An organoselenium compound inhibits Staphylococcus aureus biofilms on hemodialysis catheters in vivo

Abstract

Colonization of central venous catheters (CVCs) by pathogenic bacteria leads to catheter-related bloodstream infections (CRBSIs). These colonizing bacteria form highly antibiotic-resistant biofilms. Staphylococcus aureus is one of the most frequently isolated pathogens in CRBSIs. Impregnating CVC surfaces with antimicrobial agents has various degrees of effectiveness in reducing the incidence of CRBSIs. We recently showed that organoselenium covalently attached to disks as an antibiofilm agent inhibited the development of S. aureus biofilms. In this study, we investigated the ability of an organoselenium coating on hemodialysis catheters (HDCs) to inhibit S. aureus biofilms in vitro and in vivo. S. aureus failed to develop biofilms on HDCs coated with selenocyanatodiacetic acid (SCAA) in either static or flowthrough continuous-culture systems. The SCAA coating also inhibited the development of S. aureus biofilms on HDCs in vivo for 3 days. The SCAA coating was stable and nontoxic to cell culture or animals. This new method for coating the internal and external surfaces of HDCs with SCAA has the potential to prevent catheter-related infections due to S. aureus.

Fig 1

Selenocyanatodiacetic acid (SCAA) coating on hemodialysis catheters (HDCs) inhibits development of S. aureus biofilms. S. aureus strain AH133 was inoculated into microtiter wells containing TSB plus 3 μg erythromycin/ml. The microtiter plate assay was done as described in Materials and Methods. (a) Biofilm biomass was quantified by the crystal violet assay (absorbance at 595 nm). (b) Numbers of viable organisms (CFU) present in the biofilms. To determine stability of the SCAA coating on exposure to aqueous environment, coated and uncoated HDC segments were soaked in PBS for indicated times and used in the microtiter biofilm assay. Values represent the means of 3 or more independent experiments ± standard deviations.

Fig 2

SCAA visibly reduces S. aureus biofilm formation on HDCs. Outer and inner surfaces of uncoated (a and b, respectively) and SCAA-coated (c and d, respectively) HDC segments were examined by confocal laser scanning microscopy (CLSM) at ×20 magnification after 48 h of incubation.

Fig 3

SCAA coating inhibits the development of S. aureus biofilm on HDCs in the flowthrough continuous-culture biofilm system. Biofilms were developed for 5 days, and the outer and inner surfaces of uncoated (a and b, respectively) and SCAA-coated (c and d, respectively) HDC segments examined by CLSM at ×20 magnification.

Fig 4

Selenium eluted from SCAA-coated HDC segments is not cytotoxic. COS-1 cells were plated and incubated for 48 h with DMEM containing (a) 0.9% NaCl, (b) 0.9% NaCl incubated with uncoated HDC segments, (c) 0.9% NaCl incubated with SCAA-coated HDC segments (0.074 mM selenium), or (d) 1 mM selenium (from SCAA). Magnification is ×53. Following imaging, cells were removed from the surfaces of the wells and duplicate wells were counted using a hemocytometer. Cell counts are indicated for each condition.