Lab 3 - Antibiotic Sensitivity Flashcards
What are antibiotics?
Substances produced by microorganisms that kill or inhibit the growth of other microorganisms
What does an antibiotic sensitivity test tell you? Why is this important?
It tells you whether or not a particular antibiotic is effective against a bacteria.
It is important because not all antibiotics are effective against bacteria/infectious diseases
What are some tests to test antibiotic sensitivity?
Kirby-Bauer test and Antibiotic Strip test
Why is the diameter itself not a great indicator for antibiotic sensitivity in the Kirby Bauer?
Because the rate of diffusion of the antibiotic.
Also, the amount of bacterial growth applied could effect the results.
So it is important to used standardized conditions when testing
Which microorganisms did we test antibiotic sensitivity in this lab?
S. aureus, E. coli, and P. aeruginosa
What type of medium was used to grow bacteria?
Mueller-Hinton (MH) agar
What makes the medium used so good for testing antibiotic susceptibility?
MH agar is:
Non-selective and non-differential
It contains starch = absorbs toxins that bacteria release that could interfere with the antibiotics
It is looser agar, so it leads to a truer zone of inhibition as it allows for good diffusion
What kind of media is TSA?
General purpose media that allows a wide variety of microorganisms to grow.
What is an MIC test?
Minimum Inhibitory Concentration test
What does an MIC test tell you?
The inhibitory concentration of antibiotic needed to prevent growth of a microorganism in vitro.
It tells us the concentration of antibiotic we need to get to the site of infection to prevent growth.
How do you do an MIC test?
Get a micro well plate and use varying concentrations and see what results you get.
What does an MIC tell a physician?
It lets him choose a proper antibiotic and the dosage schedule.
How can MIC be performed on sterile body fluids?
Blood is added to tubes containing different concentration of antibiotic. Increase in turbidity indicates the growth of microorganism, and the concentration was ineffective.
Here, we don’t identify or isolate microorganisms.
What is classified as a useful antibiotic producing strain?
One that produces metabolites that inhibit the growth/reproduction of a pathogen
Where are the majority of antibiotics discovered from?
Actinomycetes (a group of soil bacteria)
