Does using Delta-treated microplates affect antibiotic screening results (MIC)? I always used untreated microplates for antibacterial susceptibility testing, but I only have the treated microplates. A researcher suggested exposing the treated plates to UV light for an hour to "untreat" them. Is this correct?
I appreciate any advice you can provide.
ThermoFisher seems to think you can...
https://www.thermofisher.com/order/catalog/product/168055?gclid=CjwKCAiApvebBhAvEiwAe7mHSHzFcPXaLQmMkbJzxt_mEv3AdMvltf-bUu2peJPcd81C4a992eZR-xoCcEwQAvD_BwE&ef_id=CjwKCAiApvebBhAvEiwAe7mHSHzFcPXaLQmMkbJzxt_mEv3AdMvltf-bUu2peJPcd81C4a992eZR-xoCcEwQAvD_BwE:G:s&s_kwcid=AL!3652!3!562127230705!!!g!!!15287362487!128563401494&cid=bid_clb_ccp_r01_co_cp0000_pjt0000_bid00000_0se_gaw_dy_pur_con
Yoram Gerchman
Thank you for your answer.
I have read the catalog page prior and only found the "antibiotic screening" feature for the untreated plates.
I have used both plates (Delta-treated and untreated), compared the results, and found two to four-fold differences between the two plates in a few isolates so far.
P.S. Regarding the advice of exposing the treated plates to U.V. light, I asked a Researcher with a background in Cell Culture, and he said that based on his knowledge, U.V. light only degrades nucleic acids but not surface molecules such as the ones used in Delta-treated plates.
Raghad Rashed Alzahrani - Interesting observation "found two to four-fold differences between the two plates in a few isolates"
What was the direction of the difference? i.e. where were the antibiotic more effective?
Yoram Gerchman
I noticed it was inconsistent and depended on the hydrophobicity of the tested drug. I'm unsure if it was related to the plate type, but I assumed it was. Hence it was the only variable.
There were no major differences in the MIC results of the hydrophilic antibiotic I was testing, unlike when I tested another hydrophobic drug--the results varied as the drug was less effective in the treated plates.
The differences in the efficacy of the hydrophilic antibiotic were interchangeable on the treated and untreated plates.
Given the description of the delta treatment I am surprised
"Nunclon Delta is a cell culture–treated surface modification that makes the polystyrene surface of your culture vessel more hydrophilic, promoting maximum adhesion for a broad range of cell types." https://www.thermofisher.com/il/en/home/life-science/cell-culture/cell-culture-plastics/nunc-adherent-cell-culture-surface.html
So, the treated plates should bind less, not more hydrophobic compounds... if compound binding is the case. Can you try feeling the plate with your compound, waiting for 10 minutes, and pipette it out to a new, untreated plate? or even a paper disk for disk diffusion assay?
Yoram Gerchman
Unfortunately, I currently don't have untreated plates or paper disks, so I am only doing my antibiotic screening while keeping the used plate type in my notes.
Thank you for your suggestions.
Pleasure and good luck.
You could get new plates more cheaply via Amazon or eBay. Many sellers out there.
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