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, 14 (11), e0216762
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Effects of Artificially Introduced Enterococcus Faecalis Strains in Experimental Necrotizing Enterocolitis

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Effects of Artificially Introduced Enterococcus Faecalis Strains in Experimental Necrotizing Enterocolitis

Patrick T Delaplain et al. PLoS One.

Abstract

Enterococcus faecalis is a ubiquitous intestinal symbiont and common early colonizer of the neonatal gut. Although colonization with E. faecalis has been previously associated with decreased pathology of necrotizing enterocolitis (NEC), these bacteria have been also implicated as opportunistic pathogens. Here we characterized 21 strains of E. faecalis, naturally occurring in 4-day-old rats, for potentially pathogenic properties and ability to colonize the neonatal gut. The strains differed in hemolysis, gelatin liquefaction, antibiotic resistance, biofilm formation, and ability to activate the pro-inflammatory transcription factor NF-κB in cultured enterocytes. Only 3 strains, BB70, 224, and BB24 appreciably colonized the neonatal intestine on day 4 after artificial introduction with the first feeding. The best colonizer, strain BB70, effectively displaced E. faecalis of maternal origin. Whereas BB70 and BB24 significantly increased NEC pathology, strain 224 significantly protected from NEC. Our results show that different strains of E. faecalis may be pathogenic or protective in experimental NEC.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Diversity of E. faecalis in rats.
Frequencies of different phenotypes (A) and different strains (B) within a group of E. faecalis isolates (n = 147) from 4-day old rats. (C) Patterns of genomic DNA HindIII fragments of indicated strains. Note dissimilarity of DNA patterns A (55–249, 49–171, and BB70) and B (265, BB24).
Fig 2
Fig 2. Activation of NF-κB by different strains of E. faecalis.
IEC-6 cells were treated with 1010 cfu/ml each strain of E. faecalis and activation of the NF-κB pathway was determined by western blotting for IκBα. β-actin reprobes are included to demonstrate lane load. Representative blots of 3 independent experiments are shown.
Fig 3
Fig 3. Biofilm formation by E. faecalis strains.
(A) Representative biofilm assay and average biofilm formation (n = 3) for different strains grown in LB. (B) Biofilm formation in strain 82 grown in the indicated media (n = 3).

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Grant support

This work was supported by: H.R.F., grant AI 014032 from National Institute of Allergy and Infectious Diseases, https://www.niaid.nih.gov/. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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