Efficacy of Lytic Bacteriophage Preparation in Reducing Salmonella In Vitro, on Turkey Breast Cutlets, and on Ground Turkey

Characterization of vB_SalS_PSa2, a T5-like Demerecviridae bacteriophage, and its potential use in food matrices

This study characterizes a newly isolated Demerecviridae phage, named vB_SalS_PSa2, belonging to the phage T5 group. The main variations between vB_SalS_PSa2 and T5 concern structural proteins related to morphology and host recognition. vB_SalS_PSa2 is infective to 19 out of the 25 tested Salmonella enterica (including the rare "Sendai" and "Equine" serotypes) and Escherichia coli isolates, most of them being multidrug resistant. vB_SalS_PSa2 displayed good thermal stability (4-60 °C) and broad pH stability (4.0-12.0). It also exhibited antibacterial activity against S. enterica sv. Paratyphi A Enb50 at 4 °C in milk during the whole tested period (5 d), and for 3-6 h at both 25 and 37 °C. Furthermore, vB_SalS_PSa2 was able to inhibit biofilm formation and to show degradation activity on mature biofilms of E. coli K12 and S. enterica sv. Paratyphi Enb50 in both LB and milk. Altogether, these results indicate that phage vB_SalS_PSa2 is a valuable candidate for controlling foodborne S. enterica and E. coli pathogens.

An Experimental Infection Model in Sheep and Goats to Evaluate Salmonella Colonization in Deep Tissue Lymph Nodes and after Carcass Vascular Rinsing with Bacteriophages in Goats

An animal infection model was evaluated on sheep and goats to confirm which species infected with Salmonella enterica serovar Enteritidis C StR (SE13) would provide a consistent and high frequency of Salmonella colonization in lymph nodes (LNs) without causing undue animal morbidity. Sheep and goats (n = 5) were intradermally inoculated with Salmonella, postincubated for 7 days, and euthanized. Superficial cervical, medial iliac, subiliac, mammary, and popliteal LNs were excised from each carcass. Goat LNs had approximately 53% greater Salmonella level compared to sheep. Also, Salmonella was inconsistently recovered from the sheep LNs. Thus, goats were selected to determine the ability of carcass vascular rinsing (with and without bacteriophages) to reduce Salmonella in infected LNs. Goats with similar characteristics were grouped together before being randomly assigned to 3 postharvest treatments; control (CN, not vascularly rinsed; n = 10), vascularly rinsed with a standard Rinse & Chill® solution (RC; 98.5% water and a blend of saccharides and phosphates; n = 10), or vascularly rinsed with a standard Rinse & Chill® solution plus the addition of bacteriophages (BP; n = 10). Rinse & Chill® system was able to successfully deliver a mean 7.0 log PFU/g to the S. Enteritidis-infected LNs (mean 3.5 log CFU/g). However, neither Rinse & Chill® without bacteriophages nor with bacteriophages caused Salmonella reduction (P > 0.05) compared to the nonrinsed goat carcasses.

Bacteriophages as an alternative for biological control of biofilm-forming Salmonella enterica

Salmonellosis is one of the most common foodborne diseases worldwide. Surface adherence and biofilm formation are among the main strategies evolved by Salmonella to survive under harsh conditions and are risk factors for its spread through the food chain. Owing to the increase in antimicrobial resistance, there is a growing need to develop other methods to control foodborne pathogens, and bacteriophages have been suggested as a potential alternative for this purpose. The aim of this study was to evaluate bacteriophages as a biological control of Salmonella enterica serotypes to inhibit and remove bacterial biofilms. A total of 12 S. enterica isolates were selected for this study, all of which were biofilm producers. Seven bacteriophages were tested, individually and in a cocktail, for their host range and efficiency of plating (EOP). The phage cocktail was evaluated for its antibiofilm effect against the Salmonella biofilms. Phages UPF_BP1, UPF_BP2, UPF_BP3, UPF_BP6, and 10:2 possessed a broad lytic spectrum and could infect all S. enterica strains. Phages 10:2, UPF_BP6, and UPF_BP3 had high EOP in 10, 9, and 9 out of the 12 S. enterica strains, respectively. The cocktail was able to infect all S. enterica strains and had a high EOP in 10 out of 12 S. enterica isolates, presenting a broader host range than any of the tested single phages. A wide variation of inhibition among strains was observed, ranging from 14.72% to 88.53%. Multidrug-resistant and strong biofilm producer strains showed high biofilm inhibition levels by phage cocktail. Our findings demonstrate the ability of the cocktail to prevent biofilm formation and remove formed biofilms of Salmonella. These results indicate that the phage cocktail is a promising candidate to be used as an alternative for the control of Salmonella biofilms through surface conditioning.

