Dear Sir. Concerning your issue about the measurement of residual low concentrations (~1ug/L) antibiotics in biofilm . A biofilm is a population of cells growing on a surface and enclosed in an exopolysaccharide matrix. Biofilms are notoriously difficult to eradicate and are a source of many recalcitrant infections. Biofilm formation was monitored by the ability of cells to adhere to the wells of microtitre plate (MTP) made of PVC (Beckon Deckson labware). The biofilm forming microorganisms recovered from IUDs were grown in LB medium and samples were drawn at 12 hour intervals. The quantification measurements were carried out in the mixed population of organisms I think the following below links may help you in your analysis:

http://medind.nic.in/iau/t03/i3/iaut03i3p161.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC90417/pdf/ac000999.pdf

http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0173559&type=printable

Thanks

can you elaborate on the nature of the biofilm. (size, form, the materials on which the biofilm is attached to).

Usually the simplest way is the bioassay. Extract your biofilm, filter and test as you do in susceptibility testing

Hi Abdelraouf,

The biofilm is attached on the inner wall of a bioreactor. The inflow of the bioreactor contained 20ug/L tetracycline hydrochloride and sulfonamide sodium @ Abdelraouf A. Elmanama

I think thin layer chromatography "TLC" would be suitable. You can collect few grams of your biofilm and process it for tetracycle extraction and then run the extract in tlc along with tetracycline standard.

https://www.google.ps/url?sa=t&source=web&rct=j&url=http://www.mdpi.com/2079-6382/6/4/34/pdf&ved=2ahUKEwjqqZPGpvPcAhXGIlAKHU4cBBwQFjAAegQIAxAB&usg=AOvVaw14-g8y219whBTnZtFEXXCQ

This link is an article for various techniques used to detect antibiotic residues from meat. Hope you can modify one to suit you

Thank you very much!@ Abdelraouf A. Elmanama @ Isam Eldin Hussein Elgailani