Title: The effect of Antimicrobial Agents on Bacteria
Introduction:
     Bacterias are microorganisms that you can find anywhere. Some are dangerous to our health but others are harmless. In fact, some of them live in our  bodies.  In this laboratory, we worked with four different bacterias. Three of them are Gram negative and the other one is Gram positive. We used the Kirby-Bauer Method to determine the sensitiveness and resistance of those bacterias to five different antibiotics.
     Antibiotics are chemical substances produced by a living organism, generally a microorganism that is detrimental to other organisms. They act over certain bacterias inhibiting their growth or killing them after they have grow. Some of this antibiotics, like bacitracin and nitrofurazone work over bacterias that we find in the skin and others, like penicillin and tetracycline work over bacterias that
are found inside our digestive tract.
     We expect that our foundings reflect this, and if they dont maybe it is because the sensitiveness or resistance of this bacterias have changed.  Our hypothesis is that E. coli should not grow in tetracycline  and P. proteus , S epidermalis and P. auroginosa should not grow in nitrofurazone, bacitracin and ciprofloxacin.Penicillin should  work over Gram negative bacterias.

Method: Kirby-Bauer

Materials:
agar plates
sterile swabs
fresh cultures of
Escherichia coli
Pseudomonas aeuroginosa
Proteus vulgaris
Staphylococcus epidermidis
Antibiotics
Penicillin
Tetracycline
Ciprofloxacin
Nitrofurazone
Bacitracin

Procedure:

1. Inoculate four agar plates with  E. coli, P. vulgaris, P. aeuroginosa and S. epidermis
2. Dispense the antibiotics onto the plates either with the multiple dispenser or individually with the single unit dispenser.
3. Incubate the plates for 16 to 18 hours

II Table

Antibiotics	E. coli	P. vulgaris	S. epidermitis	P. auroginosa	Tetracyclinde
Nitrofurazone	growth	growth
Ciprofloxacin		growth		growth
Bacitracin		growth
Penicillin		growth
Tetracycline	growth	growth		growth

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