Reduction of Nontyphoidal Salmonella enterica in Broth and on Raw Chicken Breast by a Broad-spectrum Bacteriophage Cocktail

Globally, nontyphoidal Salmonella (NTS) causes approximately 150 million foodborne illnesses annually; many of which are linked to poultry products. Thus, improving food safety interventions in the poultry sector can reduce foodborne illness associated with prevalent NTS serotypes. Bacteriophages (phages) have shown promise as food-safe alternatives to current antimicrobial practices. However, challenges such as limited host range, bactericidal effectiveness in practical production settings, and the risk of developing host resistance remain as barriers for the widespread use of phages in commercial poultry operations. A broad-spectrum three-phage cocktail was evaluated against S. enterica subsp. enterica serotypes Enteritidis, Typhimurium, and Kentucky. The impact of multiplicity of infection (MOI) on NTS growth was assessed in broth at 22°C for 18 hours (h). Then, phage cocktail efficacy was evaluated on raw chicken breast samples inoculated with the NTS cocktail and stored at 10°C or 22°C for 0, 1, and 5 days or 0, 4, 8, and 16 h, respectively. Most probable number (MPN) calculations were performed for NTS counts on chicken after phage treatment and storage at 10°C to account for samples with NTS counts below the detection limit. In general, a higher MOI corresponded to reduced NTS growth; however, residual nutrition in growth media and initial NTS contamination level affected samples treated with the phage cocktail at identical MOIs. On chicken, phage cocktail treatment significantly reduced NTS counts at 10°C and 22°C. After storage at 10°C for 5 days, NTS counts were reduced by >3.2 log compared to the control. After storage at 22°C for 16 h, NTS counts were reduced by >1.7 log compared to the control. Overall, the phage cocktail was effective at reducing a diverse set of prominent NTS strains in broth and on raw chicken breast, highlighting its potential for commercialization and use alongside other hurdles in poultry production.

Phage-Based Biosanitation Strategies for Minimizing Persistent Salmonella and Campylobacter Bacteria in Poultry

Control strategies to minimize pathogenic bacteria in food animal production are one of the key components in ensuring safer food for consumers. The most significant challenges confronting the food industry, particularly in the major poultry and swine sectors, are antibiotic resistance and resistance to cleaning and disinfection in zoonotic bacteria. In this context, bacteriophages have emerged as a promising tool for zoonotic bacteria control in the food industry, from animals and farm facilities to the final product. Phages are viruses that infect bacteria, with several advantages as a biocontrol agent such as high specificity, self-replication, self-limitation, continuous adaptation, low inherent toxicity and easy isolation. Their development as a biocontrol agent is of particular interest, as it would allow the application of a promising and even necessary "green" technology to combat pathogenic bacteria in the environment. However, bacteriophage applications have limitations, including selecting appropriate phages, legal restrictions, purification, dosage determination and bacterial resistance. Overcoming these limitations is crucial to enhance phage therapy's effectiveness against zoonotic bacteria in poultry. Thus, this review aims to provide a comprehensive view of the phage-biosanitation strategies for minimizing persistent Salmonella and Campylobacter bacteria in poultry.

Biocontrol of Salmonella Typhimurium in milk, lettuce, raw pork meat and ready-to-eat steamed-chicken breast by using a novel bacteriophage with broad host range

Salmonella spp., one of the most frequently reported bacteria, causes foodborne illness and economic losses. Due to the threat of increasing antibiotic resistant foodborne pathogens, application of bacteriophages as novel antibacterial agents in food matrices has become an emerging strategy. In this study, a novel Salmonella phage PS3-1 with high lytic activity against Salmonella Typhimurium was identified from previously isolated phages. PS3-1 belonged to the class Caudoviricetes with a broad host range, and had relatively short latent period (15 min), large burst size (92 PFU/cell), high pH stability (pH 3.0-11.0) and thermal tolerance (4-60 °C). Genome sequencing analysis showed that PS3-1 genome consisted of 107,110 bp DNA, without antibiotic resistance and virulence related genes. The results of growth curve and time-kill assay showed that PS3-1 not only inhibited the growth of S. Typhimurium, but also effectively decreased the viable cell counts (0.30-4.72 log) after 24-h incubation at 7, 25 and 37 °C (P < 0.05). Moreover, >1.28 log of established biofilm cells were effectively removed after 24-h treatment with PS3-1. Besides, PS3-1 significantly reduced the viability of S. Typhimurium in milk, lettuce, raw pork meat and ready-to-eat steamed-chicken breast at different temperatures (P < 0.05). These results demonstrated that PS3-1 may be an excellent antibacterial agent for controlling S. Typhimurium in food industry.

