Aim: To determine the mechanisms by which a stabilized oxychloro (SOC)-
based sanitizer, applied to decontaminate seeds destined for sprout production,
inactivates Escherichia coli O157:H7 ph1 and Salmonella serotype Meleagridis.
Materials and Results: The action of SOC on the metabolism, membrane and
DNA integrity of Salmonella and E. coli O157:H7 was studied. In both pathogens,
there was an oxidative burst and depletion of intracellular glutathione
(GSH) upon initial exposure to 200 ppm SOC. Metabolic activity, measured
via bioluminescence, decreased over a 4-h period in E. coli O157:H7 ph1 cells
exposed to SOC. Membrane integrity, assessed through viability staining,
decreased progressively over 23 h when exposed to SOC. The appearance of
auxotrophic mutants suggested that DNA damage had also occurred. Enzymes
rich in disulfide bonds (alkaline phosphatase and protease) were sensitive to
the chlorite-based sanitizer. Through challenging other microbial types, it was
found that Gram positive had higher tolerance to SOC than Gram negatives
with the exception of Salmonella. MS2 bacteriophage was highly sensitive; however,
Bacillus endospores were not inactivated by SOC.
Conclusions: SOC inactivates E. coli O157:H7 and Salmonella through GSH
oxidation and disruption of disulfide bonds. Ultimately, membrane damage
resulting from prolonged exposure to SOC leads to the loss of cell viability.
Significance and Impact of the Study: The results provide a basis for understanding
why extended treatment times are required to inactivate bacteria using
SOC.