Discipline: Biological Sciences
Ashley Bonney - Rochester Institute of Technology
Co-Author(s): Dr. Robert C. Osgood, Rochester Institute of Technology, Rochester, NY
Moraxella catarrhalis (M.cat), Nontypeable Haemophilus influenzae (NTHi) and Streptococcus pneumoniae (S.pn) all inhabit the upper respiratory tract and are the top three etiological agents of otitis media. All exhibit both planktonic and biofilm growth. Biofilms are self-adhered communities of organisms attached to living or non-living surfaces, while encased within a self-produced extracellular matrix. M.cat is often Beta-lactamase positive and therefore resistant to β-lactams such as penicillins and cephalosporins. Previous crystal violet biofilm assays using varying pH and oxygen concentrations on NTHi clinical isolates, clinical data obtained from pH testing of middle ear fluid collected by tympanocentesis and subsequent gene expression studies that monitored biofilm gene expressions over a pH range that included pH 8.0 have shown that NTHi favors a pH of 8.0 for biofilm formation under reduced oxygen concentrations. Our hypothesis states that since M.cat, NTHi and S.pn occupy the same human ecological niches and since NTHi has been shown to prefer a pH of 8.0 for biofilm production, M.cat shares the same preference for biofilm production at pH 8.0 under reduced oxygen conditions. This may allow a unique treatment. An M.cat reference isolate (ATCC 25238) and several M.cat clinical isolates were grown under environmentally germane conditions in brain heart infusion medium supplemented with human serum and then subjected to replicate crystal violet biofilm assays performed under aerobic and anaerobic conditions at pH 7.0 and 8.0. Subsequently, confocal microscopy and live-dead staining was used to analyze and investigate the viability of M.cat within biofilm grown at pH 8.0. Follow up statistical evaluation of replicate data and image analysis of M.cat using Comstat 2.0 biofilm analysis software and the freeware program, ICY, indicated that M.cat, like NTHi, preferably forms more biofilm at pH 8.0 as compared to pH 7.0 under reduced oxygen conditions. Furthermore, M.cat viability remained high within the established biofilms after 48 hours. Interestingly, it was also observed that clinical isolates of M.cat exhibited auto-aggregation when grown in liquid media, while the M.cat reference did not. Future research is aimed at expanding the number and clinical origin of M.cat isolates tested. Additionally, serotype specific isolates of S.pn will also be similarly investigated before analyzing biofilms consisting of combinations of two or three otopathogen species.Not Submitted
Funder Acknowledgement(s): I am thankful to the technicians at the confocal microscopy facility for their help with producing confocal images. I would also like to thank my fellow colleagues for their encouragement and support. Funding was provided by the Department of Biomedical Sciences at the Rochester Institute of Technology.
Faculty Advisor: Dr. Robert C. Osgood, firstname.lastname@example.org
Role: I performed the isolation of Moraxella catarrhalis, the dilution of the sample for crystal violet biofilm assay, and the crystal violet biofilm assay procedure indicating biofilm formation.