A Genomic Analysis of the Bacillus Bacteriophage Kirovirus kirovense Kirov and Its Ability to Preserve Milk

Bacteriophages are widely recognized as alternatives to traditional antibiotics commonly used in the treatment of bacterial infection diseases and in the food industry, as phages offer a potential solution in combating multidrug-resistant bacterial pathogens. In this study, we describe a novel bacteriophage, Kirovirus kirovense Kirov, which infects members of the Bacillus cereus group. Kirovirus kirovense Kirov is a broad-host-range phage belonging to the Caudoviricetes class. Its chromosome is a linear 165,667 bp double-stranded DNA molecule that contains two short, direct terminal repeats, each 284 bp long. According to bioinformatics predictions, the genomic DNA contains 275 protein-coding genes and 5 tRNA genes. A comparative genomic analysis suggests that Kirovirus kirovense Kirov is a novel species within the Kirovirus genus, belonging to the Andregratiavirinae subfamily. Kirovirus kirovense Kirov demonstrates the ability to preserve and decontaminate B. cereus from cow milk when present in milk at a concentration of 104 PFU/mL. After 4 h of incubation with the phage, the bacterial titer drops from 105 to less than 102 CFU/mL.

A review of food additives to control the proliferation and transmission of pathogenic microorganisms with emphasis on applications to raw meat-based diets for companion animals

Raw meat-based diets (RMBDs) or sometimes described as biologically appropriate raw food (BARFs) are gaining in popularity amongst dog and cat owners. These pet guardians prefer their animals to eat minimally processed and more “natural” foods instead of highly heat-processed diets manufactured with synthetic preservatives. The market for RMBDs for dogs and cats is estimated at $33 million in the United States. This figure is likely underestimated because some pet owners feed their animals raw diets prepared at home. Despite their increasing demand, RMBDs have been plagued with numerous recalls because of contamination from foodborne pathogens like Salmonella, E. coli, or Campylobacter. Existing literature regarding mitigation strategies in RMBD's for dogs/cats are very limited. Thus, a comprehensive search for published research was conducted regarding technologies used in meat and poultry processing and raw materials tangential to this trade (e.g., meats and poultry). In this review paper, we explored multiple non-thermal processes and GRAS approved food additives that can be used as potential antimicrobials alone or in combinations to assert multiple stressors that impede microbial growth, ultimately leading to pathogen inactivation through hurdle technology. This review focuses on use of high-pressure pasteurization, organic acidulants, essential oils, and bacteriophages as possible approaches to commercially pasteurize RMBDs effectively at a relatively low cost. A summary of the different ways these technologies have been used in the past to control foodborne pathogens in meat and poultry related products and how they can be applied successfully to impede growth of enteric pathogens in commercially produced raw diets for companion animals is provided.

Isolation and characterization of Escherichia coli O157: H7 novel bacteriophage for controlling this food-borne pathogen

Escherichia coli O157: H7 is known as a high-risk food-born pathogen, and its removal is vital for maintaining food safety. The increasing trend of food-borne diseases caused by this bacterium and other pathogens indicates the low efficiency of the methods to remove pathogens from foodstuffs. One of the new and effective methods is to use of a bio-control agent called bacteriophage, which has shown good function in eliminating and reducing pathogens. In this study, a novel bacteriophage was isolated and identified from the slaughterhouse wastewater to control E. coli O157: H7. This bacteriophage belonged to the Myoviridae family. Two bacterial genera including E. coli and Salmonella, were allocated to determine the bacteriophage host range; the result showed that the anti- Salmonella effect of phage was low. The phage was stable at high temperature (80°C) and caused an acceptable reduction in the E. coli O157: H7 (4.18 log CFU / mL for 10 hours). The isolated bacteriophage was corroborated to be completely safe based on the whole genome sequencing and lack of any virulence factor from the host bacteria. Considering the characteristics of this phage and its function in vitro, this bacteriophage may be used as an effective bio-control agent in foods with the possible E. coli O157: H7 -induced contamination.

