Multidrug-resistant organisms, wounds and topical antimicrobial protection

Abstract

Multidrug-resistant organisms (MDROs) are increasingly implicated in both acute and chronic wound infections. The limited therapeutic options are further compromised by the fact that wound bacteria often co-exist within a biofilm community which enhances bacterial tolerance to antibiotics. As a consequence, topical antiseptics may be an important consideration for minimising the opportunity for wound infections involving MDROs. The objective of this research was to investigate the antimicrobial activity of a silver-containing gelling fibre dressing against a variety of MDROs in free-living and biofilm states, using stringent in vitro models designed to simulate a variety of wound conditions. MDROs included Acinetobacter baumannii, community-associated methicillin-resistant Staphylococcus aureus, and extended-spectrum beta-lactamase-producing bacteria. Clostridium difficile was also included in the study because it carries many of the characteristics seen in MDROs and evidence of multidrug resistance is emerging. Sustained in vitro antimicrobial activity of the silver-containing dressing was shown against 10 MDROs in a simulated wound fluid over 7 days, and inhibitory and bactericidal effects against both free-living and biofilm phenotypes were also consistently shown in simulated colonised wound surface models. The in vitro data support consideration of the silver-containing gelling fibre dressing as part of a protocol of care in the management of wounds colonised or infected with MDROs.

Figure 1

Use of topical and systemic antimicrobials in colonised/infected wounds.

Figure 2

Simulated wound fluid model (SWF): antimicrobial action of the HFS dressing against MDROs over 7 days using the SWF model.

Figure 3

Examples of: growth of A. baumannii (NCTC 13421) (A) and community‐associated methicillin‐resistant Staphylococcus aureus (CA‐MRSA) (B) beneath the HFS dressing in the simulated colonised shallow wound (SCSW) model; bactericidal activity of the HFS dressing against K. pneumoniae (C; with the exception of persister cell variant colonies) and CA‐MRSA (D) in the simulated colonised wound surface (SCWS) model; zones of inhibition against A. baumannii (NCTC 13421) (E) and C. difficile (F) in the biofilm model.

Figure 4

Poloxamer biofilm model: Inhibitory activity of the HFS dressing against MDROs (zone size in mm).