Topical honey: for bears, not for ICU catheters?

Catheters are most often colonized and become infected via the skin and their external surfaces in the ICU. Therefore, topical antimicrobials, including medical honey, placed at the insertion site should decrease skin colonization and catheter infections. This commentary reviews the main studies on, and the possible reasons of, topical antimicrobial failure in ICUs compared to the reported efficacy of chlorhexidine-impregnated dressings.

iodine, mupirocin and polysporin (polymyxin, bacitracin, and neomycin) have been studied [6]. Results of randomized controlled trials (RCTs) on the effi cacy of triple antibiotic ointment (polymyxin, bacitracin, and neo my cin) applied to catheter insertion sites are indeterminate for central venous catheters due to the low number of CR-BSIs observed. In a double blind RCT performed in longterm hemodialysis (HD) patients, polysporin signifi cantly decreased exit site infection (relative risk 0.25, 95% confi dence interval (CI) 0.19 to 0.31) and bacteremia (relative risk 0.25, 95% CI 0.19 to 0.34) [7]. Increased catheter colonization by Stenotro pho monas maltophilia and Candida species associated with use of triple antibiotic ointment may limit further investigations in the ICU [2].
Again, while the effi cacy of povidone iodine ointment in decreasing bacteremia and local infection has been shown [8] in HD patients with long-term catheters, results of randomized studies of prophylactic use of povidone iodine ointment applied to insertion sites of short-term catheters for the prevention of CR-BSI are inconclusive (relative risk 1.0, 95% CI 0.1 to 7.1 [2]). However, given the results of small before-and-after studies, RCTs should be promoted to test povidone iodine ointment effi cacy in ICU settings [9].
Application of mupirocin ointment to insertion sites for temporary HD catheters reduces the risk for CR-BSI with Staphylococcus aureus (relative risk 0.1, 95% CI 0.0 to 0.7) [6]. However, the emergence of mupirocin-resistant organisms and interference with the polyurethane of the catheters limit its use.
Honey is known to possess antimicrobial properties. Activity is due to the approximately 80% sugar content, low pH, free radical production and other fl oral or bee components. Antimicrobial properties vary according to the environment where honey is collected and microbial resistance has never been reported. On healthy volunteer skin, medical grade honey is eff ective at concentrations greater than 20% for antibiotic-susceptible and -resistant bacteria [10]. For CR-BSI prevention, honey was as eff ective as mupirocin in long-term HD patients [6]. In a recent issue of Critical Care, Kwakman and colleagues report results of a single-ICU open-label RCT testing the added eff ect of medical grade honey in decreasing cutaneous colonization and infection of central vein catheters [11]. Th ey found that colonization at the last sampling was nearly identical between patients with and without honey.
As the authors pointed out, the absence of effi cacy of honey might be due to dilution or inactivation of honey in the skin moistures of diaphoretic patients, or to dressing disruption. Indeed, we found that transparent dressing changes earlier than the planned date because of disrup tion or leakage occurs up to 66% of the time in ICUs [12] and may favor topical antimicrobial leakage. Th ese mechanisms may, more generally, explain the disappointing results with topical antimicrobials in preventing catheter-related infections in the ICU.

Conclusion
Further studies may use concentrations of topical antimicrobials that exceed by far the concentration necessary to kill skin microorganisms. However, considering the pathophysiology of CR-BSI with short-term catheter use, the potential of topical antimicrobials in decreasing catheter-related infection needs to be further tested.