title: Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma evokes distinct changes in morphology and integrity of spores.
abstract: Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity.
authors.affiliation: Wageningen UR Food and Biobased Research, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Hermien
authors.initials: H
authors.lastname: van Bokhorst-van de Veen
authors.affiliation: Wageningen UR Food and Biobased Research, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Houyu
authors.initials: H
authors.lastname: Xie
authors.affiliation: Wageningen UR Food and Biobased Research, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Esveld
authors.affiliation: Laboratory of Food Microbiology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Tjakko
authors.initials: T
authors.lastname: Abee
authors.affiliation: Wageningen UR Food and Biobased Research, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands.
authors.forename: Hennie
authors.initials: H
authors.lastname: Mastwijk
authors.affiliation: Wageningen UR Food and Biobased Research, Bornse Weilanden 9, P.O. Box 17, 6700 AA Wageningen, The Netherlands. Electronic address: masja.nieropgroot@wur.nl.
authors.forename: Masja
authors.initials: M
authors.lastname: Nierop Groot
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D001407:Bacillus / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D001409:Bacillus cereus / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D004202:Disinfectants / Q000494:pharmacology; D005506:Food Contamination; D005516:Food Microbiology; D056506:Geobacillus / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006997:Hypochlorous Acid / Q000494:pharmacology; D009584:Nitrogen / Q000494:pharmacology*; D058626:Plasma Gases / Q000494:pharmacology*; D013171:Spores, Bacterial; D013242:Sterilization / Q000379:methods; D014466:Ultraviolet Rays
chemical_list: D000890:Anti-Infective Agents; D004202:Disinfectants; D058626:Plasma Gases; D006997:Hypochlorous Acid; D006861:Hydrogen Peroxide; D009584:Nitrogen
keywords: Bacillus cereus; CAP; Disinfectants; Food safety; Plasma treatment; Spores