Modified MBEC model. After a 10-minute treatment with PHMB-1, PHMB-2, HOCl-1, or surfactant cleansers followed by 72 hours to allow for regrowth of the surviving P aeruginosa microorganisms, the normalized growth assessment showed approximately 2.56 ± 0.85, 3.40 ± 0.77, 2.67 ± 0.10, and 3.83 ± 1.10 times the time zero growth readings, (Figure 3). Regrowth of silver and saline cleanser-treated groups were 10.52 ± 0.19 and 10.25 ± 0.13 times the time zero readings, respectively. The differences in biofilm regrowth between the saline control and PHMB-1 (mean difference = 8.03; 95% CI, 4.20-11.86; P < .001), PHMB-2 (mean difference = 6.93; 95% CI, 3.10-10.76; P < .001), HOCl-1 (mean difference = 7.11; 95% CI, 3.29-10.95; P < .001), or surfactant cleansers (mean difference = 6.42; 95% CI, 2.59-10.25; P < .001) were statistically significant; however, differences between the PHMB-1, PHMB-2, HOCl-1, and surfactant groups were not significant.
The 72-hour regrowth of MRSA was 1.92 ± 0.62, 1.31 ± 0.34, or 1.59 ± 0.34 times the initial growth values after biofilms were treated with PHMB-1, PHMB-2, or HOCl-1, respectively, whereas the regrowth values for immature MRSA biofilm treated with surfactant, silver, or the saline control were 7.54 ± 1.09, 7.72 ± 0.21, and 6.36 ± 0.70 times higher than the time zero optical density measurements, respectively, as seen in Figure 3. Differences between the PHMB-1, PHMB-2, and HOCl-1 groups were not significant, but differences between the saline control and the PHMB-1 (mean difference = 4.44; 95% CI, 2.02-6.86; P < .001), PHMB-2 (mean difference = 5.04; 95% CI, 2.56-7.52; P < .001), or HOCl-1 (mean difference = 4.82; 95% CI, 2.45-7.20; P < .001) cleanser groups were statistically significant.
For C albicans, the 72-hour regrowth measurements were 2.44 ± 0.91, 4.01 ± 1.31, and 2.71 ± 1.12 times the time zero growth values after treatment with PHMB-1, PHMB-2, or HOCl-1, respectively; treatment with surfactant, silver, or saline resulted in a 13.22 ± 0.46, 13.11 ± 0.06, and 13.36 ± 0.09 times the initial growth values, respectively (Figure 3). The differences in biofilm regrowth between the saline control and the PHMB-1 (mean difference = 10.91; 95% CI, 7.47–14.36; P < .001), PHMB-2 (mean difference = 9.34; 95% CI, 5.89-12.79; P < .001), or HOCl-1 (mean difference = 10.66; 95% CI, 7.21-14.10; P < .001) groups were once again significant, whereas differences between the PHMB-1, PHMB-2, and HOCl-1 groups were not statistically significant.
Ex vivo porcine dermal explant studies
Effect of wound cleansers on P aeruginosa. After a single 10-minute application of the wound cleansers on P aeruginosa biofilms followed by a 72-hour incubation period (ie, to simulate a Friday to Monday dressing change), the PHMB-1 cleanser significantly reduced the mature P aeruginosa biofilm by 0.58 ± 0.45 log CFU/mL (95% CI, 0.30-0.85 CFU/mL; P < .001), whereas differences in the remaining cleansers were not statistically significant (Figure 4). The PHMB-1 treatment resulted in a mean log reduction of 0.63 ± 0.46 (95% CI, 0.35-0.90 CFU/mL; P < .001), 0.69 ± 0.46 (95% CI, 0.41-0.96 CFU/mL; P < .001), 0.59 ± 0.45 (95% CI, 0.31-0.87 CFU/mL; P < .001), and 0.48 ± 0.46 CFU/mL (95% CI, 0.20-0.75 CFU/mL; P < .001) compared with NaOCl-1, NaOCL-2, HOCl-2, and PHMB-2, respectively. These between-group results were statistically significant based on post hoc analysis.
