Disc Difussion Test - Zone of Inhibition (Sep/07/2008 )

About Antibiotic Sensitivity test(disc difussion test), what it means if the zone of inhibition is....
~Too large zone on control plates
~Too small zone on control plates
~Single disc result above or below control limits
~Colonies within zone of infection
~Overlaped zones
~Indistincted zones
~Zone within zone phenomenon
thank u

~Too large zone on control plates: zone so huge that it touches the edge of the plate / in other words , you don't see a nice circle . too high of an antibiotic conc.

~Too small zone on control plate : small indiscernible zone. too low of antibiotic conc.

~Single disc result above or below control limits : ur zone of inhibition is out of the known range / may have to use a bigger parameter i.e control disc with higher/lower conc.

~Colonies within zone of infection : @.@

~Overlaped zones : two or more discs placed too close together.

~Indistincted zone: dont know

~Zone within zone phenomenon: u get one clear zone then outside of the zone is a fainter zone.


hope that helps.