Thank you for your inquiry.
I know of no literature which has noted a difference between brands of antibiotics used for testing in terms of the validity and/or accuracy of the results. The only reason to test for a specific brand used during an event would be if you suspected a reaction to the excipient rather than the antibiotic itself. Testing with antibiotics produced by two different manufacturers should give equivalent results as long as you are testing for allergy to the antibiotic.
If you feel that a particular excipient is responsible, then testing would have to be to the excipient itself. I suppose such a reaction could occur, but if so, the incidence of such events must be extremely rare. I was not able to find any such recorded events to the excipient in an antibiotic preparation via a literature search.
Thank you again for your inquiry and we hope this response is helpful to you.
Phil Lieberman, M.D.