Bacterial Growth Kinetics under a Novel Flexible Methacrylate Dressing Serving as a Drug Delivery Vehicle for Antiseptics

Abstract

A flexible methacrylate powder dressing (Altrazeal®) transforms into a wound contour conforming matrix once in contact with wound exudate. We hypothesised that it may also serve as a drug delivery vehicle for antiseptics. The antimicrobial efficacy and influence on bacterial growth kinetics in combination with three antiseptics was investigated in an in vitro porcine wound model. Standardized in vitro wounds were contaminated with Staphylococcus aureus (MRSA; ATCC 33591) and divided into six groups: no dressing (negative control), methacrylate dressing alone, and combinations with application of 0.02% Polyhexamethylene Biguanide (PHMB), 0.4% PHMB, 0.1% PHMB + 0.1% betaine, 7.7 mg/mL Povidone-iodine (PVP-iodine), and 0.1% Octenidine-dihydrochloride (OCT) + 2% phenoxyethanol. Bacterial load per gram tissue was measured over five days. The highest reduction was observed with PVP-iodine at 24 h to log10 1.43 cfu/g, followed by OCT at 48 h to log10 2.41 cfu/g. Whilst 0.02% PHMB resulted in a stable bacterial load over 120 h to log10 4.00 cfu/g over 120 h, 0.1% PHMB + 0.1% betaine inhibited growth during the first 48 h, with slightly increasing bacterial numbers up to log10 5.38 cfu/g at 120 h. These results indicate that this flexible methacrylate dressing can be loaded with various antiseptics serving as drug delivery system. Depending on the selected combination, an individually shaped and controlled antibacterial effect may be achieved using the same type of wound dressing.

Modelling antisepsis using defined populations of facultative and anaerobic wound pathogens grown in a basally perfused biofilm model

“…Thus, the relative susceptibility of bacteria observed in the current study, and the survival of P. aeruginosa in exposed biofilms could be largely predicted based on known features of this bacterium. The observed inactivation kinetics could be explained by phenotypic adaptation within the biofilm, whilst the varied tolerance to antimicrobial exposure observed in the basal perfusion model against the three compounds resembles that previously reported by Forstner et al (2013) using a porcine wound model. Since distinct bacteria often exhibited distinct antimicrobial susceptibly profiles to antiseptics as well as to antibiotics, such variable antibacterial effects may be an important but relatively little studied variable in wound antisepsis (Davis et al 2006, James et al 2008, Roy et al 2014, Saye 2007.…”

Polyhexamethylene Biguanide:Polyurethane Blend Nanofibrous Membranes for Wound Infection Control

“…It has proven to be effective against a wide range of pathogens, including strains of Escherichia coli [11,13], Staphylococcus epidermidis [13,14], and even the Protista Acanthamoeba castellanii [14]. It has previously been thought to work primarily through microbial membrane disruption [11,13,15,16], however, more recently it was reported to also selectively bind and condense bacterial DNA, arresting bacterial cell division. This mechanical antimicrobial mechanism of action may help explain why PHMB has a low risk for antimicrobial resistance, of which, none has been recorded despite extensive testing since its first synthesis [11].…”

“…Many different methods have been evaluated in attempts to improve the release of PHMB [16,18,19]. For example, there is evidence that the method of loading and the use of other substances are important factors for maintaining PHMB’s microbicidal properties [19,20].…”

Consensus on Wound Antisepsis: Update 2018

“…When tested on metal carriers under load (artificial wound fluid), PVP-I solution was effective within in a time frame of 5 min, whereas gels based on OCT (0.05%) or PHMB (0.04 or 0.02%) needed 30 min or 3 h (PHMB 0.02%) to take effect [39]. PVP-I was also most effective in an in vitro wound model with S. aureus , followed by OCT and PHMB [54]. However, OCT showed superior efficacy in a biofilm model with P. aeruginosa PVP-I [55].…”