Phage‐Based Biosensor and Optimization of Surface Blocking Agents to Detect Salmonella Typhimurium on Romaine Lettuce

Abstract

The development of rapid detection technologies in parallel with understanding production practices will markedly improve the microbiological safety of leafy vegetables. The objective of this study was on the application of phage-based magnetoelastic (ME) biosensors and optimization of selected surface blocking agents for a rapid detection for Salmonella Typhimurium on Romaine lettuce. Initially, Romaine lettuce hearts surface was examined for structural differences followed by attachment and distribution of S. Typhimurium using scanning electron microscopy (SEM). Furthermore, selected surface blocking agents were compared and optimized for the application of phage-based ME biosensors surface. A total of 156 observations, ranging from 1 to 8 logs CFU/ml, and 18 frequency measurements were recorded and analyzed. Both measurement (with E2 phage) and control (without E2 phage) sensors were blocked with selected blocking agents to prevent nonspecific binding. Statistical analysis using ANOVA revealed that there was a significant difference between controls and measurements (P < 0.001). The comparison showed that 5 3 10 2 CFU/mL and higher concentrations of S. Typhimurium were detected on Romaine lettuce surface, and PEG performed better as a blocking agent of choice. Understanding the complexity of the bacteria-plant surface interaction and improved detection protocol will provide a solid foundation to design feasible control strategies. PRACTICAL APPLICATIONSSalmonella species are generally associated with food products of animal origin and recently leafy green vegetables have been considered as a major public health concern and source of the bacteria. There is still a need to explore swift and reliable detection protocol, which could be easily applied to leafy vegetables from the farm to consumer. In this study, we have demonstrated the rapid detection for Salmonella Typhimurium on Romaine lettuce using phage-based protocol. Furthermore, better surface blocking agent was optimized for the protocol. Further optimization of phage-based detection approach could be instrumental to develop better Salmonella detection approach that can be adopted and used from farms to the consumer level.

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