Impact of Food Disinfectants on Formation of VBNC Cells in Salmonella

Introduction: In modern-day industries food products are often subjected to chemical interventions aimed at reducing microbiological hazards. However, many bacterial species including major foodborne pathogens such as Salmonella have evolved ways to evade stressful environmental conditions including exposures to potentially lethal chemicals by entering a so called Viable But Non-Culturable (VBNC) state.

Purpose: The goal of this study was to evaluate the impact of commercial food disinfectants on formation of the VBNC state in Salmonella.

Methods: A laboratory-based spray model was used to test Salmonella enterica bearing chicken parts sprayed with the following disinfectants: acetic acid (AA), citric acid (CA), lactic acid (LA), peracetic acid (PAA), hydrogen peroxide (H₂O₂), or 1, 3-Dibromo-5, 5-dimethylhydantoin (DBDMH). The reduction of Salmonella for each test biocide was enumerated by conventional culture plate methods coupled with the direct viability assessment via the LIVE/DEAD fluorescent dyes.

Results: The results show that all the disinfectants with the exception to DBMHD generated up to 1.16, 0.81, 0.46, 0.43, and 0.31 log VBNC Salmonella cells in PAA, H₂O₂, CA, LA, and AC treated samples, respectively. The viability of the VBNC cells was further confirmed by a series of resuscitation experiments in which the CA, LA and AC induced VBNC cells were recovered on culture plates by overnight incubation in the low oxygen environment (10% CO₂, 5% O₂, balance N₂). The PAA induced VBNC cells were resuscitated with brief co-incubation with catalase solution (2,000 units/ml).

Significance: Our studies show that some commercially used food disinfectants can induce formation of the VBNC state in Salmonella.  These VBNC cells did not grow on nutrient rich media while remaining viable and potentially infectious.