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Blue 470 nm light suppresses the growth of Salmonella enterica and methicillin‐resistant Staphylococcus aureus (MRSA) in vitro
Author(s) -
Bumah Violet V.,
MassonMeyers Daniela S.,
Enwemeka Chukuka S.
Publication year - 2015
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.22385
Subject(s) - salmonella enterica , staphylococcus aureus , methicillin resistant staphylococcus aureus , microbiology and biotechnology , salmonella , in vitro , blue light , micrococcaceae , biology , bacteria , materials science , optoelectronics , genetics
Background and Objective Emerging evidence suggests that blue light can photo‐inactivate some bacteria of clinical importance. Consequently, we tested the hypothesis that 470 nm light can suppress growth of two recalcitrant bacteria, MRSA and Salmonella . Materials and Methods We plated 5 × 10 6 and 7 × 10 6 CFU/ml USA300 strain of MRSA and 1 × 10 6 CFU/ml of Salmonella enterica serovars Typhimurium and Heidelberg. Plates were irradiated with 55, 110, 165 and 220 J/cm 2 of blue light, incubated at 37°C for 24 hours and colony counts determined. Results Compared with controls, blue light irradiation produced a significant dose‐dependent reduction in the number of colonies formed by each bacterial strain ( P < 0.001). Irradiation of 5 × 10 6 and 7 × 10 6 CFU/ml MRSA with 55 J/cm 2 produced 92% (4.6 × 10 6 CFU/ml) and 86% (6 × 10 6 CFU/ml) inactivation respectively, while 110 and 220 J/cm 2 suppressed each MRSA density 100%. Irradiation of Salmonella Typhimurium with 55 and 110 J/cm 2 suppressed bacterial growth 31% (3.1 × 10 5 CFU/ml) and 93% (9.3 × 10 5 CFU/ml) respectively; while Salmonella Heidelberg was inhibited 11% (1.1 × 10 5 CFU/ml) and 84% (8.4 × 10 5 CFU/ml) respectively by the two fluences. Complete inactivation of each Salmonella strain was achieved using 165 or 220 J/cm 2 . Conclusion The observed inhibition of Gram‐positive (MRSA) and Gram‐negative ( Salmonella ) bacteria suggests the versatility of blue light in bacteria eradication, making it a viable intervention strategy for decontamination of food and environments that harbor such bacteria. Lasers Surg. Med. 47:595–601, 2015. © 2015 Wiley Periodicals, Inc.