Isolation and Characterization of Group III Campylobacter jejuni-Specific Bacteriophages From Germany and Their Suitability for Use in Food Production

Bacteriophages: Natural antimicrobial bioadditives for food preservation in active packaging

Developing innovative films and coatings is paramount for extending the shelf life of numerous food products and augmenting the barrier and antimicrobial properties of food packaging materials. Many synthetic chemicals used in active packaging and food storage have the potential to leach into food, posing long-term health risks. It is imperative for active packaging materials to inherently possess biological protective properties to ensure food quality and safety throughout its storage. Bacteriophages, or simply phages, are bacteria-eating viruses that serve as promising natural biocontrol agents and antimicrobial bioadditives in food packaging materials, specifically targeting bacterial foodborne pathogens. These phages are generally recognized as safe (GRAS) by regulatory authorities for food safety applications. They exhibit targeted action against various Gram-positive and -negative foodborne pathogens, including Bacillus spp., Campylobacter spp., Escherichia coli, Listeria monocytogenes, Salmonella spp., Shigella spp., and Vibrio spp., associated with foodborne spoilage and illness without affecting the beneficial microbes. Phage cocktails can be applied directly on food surfaces, incorporated into food packaging materials, or utilized during food processing treatments. Unlike chemical agents, phage activity increases proportionally with the rise in pathogenic bacterial populations. Researchers are exploring various packaging materials to deliver phages with broad host range, stability, and viability ensuring their effectiveness in safeguarding various food systems. The effectiveness of phage immobilization or encapsulation on active food packaging materials depends on various factors, including the characteristics of polymers, the choice of solvents, the type of phage, and its loading efficiency. Factors such as the orientation of phage immobilization on substrates, pH, temperature, exposure to carbohydrates and amino acids, exopolysaccharides, lipopolysaccharides, and metals can also influence phage activity. In this review, we comprehensively discuss the various active packaging systems utilizing bacteriophages as natural biocontrols and antimicrobial bioadditives to reduce the incidence of foodborne illness and enhance consumer confidence in the safety of food products.

A broad host phage, CP6, for combating multidrug-resistant Campylobacter prevalent in poultry meat

Campylobacter is a major cause of bacterial foodborne diarrhea worldwide. Consumption of raw or undercooked chicken meat contaminated with Campylobacter is the most common causative agent of human infections. Given the high prevalence of contamination in poultry meat and the recent rise of multi-drug-resistant (MDR) Campylobacter strains, an effective intervention method of reducing bird colonization is needed. In this study, the Campylobacter-specific lytic phage CP6 was isolated from chicken feces. Phage CP6 exhibited a broad host range against different MDR Campylobacter isolates (97.4% of strains were infected). Some biological characteristics were observed, such as a good pH (3-9) stability and moderate temperature tolerance (<50 ℃). The complete genome sequence revealed a linear double-stranded DNA (178,350 bp, group II Campylobacter phage) with 27.51% GC content, including 209 predicted open reading frames, among which only 54 were annotated with known functions. Phylogenetic analysis of the phage major capsid protein demonstrated that phage CP6 was closely related to Campylobacter phage CPt10, CP21, CP20, IBB35, and CP220. CP6 phage exerted good antimicrobial effects on MDR Campylobacter in vitro culture and reduced CFUs of the host cells by up to 1-log compared with the control in artificially contaminated chicken breast meat. Our findings suggested the potential of CP6 phage as a promising antimicrobial agent for combating MDR Campylobacter in food processing.

Bacteriophages in nature: recent advances in research tools and diverse environmental and biotechnological applications

Bacteriophages infect and replicate within bacteria and play a key role in the environment, particularly in microbial ecosystems and bacterial population dynamics. The increasing recognition of their significance stems from their wide array of environmental and biotechnological uses, which encompass the mounting issue of antimicrobial resistance (AMR). Beyond their therapeutic potential in combating antibiotic-resistant infections, bacteriophages also find vast applications such as water quality monitoring, bioremediation, and nutrient cycling within environmental sciences. Researchers are actively involved in isolating and characterizing bacteriophages from different natural sources to explore their applications. Gaining insights into key aspects such as the life cycle of bacteriophages, their host range, immune interactions, and physical stability is vital to enhance their application potential. The establishment of diverse phage libraries has become indispensable to facilitate their wide-ranging uses. Consequently, numerous protocols, ranging from traditional to cutting-edge techniques, have been developed for the isolation, detection, purification, and characterization of bacteriophages from diverse environmental sources. This review offers an exploration of tools, delves into the methods of isolation, characterization, and the extensive environmental applications of bacteriophages, particularly in areas like water quality assessment, the food sector, therapeutic interventions, and the phage therapy in various infections and diseases.

