Visualisation of bacterial sequestration and bactericidal activity within hydrating Hydrofiber® wound dressings

The fluid handling and microbiological properties of a non-antimicrobial Hydrofiber (R) (NAH) wound dressing have been compared with those of a silver salt-containing Hydrofiber (R) (SCH). Fluorescent dyes (BacLight (TM), Live/Dead (TM) Kit) were added to fresh cultures of two wound pathogens (Pseudomonas aeruginosa and Staphylococcus aureus), and used to visualise their viability. Live bacteria stained green and dead/dying bacteria, turned red. When inoculated into samples of the NAH and SCH dressings, the viability of the bacteria could be effectively monitored over time using a rapid form of confocal laser scanning microscopy (RCLSM-Leica (R) UK). When the NAH dressing was hydrated with stained bacterial Culture, its fibres swelled quickly, reducing interstitial spaces between the fibres, resulting in the formation of a cohesive gel. Bacteria became immobilised in the gel, forming characteristic clumps, but remained largely green (viable) for more than 20 h with no apparent increase in numbers. The SCH initially behaved in a similar manner, however, using 3-D data from RCLSM time-lapse sequences P. aeruginosa was observed to turn progressively red (i.e. died) within 1.5-3 h and S. aureus similarly turned red within 5-7 h of contact with the SCH dressing. The ability of both Hydrofiber (R) dressings to sequester and immobilise potentially pathogenic wound micro-organisnis has been demonstrated. Additionally the SCH dressing was shown to kill immobilised bacteria, as a consequence of the ionic silver bactericide. These properties of the Hydrofiber (R) dressings may contribute to providing an environment that is supportive to wound healina. (c) 2005 Elsevier Ltd. All rights reserved.