Impact of Phage Therapy on Multidrug-Resistant Escherichia coli Intestinal Carriage in a Murine Model

Abstract

Introduction: The growing resistance of bacteria to antibiotics is a major global public health concern. An important reservoir of this resistance is the gut microbiota. However, limited data are available on the ability of phage therapy to reduce the digestive carriage of multidrug-resistant bacteria.

Materials and methods: Four novel lytic phages were isolated in vitro for efficacy against an extended-spectrum beta-lactamase-producing (ESBL) Escherichia coli strain also resistant to carbapenems through a carbapenemase OXA-48. The first step was to develop models of ESBL E. coli digestive carriage in mice. The second step was to test the efficacy of an oral and rectal phage therapy (a cocktail of four phages or microencapsulated phage) to reduce this carriage.

Results: The two most intense models of digestive carriage were obtained by administering amoxicillin (0.5 g·L^-1) continuously in the drinking water (Model 1) or pantoprazole (0.1 g·L^-1) continuously in the drinking water, combined with amoxicillin (0.5 g·L^-1), for the first 8 days (Model 2). Oral administration of the phage cocktail to Model 1 resulted in a transient reduction in the concentration of ESBL E. coli in the faeces 9 days after the bacterial challenge (median = 5.33 × 10⁸ versus 2.76 × 10⁹ CFU·g^-1, p = 0.02). In contrast, in Model 2, oral or oral + rectal administration of this cocktail did not alter the bacterial titre compared to the control (area under the curve, AUC, 3.49 × 10⁹; 3.41 × 10⁹ and 3.82 × 10⁹ for the control, oral and oral + rectal groups, respectively; p-value > 0.8 for each two-by-two group comparison), as well as the administration of an oral microencapsulated phage in Model 1 (AUC = 8.93 × 10⁹ versus 9.04 × 10⁹, p = 0.81).

Conclusions: Oral treatment with amoxicillin promoted digestive carriage in mice, which was also the case for the addition of pantoprazole. However, our study confirms the difficulty of achieving efficacy with phage therapy to reduce multidrug-resistant bacterial digestive carriage in vivo.

Keywords: Escherichia coli; drug resistance; enterobacteriaceae; extended-spectrum beta-lactamase; intestinal carriage; multidrug-resistant bacteria; phage therapy.

Figure 1

Murine model of ESBL E. coli intestinal colonisation (6 mice per group) (A), Experimental protocol. (B), Faecal concentration of ESBL E. coli.

Figure 2

Experiment 1: oral cocktail of phages (A), Experimental protocol. (B), Faecal concentration of ESBL E. coli. Control group (n = 6), oral bacteriophages group (n = 6).

Figure 3

Experiment 2: microencapsulated phages (A), Experimental protocol. (B), Faecal concentration of ESBL E. coli. Control group (n = 4), oral microencapsulated phages group (n = 8).

Figure 4

Experiment 3: oral and rectal cocktail of phages with pantoprazole (A), Experimental protocol. (B), Faecal concentration of ESBL E. coli. Placebo group (n = 8), oral phages group (n = 8), oral and rectal phages group (n = 8).