Effectiveness of Sanitizer D7™ against Escherichia coli O157:H7 and Salmonella Biofilms

Introduction: Biofilm formation by Escherichia coli O157:H7 and Salmonella enterica at meat processing plants poses a serious risk of meat product contamination. Available studies have shown that many common sanitizers were unable to completely eradicate biofilms by these foodborne pathogens due to the three-dimensional biofilm structure and the bacterial polymeric extracellular substances (EPS). D7™ is a sanitizer product consisting of quaternary ammonium compound, hydrogen peroxide, and an optional accelerator, diacetin. This product has been tested on Listeria and Pseudomonas biofilms and showed promising results. However, the effectiveness of D7™ against E. coli O157:H7 and Salmonella biofilms under meat processing conditions has not been evaluated.

Purpose: To evaluate the effectiveness of D7™ in inactivating and removing E. coli O157:H7 and Salmonella biofilms.

Methods:  Escherichia coli O157:H7 and Salmonella biofilms on food contact surfaces were treated with 10, 20, or 100% D7™ for 10 min, 1 h, or 6 h to measure log reduction of biofilm cells. Scanning electron microscope (SEM) was applied to evaluate the effect of D7™ treatment on biofilm removal and bacterial morphology.

Results: Treatment with 10, 20, or 100% D7™ reduced biofilm cells to nondetectable level, even with 10 min exposure time. SEM analysis of water-treated control samples exhibited three-dimensional biofilm structure with strong EPS matrix connecting bacteria with contact surface. Treatment with 20% D7™ for 10 min significantly reduced biofilm mass and weakened EPS connection. Majority of the bacteria exhibited altered morphology with compromised membrane integrity. Treatment with 100% D7™ for 10 min dissolved EPS matrix and no intact biofilm structure was observed, instead, scattered clusters of bacterial aggregates were detected, indicating the loss of cell viability and biofilm removal.

Significance: D7™ is highly effective, even at significantly diluted concentrations, against E. coli O157:H7 and Salmonella biofilms.