Antimicrobic Sensitivity

Question 0

The 1 st antibiotic used commercially was

Answer 0

Penicillin derived from penicillium mold

Question 1

Definition of antibiotics

Answer 1

• Are compound use to control the growth of Bac.

- Are chemical metabolites specifically used in treating bacterial infection.

Question 2

How many form of antibiotic do we have? Name and give a description?

Answer 2

There are 3 forms of antibiotic:

• Natural antibiotics : produce in nature, inhibit growth of other microbes and provide an environmental advantage for those resistant to the effects of the antibiotic.
• Semi-synthetic antibiotic: are those produced chemically by keeping the active moiety intact but modifying an R group.
• Synthetic antibiotic: such as sulfonamides, are entirely produced in laboratories.

Question 3

Give the #ce between bactericidal and bacteriostatic ?

Answer 3

• Bactericidal: are antibiotics that kill bacteria.

- Bacteriostatic: are antibiotics that only inhibit the growth of bacteria.

Question 4

Give the #ce between narrow and broad spectrum?

Answer 4

• Narrow spectrum: are antibiotics that target single groups

- Board spectrum: are antibiotics that target more than one group of bacteria such as tetracycline.

Question 5

Which spectrum ( narrow and broad) is better or have more advantage? Why? 
Which one does a doctor do in order to find out what Bac the patient have?

Answer 5

• Board spectrum antibiotics may have the advantage of inhibiting many types of Bac when the biological agent in the infection is not know, they have the disadvantage of removing normal microbiota, in the colon in particular.
• the 1st thing doctor do in order to find out what Bac patients have is: the spectrum board

Question 6

How to measure the zone of inhibition?

Answer 6

I am measuring the Diameter in “mm”

Question 7

The standardized variables for Kirby-Bauer method include the use of what?

Answer 7

• Mueller-Hinton II agar @ pH 7.2-7.4
• agar thickness of 4mm in a petri plate.
• Bac are growth in the broth to a density standard indicating 10 power 7 bacterial cells/ml
• Incubate the plate for 16-18 hours.

Question 8

What is the zone of inhibition? How is it measure?

Answer 8

Is the area around the disk in which no Bac grow.

It is measured in mm and compare to the standard chart to edit the rating.

Question 9

NaCl (salt) concentration: 0,5,10,15,20,25 %
Escherichia coli
Staphylococcus aureus
Halobacterium salinarium

Answer 9

• E. coli: grow @ 0% n 5%
• S. Aureus: grow @ 0%, 5% n 10%
• H salinarium: grow well @ 25% salt concentration.

Question 10

Why E. Coli and Staphylococcus aureus can not grow @ 25% NaCl?
Why do Halobacterium salinitium grow @ 25% NaCl?

Answer 10

• because @ high 25% concentration some bacteria shrink and die.
• H Salinitium grow @ high contraction b/c they have special adaptation membrane pump that pump the solute into the cell.

Question 11

At what temperature E. coli grow?

Why are Bac temperature dependent?

Answer 11

• 25-37degrees.

- Bac are t dependent because at different temp Bac fold #tly.