A South African Perspective on the Microbiological and Chemical Quality of Meat: Plausible Public Health Implications

Meat comprises proteins, fats, vitamins, and trace elements, essential nutrients for the growth and development of the body. The increased demand for meat necessitates the use of antibiotics in intensive farming to sustain and raise productivity. However, the high water activity, the neutral pH, and the high protein content of meat create a favourable milieu for the growth and the persistence of bacteria. Meat serves as a portal for the spread of foodborne diseases. This occurs because of contamination. This review presents information on animal farming in South Africa, the microbial and chemical contamination of meat, and the consequential effects on public health. In South Africa, the sales of meat can be operated both formally and informally. Meat becomes exposed to contamination with different categories of microbes, originating from varying sources during preparation, processing, packaging, storage, and serving to consumers. Apparently, meat harbours diverse pathogenic microorganisms and antibiotic residues alongside the occurrence of drug resistance in zoonotic pathogens, due to the improper use of antibiotics during farming. Different findings obtained across the country showed variations in prevalence of bacteria and multidrug-resistant bacteria studied, which could be explained by the differences in the manufacturer practices, handling processes from producers to consumers, and the success of the hygienic measures employed during production. Furthermore, variation in the socioeconomic and political factors and differences in bacterial strains, geographical area, time, climatic factors, etc. could be responsible for the discrepancy in the level of antibiotic resistance between the provinces. Bacteria identified in meat including Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, Campylobacter spp., Salmonella spp., etc. are incriminated as pathogenic agents causing serious infections in human and their drug-resistant counterparts can cause prolonged infection plus long hospital stays, increased mortality and morbidity as well as huge socioeconomic burden and even death. Therefore, uncooked meat or improperly cooked meat consumed by the population serves as a risk to human health.

The Biotechnological Application of Bacteriophages: What to Do and Where to Go in the Middle of the Post-Antibiotic Era

Amid the escalating challenges of antibiotic resistance, bacterial infections have emerged as a global threat. Bacteriophages (phages), viral entities capable of selectively infecting bacteria, are gaining momentum as promising alternatives to traditional antibiotics. Their distinctive attributes, including host specificity, inherent self-amplification, and potential synergy with antibiotics, render them compelling candidates. Phage engineering, a burgeoning discipline, involves the strategic modification of bacteriophages to enhance their therapeutic potential and broaden their applications. The integration of CRISPR-Cas systems facilitates precise genetic modifications, enabling phages to serve as carriers of functional genes/proteins, thereby enhancing diagnostics, drug delivery, and therapy. Phage engineering holds promise in transforming precision medicine, addressing antibiotic resistance, and advancing diverse applications. Emphasizing the profound therapeutic potential of phages, this review underscores their pivotal role in combatting bacterial diseases and highlights their significance in the post-antibiotic era.

Bacteriophage cocktail application for Campylobacter mitigation - from in vitro to in vivo

BACKGROUND

Effective strategies are urgently needed to control Campylobacteriosis, one of the most important foodborne gastrointestinal diseases worldwide. Administering bacteriophages (phages) is under evaluation as a possible intervention strategy in primary poultry production to reduce the public health risk of human infection. A major challenge is the translation of results from small-scale animal studies to large broiler flocks. In this study, the in vitro lytic activity of 18 Campylobacter-specific group II phages and 19 group III phages were examined singly, and in different combinations from the same group and from both groups using a planktonic killing assay. Based on these results, a combination of phage NCTC 12,673 (group III) and vB_CcM-LmqsCPL1/1 (group II) was selected for in vivo application in a seeder bird model to study its effectiveness under conditions as close as possible to field conditions. One hundred eighty Ross 308 broiler chickens were divided into a control and a treatment group. Ten days post hatch, seeder birds were orally inoculated with the C. jejuni target strain. Phages were administered via drinking water at a total concentration of 107 PFU/mL four, three, and two days before necropsy.

RESULTS

Combining group II and group III phages resulted in significantly higher in vitro growth inhibition against the C. jejuni target strain BfR-CA-14,430 than single application or combinations of phages from the same group. The results of the animal trial showed that the application of the two phages significantly reduced Campylobacter counts in cloacal swabs. At necropsy, Campylobacter counts in colonic content of the treatment group were significantly reduced by 2 log10 units compared to the control group.

CONCLUSIONS

We demonstrated that combining phages of groups II and III results in significantly increased lytic activities. The in vitro results were successfully translated into practical application in a study design close to field conditions, providing new data to apply phages in conventional broiler flocks in the future. Phage application reduced the fecal Campylobacter excretion and Campylobacter concentrations in the colon of broilers.

