Dawan, Jirapat

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Dawan, Jirapat
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jirapat.da@kmitl.ac.th

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    Antibiofilm strategies using mixed disinfectants and cubosome nanocarriers to combat Staphylococcus aureus on sandblasted stainless steel disc surfaces
    (2025-09-01)
    Dawan, Jirapat
    ;
    Guo, Yuyuan
    ;
    Lee, Sang Soo
    ;
    Kim, Jin Chul
    Bacterial biofilms are complex communities in which microorganisms are adhered and encapsulated in a self-produced extracellular polymeric material (EPS) matrix. Biofilm acts as a protective barrier, enhancing the resistance of bacteria to environmental stressors, cleaning agents and antimicrobial treatments. Therefore, this study aimed to evaluated the effectiveness of a mixed disinfectant suspension (MIX) against Staphylococcus aureus biofilms on sandblasted stainless steel disc surfaces. A cubic phase containing MIX was prepared, and its anti-biofilm ability was assessed in comparison to free MIX. The susceptibility of S. aureus ATCC 15,564 (SA<sup>ATCC</sup>) and multidrug-resistant S. aureus CCARM 3080 (SA<sup>CCARM</sup>) biofilms to single and mixed disinfectants (MIX) was evaluated. The incorporation of MIX into cubosomes was performed to evaluate its potential enhancement in antibiofilm activity. 1% MIX demonstrated the most effective anti-biofilm activity. Extracellular DNA (eDNA) and polysaccharides were also significantly reduced in biofilms treated with 1% MIX. TEM analysis revealed that 1% MIX effectively disrupted bacterial cell clusters within the biofilms. The incorporation of 1% MIX into cubosomes enhanced its antibiofilm activity, with cubosome-encapsulated MIX exhibiting superior results compared to free MIX. This study demonstrates the effectiveness of a mixed disinfectant suspension in reducing S. aureus biofilms on sandblasted stainless steel disc surfaces. Furthermore, the incorporation of MIX into lipid-based nanocarriers, such as cubosomes, enhanced its antibiofilm efficacy compared to the free disinfectant.
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    Mechanistic insights into mixed bile salt–weak base disinfectants against wild-type and multidrug-resistant Staphylococcus aureus biofilms
    (2026-12-01)
    Dawan, Jirapat
    ;
    Yoo, Yong Hyeok
    ;
    Kim, Jin Chul
    ;
    Lee, Sang Soo
    Staphylococcus aureus biofilms on stainless-steel surfaces show high tolerance to disinfectants, particularly in multidrug-resistant (MDR) strains, posing risks in food and pharmaceutical processing. Repurposing Generally Recognized as Safe (GRAS) compounds for low-dose biofilm control is therefore attractive. This study evaluated the antibacterial and antibiofilm efficacy and key mechanisms of mixed bile salt–weak base disinfectants against wild-type and MDR S. aureus biofilms. In brief, sodium cholate (CHO) and sodium chenodeoxycholate (CHE) were combined with ammonium hydroxide (AMH) or sodium bicarbonate (BIC) and tested against SA. ATCC and a multidrug-resistant SA. CCARM strains. Antibacterial activity and interactions were determined by minimum inhibitory concentration and checkerboard assays. Biofilms on sandblasted stainless-steel discs were assessed by viable cell counts, biofilm formation index, and extracellular DNA and polysaccharide levels. Transmission electron microscopy and quantitative real-time PCR of selected genes were used to examine structural damage and stress-response modulation. All preparations showed antibacterial activity, with higher MICs in the MDR strain. CHO + AMH displayed clear synergy against both strains, whereas CHE + BIC ranged from synergistic to additive. On stainless steel, CHO + AMH produced the greatest and most sustained reduction in biofilm-associated cells and the lowest biofilm formation indices, together with marked depletion of matrix components. TEM revealed extensive envelope disruption and cell damage under CHO + AMH compared with single agents. Combination treatments altered stress-response and efflux gene expression in patterns consistent with severe cellular injury and limited adaptive capacity. Accordingly, mixed bile salt–weak base disinfectants, particularly CHO + AMH, enhance antibacterial and antibiofilm activity against wild-type and MDR S. aureus by targeting cell envelopes, biofilm matrix, and stress-adaptation pathways. These GRAS-based combinations represent promising low-dose disinfectant candidates for controlling S. aureus biofilms on stainless-steel surfaces in processing environments.
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    Enhanced eradication of Staphylococcus aureus biofilms by combination disinfectants: comparative analysis of antimicrobial and anti-biofilm efficacy
    (2025-10-01)
    Dawan, Jirapat
    ;
    Pomseethong, Panalee
    ;
    Hwang, Jeong Seon
    ;
    Kim, Jae Kyu
    ;
    Lee, Sang Soo
    Biofilms of Staphylococcus aureus pose significant challenges in various environments due to their resilience against antimicrobial agents. This study evaluated the antimicrobial efficacy of single disinfectant including 0.25% calcium hydroxide, 0.25% sodium hypochlorite, 0.25% deoxycholate, 0.25% poly(vinylpyrrolidone)-iodine complex and combination (0.25%) disinfectant suspensions against S. aureus (SA<sup>ATCC</sup> and SA<sup>CCARM</sup>) biofilms on metal disc surfaces. The results revealed that all treatments significantly reduced biofilm formation compared to the untreated control, with the combination treatment exhibiting the most potent and sustained anti-biofilm activity. After 4 h of incubation, biofilm cells were undetectable under the combination treatment (< 20 CFU/mL), indicating complete eradication. Crystal violet staining and biofilm formation index analysis confirmed that the combination treatment resulted in the lowest biofilm biomass. Additionally, extracellular DNA and polysaccharide levels were markedly reduced, further supporting the disruption of biofilm integrity. Gene expression analysis demonstrated a significant downregulation of biofilm-associated genes, including norB, clpP, clpX, and dnaK, under all treatments, with the combination treatment showing the highest inhibitory effect. Transmission electron microscopy analysis revealed severe morphological alterations and biofilm dispersal in the combination-treated samples. Collectively, these findings suggest that the combination disinfectant formulation is the most effective strategy for eradicating S. aureus biofilms, offering a promising approach for biofilm control in medical, industrial, and environmental applications.