Why is it necessary to use an antibiotic susceptibility chart (rather than simply the size of the zone of inhibition) to determine whether a bacterial isolate is sensitive, intermediate, or resistant to a particular antibiotic?
Antibiotic susceptible chart directs the doctor in chosing of the medicine to cure disease. It helps to inhibit growth of bacteria causing infection.
If the size of inoculum is too small the zone of inhibition will be larger than what is supposed to be and if the inoculum is too large the zone of inhibition will be smaller. The zone sizes are looked up to a standardized chart to give a result of sensitive, resistant or intermediate.