Salmonella Enteritidis Bacteriophages Isolated from Kenyan Poultry Farms Demonstrate Time-Dependent Stability in Environments Mimicking the Chicken Gastrointestinal Tract

Salmonella Enteritidis Bacteriophages

The threat of multidrug-resistant bacteria is a growing concern in the food industry, particularly in relation to outbreaks of Salmonella enterica Enteritidis.

As conventional antibiotics become less effective in treating these infections, the search for alternative solutions is becoming increasingly important.

One possible solution? Bacteriophages or “phages,” which are viruses that specifically infect and destroy bacterial cells. In this study, researchers looked at phages isolated from Kenyan poultry farms and how stable they were in different environments, including simulated stomach and intestinal fluids.

Why it matters

The harsh environment of the chicken gastrointestinal tract can be incredibly taxing for phages, which could compromise their effectiveness in treatment. However, phages that can survive these conditions may have greater therapeutic potential to reduce the incidence of MDR salmonella in poultry products. This exploration of phage stability is a critical step toward finding viable alternatives to conventional antibiotics in the fight against drug-resistant bacteria.

On 16 August 2022, the authors Amos Lucky Mhone, Angela Makumi, Josiah Odaba, Linda Guantai, K M Damitha Gunathilake, Stéphanie Loignon, Caroline Wangari Ngugi, Juliah Khayeli Akhwale, Sylvain Moineau, and Nicholas Svitek published their article: Salmonella Enteritidis Bacteriophages Isolated from Kenyan Poultry Farms Demonstrate Time-Dependent Stability in Environments Mimicking the Chicken Gastrointestinal Tract.

Key points include:

10 different S. Enteritidis phages were isolated from Kenyan poultry farms and evaluated for stability in various pH-adjusted media, incubation temperatures, and simulated gastric and intestinal fluids (SGF and SIF, respectively).
Phages were relatively stable for 12 hours at pH values between 5 and 9 and at temperatures between 25 °C and 42 °C. At pH 3, a loss of viral titer of up to three logs was observed after 3 hours of incubation.
In SGF, phages were stable for 20 minutes, after which they began to lose infectivity. In SIF, phages were relatively stable for up to 2 hours. The effectiveness of phages in controlling Salmonella growth was greatly reduced in media with pH 2 and 3 and in SGF at pH 2.5, while it was less affected in SIF at pH 8.
River water had the strongest negative effect on phages, while the other waters tested had a limited effect on phages.

Abstract

Multi-drug resistant (MDR) Salmonella enterica Enteritidis is one of the major causes of foodborne illnesses worldwide.

This non-typhoidal Salmonella (NTS) serovar is mainly transmitted to humans through poultry products.

Bacteriophages (phages) offer an alternative to antibiotics for reducing the incidence of MDR NTS in poultry farms.

Phages that survive the harsh environment of the chicken gastrointestinal tract (cGIT), which have low pH, high temperatures, and several enzymes, may have a higher therapeutic or prophylactic potential.

In this study, we analysed the stability of 10 different S. Enteritidis phages isolated from Kenyan poultry farms in different pH-adjusted media, incubation temperatures, as well as simulated gastric and intestinal fluids (SGF and SIF, respectively). Furthermore, their ability to persist in water sources available in Kenya, including river, borehole, rain and tap water, was assessed. All phages were relatively stable for 12 h at pHs ranging from 5 to 9 and at temperatures ranging from 25 °C to 42 °C. At pH 3, a loss in viral titre of up to three logs was observed after 3 h of incubation. In SGF, phages were stable for 20 min, after which they started losing infectivity. Phages were relatively stable in SIF for up to 2 h. The efficacy of phages to control Salmonella growth was highly reduced in pH 2- and pH 3-adjusted media and in SGF at pH 2.5, but less affected in SIF at pH 8.

River water had the most significant detrimental effect on phages, while the other tested waters had a limited impact on the phages.

Our data suggest that these phages may be administered to chickens through drinking water and may survive cGIT to prevent salmonellosis in poultry.

Keywords: Salmonella enterica; pH stability; phages; simulated gastric fluid; simulated intestinal fluid.