M. Barneck2,3, M. De La Presa1, A. Poursaid1, M. Nourian1, M. A. Firpo1, J. T. Langell1,2 1University Of Utah,School Of Medicine, Department Of Surgery,Salt Lake City, UT, USA 2University Of Utah,Engineering,Salt Lake City, UT, USA 3Oregon Health And Science University,School Of Medicine,Portland, OR, USA
Introduction: Hospital Acquired infections (HAIs) are the most frequent adverse event in healthcare delivery worldwide, occuring in 5 -10% of acute care hospital admissions, costing the healthcare system an estimated $28-$45 billion annually. Increasing rates of antimicrobial resistant bacteria have increased the morbidity, mortality and cost of treating these infections.
Visible light sterilization (VLS) using high intensity LEDs and lasers have been adapted into several medical applications and have shown bactericidal activity. The inactivation mechanism is believed to be oxygen dependent photoexcitation of bacterial endogenous porphyrins, which leads to the production of a cytotoxic singlet oxygen species. While some research has been done in this field, an in depth comparison of common clinically pathogenic bacteria in a single study has not been published. Here we demonstrate a comprehensive evaluation of common gram-positive and gram-negative species at varying treatment times, intensities, bacterial concentrations, and photokinetic doses.
Methods: Visible light emitting diodes centered at 403.0-nm ± 10.8 were used to illuminate a panel of four relevant HAI facultative anaerobic bacteria, Escherichia coli, Staphylococcus Aureus (ATCC 29213), Pseudomonas Aeruginosa (ATCC 27853), and Streptococcus Pneumoniae (ATCC 49619). The E. coli K-12 strain transformed with the pCIG mammalian expression vector conferring ampicillin resistance via expression of the β-lactamase gene. Each bacteria was tested against the VLS with varying treatment durations, light intensities and colony forming unit (CFU) density. Treatment times ranged from 10 minutes to 16 hours, irradiance levels between 2.4mW/cm2 ± 0.3 and 8.9mW/cm2 ± 0.6, and fluence levels up to 132.98 ± 6.69 J/cm2.
Results: Dose dependent effects were visible in visible in all species. The largest inactivation occurred in β -lactam resistant E. coli at 6.27 ± 0.54 log for 250 minutes. Statistically significant results (<0.0001**) were found at each time point.
Conclusion: We have successfully demonstrated high efficacy bacterial reduction using a visible light sterilization system. The VLS showed statistical significance against both gram positive and gram-negative species within the given treatment times. The β-lactam antibiotic-resistant E. coli showed very significant reduction levels which suggests that light therapy could a suitable option for sterilization in drug resistant species of bacteria. Our research illustrates the potential of using VLS in treating clinically relevant bacterial infections in vivo.
