Micro Lab Flashcards
- Be able to transfer bacteria from one medium to another using proper aseptic techniques - Be able to isolate colonies of bacteria from mixed specimens by the streak plate technique - Be able to perform and interpret Gram stains - Recognize complexity of normal flora - describe the use of selective and differential media - describe bacterial antimicrobial susceptibility testing
Throat and Mouth normally contain what?
Viridans Streptococci
Neisseria
Staphylococcus Epidermidis
Normally, skin contains what bacteria?
staph. epidermidis
What is the common cause of central line infection?
staph Epidermidis
What is the common cause of Healthcare-associated infection (HAI)?
Staph aureus
Partial lysis of RBC characterized by green zone around colonies is
alpha hemolytic
complete lysis of RBC characterized by clear zone around colonies is
beta hemolytic
BAP is unchanged around colonies
non-hemolytic
How is eosin methylene blue (EMB) agar selective and differential?
Selective for Gram - bacteria–> contains dye that inhibits the growth of Gram + bacteria
Differential: contain lactose, + lactose = dark black/purple
How is mannitol salt agar plate selective and differential?
Selective: Staphylococci because high salt content inhibits growth of most organisms
Differential: pH indicator red–> yellow below pH 6.8
S. Aureus undergo fermentation of manitol causing it to produce acid and change color.
S. Epidermidis does not change color
How is Sodium Chloride selective?
Selective because high salt inhibits growth of most organisms except enterococci (once class D strep) and 80% of Strep B.
How is coagulase test useful?
Clinical useful in differentiating Staph. Aureus from other Staph (like S. Epidermidis)
+ test = S. Aureus
When do you use Optochind Disc (Taxo P)
To differentiate Viridans Streptococcus from Streptococcus Pneumoniae.
S. Pneumoniae is sensitive to Taxo P (zone of no growth)
Viridans Strep. is resistant
How is Bacitracin disc (taxo A) useful?
Differentiates Group A beta-hemolytic strep from other B-hemo strep.
S. Pyogenes is sensitive
Other Strept are rarely sensitive
What is the purpose of catalase test?
To test if the bacteria have the enzyme catalase to convert H2O2 to water.
