Effectiveness of bacteriophages against bloater-causing bacteria Enterobacter cloacae in a model food system

Effectiveness of bacteriophages against bloater-causing bacteria Enterobacter cloacae in a model food system Department of Molecular and Cellular Biology Ashley Reed, Dzhuliya Ignatova, Sandra Kopic, Unique Sardeneta, and Jean Lu Abstract Cucumber fermentation is one of the most important vegetable fermentations in the United States and Europe. Enterobacter cloacae and other gas-producing bacteria can cause bloater defect (the gas pockets or hollow cavities formed in fermented cucumbers) which lowers the quality and the yield of fermented cucumbers, thereby resulting in significant economic losses to the pickling industry. Cost-effective strategies to control E. cloacae and other microbiota need to be developed. Using bacteriophages (phages) to eliminate undesired bacteria is an emerging and promising biocontrol method. Our lab recently isolated two phages, F107E and F115E, infecting E. cloacae strains 107E and 115E, respectively. In this study, we measured 1-step growth curve of phage F107E at a multiplicity of infection (MOI) of 0.01 and 37°C in cucumber juice. The data showed that the eclipse period (not including 10-min adsorption) is only 10 min and the burst size is 28 virions per infected cell. We also evaluated the effectiveness of the two phages as biocontrol agents against E. cloacae in cucumber juice. The infection with F107E at MOI of 100 or 1 effectively eliminated its host within 2 or 3 hours, indicating very high lytic activity against its host. The infection with F115E at MOI of 0.2 or 0.02 caused more than 3 log unit reduction in its host concentration within 2 or 3 hours. But thereafter, phage-resistant bacterial mutants emerged. Thus, phage F107E has a greater potential to be used in commercial cucumber fermentation to eliminate its host in order to reduce bloater defect

Biocontrol of Foodborne Pathogens Using Bacteriophages

Biocontrol of Foodborne Pathogens Using Bacteriophages Dzhuliya Ignatova, Erion Hogan, Simone Dakare, and Jean Lu Department of Molecular and Cellular Biology Abstract Salmonella and Shigella are two important groups of foodborne bacterial pathogens. Salmonella cause an illness called salmonellosis while Shigella cause shigellosis (bacillary dysentery). The most common symptoms of these illnesses are abdominal cramps, diarrhea, and fever. Shigella can also cause bloody diarrhea. It was estimated that each year Salmonella cause 93.8 million cases of gastroenteritis and 155,000 deaths globally. Shigella causes 164.7 million cases and 1.1 million deaths throughout the world yearly. People get these illnesses mainly by eating food or drinking water contaminated Salmonella and Shigella. Thus, to protect the public\u27s health, it is crucial to effectively control of these pathogens in food systems. Bacteriophages (or phages) are viruses that kill bacteria. Phages have emerged as promising biocontrol agents against bacterial pathogens because 1) phages can cause rapid bacterial death, 2) phages do not replicate in foods unless their bacterial hosts are present, 3) phages do not infect humans and other animals, and 4) phages do not alter food color, odor, taste, and nutritional value. This project isolated two phages infecting Salmonella and Shigella. Both phages are tailed phages and belong to Siphoviridae or Myoviridae family. They have broad host range infecting several species. The kinetic study showed that the burst sizes of the two phages are about 100 phage particles per infected cell. Salmonella phage infection in cucumber juice (as a model food system) caused rapid cell lysis within 4 hours, resulting in 5- log unit reduction (or 99.999% decrease) in host cell concentration compared with the control

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