The antimicrobial effect of Histoacryl ® skin adhesive

Epidural abscess formation is increasingly reported as a potentially disastrous complication of epidural analgesia, with a incidence of between 0.01% and 0.05%, and is a major factor limiting the duration of their use for post-operative analgesia [1]. The most common causative organisms are Gram positive cocci, particularly staphylococci, suggesting that contamination at insertion and/or colonisation by skin commensals are the common sources of such infection [2]. Epidural fall out rate has been significantly reduced by using Histoacryl® skin adhesive (B. Braun, Melsungen, Germany) to secure epidural catheters and we wished to investigate the antimicrobial properties of this product [3]. Histoacryl® was tested against some of the most common organisms associated with epidural abscesses using a similar method to that described previously by Quinn et al. [4]. National Collection of Type Cultures (NCTC) (National Public Health Laboratory, Colindale Avenue, London, UK) strains of the following organisms were used: Methicillin-sensitive Staphylococcus aureus (NCTC6571) (MSSA); Methicillin-resistant Staphylococcus aureus (NCTC12493) (MRSA); Enterococcus faecalis (NCTC12697); Escherichia coli (NCTC10418); Streptococcus pneumoniae (NCTC7466) and Pseudomonas aeruginosa (NCTC12934). One laboratory strain of coagulase negative staphylococcus and Candida albicans were also tested. Agar plates were prepared with standard inocula of the organisms according the British Society for Antimicrobial Chemotherapy, susceptibility testing method [5]. For the Candida albicans a 0.5 McFarland suspension of the organism in nutrient broth was used to inoculate IsoSensitest agar (CM471, Oxoid, Basingstoke, UK). Each organism was tested in triplicate. A drop of Histoacryl® was carefully applied to each inoculated plate to cover as small an area as possible. The plates were then incubated at 35–37 °C for 18–20 h. We then measured the diameter of the Histoacryl® droplet and the diameter of the zone of inhibition around the drop and calculated mean zone diameters for each organism. We found that Histoacryl® appeared to physically alter the culture medium in the area immediately surrounding the drop, as also seen by Quinn et al. [4]. In this area the agar appeared dehydrated and did not support bacterial growth. We called this area zone 1 (Fig. 6a). This effect was seen in all the agar plates and was considered to be non-specific. Any inhibition beyond zone 1 was deemed to have resulted from specific effect of the Histoacryl®. This area was called zone 2 (Fig. 6b). For each organism, cultured, the actual and mean diameters of the Histoacryl® droplets were recorded, along with actual and mean diameters of zone 1 and zone 2 (Table 1). Histoacryl® showed a specific inhibitory effect on all of the Gram positive organisms, but not the Gram negative organisms or Candida albicans. We found that Histoacryl® skin adhesive has a specific inhibitory effect on all the gram positive organisms we tested. It is particularly encouraging that this effect is seen against MRSA (Fig. 6c), an often difficult to treat cause of hospital acquired infection. Examples of the effect of Histoacryl® upon the growth of (a) Candida Albicans demonstrating Zone1, (b) Enterococcus faecalis demonstrating zones 1 and 2, (c) Methicillin resistant Staphylococcus aureus. Histoacryl® skin adhesive provides a reliable method of epidural catheter fixation, and reduces fall out rates [3]. It is encouraging to know that this substance, when applied to the skin entry site may reduce the incidence of bacterial colonisation of the catheter, potentially reducing epidural catheter related infection and abscess formation, and may allow the catheter to be used for longer. A clinical trial to demonstrate this effect would probably be unfeasible given the rarity of epidural abscess as a complication of epidural analgesia; however this would be a useful area for future research.