Org is not inhibited by the salt. Mannitol is not fermented to acid - > Staphylococcus species. |
No growth for mannitol salt agar? | No growth, no color change of medium around growth ----> Org is inhibited by the salt. NOT a Staphylococcus species. |
What is coagulase? | is an enzyme that clots blood plasma. Staphylococcus aureus produces this enzyme. |
Positive for coagulase? | Rabbit plasma is coagulated -> organism secretes coagulase that clots the plasma -> PATHOGENIC STAPHYLOCOCCUS AUREAUS |
Negative for coagulase? | Rabbit plasma is not coagulated -> organism not secretes coagulase. --> NOT S. aureus. |
What is Catalase? | Is an enzyme that degrades hydrogen peroxide H2O2 to water and oxygen gas-> bubbles are emitted. |
What is the importance of Catalase Test? | to differentiate the Staphylococcus Species from Streptococcus. |
HOw to read result for Catalase Test? | Bubbles -> Catalase positive -> Catalase degrades H2O2 to water and oxygen. No bubbles -> Catalase negative -> Org doesn’t secrete catalase which degrade H2O2 to water and bubbles. |
What is the purpose of using MSA? | Mannitol Salt Agar: isolate (selective) org who can tolerate salt and know which one can do mannitol fermentation. In general, isolate and differentiate of pathogenic staphylococcus. |
What is the purpose of using Coagulase? | Differentiate Staphylococcus aureus from their Gram-positive cocci. |
What is the purpose of using Catalase? | used to identify org produce the enzyme catalase (differentiate staphylococcus from streptococcus. |