Open Access
Protein A-mediated multicellular behavior in Staphylococcus aureus
(American Society for Microbiology, 2008) Merino Barberá, Nekane; Toledo Arana, Alejandro; Vergara Irigaray, Marta; Valle Turrillas, Jaione; Solano Goñi, Cristina; Calvo, Enrique; Lopez, Juan Antonio; Foster, Timothy J.; Penadés, José R.; Lasa Uzcudun, Íñigo; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
The capacity of Staphylococcus aureus to form biofilms on host tissues and implanted medical devices is one of the major virulence traits underlying persistent and chronic infections. The matrix in which S. aureus cells are encased in a biofilm often consists of the polysaccharide intercellular adhesin (PIA) or poly-N-acetyl glucosamine (PNAG). However, surface proteins capable of promoting biofilm development in the absence of PIA/PNAG exopolysaccharide have been described. Here, we used two-dimensional nano-liquid chromatography and mass spectrometry to investigate the composition of a proteinaceous biofilm matrix and identified protein A (spa) as an essential component of the biofilm; protein A induced bacterial aggregation in liquid medium and biofilm formation under standing and flow conditions. Exogenous addition of synthetic protein A or supernatants containing secreted protein A to growth media induced biofilm development, indicating that protein A can promote biofilm development without being covalently anchored to the cell wall. Protein A-mediated biofilm formation was completely inhibited in a dose-dependent manner by addition of serum, purified immunoglobulin G, or anti-protein A-specific antibodies. A murine model of subcutaneous catheter infection unveiled a significant role for protein A in the development of biofilm-associated infections, as the amount of protein A-deficient bacteria recovered from the catheter was significantly lower than that of wild-type bacteria when both strains were used to coinfect the implanted medical device. Our results suggest a novel role for protein A complementary to its known capacity to interact with multiple immunologically important eukaryotic receptors.
Open Access
Role of biofilm-associated protein bap in the pathogenesis of bovine Staphylococcus aureus
(American Society for Microbiology, 2004) Cucarella, Carme; Tormo Más, María Ángeles; Ubeda, Carles; Trotonda, María Pilar; Monzón, Marta; Peris, Cristòfol; Amorena Zabalza, Beatriz; Lasa Uzcudun, Íñigo; Penadés, José R.; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Staphylococcus aureus is a common cause of intramammary infections, which frequently become chronic, associated with the ability of the bacteria to produce biofilm. Here, we report a relationship between the ability to produce chronic bovine mastitis and biofilm formation. We have classified bovine mastitis S. aureus isolates into three groups based on the presence of particular genetic elements required for biofilm formation: group 1 (ica+ bap+), group 2 (ica+, bap negative), and group 3 (ica negative, bap negative). Overall, animals naturally infected with group 1 and 2 isolates had a lower milk somatic cell count than those infected with isolates of group 3. In addition, Bap-positive isolates were significantly more able to colonize and persist in the bovine mammary gland in vivo and were less susceptible to antibiotic treatments when forming biofilms in vitro. Analysis of the structural bap gene revealed the existence of alternate forms of expression of the Bap protein in S. aureus isolates obtained under field conditions throughout the animal's life. The presence of anti-Bap antibodies in serum samples taken from animals with confirmed S. aureus infections indicated the production of Bap during infection. Furthermore, disruption of the ica operon in a bap-positive strain had no effect on in vitro biofilm formation, a finding which strongly suggested that Bap could compensate for the deficiency of the PIA/PNAG product (a biofilm matrix polysaccharide). Altogether, these results demonstrate that, in the bovine intramammary gland, the presence of Bap may facilitate a biofilm formation connected with the persistence of S. aureus.
Open Access
Expression of the biofilm-associated protein interferes with host protein receptors of Staphylococcus aureus and alters the infective process
(American Society for Microbiology, 2002) Cucarella, Carme; Tormo Más, María Ángeles; Knecht, Erwin; Amorena Zabalza, Beatriz; Lasa Uzcudun, Íñigo; Foster, Timothy J.; Penadés, José R.; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
The adherence of Staphylococcus aureus to soluble proteins and extracellular-matrix components of the host is one of the key steps in the pathogenesis of staphylococcal infections. S. aureus presents a family of adhesins called MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) that specifically recognize host matrix components. We examined the influence of biofilm-associated protein (Bap) expression on S. aureus adherence to host proteins, epithelial cell cultures, and mammary gland sections and on colonization of the mammary gland in an in vivo infection model. Bap-positive strain V329 showed lower adherence to immobilized fibrinogen and fibronectin than isogenic Bap-deficient strain m556. Bacterial adherence to histological sections of mammary gland and bacterial internalization into 293 cells were significantly lower in the Bap-positive strains. In addition, the Bap-negative strain showed significantly higher colonization in vivo of sheep mammary glands than the Bap-positive strain. Taken together, these results strongly suggest that the expression of the Bap protein interferes with functional properties of the MSCRAMM proteins, preventing initial bacterial attachment to host tissues and cellular internalization.

Lasa Uzcudun, Íñigo

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