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Cholappadi V Sundar-Raj, Nicholas A Stella, Regis P Kowalski, Robert M Q Shanks; Phenotypic microarray analysis of Moraxella keratitis isolates. Invest. Ophthalmol. Vis. Sci. 2019;60(9):828. doi: https://doi.org/.
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Bacterial keratitis is a vision threatening infection generally treated with topical antibiotics. Despite antibiotic susceptibility of most isolates, Moraxella can cause lingering keratitis symptoms. The mechanism for this is unknown, and we hypothesize that biofilm formation plays a role in this disease process. In order to study Moraxella nonliquefasciens in vitro we are developing laboratory protocols to establish optimal methods for growth and biofilm formation. The purpose of this study is to use the Biolog phenotypic microarray system to identify carbon sources that will enable Moraxella growth and biofilm formation.
De-identified Moraxella clinical keratitis and endophthalmitis isolates from the Charles T. Campbell Laboratory were taken from -80oC storage and streaked onto TSB blood agar plates. Colonies for 7 independent isolates were suspended in LB broth and inoculated into Biolog PM1 microplates. After growth at 37oC, culture density was measured using a plate reader at 24 and 48 hrs, and at 48 hrs, biofilm formation was ascertained using crystal violet staining. Plates with LB and no bacteria were used as negative controls.
We have identified carbon sources that allow for robust growth and biofilm formation by Moraxella nonliquefasciens in LB broth. Five out of seven isolates were able to grow more robustly in with Tween 40 and two out of seven isolates grew more robustly with acetoacetic and acetic acid. Tween 40 was able to stimulate biofilm formation in one out of seven isolates while biofilm formation was not stimulated by acetic acid. Dose response analysis was performed to confirm the findings.
Using Biolog phenotypic array plates we have developed methods that will aid in experiments to uncover the mechanisms underpinning the difficulties in treating Moraxella keratitis. Since Tween 40 demonstrated the ability to stimulate growth and biofilm formation, it is a candidate carbon source for future studies.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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