Question

What is the name of the medium used in the Kirby-Bauer antimicrobial sensitivity test?

Answer 1

1. THE MODIFIED KIRBY-BAUER METHOD• Mueller-Hinton agar•
2. 1. Mueller-Hinton agar should be prepared from a dehydrated base according to the manufacturers recommendations. The medium should be such that control zone sizes within the standard limits are produced. It is important not to overheat the medium.
3. • 2. Cool the medium to 45-50'C and pour into the plates. Allow to set on a level surface, to a depth of approximately 4 mm. A 9 cm diameter plate requires approximately 25 mL of the medium
4. .• 3. When the agar has solidified, dry the plates for immediate use for l0-30 minutes at 36oC by placing them in an upright position in the incubator with the lids tilted.
5. 4. Any unused plates may be stored in a plastic bag, which should be sealed and placed in the refrigerator. Plates stored in this way can be kept for 2 weeks.• To ensure that the zone diameters are sufficiently reliable for testing susceptibility to sulfonamides and co-trimoxazole, Mueller-Hinton agar must have low concentrations of the inhibitors thymidine and thymine. Each new lot of Mueller-Hinton agar should therefore be tested with a control strain of Enterococcus faecalis and a disc of co-trimoxazole. A satisfactory lot of medium will give a distinct inhibition zone of 20 mm or more that is essentially free of hazy growth or fine colonies