The lytic siphophage vB_StyS-LmqsSP1 reduces Salmonella Typhimurium isolates on chicken skin

Phage-based biocontrol of bacteria is considered as a natural approach to combat food-borne pathogens. Salmonella spp. are notifiable and highly prevalent pathogens that cause foodborne diseases globally. In this study, six bacteriophages were isolated and further characterized that infect food-derived Salmonella isolates from different meat sources. The siphovirus VB_StyS-LmqsSP1, which was isolated from a cow´s nasal swab, was further subjected to in-depth characterization. Phage-host interaction investigations in liquid medium showed that vB_StyS-LmqsSP1 can suppress the growth of Salmonella spp. isolates at 37°C for ten hours and reduce the bacterial titer at 4°C significantly. A reduction of 1.4 to 3 log units was observed in investigations with two food-derived Salmonella isolates and one reference strain under cooling conditions using MOIs of 10⁴ and 10⁵. Phage application on chicken skin resulted in a reduction of about 2 log units in the tested Salmonella isolates from the first three hours throughout a one-week experiment at cooling temperature and an MOI of 10⁵. The one-step growth curve analysis using vB_StyS-LmqsSP1 demonstrated a 60-min latent period and a burst size of 50-61 PFU/infected cell for all tested hosts. Furthermore, the genome of the phage was determined to be free from genes causing undesired effects. Based on the phenotypic and genotypic properties, LmqsSP1 was assigned as a promising candidate for biocontrol of Salmonella Typhimurium in food. Importance: Salmonella enterica is one of the major global causes of foodborne enteritis in humans. The use of chemical sanitizers for reducing bacterial pathogens in the food chain can result in the spread of bacterial resistance. Targeted and clean label intervention strategies can reduce Salmonella contamination in food. The significance of our research demonstrates the suitability of a bacteriophage (vB_StyS-LmqsSP1) for biocontrol of Salmonella enterica serovar Typhimurium on poultry due to its lytic efficacy under conditions prevailing in food production environments.

The Age of Phage: Friend or Foe in the New Dawn of Therapeutic and Biocontrol Applications?

Extended overuse and misuse of antibiotics and other antibacterial agents has resulted in an antimicrobial resistance crisis. Bacteriophages, viruses that infect bacteria, have emerged as a legitimate alternative antibacterial agent with a wide scope of applications which continue to be discovered and refined. However, the potential of some bacteriophages to aid in the acquisition, maintenance, and dissemination of negatively associated bacterial genes, including resistance and virulence genes, through transduction is of concern and requires deeper understanding in order to be properly addressed. In particular, their ability to interact with mobile genetic elements such as plasmids, genomic islands, and integrative conjugative elements (ICEs) enables bacteriophages to contribute greatly to bacterial evolution. Nonetheless, bacteriophages have the potential to be used as therapeutic and biocontrol agents within medical, agricultural, and food processing settings, against bacteria in both planktonic and biofilm environments. Additionally, bacteriophages have been deployed in developing rapid, sensitive, and specific biosensors for various bacterial targets. Intriguingly, their bioengineering capabilities show great promise in improving their adaptability and effectiveness as biocontrol and detection tools. This review aims to provide a balanced perspective on bacteriophages by outlining advantages, challenges, and future steps needed in order to boost their therapeutic and biocontrol potential, while also providing insight on their potential role in contributing to bacterial evolution and survival.

Effects of bacteriophages and peroxyacetic acid applications on beef contaminated with Salmonella during different grinding stages

Research has suggested that the incidence of Salmonella in ground beef may be associated with contaminated lymph nodes that are not removed from trimmings destined for grinding. In this study, we tested the application of bacteriophages and peroxyacetic acid solutions on trimmings and on coarse and fine ground beef to simulate different scenarios of contamination. Overall, peroxyacetic acid applications did not reduce Salmonella loads on ground beef when applied on trimmings or at any stage of grinding. When applied on contaminated trim, bacteriophage solutions at 1 × 10⁸ PFU/g and 1 × 10⁹ PFU/g reduced more than 1 log cfu/g of Salmonella. When applied directly on contaminated coarse or fine ground beef, bacteriophage solutions at 1 × 10⁹ PFU/g reduced approximately 1.6 log cfu/g. Results of this study suggest that bacteriophage applications on contaminated, comminuted beef may be used as an aid to decrease Salmonella loads.

