Open Access

Because of its antimicrobial properties, nonthermal plasma could serve as an alternative to chemical antisepsis in wound treatment. Therefore, this study investigated the inactivation of biofilm-embedded Pseudomonas aeruginosa SG81 by a surface barrier-discharged (SBD) plasma for 30, 60, 150 and 300 s. In order to optimize the efficacy of the plasma, different carrier gases (argon, argon admixed with 1% oxygen, and argon with increased humidity up to approx. 80%) were tested and compared against 0.1% chlorhexidine digluconate (CHG) exposure for 600 s. The antimicrobial efficacy was determined by calculating the difference between the numbers of colony-forming units (CFU) of treated and untreated biofilms. Living bacteria were distinguished from dead by fluorescent staining and confocal laser scanning microscopy. Both SBD plasmas and CHG showed significant antimicrobial effects compared to the untreated control. However, plasma treatment led to a higher antimicrobial reduction (argon plasma 4.9 log₁₀ CFU/cm², argon with admixed oxygen 3 log₁₀ CFU/cm², and with increased gas humidity 2.7 log₁₀ CFU/cm² after 300 s) compared to CHG. In conclusion, SBD plasma is suitable as an alternative to CHG for inactivation of Pseudomonas aeruginosa embedded in biofilm. Further development of SBD plasma sources and research on the role of carrier gases and humidity may allow their clinical application for wound management in the future.

Aim: The efficacy of antimicrobial compounds included in wound dressings has been determined using the quantitative suspension test according to EN 13727 before. However, as suspension tests are not an accurate reflection of the conditions under which wound antiseptics are used, it was investigated if a disc carrier test would yield results simulating practical conditions on wound surfaces. A silver-leaching foam wound dressing was used for evaluation of the disc carrier test method. Method: The disc carriers consisted of circular stainless-steel discs measuring 2 cm in diameter and 1.5 mm in thickness, complying with the requirements of EN 10088-2. Carriers were contaminated with Staphylococcus aureus, methicillin-resistant S. aureus or Pseudomonas aeruginosa, respectively, together with an artificial wound secretion and left to dry at room temperature for 30 min. The wound dressings being tested were placed on the discs for the length of the exposure time, and after neutralization by thioglycolate in phosphate-buffered saline the number of surviving test organisms was then counted. The logarithmic reduction factor was calculated from the difference between the initial inoculum and the number of recovered test organisms. Results: The disc carrier test allowed determination of an antimicrobial efficacy in a realistic setting. It also imposed more stringent requirements on efficacy over time than the quantitative suspension test. The silver foam wound dressing showed a time-dependent antimicrobial efficacy. After 24-hour application time, the reduction factors against S. aureus, P. aeruginosa and the methicillin-resistant S. aureus were 1.9 ± 0.15, 2.1 ± 0.14 and 3.1 ± 0.18, respectively. Conclusion: The disc carrier test was a useful method for testing the antimicrobial efficacy of a foam silver dressing. The antimicrobial dressing exhibited an antimicrobial effect after 3 h and achieved a reduction >2 log against the tested bacterial strains in the presence of a simulated wound secretion after 24 h.

The exact qualitative and quantitative analysis of wound healing processes is a decisive prerequisite for optimizing wound care and for therapy control. Transepidermal water loss (TEWL) measurements are considered to be the standard procedure for assessing the progress of epidermal wound healing. The damage to the stratum corneum correlates with an increased loss of water through the skin barrier. This method is highly susceptible to failure by environmental factors, in particular by temperature and moisture. This study was aimed at comparing TEWL measurements and in vivo laser scanning microscopy (LSM) for the characterization of the epidermal wound healing process. LSM is a high-resolution in vivo method permitting to analyze the kinetics and dynamics of wound healing at a cellular level. While the TEWL values for the individual volunteers showed a wide scattering, LSM permitted the wound healing process to be clearly characterized at the cellular level. However, a comparison between the two methods was very difficult, because the results provided by LSM were images and not numerical. Therefore, a scoring system was set up which evaluates the stages of wound healing. Thus, the healing process could be numerically described. This method is independent of any environmental factors. Providing morphologically qualitative and numerically quantitative analyses of the wound healing process and being far less vulnerable to failure, LSM is advantageous over TEWL.