Question

E. coli S. aureus Plate 1 is E. coll tested with four antibiotics (1-4): plate 2 is S. aureus tested with the same four antibiotics. Which antibioticis most effective on S. aureus? < Prev 2 of 10 Score answer >

Answer 1

Antibiotic resistance test is one of the qualitative method used in microbiology to determine the growth inhibitory nature of particular antibiotic against the microorganisms.

So the test organisms can be swabed on the agar plate,which are incubated with the appropriate antimicrobial agents.

If the microorganisms are susceptible to the anti microbial agent then in the agar plate it leads to formation of zone of inhibition i.e. the region where no growth occurs.(transparent circular area around the antibiotic disk is said to zone of inhibition).

If the microorganisms show resistance to those antibiotics there will be no zone of inhibition.

Based on the radius and size of the zone the anti microbial activity can be determined.Larger the zone higher the activity.

From the above picture it is clear that the antibiotic which is numbered 3 shows larger zone of inhibition and radius is larger when compared to others.Thus the organism is more susceptible to the antibiotic (3).Therefore compared to other antibiotics 3rd one is more effective for S.aureus

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