Laser disruption and killing of methicillin-resistant Staphylococcus aureus biofilms

Krespi, Yosef P, Kizhner, Victor, Nistico, Laura, Hall-Stoodley, Luanne and Stoodley, Paul (2011) Laser disruption and killing of methicillin-resistant Staphylococcus aureus biofilms. American Journal of Otolaryngology, 32 (3), 198-202. (doi:10.1016/j.amjoto.2010.01.010). (PMID:20434806)

Abstract

OBJECTIVE: The aim of the study was to study the efficacy of 2 different lasers in vitro, in disrupting biofilm and killing planktonic pathogenic bacteria. MATERIALS AND METHODS: Biofilms of a stable bioluminescent of Staphylococcus aureus Xen 31 were grown in a 96-well microtiter plate for 3 days. The study included 7 arms: (a) control; (b) ciprofloxacin (3 mg/L, the established minimum inhibitory concentration [MIC]) alone; (c) shock wave (SW) laser alone; (d) near-infrared (NIR) laser alone; (e) SW laser and ciprofloxacin; (f) SW and NIR lasers; (g) SW, NIR lasers, and ciprofloxacin. The results were evaluated with an in vivo imaging system (IVIS) biophotonic system (for live bacteria) and optical density (OD) for total bacteria. RESULTS: Without antibiotics, there was a 43% reduction in OD (P < .05) caused by the combination of SW and NIR suggesting that biofilm had been disrupted. There was an 88% reduction (P < .05) in live biofilm. Ciprofloxacin alone resulted in a decrease of 28% of total live cells (biofilm remaining attached) and 58% of biofilm cells (both P > .05). Ciprofloxacin in combination with SW and SW + NIR lasers caused a decrease of more than 60% in total live biomass and more than 80% of biofilm cells, which was significantly greater than ciprofloxacin alone (P < .05). CONCLUSIONS: We have demonstrated an effective nonpharmacologic treatment method for methicillin-resistant Staphylococcus aureus (MRSA) biofilm disruption and killing using 2 different lasers. The preferred treatment sequence is a SW laser disruption of biofilm followed by NIR laser illumination. Treatment optimization of biofilm is possible with the addition of ciprofloxacin in concentrations consistent with planktonic MIC.

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Contributors

Author: Paul Stoodley

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