Bacteriophages Isolated From Turkeys Infecting Diverse Salmonella Serovars

Salmonella is one of the leading causes of foodborne illnesses worldwide. The rapid emergence of multidrug-resistant Salmonella strains has increased global concern for salmonellosis. Recent studies have shown that bacteriophages (phages) are novel and the most promising antibacterial agents for biocontrol in foods because phages specifically kill target bacteria without affecting other bacteria, do not alter organoleptic properties or nutritional quality of foods, and are safe and environmentally friendly. Due to the vast variation in Salmonella serotypes, large numbers of different and highly virulent Salmonella phages with broad host ranges are needed. This study isolated 14 Salmonella phages from turkey fecal and cecal samples. Six phages (Φ205, Φ206, Φ207, ΦEnt, ΦMont, and Φ13314) were selected for characterization. These phages were from all three families in the Caudovirales order. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that each phage had a unique structural protein profile. Each phage had a distinct host range. Φ207 and ΦEnt are both siphophages. They shared eight hosts, including seven different Salmonella serovars and one Shigella sonnei strain. These two phages showed different restriction banding patterns generated through EcoRI or HindIII digestion, but shared three bands from EcoRI digestion. ΦEnt displayed the broadest and very unusual host range infecting 11 Salmonella strains from nine serovars and three Shigella strains from two species, and thus was further characterized. The one-step growth curve revealed that ΦEnt had a short latent period (10 min) and relatively large burst size (100 PFU/infected cell). ΦEnt and its host showed better thermal stabilities in tryptic soy broth than in saline at 63 or 72°C. In the model food system (cucumber juice or beef broth), ΦEnt infection [regardless of the multiplicity of infections (MOIs) of 1, 10, and 100] resulted in more than 5-log10 reduction in Salmonella concentration within 4 or 5 h. Such high lytic activity combined with its remarkably broad and unusual host range and good thermal stability suggested that ΦEnt is a novel Salmonella phage with great potential to be used as an effective biocontrol agent against diverse Salmonella serovars in foods.

Isolation and Characterization of Lytic Bacteriophages Specific for Campylobacter jejuni and Campylobacter coli

In this study, two lytic bacteriophages designated as vB_CjP and vB_CcM were isolated and evaluated for their ability to combat multidrug-resistant bacteria Campylobacter jejuni and Campylobacter coli, respectively. A morphological analysis of these phages by transmission electron microscopy revealed that the vB-CjP bacteriophage had a mean head dimension of 66.6 ± 2.1 nm and a short non-contractile tail and belongs to the Podoviridae family, whereas vB_CcM had a mean head dimension of 80 ± 3.2 nm, a contractile tail, and a length calculated to be 60 ± 2.5 nm and belongs to the Myoviridae family. The results of the host range assay showed that vB_CjP could infect 5 of 10 C. jejuni isolates, whereas vB_CcM could infect 4 of 10 C. coli isolates. Both phages were thermostable and did not lose their infectivity and ability to lyse their host following exposure to 60 °C for 10 min; furthermore, phage particles were relatively stable within a pH range of 6–8. A one-step growth curve indicated that the phages produced estimated burst sizes of 110 and 120 PFU per infected cell with latent periods of 10 and 15 min, for vB-CjP and vB-CcM, respectively. The lytic activity of these phages against planktonic Campylobacter showed that these phages were able to control the growth of Campylobacter in vitro. These results suggest that these phages have a high potential for phage applications and can reduce significantly the counts of Campylobacter spp. The lytic activity of vB-CjP and vB-CcM phages at different (MOIs) against multidrug resistance Campylobacter strains was evaluated. The bacterial growth was slightly delayed by both phages, and the highest efficiency of both phages was observed when MOI = 1 was applied.

Campylobacter Bacteriophage Cocktail Design Based on an Advanced Selection Scheme

Campylobacteriosis is a worldwide-occurring disease and has been the most commonly reported zoonotic gastrointestinal infection in the European Union in recent years. The development of successful phage-based intervention strategies will require a better understanding of phage-bacteria interactions to facilitate advances in phage cocktail design. Therefore, this study aimed to investigate the effects of newly isolated group II and group III phages and their combinations on current Campylobacter field strains. A continuous workflow for host range and efficiency of plating (EOP) value determination was combined with a qPCR-based phage group identification and a liquid-based planktonic killing assay (PKA). An advanced analysis scheme allowed us to evaluate phage cocktails by their efficacy in inhibiting bacterial population growth and the resulting phage concentrations. The results of this study indicate that data obtained from PKAs are more accurate than host range data based on plaque formation (EOP). Planktonic killing assays with Campylobacter appear to be a useful tool for a straightforward cocktail design. Results show that a group II phage vB_CcM-LmqsCP218-2c2 and group III phage vB_CjM-LmqsCP1-1 mixture would be most promising for practical applications against Campylobacter coli and Campylobacter jejuni.