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Oxidative catabolism requires what to grow bacteria
Fermentative catabolism uses what to grow bacteria?
starch hydrolysis (either peptone or glucose)
Fermentation of bacteria using peptone does what to the medium?
- Turns OF-glucose medium green to blue
- pH goes up (alkaline)
Fermentation of bacteria using glucose
- Turns OF-glucose medium green to yellow
- pH goes down (acidic)
How can organisms that don’t use starch grow on a starch agar plate?
They use peptones
MRVP broth (RED) is used to determine the energy source ??? in fermentation
- organisms that produce large amounts of acid from glucose
- Remains red = positive and pH below 4.4 (acidic)
- Turns yellow = neutral and pH above 6.0 (alkaline)
Citrate agar (GREEN) is used to determine the energy source ??? in fermentation
- Citrate use
- Bacteria with the enzyme citrate lyase can break down citrate to form pyruvate
- Turns blue = positive for the use of citrate acid
During prolonged periods (greater than 24-hours) what may happen to the bacteria in a fermentation tube?
- Exhausts the carbohydrate supplied
- Grows oxidatively on the peptone
- Turns red because of ammonia production
chemical agents used on inanimate objects to lower the level of microbes on their surfaces?
chemicals used on living tissue to decrease the number of microbes
Refers to agents used to kill bacteria
Agent causing temporary inhibition of growth
Variables to consider in selecting an antimicrobial agent
- organic material present
- length of contact
Explain Disk-Diffusion method
- Petri plate with agar
- Inoculate uniformly over entire surface
- Impregnate with paper disks (ABX, mouthwash, etc.)
What is the Minimum Inhibitory Concentration (MIC)?
the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism
Name bacteria that reside on the skin
- staphylococcus aureus
- staphylococcus epidermidis
Why is S. Aureus different than the other microbiota of the skin?
produces coagulase (enzyme that clots is pathogenic)
What allows bacteria of the skin to survive?
- resist drying
- salt tolerant
What bacteria primarily exist at the back of the throat?
Beta-hemolytic group A streptococci (GAS) is which type of strep?
The importance of S. Pyogenes?
- Most pathogenic bacterium in the whole genus (strep throat to toxic shock to necrotizing fasciitis)
- Causes most Strep infections
Greenish color around colonies on blood agar, partial destruction of RBC's is what type?
- S. pneumoniae
- S. veridians
complete hemolysis of RBC's on blood agar, a clear zone around the colony is what type?
no hemolysis and no change in the blood agar around the colony is what type?
S. pneumoniae vs. S. pyogenes
S. pneumoniae will turn green on blood agar where S. pyogenes will have a clear zone around colony
- S. pneumoniae
- Optochin sensitivity
- Bile solubility – activates an enzyme that lyses the cell wall
- S. pyogenes
- Sensitive to bacitracin – no others are
What is the purpose of the Enterotube?
- Rapid identification
- Large number of results from one inoculation
a protein enzyme that enables the conversion of fibrinogen to fibrin
What does it mean when coagulase causes clumping?
positive result - used to distinguish between different types of staph
a common enzyme found in nearly all living organisms exposed to oxygen
What is the result if Catalase causes bubbles?
- positive result
- It catalyzes the decomposition of hydrogen peroxide
What is the test that estimates the concentration of antibody in serum?
Why is the agglutination (titer of antibodies) titration test done?
- Used to determine whether a particular organism may be causing the patient’s symptoms
- An increase in titer in successive days is most likely a positive result
Simple dilution problem...
- 1ml bacteria added to 9ml nutrient broth = 1:10
- take 1ml of that dilution add to 9ml = 1:100…10x10x10x10x10 = 1:100,000
- number of colonies on plate of 1:1000 dilution is 54,
- then the count is 54 x 1000 = 54,000 bacteria/ml in sample