RP2 - Microbiology Flashcards

1
Q

What antiseptic techniques can be used to avoid contamination?

A

● Spray working area with disinfectant and wipe dry
● Wash hands with antibacterial wash
● Flame the neck of the culture bottle
● Lift the lid of the agar plate at an angle
● Dip spreader in ethanol and pass through Bunsen flame before spreading bacteria
● Use forceps to place antibiotic discs

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2
Q

Describe how you could investigate the effect of antibiotics on bacterial growth using zones of inhibition

A

● Divide agar plate with bacteria into three segments
● Use forceps to place filter paper disc with antiseptic in each zone
● Loosely tape lid onto agar plate to allow oxygen to reach bacteria
● Incubate at 25°C for 48 hours
● Measure the diameter of clear zones (zones of inhibition) using a ruler
from two opposite directions - calculate mean of measurements
● Calculate area of clear zones

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3
Q

How would you measure the zone of inhibition?

A

Use a ruler to measure from a point on one side to a point directly opposite (with lid still in place)
Measure again at 90° to first diameter measurement in order to calculate a mean

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4
Q

Why should you not completely seal the Agar plate?

A

To allow oxygen to enter the agar plate, preventing the growth of harmful anaerobic bacteria

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5
Q

Why is it necessary to measure the diameter of the zone of inhibition twice?

A

Clear zones are not always uniform - taking more than one measurement allows a mean diameter to be calculated

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6
Q

What equation is used to calculate the area of clear zones?

A

Area = πr2

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