Staphylococcus epidermidis Uses Distinct Mechanisms of Biofilm Formation To Interfere with Phagocytosis and Activation of Mouse Macrophage-Like Cells 774A.1

Abstract

Assembly of adherent biofilms is the key mechanism involved in Staphylococcus epidermidis virulence during device-associated infections. Aside from polysaccharide intercellular adhesin (PIA), the accumulation-associated protein Aap and the extracellular matrix binding protein Embp act as intercellular adhesins, mediating S. epidermidis cell aggregation and biofilm accumulation. The aim of this study was to investigate structural features of PIA-, Aap-, and Embp-mediated S. epidermidis biofilms in more detail and to evaluate their specific contributions to biofilm-related S. epidermidis immune escape. PIA-, Embp-, and Aap-mediated biofilms exhibited substantial morphological differences. Basically, PIA synthesis induced formation of macroscopically visible, rough cell clusters, whereas Aap-and Embp-dependent biofilms preferentially displayed a smooth layer of aggregated bacteria. On the microscopic level, PIA was found to form a string-like organized extracellular matrix connecting the bacteria, while Embp produced small deposits of intercellular matrix and Aap was strictly localized to the bacterial surface. Despite marked differences, S. epidermidis strains using PIA, Aap, or Embp for biofilm formation were protected from uptake by J774A.1 macrophages, with similarly efficiencies. In addition, compared to biofilm-negative S. epidermidis strains, isogenic biofilm-forming S. epidermidis induced only a diminished inflammatory J774A.1 macrophage response, leading to significantly (88.2 to 88.7%) reduced NF-B activation and 68.8 to 83% reduced interleukin-1␤ (IL-1␤) production. Mechanical biofilm dispersal partially restored induction of NF-B activation, although bacterial cell surfaces remained decorated with the respective intercellular adhesins. Our results demonstrate that distinct S. epidermidis biofilm morphotypes are similarly effective at protecting S. epidermidis from phagocytic uptake and at counteracting macrophage activation, providing novel insights into mechanisms that could contribute to the chronic and persistent course of biofilm-related S. epidermidis foreign material infections.

Accumulation-Associated Protein Enhances Staphylococcus epidermidis Biofilm Formation under Dynamic Conditions and Is Required for Infection in a Rat Catheter Model

“…Multiples studies also have demonstrated a fitness defect resulting from decreased resistance to the host immune response in PIA-negative strains (15,94); however, this difference is negated in our model as a consequence of CP treatment. Additionally, as S. epidermidis produces few virulence factors, the tissue damage observed in the PIA-producing strain most likely was a consequence of the host immune response that again would not be expected in our model due to the severe CP-induced immunosuppression (76) (see Fig.…”

“…S. epidermidis biofilm matrix composition varies between strains and may be composed of a combination of polysaccharide (polysaccharide intercellular adhesin; PIA), proteins (e.g., accumulation-associated protein [Aap] and extracellular matrix-binding protein [Embp]), and/or extracellular DNA (eDNA) (2,(10)(11)(12)(13)(14). Although these components have unique structural characteristics, PIA-, Embp-, and Aap-dependent biofilms all are resistant to phagocytosis due to their ability to inhibit NF-B activation and interleukin-1␤ (IL-1␤) production (15,16). Recently, it also was demonstrated that S. aureus biofilms skew the immune response, generating alternatively activated macrophages (17,18) that promote a fibrotic rather than bactericidal response, thereby facilitating bacterial persistence.…”

Hyaluronan Breakdown Contributes to Immune Defense against Group A Streptococcus

“…Immunostaining-Localization of GAS bacteria during infection of the macrophage cell line MH-S or primary macrophages was determined using the double-fluorescence immunostaining method described previously (20,21). This method is based on the application of two different fixation methods.…”

Antibacterial and Biocompatible Titanium-Copper Oxide Coating May Be a Potential Strategy to Reduce Periprosthetic Infection: An In Vitro Study

“…Staphylococcus epidermidis is recognized as a leading nosocomial pathogen. This microorganism has a strong ability to establish adherent biofilms on artificial surfaces such as central venous catheters, artificial heart valves, and prosthetic joints [36].…”