Transient carriage and low-level colonization of orally administrated lytic and temperate phages in the gut of mice

Hongduo Bao,Ademola Olaniran,Maoda Pang,Khashayar Shahin,Yan Zhou,Hui Zhang,Ran Wang,Shujiao Zhu,Stefan Schmidt

doi:10.1186/s43014-020-00029-7

Abstract

Many studies have shown the efficacy of phage therapy in reducing gastrointestinal pathogens. However, it is unclear whether phages can successfully colonize the gut when administered in an adequate amount for a long time. About 1 × 108 PFU/mL of purified lytic phage PA13076 or temperate phage BP96115 were fed daily to mice via drinking water over 31 days, to elucidate the distribution of phages in the gastrointestinal tract. At day 16 and 31, six different segments of the gastrointestinal tract with their contents, including stomach, duodenum, jejunum, ileum, cecum, colon, and fresh feces, were aseptically collected. The phage titers were determined using the double-layered plate method with S. Enteritidis ATCC 13076 or S. Pullorum SPu-109 used as host cells. The results indicated that a small portion of administered phages survived exposure to gastric acid and entered the intestinal tract. The prevalence of phages in the gastrointestinal tract was lower than 1% of the primary phage count. Highest phage titers were detected in the cecum with 104 ~ 105 PFU/g, and most of the phages were eliminated from the body via feces with 106 PFU/g. On day 16 and day 31, the same level of phage titers in different segments of the gastrointestinal tract indicated that the colonization of phages had reached saturation at day 16. These results demonstrate transient phage carriage and low-level colonization of orally administrated lytic and temperate gut phages in mice.Graphical abstract

Highlights

The colonization of livestock by pathogenic bacteria poses a significant problem in industrialized farming and is a major source of human foodborne illness
As temperate phages may mediate gene transfer from one bacterial cell to another, they are generally avoided for direct use as therapeutics (Gordillo Altamirano and Barr 2019; Górski et al 2003)
Distribution of the phages in the gastrointestinal tract Significantly increased phage loads were detected in all analyzed gastrointestinal tract segments of treated mice for the lytic gut phage PA13076 (Fig. 1a), and the temperate phage BP96115 (Fig. 1b), indicating that both phages were transiently carried along the gastrointestinal tract

Summary

Introduction

The colonization of livestock by pathogenic bacteria poses a significant problem in industrialized farming and is a major source of human foodborne illness. Phage preparations usually contain large amounts of bacterial endotoxin due to host cell lysis (Gu et al 2011). Even small amounts of LPS (1 ng/mL) present in phage preparations can induce cytokine production, pyrogenic reactions, and septic shock in humans and experimental animals (Abaev et al 2013; Romanovsky et al 1996). Studying the distribution of phages in the gastrointestinal environment is an essential basis for understanding their role in the gut ecosystem. Limited data on the distribution of phages in the gut and their ability to enter the animal tissue and bloodstream remains a major problem. Phage survival, as well as gut colonization and distribution in the gastrointestinal tract, are still poorly understood. This study aimed to elucidate the abundance and distribution of phage particles in the gastrointestinal tract when mice were orally fed phages for 1 month

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