Sporicidal effects of high-intensity 405 nm visible light on endospore-forming bacteria

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Abstract

Resistance of bacterial endospores to treatments including biocides, heat and radiation is a persistent problem. This study investigates the susceptibility of Bacillus and Clostridium endospores to 405-nm visible light, wavelengths which have been shown to induce inactivation of vegetative bacterial cells. Suspensions of B. cereus endospores were exposed to high-intensity 405-nm light generated from a light-emitting diode array and results demonstrate the induction of a sporicidal effect. Up to a 4-log10 CFU mL-1 reduction in spore population was achieved after exposure to a dose of 1.73 kJcm-2. Similar inactivation kinetics were demonstrated with B. subtilis, B. megaterium and C. difficile endospores. The doses required for inactivation of endospores were significantly higher than those required for inactivation of B. cereus and C. difficile vegetative cells, where approximately 4-log10 CFU mL-1 reductions were achieved after exposure to doses of 108 and 48 Jcm-2, respectively. The significant increase in dose required for inactivation of endospores compared to vegetative cells is unsurprising due to the notorious resilience of these microbial structures. However, the demonstration that visible light of 405-nm can induce a bactericidal effect against endospores is significant, and could have potential for incorporation into decontamination methods for the removal of bacterial contamination including endospores.
Original languageEnglish
Pages (from-to)120-126
Number of pages7
JournalPhotochemistry and Photobiology
Volume89
Issue number1
Early online date30 Aug 2012
DOIs
Publication statusPublished - Jan 2013

Keywords

  • endospores
  • endospore-forming bacteria
  • photochemistry
  • photobiology

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