Hi all,
I was hoping you could light me up on some results that I recently obtained with a biofilm assay. I am growing P.aeruginosa culture in a 96well plate to perform a simple biofilm assay with Crystal Violet staining. It turns out that the higher the concentration of Polymyxin B is, the more biofilm I have. I would have expected the opposite. Is there any evidence in the literature that higher concentrations of Polymyxin B could be less efficient to destroy biofilms ?
Thanks for your help.
Regards.
Melanie
Your polymyxin B is attracting bacterial growth (possibly due electric charge compatibility, as you have several amino groups and the bacterial cell wall is negatively charged) making them flocculate activating quorum sensing then biofilm growth.
This have been reported, positively charged structures attract bacterial growth.
As indicated by José Luis you may have an agregation facilitation due to Polymixin B, so an increase in adherent (or deposited!) cells. On another hand you have to check a possible interference between Polymixin B and Crystal violet staining. I suggest to add another method of biofilm characterization (adherent CFU or at last SEM or confocal observations) to ensure if there is a biofilm enhancement
Thank you both for your reply. Do you have any evidence of this in publications ? I am struggling a bit finding publications about increase of biofilm adherence when treated with Polymyxin B (or any other antimicrobial)
Thanks.
Mel
There are publications with similars approach using positively charged polymers to attract bacterial growth (some people at my team are involved into this line of work).
Here is an example of polymixin used to attract LPS of G- bacteria as yours, is an start.
http://www.ncbi.nlm.nih.gov/pubmed/23193598
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