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. 2021 Jul 16:11:698807.
doi: 10.3389/fcimb.2021.698807. eCollection 2021.

Characterization of an Enterococcus faecalis Bacteriophage vB_EfaM_LG1 and Its Synergistic Effect With Antibiotic

Min Song  1 , Dongmei Wu  1 , Yang Hu  1 , Haiyan Luo  1 , Gongbo Li  1
Affiliations

Characterization of an Enterococcus faecalis Bacteriophage vB_EfaM_LG1 and Its Synergistic Effect With Antibiotic

Min Song et al. Front Cell Infect Microbiol. .

Abstract

Enterococcus faecalis is a Gram-positive opportunistic pathogen that could cause pneumonia and bacteremia in stroke patients. The development of antibiotic resistance in hospital-associated E. faecalis is a formidable public health threat. Bacteriophage therapy is a renewed solution to treat antibiotic-resistant bacterial infections. However, bacteria can acquire phage resistance quite quickly, which is a significant barrier to phage therapy. Here, we characterized a lytic E. faecalis bacteriophage Vb_EfaM_LG1 with lytic activity. Its genome did not contain antibiotic resistance or virulence genes. Vb_EfaM_LG1 effectively inhibits E. faecalis growth for a short period, and phage resistance developed within hours. However, the combination of antibiotics and phage has a tremendous synergistic effect against E. faecalis, prevents the development of phage resistance, and disrupts the biofilm efficiently. Our results show that the phage-antibiotic combination has better killing efficiency against E. faecalis.

Keywords: Enterococcus faecalis; antibiotic resistance; bacteriophage; phage therapy; phage-antibiotic combination.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Biological characterization of E. faecalis phage vB_EfaM_LG1. The plaque (A) and transmission electron micrograph (B) of LG1. (C) The optimal MOI test of phage. (D) The one-step growth curve of LG1. (E) The adsorption rate of LG1 against host strain ef118 within 60 min.
Figure 2
Figure 2
Genomic characterization of vB_EfaM_LG1. LG1 is a dsDNA phage with 231 proteins predicted based on sequence homology and five tRNA genes.
Figure 3
Figure 3
Stability of LG1. (A) Phage LG1 is stable under pH4~11 but significantly inactivated under pH4 or above pH11. (B) LG1 is inactivated by 80°C treatment. (C) LG1 is non-sensitive to chloroform treatment. (D) LG1 is stable for 3 months without a significant decrease of titer when stored at 4°C. ND, not detected.
Figure 4
Figure 4
Phage-antibiotic synergism. (A) Phage could only inhibit the growth of E. faecalis for several hours, and then the phage resistance mutant grows to a high density. (B) The phage-antibiotic combination has better efficacy in destroying the biofilm than phage or antibiotic alone (***P < 0.05).
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