Identification of Staphylococcus aureus Proteins Recognized by the Antibody-Mediated Immune Response to a Biofilm Infection

Abstract

Staphylococcus aureus causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an S. aureus biofilm infection, the tibias of rabbits were infected with methicillin-resistant S. aureus to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated ␤-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic S. aureus infections. Previous works have identified S. aureus proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic S. aureus biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.

Staphylococcus aureus adherence to Candida albicans hyphae is mediated by the hyphal adhesin Als3p

“…Cells were washed with sterile PBS and grown in RPMI 1640 (without phenol red) medium supplemented with glutamine and buffered with HEPES (Invitrogen) or complete yeast nitrogen base (YNB) at 37 uC to induce hyphal formation. Meticillin-resistant St. aureus strain M2, originally isolated from a patient with osteomyelitis at the University of Texas Medical Branch, was used in all studies (Brady et al, 2006 Polymicrobial biofilm growth. Microscopic analysis was performed to visualize the interactions between St. aureus and C. albicans as they co-adhered to a surface during biofilm growth.…”

The high-affinity phosphate transporter Pst in Proteus mirabilis HI4320 and its importance in biofilm formation

“…A variation of the in vitro flow reactor system utilized in our laboratory for Staphylococcus aureus biofilm culture (Brady et al, 2006) was used. The reactor system was constructed within a 37 uC incubator and consisted of silicone tubing through which pooled human urine (pH 5.0-6.5) flowed under the control of a peristaltic pump into a waste container.…”

The clinical impact of bacterial biofilms

“…Identification of the components of the biofilm matrix requires specialized staining techniques. Some results, however, indicate that biofilm-specific antibodies develop and can be used as diagnostics [3,18]. This is important, since ordinary sampling techniques may not be sufficient to detect biofilm growing bacteria unless the bacteria are released by ultrasonic treatment [19][20].…”