Listeria monocytogenes is a significant foodborne pathogen that poses a serious threat to human health. This bacterium is responsible for listeriosis, which can result in a high fatality rate of up to 30% among high-risk individuals [1]. It is commonly associated with and can survive in various foods or food-associated systems, particularly fresh produce [2,3,4,5]. Due to the vulnerability of fresh produce to physical decontamination, physical approaches such as pasteurization are typically not applied in preventing pathogen contamination in fresh produce [6,7]. Additionally, L. monocytogenes can survive and grow in cold temperatures, increasing the risk of contamination of even properly stored produce [8]. Therefore, postharvest control methods are limited for fresh produce and effective preharvest control measures to prevent L. monocytogenes contamination are critical for ensuring fresh produce safety.

Biological soil amendments of animal origin (BSAAO) including raw animal manures and composts are commonly used to enhance the yield of fresh produce and other agricultural crops [9]. However, inadequately treated BSAAO can also be a potential source of L. monocytogenes contamination in fresh produce [10]. While studies have been focused on the fate of L. monocytogenes in BSAAO, the essential factors that can impact the persistence of L. monocytogenes in BSAAO have not been comprehensively reviewed [11]. Therefore, it is important to understand the behavior of L. monocytogenes in BSAAO and the potential preharvest prevention measures which can be used for fresh produce.

Raw animal manure contains feces, urine, bedding materials, and other secretions from the animal. As the rich sources of plant nutrients, animal wastes are commonly used as fertilizers or biological soil amendments [12,13]. However, the application of untreated animal wastes may introduce potential microbial hazards to crop fields; thereby, it is required that the raw animal manure be incorporated into the soil more than 90 days prior to harvest for crops that have no direct contact with soil, and 120 days if the produce has direct contact with soil [14]. The application of raw manure must not contact produce during application, and the potential for contact with produce after application should be minimized [14]. Sheng et al. [15] conducted a 2-year field study to evaluate the impacts of dairy manure fertilizer application on the microbial safety of red raspberries. Although no Shiga-toxin-producing E. coli (STEC) or L. monocytogenes was detected in fertilizer, soil, foliar, or raspberry fruit samples throughout the sampling period of 2 years, Salmonella in soil amended with contaminated fertilizer was reduced to an undetectable level after 2 or 4 months of application.

The harmful or pathogenic microorganisms in BSAAO can be reduced or eliminated through composting. Composting is a controlled biological process that broadly consists of four typical phases based on the temperature generated and active microbial community: mesophilic, thermophilic, cooling, and maturation phases. Normally, composting process proceeds with solid or liquid materials within a moisture level range of 40 to 50% or 90 to 98%, respectively [16]. During a satisfactory composting process, mesophilic, thermophilic, and thermotolerant bacteria, fungi, and actinomycetes are actively involved [17]. Pathogens are killed primarily by the accumulation of heat (45 to 75 °C) generated by indigenous microorganisms during the early phases of aerobic composting of animal manures [18,19,20]. However, due to the complex composting process or the recontamination during storage, the pathogenic bacteria can be reintroduced to the finished compost. As specified by the Food Safety Modernization Act (FSMA) Produce Safety Rule, microbial standards for biological soil amendments of animal origin include less than 0.3 most probable number (MPN) per gram or milliliter of analytical portion for E. coli O157:H7, less than 3 MPN per 4 g or mL of total solids for Salmonella spp., and less than 1 CFU per 5 g or mL of analytical portion for L. monocytogenes [14]. To achieve these standards, the FSMA’s Produce Safety Rule mandates the incorporation of alternative treatments for reducing or eliminating human pathogens in raw animal wastes before land application [21].

Physical and chemical methods for controlling pathogens in BSAAO often have adverse environmental impacts, such as greenhouse gas emissions and odor pollution, and may be costly [11,22]. To address these challenges, researchers have explored biological methods for reducing or inhibiting pathogen populations in BSAAO [22]. One promising approach is the use of competitive exclusion (CE) microorganisms, in which multiple beneficial microorganisms are allowed to grow and establish a community that can inhibit the growth of pathogens like L. monocytogenes [23,24]. CE offers a cost-effective and environmentally sustainable means of reducing pathogen populations in BSAAO by leveraging the natural properties of microbiological communities [25]. Moreover, the metabolic activities of microbiological communities in BSAAO can provide essential nutrients for plant growth, making this approach both effective and sustainable [11]. Lactic acid bacteria have been well studied to competitively exclude pathogens like Escherichia coli O157:H7, Salmonella, and L. monocytogenes in foods [26,27], but their effectiveness against L. monocytogenes in BSAAO is not conclusive. Furthermore, microbial communities, including other species that effectively control L. monocytogenes are unclear.

2. Factors That Impact the Fate of L. monocytogenes in BSAAO