Effect of two lytic bacteriophages against multidrug-resistant and biofilm-forming Salmonella Gallinarum from poultry

1. Salmonella Gallinarum (SG) infections cause fowl typhoid, which leads to important economic losses. Multidrug resistance (MDR) and the capacity for bacteria to form biofilms could play an important role in the persistence of SG in poultry flocks resulting in intermittent disease outbreaks. The aim of the following study was to assess the lytic activity of two new bacteriophages (Salmonella phages UPF_BP1 and UPF_BP2) against MDR and biofilm-forming SG. 2. Forty-six strains of SG, isolated in 2015, were characterised by antimicrobial resistance, biofilm formation profiles and susceptibility to two new bacteriophages. 3. Of these strains, 24% were multidrug resistant and more than 80% formed biofilm, with no statistical difference between incubation temperatures (42°C or 22°C). With regard to the lytic activity of the phages, 85% of strains were susceptible to at least one phage. Of these, 74% were lysed by both phages, including MDR and biofilm producing strains. 4. The use of salmonella phages UPF_BP1 and UPF_BP2 were shown to be promising alternatives for the biological control of fowl typhoid.

Application of MS bacteriophages on contaminated trimmings reduces Escherichia coli O157 and non-O157 in ground beef

According to the United States Food and Drug Administration (FDA) agency, bacteriophage solutions targeting the serotype O157:H7 are Generally Recognized as Safe (GRAS) to control STEC during beef processing. However, outbreaks involving the "Big Six" STEC increased the industry concern about those serotypes. The objective of this study was to test the efficacy of MS bacteriophages to reduce the "Big Six" non-O157 STEC in beef. The lysing efficacy of phages isolated for each specific serotype varied from 96.2% to 99.9% in vitro. When applied to contaminated trim, reductions ranging from 0.7 to 1.3 Log of all STEC were observed in ground beef. Bacteriophages may provide an additional barrier against the "Big Six" STEC in ground beef. Results of this research provide support documentation to the FDA to extend GRAS status for bacteriophages as processing aids against all adulterant STEC.

Isolation, characterization and application of a polyvalent phage capable of controlling Salmonella and Escherichia coli O157:H7 in different food matrices

Salmonella Enteritidis, Salmonella Typhimurium, and Escherichia coli O157:H7 are the most important foodborne pathogens, causing serious food poisoning outbreaks worldwide. Bacteriophages are increasingly considered as novel antibacterial agents to control foodborne pathogens. In this study, 8 Salmonella phages and 10 E. coli O157:H7 phages were isolated from chicken products. A polyvalent phage PS5 capable of infecting S. Enteritidis, S. Typhimurium, and E. coli O157:H7 was further characterized and its efficacy in reducing these foodborne pathogens was evaluated in in vitro and in foods. Morphology, one-step growth, and stability assay showed that phage PS5 was a myovirus, with relatively short latent periods, large burst sizes, and high stability. Genome sequencing analysis revealed that the genome of PS5 does not contain any genes associated to antibiotic resistance, toxins, lysogeny, and virulence factors. In broth, phage PS5 significantly decreased the viable counts of all the three bacterial hosts by more than 1.3 log CFU/mL compared to controls after 2 h of incubation at 4 °C and 24 °C. In foods, treatment with PS5 also resulted in significant reductions of viable counts of all the three bacterial hosts compared to controls at temperatures tested. This is the first report on single phage capable of simultaneously controlling S. Enteritidis, S. Typhimurium and E. coli O157:H7 in both in vitro and in foods.

Salmonella Infantis and Salmonella Enteritidis specific bacteriophages isolated form poultry faeces as a complementary tool for cleaning and disinfection against Salmonella

Salmonellosis represents an important public health concern. Several authors point out the inefficiency of the cleaning and disinfection protocols to remove the bacteria from the field. For this reason, innovative techniques, as bacteriophages, could be implemented to control the bacteria. The main objectives of this study were to assess the effect of bacteriophages against Salmonella Infantis and Salmonella Enteritidis on farm surfaces, and to evaluate bacteriophage procedure application as sanitiser against Salmonella in field conditions. Thus, most prevalent serovars in poultry production were selected (Salmonella Infantis and Salmonella Enteritidis) to contaminate farm facilities. Then, two specific bacteriophages isolated from poultry faeces were applied against them. Results showed Salmonella Infantis and Salmonella Enteritidis decreased of 4.55 log₁₀CFU/mL and 3.85 log₁₀CFU/mL, respectively; the maximum reduction in Salmonella was the 5^th day, after 10⁸ PFU/mL and 10³ PFU/mL bacteriophage application. These results highlight bacteriophages as a promising tool together with cleaning and disinfection.