Following 3 daily applications over 72 hours to simulate daily dressing changes, PHMB-2, PHMB-1, and NaOCl-2 showed significant reductions in P aeruginosa biofilms of approximately 2.27 ± 0.10 (95% CI, 1.49-3.05 CFU/mL; P < .001), 3.11 ± 0.82 (95% CI, 2.33-3.89 CFU/mL; P < .001) , and 4.42 ± 0.43 (95% CI, 3.64-5.19 CFU/mL; P < .001) log CFU/mL, respectively, compared with the saline control, whereas differences between HOCl-2 and NaOCl-1 and saline were not statistically significant (Figure 4). Post hoc analysis showed that the 0.84 ± 0.65 log CFU/mL reduction between PHMB-2 and PHMB-1 (95% CI, 0.06-1.62 CFU/mL; .01 < P < .05) groups, and 1.3 ± 0.93 CFU/mL mean log reduction between the PHMB-1 and NaOCl-2 (95% CI, 0.53-2.08 CFU/mL; P < .001), were both significant.
Effect of wound cleansers on MRSA. After a single application of wound cleanser followed by a 72-hour incubation period to mimic a Friday through Monday dressing change, the differences in average log CFU/mL of all test cleansers and the control, saline, were not significant, though PHMB-1 sustained an 1.40 ± 0.81 log CFU/mL reduction in comparison with saline (Figure 5).
Daily applications to simulate daily dressing changes resulted in PHMB-1 effectively eliminating MRSA biofilms with a 8.1 log CFU/mL reduction, whereas NaOCl-2 solution resulted in an approximately 3.22 ± 0.65 mean log reduction (95% CI, 2.04-4.39 CFU/mL; P < .001) compared with saline (Figure 5). PHMB-1 resulted in a 4.88 ± 0.68 mean log reduction (CFU/mL) in MRSA mature biofilms in comparison to NaOCl-2 (95% CI, 3.71-6.05 CFU/mL; P < 0.001), and a 7.49 ± 0.31 (95% CI, 6.32-8.66 CFU/mL; P < .001), 8.13 ± 0.311 (95% CI, 6.96-9.30 CFU/mL; P < .001), or 8.33 ± 0.29 CFU/mL (95% CI, 7.16-9.50 CFU/mL; P < .001) mean log reduction in comparison to the PHMB-2, HOCl-2, or NaOCl-1, respectively.
Effect of wound cleansers on C albicans. PHMB-1 showed a statistically significant 1.36 ± 0.14 CFU/mL mean log reduction (95% CI, 0.51-2.20 CFU/mL; .001 < P < .01) in C albicans mature biofilm compared with the saline control after a single application followed by 72 hours of incubation to simulate a 3-day dressing change (Figure 6). Differences between saline and the HOCl-2, NaOCl-1, NaOCl-2, and PHMB-2 treatment groups were not statistically significant. PHMB-1 also showed statistically significant (.001 ≤ P < .01) differences compared with other groups according to post hoc analysis.
Daily application for 3 days with PHMB-1 resulted in a 7.12 ± 0.21 CFU/mL (95% CI, 5.41-8.84 CFU/mL; P < .001) mean log reduction of C albicans mature biofilm compared with the saline control (Figure 6). Differences between the PHMB-1 cleansers and other groups were 7.27 ± 0.26, 7.18 ± 0.21, 5.66 ± 0.41, and 6.11 ± 0.23 in comparison to NaOCl-1 (95% CI, 5.55-8.98 CFU/mL; P < .001), HOCl-2 (95% CI, 5.46-8.89 CFU/mL; P < .001), NaOCl-2 (95% CI, 3.94-7.37 CFU/mL; P < 0.001), and PHMB-2 (95% CI, 4.40-7.82 CFU/mL; P < .001) groups, respectively. PHMB-2 and NaOCl-2 showed 1.01 ± 0.10 and 1.46 ± 0.35 CFU/mL log reduction of mature C albicans, respectively, whereas the other groups were comparable to the saline control; no statistical differences were observed between these groups.