EbpA vaccine antibodies block binding of Enterococcus faecalis to fibrinogen to prevent catheter-associated bladder infection in mice

Abstract

Enterococci bacteria are a frequent cause of catheter-associated urinary tract infections, the most common type of hospital-acquired infection. Treatment has become increasingly challenging because of the emergence of multiantibiotic-resistant enterococcal strains and their ability to form biofilms on catheters. We identified and targeted a critical step in biofilm formation and developed a vaccine that prevents catheter-associated urinary tract infections in mice. In the murine model, formation of catheter-associated biofilms by Enterococcus faecalis depends on EbpA, which is the minor subunit at the tip of a heteropolymeric surface fiber known as the endocarditis-and biofilm-associated pilus (Ebp). We show that EbpA is an adhesin that mediates bacterial attachment to host fibrinogen, which is released and deposited on catheters after introduction of the catheter into the mouse bladder. Fibrinogen-binding activity resides in the amino-terminal domain of EbpA (EbpANTD), and vaccination with EbpA and EbpANTD, but not its carboxyl-terminal domain or other Ebp subunits, inhibited biofilm formation in vivo and protected against catheter-associated urinary tract infection. Analyses in vitro demonstrated that protection was associated with a serum antibody response that blocked EbpA binding to fibrinogen and the formation of a fibrinogen-dependent biofilm on catheters. This approach may provide a new strategy for the prevention of catheter-associated urinary tract infections.

Catheterization alters bladder ecology to potentiate Staphylococcus aureus infection of the urinary tract

“…Catheterization has been shown to induce a strong, localized inflammatory response that results in tissue damage and edema (26,37,38). Bladder inflammation in this model, measured via a change in bladder weight (37), was significantly increased in mock-infected implanted mice compared with naïve, as expected (naïve vs. PBS-I, 6 h; Fig.…”

“…This results in the up-regulation of virulence factors essential for survival and dissemination (34,35). The findings that urinary catheterization alters the UT environment by triggering the release of Fg (26) and that MRSA UTI is predominately associated with urinary catheterization (26,(36)(37)(38) suggest that MRSA may exploit the presence of this host protein to cause disease. Additionally, this process is known to be true for Enterococcus faecalis, which expresses an endocarditis-and biofilm-associated (Ebp) pilus that is tipped with the Fg-binding protein EbpA.…”

“…Catheterization induces the release of Fg in the bladders of both humans and mice (2,26). Since it is wellestablished that Fg interactions promote MRSA pathogenesis in a diverse range of diseases (28)(29)(30)(31)(32)(33), we hypothesized that Fg may play a key role in altering the UT environment to facilitate MRSA CAUTI.…”

“…Previous studies have shown that the placement of a catheter into the bladder leads to a specific and localized inflammatory response resulting in the release of the host protein fibrinogen (Fg), which accumulates in the bladder and on the catheter (26). Further, urinary catheters removed from humans have been shown to be coated with Fg (27).…”

Enterococcus faecalis Ebp pili are important for cell-cell aggregation and intraspecies gene transfer

“…In addition, deletion of the ebp locus resulted in a diminished capacity of E. faecalis OG1RF to colonize kidneys and bladders in a murine model of ascending urinary tract infection (UTI) and in experimental cathether-associated UTI (CAUTI) Nielsen et al, 2012). Monoclonal antibodies raised specifically against the major pilin component EbpC, as well as polyclonal anti-EbpA antibodies, were shown to provide protection against E. faecalis CAUTI in mice and infective endocarditis in rats (Flores-Mireles et al, 2014;Pinkston et al, 2014).…”