Overcoming barriers to phage application in food and feed

Bacteriophages (phages) can play a useful role as narrow spectrum antimicrobials in food safety and in food production. Consumer attitudes towards traditional additives have led to a search for natural, potentially clean label, alternatives. At the same time, the rise in antimicrobial resistance has created a need for alternative antimicrobials for disease prevention and treatment in animal husbandry. Phages represent a viable option for both of these applications. We highlight important barriers which should be considered to improve the chance of a positive outcome when using phages in food and food production. These include the feasibility of adding high concentrations of phages, the physico-chemical properties of the food or target, how and when phages are applied, and which phages are chosen.

SalmoFresh™ effectiveness in controlling Salmonella on romaine lettuce, mung bean sprouts and seeds

The purpose of this study was to determine the effectiveness of a commercial Salmonella bacteriophage mixture (SalmoFresh™ 6-phage strains) and to compare its effectiveness with a chlorinated water treatment to reduce Salmonella on produce and seeds at different temperatures and storage times. Two sets of experiments were designed to test phage and chlorinated water effectiveness on produce at 2, 10 and 25 °C at different storage times (1, 24, 48 and 72 h). First, SalmoFresh™ was applied to the surface of lettuce, mung bean sprouts and mung bean seeds that were spot-inoculated with a five Salmonella strain mixture (Newport, Braenderup, Typhimurium, Kentucky, and Heidelberg, 105 CFU/mL) by spraying phages onto lettuce (n = 48 pieces, 3×3 cm2 per treatment) and sprouts (n = 48 pieces per treatment). A second set of experiments (scaled-up) consisted in the application of phages by immersion to Salmonella adulterated lettuce (600 g), 300 g sprouts (300 g) or mung bean seeds (30 g) in a phage cocktail (108 PFU/mL) for 15 min (lettuce and sprouts) or 1 h (seeds). Another group of samples was washed with chlorinated water and yet another group was treated with a combination of chlorinated water followed by phage cocktail. Each experiment was repeated three times by quadruplicates. After the treatments for spot-inoculated and scaled-up experiments, lettuce and sprouts were separated into different lots (10 g/lot) and stored at 2, 10 and 25 °C; Salmonella was enumerated after 1, 24, 48 and 72 h. Adulterated phage-treated seeds were packaged and stored dry at 25 °C. Salmonella was enumerated after 72 h of storage. Groups of phage treated mung bean seeds (720 g) were germinated, and the reduction in Salmonella determined. Results of microplate virulence assays indicated that SalmoFresh™ reduced (P = 0.007) Salmonella by an average of 5.34 logs CFU/mL after 5 h at 25 °C. Spraying SalmoFresh™ onto lettuce and sprouts reduced Salmonella by 0.76 and 0.83 log10 CFU/g, respectively (P < 0.01). Immersion of produce in a phage solution was better at killing Salmonella P < 0.05) than spraying it onto the surface, reducing Salmonella by 2.43 and 2.16 log10 CFU/g on lettuce and sprouts, respectively. SalmoFresh™ was an effective biocontrol intervention to reduce Salmonella on lettuce and sprouts. On seeds, although a reduction was observed, Salmonella was able to grow exponentially during germination; therefore, the phage cocktail was not effective on mung bean seeds or sprouts obtained from adulterated seeds. The combination of hurdles, chlorination fallowed by the phage cocktail was the most effective treatment to reduce Salmonella on lettuce and sprouts.

Application of a Phage Cocktail for Control of Salmonella in Foods and Reducing Biofilms

Salmonella contamination in foods and their formation of biofilms in food processing facility are the primary bacterial cause of a significant number of foodborne outbreaks and infections. Broad lytic phages are promising alternatives to conventional technologies for pathogen biocontrol in food matrices and reducing biofilms. In this study, 42 Salmonella phages were isolated from environmentally-sourced water samples. We characterized the host range and lytic capacity of phages LPSTLL, LPST94 and LPST153 against Salmonella spp., and all showed a wide host range and broad lytic activity. Electron microscopy analysis indicated that LPSTLL, LPST94, and LPST153 belonged to the family of Siphoviridae, Ackermannviridae and Podoviridae, respectively. We established a phage cocktail containing three phages (LPSTLL, LPST94 and LPST153) that had broad spectrum to lyse diverse Salmonella serovars. A significant decrease was observed in Salmonella with a viable count of 3 log10 CFU in milk and chicken breast at either 25 °C or 4 °C. It was found that treatment with phage cocktail was able to significantly reduced biofilm on a 96-well microplate (44-63%) and on a stainless steel surface (5.23 to 6.42 log10). These findings demonstrated that the phage cocktail described in this study can be potentially used as a biological control agent against Salmonella in food products and also has the effect to reduce Salmonella formed biofilms.

