Abstract
Enterococcus faecalis is a commensal of the human gastrointestinal tract; it is also an opportunistic pathogen and one of the leading causes of hospital-acquired infections. E. faecalis produces biofilms that are highly resistant to antibiotics, and it has been previously reported that certain genes of the epa operon contribute to biofilm-associated antibiotic resistance. Despite several studies examining the epa operon, many gene products of this operon remain annotated as hypothetical proteins. Here, we further explore the epa operon; we identified epaQ, currently annotated as encoding a hypothetical membrane protein, as being important for biofilm formation in the presence of the antibiotic daptomycin. Mutants with disruptions of epaQ were more susceptible to daptomycin relative to the wild type, suggesting its importance in biofilm-associated antibiotic resistance. Furthermore, the Δ epaQ mutant exhibited an altered biofilm architectural arrangement and formed small aggregates in liquid cultures. Our cumulative data show that epa mutations result in altered polysaccharide content, increased cell surface hydrophobicity, and decreased membrane potential. Surprisingly, several epa mutations significantly increased resistance to the antibiotic ceftriaxone, indicating that the way in which the epa operon impacts antibiotic resistance is antibiotic dependent. These results further define the key role of epa in antibiotic resistance in biofilms and in biofilm architecture. IMPORTANCE E. faecalis is a common cause of nosocomial infection, has a high level of antibiotic resistance, and forms robust biofilms. Biofilm formation is associated with increased antibiotic resistance. Therefore, a thorough understanding of biofilm-associated antibiotic resistance is important for combating resistance. Several genes from the epa operon have previously been implicated in biofilm-associated antibiotic resistance, pathogenesis, and competitive fitness in the GI tract, but most genes in this locus remain uncharacterized. Here, we examine epaQ, which has not been characterized functionally. We show that the Δ epaQ mutant exhibits reduced biofilm formation in the presence of daptomycin, altered biofilm architecture, and increased resistance to ceftriaxone, further expanding our understanding of the contribution of this operon to intrinsic enterococcal antibiotic resistance and biofilm growth.
Original language | English (US) |
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Article number | e00078-19 |
Journal | Journal of bacteriology |
Volume | 201 |
Issue number | 18 |
DOIs | |
State | Published - Sep 1 2019 |
Bibliographical note
Funding Information:This work was supported by the National Institutes of Health (grant AI122742) as well as the NIH’s National Center for Advancing Translational Sciences (grants TL1R002493 and UL1TR002494). Parts of this work were carried out in the Characterization Facility at the University of Minnesota, which receives partial support from the National Science Foundation (NSF) through the MRSEC program. Polysaccharide composition analysis was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy grant (DESC0015662) at the Center for Plant and Microbial Complex Carbohydrates in the Complex Carbohydrate Research Center (CCRC) at the University of Georgia.
Funding Information:
We thank Julia Willett for providing the attachment assay and eDNA quantification protocols and Aaron Barnes for guidance with microscopy. This work was supported by the National Institutes of Health (grant AI122742) as well as the NIH's National Center for Advancing Translational Sciences (grants TL1R002493 and UL1TR002494). Parts of this work were carried out in the Characterization Facility at the University of Minnesota, which receives partial support from the National Science Foundation (NSF) through the MRSEC program. Polysaccharide composition analysis was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy grant (DESC0015662) at the Center for Plant and Microbial Complex Carbohydrates in the Complex Carbohydrate Research Center (CCRC) at the University of Georgia. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, NSF, or CCRC.
Publisher Copyright:
© 2019 American Society for Microbiology.
Keywords
- Cell wall polysaccharide
- Cell wall stress
- Functional genomics
- Intrinsic resistance to antibiotics
PubMed: MeSH publication types
- Journal Article