Organo-Selenium-Containing Polyester Bandage Inhibits Bacterial Biofilm Growth on the Bandage and in the Wound

Abstract

The dressing material of a wound plays a key role since bacteria can live in the bandage and keep re-infecting the wound, thus a bandage is needed that blocks biofilm in the bandage. Using an in vivo wound biofilm model, we examined the effectiveness of an organo-selenium (OS)-coated polyester dressing to inhibit the growth of bacteria in a wound. Staphylococcus aureus (as well as MRSA, Methicillin resistant Staph aureus), Stenotrophomonas maltophilia, Enterococcus faecalis, Staphylococcus epidermidis, and Pseudomonas aeruginosa were chosen for the wound infection study. All the bacteria were enumerated in the wound dressing and in the wound tissue under the dressing. Using colony-forming unit (CFU) assays, over 7 logs of inhibition (100%) was found for all the bacterial strains on the material of the OS-coated wound dressing and in the tissue under that dressing. Confocal laser scanning microscopy along with IVIS spectrum in vivo imaging confirmed the CFU results. Thus, the dressing acts as a reservoir for a biofilm, which causes wound infection. The same results were obtained after soaking the dressing in PBS at 37 °C for three months before use. These results suggest that an OS coating on polyester dressing is both effective and durable in blocking wound infection.

Keywords: anti-biofilm formation; dressing technology; organo-selenium; wound healing.

Figure 1

Graph of the colony-forming units of (A) Staphylococcus aureus GFP AH133, (B) Stenotrophomonas maltophilia ATCC^® 53199™, (C) Pseudomonas aeruginosa PAO1 GFP, (D) Enterococcus faecalis GFP, (E) Methicillin-resistant Staphylococcus aureus CI 1, (F) Methicillin-resistant Staphylococcus aureus CI 2, and (G) Staphylococcus epidermidis CI biofilms formed on untreated polyester and 1% Se-AAEMA polyester. Values represent the means of triplicate experiments ± SEM. A two-tailed unpaired t test was used to determine statistical significance. Untreated polyester has AAEMA but no selenium.

Figure 2

In Vitro study. Representative confocal laser scanning microscopy images of (A) Staphylococcus aureus GFP AH133, (B) Pseudomonas aeruginosa PAO1 GFP, and (C) Enterococcus faecalis GFP biofilm formed on untreated polyester and 1% Se-AAEMA polyester. Untreated polyester has AAEMA but no selenium. (D–F) are the same samples as those above however they have Se-AAEMA. As seen all the bacteria are eliminated. The bar is 200 μm.

Figure 3

Graph of the colony-forming units of (A) Staphylococcus aureus GFP AH133, (B) Pseudomonas aeruginosa PAO1 GFP, (C) Methicillin-resistant Staphylococcus aureus CI 1, and (D) Methicillin-resistant Staphylococcus aureus CI 2 biofilms formed on the polyester dressings and in the tissue under the polyester dressings on a mouse wound. Values represent the means of six replicate experiments ± SEM. A two-tailed unpaired t test was used to determine statistical significance. Untreated polyester has AAEMA but no selenium.

Figure 4

Mouse wounds after 5 days. Representative confocal laser scanning microscopy images of (A) Staphylococcus aureus GFP AH133 with untreated polyester showing bacteria in the AAEMA bandage, and (B) is the same except it is with a Se-AAEMA bandage, while (E) is the tissue under bandage (A), and (F) is the tissue under bandage (B). (C) is Pseudomonas aeruginosa PAO1 GFP biofilms formed on the AAEMA treated polyester dressings and (D) is the same as (A) except it is with the SeAAEMA treated dressing. (G) is the tissue under the polyester dressings (A), and (H) is the tissue under the SeAAEMA bandage (D). Bar is 100 μm.

Figure 5

Graphs of the colony-forming units recovered from the effect of AAEMA and SeAAEMA coated polyester dressing (A) S. aureus Lux Xen29 and (B) P. aeruginosa Lux Xen5 in the polyester dressings and the mouse wound tissue. Untreated polyester has AAEMA but no selenium.

Figure 6

Representative IVIS in vivo live images of (A) S. aureus Lux Xen29 under AAEMA polyester dressing and (B) Se-AAEMA polyester dressing. (C) P. aeruginosa Lux Xen5 biofilms formed under the AAEMA polyester dressings and (D) the Se-AAEMA polyester dressing.

Figure 7

Stability study of bandage after one month in PBS at 37 °C. The inhibitory effect of the organo-selenium coating is long-lasting against Staphylococcus aureus GFP AH133 biofilms formed on untreated polyester and 1% Se-AAEMA polyester, which were previously soaked in 1× PBS (pH = 7.4) for three months. Values represent the means of quadruplicate experiments ± SEM. (A) two-tailed unpaired t test was used to determine statistical significance. Representative confocal laser scanning microscopy images of (B) Staphylococcus aureus GFP AH133 biofilms formed on untreated polyester and (C) 1% Se-AAEMA polyester, which were previously soaked in 1× PBS (pH = 7.4) for three months. Untreated polyester has AAEMA but no selenium. Bar is 200 m.