Comparative analysis of biofilm models to determine the efficacy of antimicrobials

Biofilms are one of the greatest challenges in today's treatment of chronic wounds. While antimicrobials kill platonic bacteria within seconds, they are rarely able to harm biofilms. In order to identify effective substances for antibacterial therapy, cost-efficient, standardized and reproducible models that aim to mimic the clinical situation are required. In this study, two 3D biofilm models based on human plasma with immune cells (lhBIOM) or based on sheep blood (sbBIOM) containing S. aureus or P. aeruginosa, are compared with the human biofilm model hpBIOM regarding their microscopic structure (scanning electron microscopy; SEM) and their bacterial resistance to octenidine hydrochloride (OCT) and a sodium hypochlorite (NaOCl) wound-irrigation solution. The three analyzed biofilm models show little to no reaction to treatment with the hypochlorous solution while planktonic S. aureus and P. aeruginosa cells are reduced within minutes. After 48 h, octenidine hydrochloride manages to erode the biofilm matrix and significantly reduce the bacterial load. The determined effects are qualitatively reflected by SEM. Our results show that both ethically acceptable human and sheep blood based biofilm models can be used as a standard for in vitro testing of new antimicrobial substances. Due to their composition, both fulfill the criteria of a reality-reflecting model and therefore should be used in the approval for new antimicrobial agents.

Effect of antiseptic irrigation on infection rates of traumatic soft tissue wounds: a longitudinal cohort study

OBJECTIVE

Acute traumatic wounds are contaminated with bacteria and therefore an infection risk. Antiseptic wound irrigation before surgical intervention is routinely performed for contaminated wounds. However, a broad variety of different irrigation solutions are in use. The aim of this retrospective, non-randomised, controlled longitudinal cohort study was to assess the preventive effect of four different irrigation solutions before surgical treatment, on wound infection in traumatic soft tissue wounds.

METHOD

Over a period of three decades, the prophylactic application of wound irrigation was studied in patients with contaminated traumatic wounds requiring surgical treatment, with or without primary wound closure. The main outcome measure was development of wound infection. From 1974-1983, either 0.04 % polihexanide (PHMB), 1 % povidone-iodine (PVP-I), 4 % hydrogen peroxide, or undiluted Ringer's solution were concurrently in use. From 1984-1996, only 0.04 % PHMB or 1 % PVP-I were applied. From 1997, 0.04 % PHMB was used until the end of the study period in 2005.

RESULTS

The combined rate for superficial and deep wound infection was 1.7 % in the 0.04 % PHMB group (n=3264), 4.8 % in the 1 % PVP-I group (n=2552), 5.9 % in the Ringer's group (n=645), and 11.7 % in the 4 % hydrogen peroxide group (n=643). Compared with all other treatment arms, PHMB showed the highest efficacy in preventing infection in traumatic soft tissue wounds (p<0.001). However, compared with PVP-I, the difference was only significant for superficial infections.

CONCLUSION

The large patient numbers in this study demonstrated a robust superiority of 0.04 % PHMB to prevent infection in traumatic soft tissue wounds. These retrospective results may further provide important information as the basis for power calculations for the urgently needed prospective clinical trials in the evolving field of wound antisepsis.