Prevalence, Serotyping, Molecular Typing, and Antimicrobial Resistance of Salmonella Isolated From Conventional and Organic Retail Ground Poultry

Ground poultry is marketed as a healthier alternative to ground beef despite the fact that poultry is a major source of foodborne Salmonella. The objectives of this study were to determine the prevalence of Salmonella in Oklahoma retail ground poultry and to characterize representative isolates by serotyping, antimicrobial resistance, PFGE patterns, and large plasmid profiling. A total of 199 retail ground poultry samples (150 ground turkey and 49 ground chicken) were investigated. The overall prevalence of Salmonella in ground poultry was 41% (82/199), and the incidence in conventional samples (47%, 66/141) was higher than in organic samples (27%, 16/58). The prevalence of Salmonella in organic ground chicken and organic ground turkey was 33% (3/9) and 26% (13/49), respectively. Twenty six Salmonella isolates (19 conventional and 7 organic) were chosen for further characterization. The following six serotypes and number of isolates per serotype were identified as follows: Tennessee, 8; Saintpaul, 4; Senftenberg, 4; Anatum, 4 (one was Anatum_var._15+); Ouakam, 3; and Enteritidis, 3. Resistance to 16 tested antimicrobials was as follows: gentamycin, 100% (26/26); ceftiofur, 100% (26/26); amoxicillin/clavulanic acid, 96% (25/26); streptomycin, 92% (24/26); kanamycin, 88% (23/26); ampicillin, 85% (22/26); cephalothin, 81% (21/26); tetracycline, 35% (9/26); sulfisoxazole, 27% (7/26); nalidixic acid, 15% (4/26); and cefoxitin, 15% (4/26). All isolates were susceptible to amikacin, chloramphenicol, ceftriaxone, and trimethoprim/sulfamethoxazole. All screened isolates were multidrug resistant (MDR) and showed resistance to 4-10 antimicrobials; isolates from organic sources showed resistance to 5-7 antimicrobials. PFGE was successful in clustering the Salmonella isolates into distinct clusters that each represented one serotype. PFGE was also used to investigate the presence of large plasmids using S1 nuclease digestion. A total of 8/26 (31%) Salmonella isolates contained a ∼100 Kb plasmid that was present in all Anatum and Ouakam isolates. In conclusion, the presence of multidrug resistant Salmonella with various serotypes, PFGE profiles, and large plasmids in ground poultry stresses the importance of seeking novel interventions to reduce the risk of this foodborne pathogen. Multidrug resistance (MDR) is considered a high additional risk and continued surveillance at the retail level could minimize the risk for the consumer.

Phages for biocontrol in foods: What opportunities for Salmonella sp. control along the dairy food chain?

Controlling the presence of pathogenic bacteria, such as Salmonella sp., in dairy products production is a burning issue since contamination with Salmonella can occur at any stage of the production chain. The use of Salmonella-phages applied as control agents has gained considerable interest. Nonetheless, Salmonella-phage applications specifically intended for ensuring the safety of dairy products are scarce. This review identifies recent advances in the use of Salmonella-phages that are or could be applied along the dairy food chain, in a farm-to-fork approach. Salmonella-phages can be promising tools to reduce the shedding of Salmonella in cattle, and to reduce and control Salmonella occurrence in postharvest food (such as food additives), and in food processing facilities (such as biosanitizing agents). These control measures, combined with existing methods and other biocontrol agents, constitute new opportunities to reduce Salmonella occurrence along the dairy food production, and consequently to alleviate the risk of Salmonella contamination in dairy products.

Bacteriophages Synergize with the Gut Microbial Community To Combat Salmonella

Antibiotic-resistant bacteria are a global threat. Therefore, alternative approaches for combatting bacteria, especially antibiotic-resistant bacteria, are urgently needed. Using a human gut microbiota model, we demonstrate that bacteriophages (phages) are able to substantially decrease pathogenic Salmonella without perturbing the microbiota. Conversely, antibiotic treatment leads to the eradication of close to all commensal bacteria, leaving only antibiotic-resistant bacteria. An unbalanced microbiota has been linked to many diseases both in the gastrointestinal tract or “nonintestinal” diseases. In our study, we show that the microbiota provides a protective effect against Salmonella. Since phage treatment preserves the healthy gut microbiota, it is a feasible superior alternative to antibiotic treatment. Furthermore, when combating infections caused by pathogenic bacteria, gut microbiota should be considered.

