Abstract
Bacteriophages can be used successfully to treat pathogenic bacteria in the food chain including zoonotic pathogens that colonize the intestines of farm animals. However, harsh gastric conditions of low pH and digestive enzyme activities affect phage viability, and accordingly reduce their effectiveness. We report the development of a natural protective barrier suitable for oral administration to farm animals that confers acid stability before functional release of bead-encapsulated phages. Escherichia coli bacteriophage ZSEC5 is rendered inactive at pH 2.0 but encapsulation in chitosan–alginate bead with a honey and gelatin matrix limited titer reductions to 1 log10 PFU mL−1. The encapsulated phage titers were stable upon storage in water but achieved near complete release over 4–5 h in a simulated intestinal solution (0.1% bile salt, 0.4% pancreatin, 50 mM KH2PO4 pH 7.5) at 37 °C. Exposure of E. coli O157:H7 to the bead-encapsulated phage preparations produced a delayed response, reaching a maximal reductions of 4.2 to 4.8 log10 CFU mL−1 after 10 h at 37 °C under simulated intestinal conditions compared to a maximal reduction of 5.1 log10 CFU mL−1 at 3 h for free phage applied at MOI = 1. Bead-encapsulation is a promising reliable and cost-effective method for the functional delivery of bacteriophage targeting intestinal bacteria of farm animals.
Highlights
Antibiotic resistance is a serious public health problem worldwide
We have examined the protection afforded by the beads for E. coli O157:H7 bacteriophages under simulated GI conditions and storage conditions with respect to retention of bacteriophage titers
Bacterial strains were grown on tryptic soy agar (TSA; Oxoid, England) overnight and infections carried out in Tryptic Soya Broth (TSB; Oxoid, England) in Erlenmeyer flasks at 37 °C and 120 RPM to reach OD600 approximately 0.3
Summary
Antibiotic resistance is a serious public health problem worldwide. Many intestinal bacterial infections are showing greater virulence and/or persistence (Munot and Kotler 2016). Such resistance phenotypes are generally attributed to the misuse of antibiotics, which have increased invulnerability to hamper the treatment of infection, and indirectly increase the rate of mortality. Enterohemorrhagic Escherichia coli O157:H7 is a zoonotic pathogen frequently isolated from healthy cattle and other farm animals. E. coli O157:H7 can be acquired from direct contact with infected animals (Belongia et al 1991), or through cross-contamination of raw materials in the preparation of foods, or through the consumption of contaminated food (Neil et al 2012). E. coli O157:H7 remains a threat to public health
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