Dr Rebecca McLean1, Dr Aliya Bryce1, Dr Susan Morpeth1, Dr Susan Taylor1, Mr Paul Baker1
1Counties Manukau District Health Board, Auckland, New Zealand
Patients who sustain large burns often have polymicrobial skin and soft tissue infections and experience high mortality from these, exacerbated by patient immunosuppression¹²³. Antimicrobial solutions and dressings are used in burns operating theatres to clean wounds and reduce the risk of infection and sepsis⁴. We aim to compare the antimicrobial effect of common burns dressings and solutions.
A standardised concentration of 1-1.5×10⁸ colony forming units of Staphoylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, extended-spectrum beta-lactamase producing Klebsiella pneumonia and Candida albicans was plated onto Muller-Hinton agar plates. Chosen sterile dressings (Bactigras, Acticoat, Mepilex Ag, Aquacel Ag) were cut into 1cm² squares or 1cm² sterile filter paper was saturated with chosen solutions (aqueous chlorhexidine, aqueous betadine, Dakin’s solution (sodium hypochlorite) or normal saline (control). The dressings or filter paper were placed onto the plates and incubated at 38°C in anaerobic conditions. At 48 hours the zone of inhibition (ZOI) was read with a metric ruler. The experiment was repeated in triplicate.
ZOIs differed between dressings and organisms. Aqueous betadine and chlorhexidine solutions had large ZOI of 7.2 and 6.8mm respectively; Acticoat and Aquacel Ag had moderate size ZOI of 3.6 and 4.6mm respectively. Bactigras (0.6mm), Dakin’s solution (0.8mm) and Mepilex Ag (0.7mm) had minimal ZOI.
The above methodology demonstrates some solutions and dressings outperform others. Further work is required to determine if the in vitro results correlate clinically, however this could have important implications for the selection of antimicrobial dressings and solutions in theatre.
Rebecca is a Plastic Surgery Registrar working in Auckland, New Zealand currently as the Burns Registrar at the National Burn Centre