In Vitroactivity of Manuka Honey and polyhexamethylene biguanide on filamentous fungi and toxicity to human cell lines

Abstract

Soft-tissue invasive fungal infections are increasingly recognized as significant entities directly contributing to morbidity and mortality. They complicate clinical care, requiring aggressive surgical debridement and systemic antifungal therapy. To evaluate new topical approaches to therapy, we examined the antifungal activity and cytotoxicity of Manuka Honey (MH) and polyhexamethylene biguanide (PHMB). The activities of multiple concentrations of MH (40%, 60%, 80%) and PHMB (0.01%, 0.04%, 0.1%) against 13 clinical mold isolates were evaluated using a time-kill assay between 5 min and 24 h. Concentrations were selected to represent current clinical use. Cell viability was examined in parallel for human epidermal keratinocytes, dermal fibroblasts and osteoblasts, allowing determination of the 50% viability (LD50) concentration. Antifungal activity of both agents correlated more closely with exposure time than concentration. Exophiala and Fusarium growth was completely suppressed at 5 min for all PHMB concentrations, and at 12 and 6 h, respectively, for all MH concentrations. Only Lichtheimia had persistent growth to both agents at 24 h. Viability assays displayed concentration-and time-dependent toxicity for PHMB. For MH, exposure time predicted cytotoxicity only when all cell types were analyzed in aggregate. This study demonstrates that MH and PHMB possess primarily time-dependent antifungal activity, but also exert in vitro toxicity on human cells which may limit clinical use. Further research is needed to determine ideal treatment strategies to optimize antifungal activity against molds while limiting cytotoxicity against host tissues in vivo.

Anti-pseudomonad Activity of Manuka Honey and Antibiotics in a Specialized ex vivo Model Simulating Cystic Fibrosis Lung Infection

“…Concentrations in the region of 40% (w/v) could be achievable; however, efficacy at this concentration needs to be experimentally tested. This potentially brings its own challenges as manuka honey can exert in vitro toxicity on human cells (Yabes et al, 2017). The differences between EVPL bronchiole tissue in the presence of 64% (w/v) manuka honey may be subject to these similar “ in vitro” effects, however, the negative effects observed in vitro do not necessarily occur in vivo whereby 100% manuka honey is used on open wounds with positive effects, increasing wound healing (Mohamed et al, 2015).…”

Update on the role of antiseptics in the management of chronic wounds with critical colonisation and/or biofilm

“…In an in vitro cytotoxicity test using cultured human skin fibroblasts, PHMB was extremely cytotoxic and appeared to induce complete cell destruction in the majority of cells 112 . When used in vitro at or below concentrations commonly employed in human wound care, PHMB (0.01%, 0.04%, and 0.1%) demonstrated both time‐ and concentration‐dependent cytotoxicity in cultured human keratinocytes and osteoblasts, but only time‐dependent cytotoxicity in cultured fibroblasts 113 . Furthermore, exposure of cultured human endothelial cells to PHMB (0.0006%‐0.01%) resulted in a large reduction in cell number and viability 125 .…”

“…109 Studies have shown different levels of cytotoxicity among PVP-I, PHMB, and silver-containing products (Table 2). [110][111][112][113][114][115][116][117][118][119][120][121][122][123][124][125][126][127][128][129] Cytotoxicity data, in particular data derived from in vitro studies, must be interpreted with caution as any cytotoxic effects observed in cultured cell types can be magnified and may not be truly reflective of the in vivo or clinical setting. 49,130,131…”

Evolution of Honey Resistance in Experimental Populations of Bacteria Depends on the Type of Honey, and Has no Major Side Effects for Antibiotic Susceptibility

“…Honey or honey-resistance mechanisms might therefore also have downstream effects for biofilm formation or the expression of other virulence factors. On the other hand, because honey has shown effective inhibition of a wide range of pathogens (Carter et al, 2016;Hillitt et al, 2017;Yabes et al, 2017), and the principal genes involved in honey resistance in our experiment are conserved in multiple pathogenic species (e.g., nemR or analogues are present in Klebsiella pneumonia, Acinetobacter baumannii and Salmonella typhimurium), our work identifies candidate loci that may be involved in resistance in other species. This is another relevant area for future research in the context of medical honey application.…”