Serovar Diversity and Cellular State Modulate Salmonella Response to Antimicrobial Treatments

Outbreaks, illnesses, and deaths due to Salmonella contamination of food remain the leading cause of foodborne diseases in the U.S. Considering the challenge that mitigating this organism poses, this study investigates factors that may be affecting Salmonella control in food processing environments by exploring serovar variation and cellular state (biofilms vs planktonic cells) when treated with common chemical sanitizers. Seven Salmonella serovars (S. Infantis, S. Enteritidis, S. Kentucky, S. Typhimurium, S. Newport, S. Heidelberg, and S. Dublin) were subjected to treatments with sodium hypochlorite (SH) and peracetic acid (PAA) as biofilms and planktonic cells on stainless-steel. Each serovar was treated independently with SH or PAA at two concentrations (100 and 200 ppm) for contact times of 1 and 2 min. Statistically significant differences were observed between biofilms and their planktonic counterpart across all Salmonella serovars (p < 0.05), with biofilms showing lower reduction regardless of treatment compared to planktonic cells. Regarding biofilms, PAA interventions were significantly more effective (p < 0.05), with reductions ranging from 1 to 6 Log₁₀ CFU/cm², while SH produced reductions ranging from 0.6 to 4 Log₁₀ CFU/cm². Serovar-influenced differences were observed for both sanitizers, with S. Kentucky and S. Infantis showing the highest bacterial concentrations recovered after all treatments, indicating that the disinfectants' efficacy in reducing bacterial load was serovar-dependent (p < 0.05). The discovery of differences in Salmonella serovar responses to disinfectants and the decreased efficacy of sanitizers when biofilms are present should be considered by the food industry, as it requires implementing improved sanitation protocols to reduce Salmonella contamination in foods.