Bacteriophage for Biocontrol of Foodborne Pathogens: Calculations and Considerations

Abstract

The use of phage or phage products in food production has recently become an option for the food industry as a novel method for biocontrol of unwanted pathogens, enhancing the safety of especially fresh and ready-to-eat food products. While it can be expected that many more phage products currently under development might become available in the future, several questions may be raised concerning the use of such products, regarding both immediate and long-term efficacy, consumer safety, and application methods. The available evidence suggests that, with a few caveats, safety concerns have been satisfactorily addressed. Answers concerning efficacy are more complex, depending on particular applications or the target pathogens. To ensure long-term efficacy beyond what can be tested on a laboratory scale, food safety concepts employing phages will have to be well-thought out and may involve rotation schemes as used with bacterial starter cultures, the use of phage cocktails, or application of phages combined with other antimicrobials. This review will discuss these issues on the basis of the available literature as well as providing an outlook on the potential of phages in future applications.

Bacteriophage biocontrol ofListeria monocytogeneson soft ripened white mold and red-smear cheeses

“…Altogether, these findings again underline the important role of phage concentration for efficacy of using phage in foods. 28 This is especially true for foods featuring a large, uneven and moisture-absorbing surface (such as cheese), which severely limits free diffusion of the virus particles in a thin water film. 28 Our results also correlate well with other studies using phage to target food-borne bacteria.…”

“…28 This is especially true for foods featuring a large, uneven and moisture-absorbing surface (such as cheese), which severely limits free diffusion of the virus particles in a thin water film. 28 Our results also correlate well with other studies using phage to target food-borne bacteria. [29][30][31] Efficacy of phage treatment appears to be highest at target cell concentrations at or below 100 cfu/cm 2 .…”

Bacteriophage biocontrol of foodborne pathogens

“…Historically, most research on phage biocontrol has been done in liquids and usually with a high concentration of pure target bacteria (Hagens and Loessner 2010). In liquid environments, thermal motion-driven particle diffusion and mixing due to either fluid flow or active swimming (bacterial motility) increase the likelihood of phages to encounter and infect susceptible host bacteria (Murray and Jackson 1992).…”

“…First, a significant portion of targeted foods is solid rather than liquid in nature. Second, bacterial contamination would likely occur at very low numbers due to the expected high hygiene standards in place (Hagens and Loessner 2010). This problem can be overcome by inundating the food environment with overwhelming number of phages thereby increasing the chances of phage -target bacteria interaction (threshold of approximately 1×10 8 PFU/ml).…”

“…In other words, low numbers of phages are unlikely to infect low numbers of bacteria simply because phages and bacteria are unlikely to come into contact with each other. The bacterial host concentration is not a limiting factor if the critical concentration of phage numbers is reached and is able to cover the entire available surface of the targeted food matrix (Hagens and Loessner 2010). Experimental verification of this claim has been achieved when a Salmonella phage (P7) was incubated with its respective host at 24°C for up to 2 h in Luria-Bertani (LB) broth at varying ratios of phage and host cell concentrations, and the surviving host cells were counted (Bigwood et al 2009).…”