Phagovet

Bacteriophages and Salmonella Enteritidis

Salmonella enterica is a major player in the global epidemic of foodborne illness, causing millions of cases each year.

To make matters worse, many S. enterica strains have developed multidrug resistance, making it difficult to treat infections and placing a burden on our healthcare system.

Fortunately, phages offer an alternative solution. Phages – viruses that specifically target and destroy bacterial cells – have shown promise as a biocontrol agent for S. enterica.

In a recent study, researchers isolated fifteen unique phages targeting Salmonella from wastewater, sediment, and chicken feces samples. Of these fifteen phages, three were found to be particularly effective in controlling multi-drug resistant S. enterica strains.

This study highlights the potential of phage therapy as a safe and effective means of controlling Salmonella in animal production.

The authors Yue Li, Peilin Lv, Deshi Shi, Hongze Zhao, Xu Yuan, Xiue Jin, and Xiliang Wang published their findings in their article A Cocktail of Three Virulent Phages Controls Multidrug-Resistant Salmonella Enteritidis Infection in Poultry, dated 6 July 2022.

Topics:

  • Salmonella enterica is a common pathogen of poultry that can also cause foodborne illness in humans.
  • In recent years, many S. enterica isolates have developed multiple drug resistance, making them difficult to treat.
  • Phages (viruses that infect bacteria) are an attractive alternative to conventional antibiotics for treating Salmonella infections.
  • We isolated 15 Salmonella phages from sewage, sediments, and chicken manure. Of these, GRNsp6, GRNsp8, and GRNsp51 had the broadest host range against various strains of Salmonella enteritidis and Typhimurium in vitro.
  • These three phages were selected for further study due to their lytic capabilities (ability to kill bacteria). All three phage types belong to the order Caudovirales and have short latency periods with broad pH and thermal stability.
  • Genomic analysis has shown that these three phages do not encode genes associated with virulence or antibiotic resistance – meaning that they should be safe for use in humans or animals.
  • A cocktail of all three phage types was tested against infection with S. Enteritidis in a chicken model
A Cocktail of Three Virulent Phages Controls Multidrug-Resistant Salmonella Enteritidis Infection in Poultry

Abstract

Salmonella enterica is not only the most common pathogen of poultry and poultry-derived products but is also a significant foodborne pathogen.

In recent years, many S. enterica isolates have exhibited multi-drug resistance, which places huge pressure on global economy and health. Since phages are an attractive alternative to biocontrol pathogens, we isolated a total of 15 Salmonella phages from sewage effluent, sediment, and chicken manure.

The GRNsp1, GRNsp3, GRNsp6, GRNsp21, GRNsp27, GRNsp30, GRNsp50, and GRNsp51 phages exhibited a wide host range against S. enterica serovars Enteritidis and Typhimurium in vitro.

In particular, GRNsp51 exerted highly efficient lytic effects against a large proportion of S. Enteritidis and S. Typhimurium strains isolated from different regions of China.

Meanwhile, GRNsp8 expanded the host range of GRNsp6 and GRNsp51. Based on their host ranges and lytic capacities, GRNsp6, GRNssp8, and GRNsp51 were selected for further investigation.

Morphology, one-step growth curves, and stability assays revealed that GRNsp6, GRNsp8, and GRNsp51 all belong to the Caudovirales order and display relatively short latency periods with broad pH and thermal stability.

Genomic analysis indicated that the genomes of these three phages contained no genes related to virulence, antibiotic resistance, or lysogeny.

In addition, we tested the effectiveness of a cocktail composed of these three phages against S. Enteritidis in a chicken model.

Treatment with the oral phage cocktail 24 h before or alongside Salmonella challenge significantly reduced colonization of the intestinal tract and decreased the mRNA expression of IL-6, IFN-γ, and IL-1β in the duodenum.

Together, these findings indicate that a cocktail of the GRNsp6, GRNsp8, and GRNsp51 phages could serve as an effective antimicrobial therapeutic agent against multidrug-resistant Salmonella in animal production to mitigate infections by multiple zoonotic Salmonella species.

Keywords: Salmonella; genomic; multi-drug resistance; phage cocktail therapy; poultry; virulent phage.

Copyright © 2022 Li, Lv, Shi, Zhao, Yuan, Jin and Wang.