title: Versatility of Biofilm Matrix Molecules inStaphylococcus epidermidisClinical Isolates and Importance of Polysaccharide Intercellular Adhesin Expression during High Shear Stress.
abstract: Staphylococcus epidermidisis a leading cause of hospital-associated infections, including those of intravascular catheters, cerebrospinal fluid shunts, and orthopedic implants. Multiple biofilm matrix molecules with heterogeneous characteristics have been identified, including proteinaceous, polysaccharide, and nucleic acid factors. Two of the best-studied components inS. epidermidisinclude accumulation-associated protein (Aap) and polysaccharide intercellular adhesin (PIA), produced by the enzymatic products of theicaADBCoperon. Biofilm composition varies by strain as well as environmental conditions, and strains producing PIA-mediated biofilms are more robust. Clinically, biofilm-mediated infections occur in a variety of anatomical sites with diverse physiological properties. To test the hypothesis that matrix composition exhibits niche specificity, biofilm-related genetic and physical properties were compared betweenS. epidermidisstrains isolated from high-shear and low-shear environments. Among a collection of 105 clinical strains, significantly more isolates from high-shear environments carried theicaADBCoperon than did those from low-shear settings (43.9% versus 22.9%,P< 0.05), while there was no significant difference in the presence ofaap(77.2% versus 75.0%,P> 0.05). Additionally, a significantly greater number of high-shear isolates were capable of forming biofilmin vitroin a microtiter assay (82.5% versus 45.8%,P< 0.0001). However, even among high-shear clinical isolates, less than half contained theicaADBClocus; therefore, we selected forica-negative variants with increased attachment to abiotic surfaces to examine PIA-independent biofilm mechanisms. Sequencing of selected variants identified substitutions capable of enhancing biofilm formation in multiple genes, further highlighting the heterogeneity ofS. epidermidisbiofilm molecules and mechanisms.IMPORTANCEStaphylococcus epidermidisis a leading cause of infections related to biomaterials, mostly due to their ability to form biofilm. Biofilm accumulation mechanisms vary, including those that are dependent on specific proteins, environmental DNA (eDNA), or polysaccharide intercellular adhesin (PIA). We found that those isolates obtained from high-shear environments, such as the lumen of a catheter, are more likely to produce PIA-mediated biofilms than those isolates obtained from a low-shear biomaterial-related infection. This suggests that PIA functions as a mechanism that is protective against shear flow. Finally, we performed selection experiments documenting the heterogeneity of biofilm accumulation molecules that function in the absence of PIA, further documenting the biofilm-forming potential ofS. epidermidis.
authors.affiliation: Department of Pathology and Microbiology, Center for Staphylococcal Research, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Schaeffer
authors.affiliation: Department of Pathology and Microbiology, Center for Staphylococcal Research, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Tra-My N
authors.initials: TN
authors.lastname: Hoang
authors.affiliation: Department of Pathology and Microbiology, Center for Staphylococcal Research, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Craig M
authors.initials: CM
authors.lastname: Sudbeck
authors.affiliation: Bioinformatics Service Facility, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Malik
authors.initials: M
authors.lastname: Alawi
authors.affiliation: Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
authors.forename: Isaiah E
authors.initials: IE
authors.lastname: Tolo
authors.affiliation: Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, USA.
authors.forename: D Ashley
authors.initials: DA
authors.lastname: Robinson
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Horswill
authors.affiliation: Institut für Medizinische Mikrobiologie, Virologie und Hygiene, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Rohde
authors.affiliation: Department of Pathology and Microbiology, Center for Staphylococcal Research, University of Nebraska Medical Center, Omaha, Nebraska, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fey
keywords: Staphylococcus epidermidis; accumulation-associated protein; biofilms; catheter-associated infections; polysaccharide intercellular adhesin