Treatment of glue ear biofilms using a combination of N-acetylcysteine and antibiotics in a modified release form

Al-Zahid, Saif (2013) Treatment of glue ear biofilms using a combination of N-acetylcysteine and antibiotics in a modified release form. MPhil thesis, University of Nottingham.

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There is increasing evidence that biofilms are implicated in otitis media with effusion. The projects aim was to test the in-vitro efficacy of clindamycin and rifampicin with N-acetylcysteine against middle ear biofilm and elucidate the mechanism of action of N-acetylcysteineon extra-cellular slime, major constituent of biofilm. Hypothesis investigated: if N-acetylcysteine breaks down extra-cellular slime, this might enhance antibiotic eradication of bacteria by removing the protective effects of a biofilm state.


N-acetylcysteine with and without rifampicin / clindamycin combination was tested in vitro against biofilm of Staphylococcus aureus (F2315), previously isolated from glue ear fluid. Biofilms were grown on silicone discs and separately on pegs in 96 well microtitre plates- Minimum Biofilm Eradication Concentration (MBEC) assay. The effect of N-acetylcysteine on extra-cellular slime of F2315 was examined using a glycosaminoglycan alcian-blue assay and cellulose acetate electrophoresis.


Biofilms on silicone discs were eradicated by N-acetylcysteine (50mg/mL) and rifampicin / clindamycin combination 100 times above the minimum inhibitory concentration (MIC) after 24hrs. This was largely due to low pH of N-acetylcysteine. Subsequent neutralisation in the MBEC assay showed eradication of 4 day-old biofilms with N-acetylcysteine (5mg/mL) and rifampicin / clindamycin combination (100MIC) after one-week. This was not possible with N-acetylcysteine alone or antibiotics (rifampicin / clindamycin) alone at 100, 1000, or 10000 MIC after one-week. Non–pH neutralised N-acetylcysteine caused precipitation of extra-cellular slime that reversed on neutralisation. Neutralised N-acetylcysteine did not affect extra-cellular slime quantity. Addition of neutral N-acetylcysteine to extra-cellular slime changed the electrophoresis pattern, reducing stain density with disappearance of a halo.


Combining N-acetylcysteine with rifampicin and clindamycin seems effective in eradicating biofilms. N-acetylcysteine may affect the molecular structure of extra-cellular slime. The use of N-acetylcysteine with rifampicin and clindamycin as therapeutic agents delivered to the middle ear using a biodegradable polymer is being explored.

Item Type: Thesis (University of Nottingham only) (MPhil)
Supervisors: Bayston, Roger
Birchall, John P
Subjects: Q Science > QR Microbiology
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 63390
Depositing User: Jacob, Mr Tim
Date Deposited: 05 Oct 2020 08:23
Last Modified: 07 Oct 2020 08:07

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