Salmonella infection is one of the main causes of food-borne diarrheal diseases worldwide. Although most Salmonella infections can be cleared without treatment, some cause serious illnesses that require antibiotic treatment. In view of the growing emergence of antibiotic-resistant Salmonella strains, novel treatments are increasingly required. Furthermore, there is a striking paucity of data on how a balanced human gut microbiota responds to Salmonella infection. This study aimed to evaluate whether a balanced gut microbiota protects against Salmonella growth and to compare two antimicrobial approaches for managing Salmonella infection: bacteriophage (phage) treatment and antibiotic treatment. Anaerobically cultivated human intestinal microflora (ACHIM) is a feasible model for the human gut microbiota and naturally inhibits Salmonella infection. By mimicking Salmonella infection in vitro using ACHIM, we observed a large reduction of Salmonella growth by the ACHIM itself. Treatments with phage and antibiotic further inhibited Salmonella growth. However, phage treatment had less impact on the nontargeted bacteria in ACHIM than the antibiotic treatment did. Phage treatment has high specificity when combating Salmonella infection and offers a noninvasive alternative to antibiotic treatment.

IMPORTANCE Antibiotic-resistant bacteria are a global threat. Therefore, alternative approaches for combatting bacteria, especially antibiotic-resistant bacteria, are urgently needed. Using a human gut microbiota model, we demonstrate that bacteriophages (phages) are able to substantially decrease pathogenic Salmonella without perturbing the microbiota. Conversely, antibiotic treatment leads to the eradication of close to all commensal bacteria, leaving only antibiotic-resistant bacteria. An unbalanced microbiota has been linked to many diseases both in the gastrointestinal tract or “nonintestinal” diseases. In our study, we show that the microbiota provides a protective effect against Salmonella. Since phage treatment preserves the healthy gut microbiota, it is a feasible superior alternative to antibiotic treatment. Furthermore, when combating infections caused by pathogenic bacteria, gut microbiota should be considered.

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Reduction of Salmonella in ground chicken using a bacteriophage

This study's goal was to ascertain the effectiveness of a commercially available Salmonella bacteriophage during ground chicken production focusing on: water source, different Salmonella serovars, and time. Salmonella-free boneless, skinless chicken meat was inoculated with 4.0 Log CFU/cm2 of either a cocktail of 3 Salmonella isolates derived from ground chicken (GC) or a cocktail of 3 Salmonella strains not isolated from ground chicken (non-GC). Bacteriophages were spread onto the chicken using sterile tap or filtered water for 30 min or 8 h. Salmonella was recovered using standard plating method. Greater Salmonella reduction was observed when the bacteriophage was diluted in sterile tap water than in sterile filtered water: 0.39 Log CFU/cm2 and 0.23 Log CFU/cm2 reduction after 30 min, respectively (P < 0.05). The non-GC isolates showed reductions of 0.71 Log CFU/cm2 and 0.90 Log CFU/cm2 after 30 min and 8 h, respectively (P < 0.05). The GC isolates were less sensitive to the bacteriophage: 0.39 Log CFU/cm2 and 0.67 Log CFU/cm2 reductions after 30 min and 8 h, respectively (P < 0.05). In conclusion, bacteriophage reduction was dependent on water used to dilute the bacteriophage, Salmonella's susceptibility to the bacteriophage, and treatment time.

Bacteriocins and bacteriophage; a narrow-minded approach to food and gut microbiology

Bacteriocins and bacteriophage (phage) are biological tools which exhibit targeted microbial killing, a phenomenon which until recently was seen as a major drawback for their use as antimicrobial agents. However, in an age when the deleterious consequences of broad-spectrum antibiotics on human health have become apparent, there is an urgent need to develop narrow-spectrum substitutes. Indeed, disruption of the microbial communities which exist on and in our bodies can generate immediate and long-term negative effects and this is particularly borne out in the gut microbiota community whose disruption has been linked to a number of disorders reaching as far as the brain. Moreover, the antibiotic resistance crisis has resulted in our inability to treat many bacterial infections and has triggered the search for damage-limiting alternatives. As bacteriocins and phage are natural entities they are relatively easy to isolate and characterise and are also ideal candidates for improving food safety and quality, forfeiting the need for largely unpopular chemical preservatives. This review highlights the efficacy of both antimicrobial agents in terms of gut health and food safety and explores the body of scientific evidence supporting their effectiveness in both environments.