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Determination of Decimal Reduction Time (D-value) using Plasma Activated Water (PAW) for Microbial Decontamination
  • Zulaika Abdullah,
  • SK Zaaba,
  • MT Mustaffa
Zulaika Abdullah

Corresponding Author:[email protected]

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SK Zaaba
MT Mustaffa


Before selecting decontaminants for low and high (sterilizing) levels using an indirect Atmospheric Plasma Jet (APJ), also known as Plasma Activated Water or PAW, the decimal reduction time, D-value, and confidence level should be determined for the most common and persistent single microbes and poly-microbe, especially in the wound healing. Decontaminant solutions or PAW were prepared after exposure to APJ at different gas flow rates and different exposure times. The D-value of a decontaminant solution was determined by inoculating it with a bacterial suspension of 104 to 105 colony-forming units (CFU) and then transferring the mixture to 7 mL of growth media. The mixture was then incubated at optimal conditions. The D-values and confidence levels for various bacteria such as Staphylococcus Aureus (SA), Candida Albicans (CA), and Poly-microbe were determined for the following conditions which are different in gas flow rates (0 ml/min, 1000 ml/min, 1500 ml/min and 2000 ml/min) and exposure times (0s, 30s, 60s, 90s, and 120s). Different gas flow rates observed for SA, CA, and Poly-microbe were 4.15 min, 3.54 min, and 2.64 min respectively. It shows that poly-microbe has the best decimal reduction time compared to the other pathogens. The confidence levels for SA, CA, and poly-microbe were 24.90 min, 21.24 min, and 15.84 min for low-level decontaminants respectively while 49.80 min, 31.68 min, and 42.48 min for high-level decontaminants. At different exposure times, D-CA, SA, and poly-microbe D-values re 3.74 min, 3.40 min, and 2.20 min respectively. For this PAW condition, poly-microbe also showed the best D-value compared to the other pathogens. The confidence levels for SA, CA, and poly-microbe were 22.44 min, 22.40 min, and 13.20 min for low-level decontaminants respectively while 44.88 min, 40.80 min, and 36.40 min for high-level decontaminants. This result also showed that after PAW exposure, the expected decimal reduction time for wound pathogens can be achieved which is higher than 2 min and lower than 10 min. In addition, their confidence level also achieves the expected value which is higher than 10 min for the low level of decontamination and lower than 60 min for high-level decontamination This also demonstrated that PAW can be one of the suggested decontamination methods in wound healing or other medical fields. The suspension studies were an indication of the decontaminant efficacy produced by plasma devices on the microbial. For microbial decontamination, PAW can be used. For low-level and high-level decontaminants, PAW was recommended for poly-microbes compared to other microbes. Although PAW is better used for poly-microbe, PAW also can be applied to SA and CA with the same plasma parameters used. The expected effectiveness from the studied formulations showed that the decontaminant solution or PAW can be recommended for microbial decontamination.
19 Jan 2024Submitted to TechRxiv
09 Feb 2024Published in TechRxiv