Bacteriophage Administration Reduces the Concentration of Listeria monocytogenes in the Gastrointestinal Tract and Its Translocation to Spleen and Liver in Experimentally Infected Mice

Abstract

To investigate the efficacy of phage supplementation in reducing pathogen numbers, mice were treated via oral gavage with a Listeria monocytogenes phage preparation (designated ListShield) before being orally infected with L. monocytogenes. The concentrations of L. monocytogenes in the liver, spleen, and intestines were significantly lower (P < .05) in the phage-treated than in the control mice. Phage and antibiotic treatments were similarly effective in reducing the levels of L. monocytogenes in the internal organs of the infected mice. However, the significant weight loss detected in the control and antibiotic-treated groups was not observed in the infected, ListShield-treated mice. Long-term (90 days), biweekly treatment of uninfected mice with ListShield did not elicit detectable changes in the microbiota of their large intestines or deleterious changes in their health. Our data support the potential feasibility of using bacteriophages to control proliferation of L. monocytogenes in mice without affecting commensal microbiota composition.

Figure 1

Mean body weights of mice infected with L. monocytogenes and treated with PBS, ListShield, and ampicillin. The results shown are for the days postchallenge with strain Lm370. The standard deviations are indicated with brackets.

Figure 2

Recovery of L. monocytogenes from experimentally-infected mice treated with PBS, ListShield, and ampicillin. The bacterial concentrations are expressed as the number of CFU/g of specimen. The results shown are for 3 days postchallenge with strain Lm370. The standard deviations are indicated with brackets.

Figure 3

Concentrations of various white blood cells (WBC) in uninfected mice after long-term (90 days) ingestion of ListShield. The standard deviations are indicated with brackets. NE: neutrophils; LY: lymphocytes; MO: monocytes; EO: eosinophils; BA: basophils.

Figure 4

DGGE profiles of the microbiota in fecal specimens obtained from uninfected mice after long-term (90 days) ingestion of ListShield. S: standards (DNA from mix of 16S rRNA clones); PBS: profiles of the fecal microbiota in PBS control mice; LMP-102: profiles of the fecal microbiota in ListShield test mice.