Microscopic and physiologic evidence for biofilm‐associated wound colonization in vivo

Abstract

A biofilm is a collection of microbial cells that are attached to a surface and embedded in a self-produced extrapolymeric substance. The understanding of the biofilm phenotype is important in the understanding of bacteria in vitro but it has been difficult to translate biofilm science to the clinical setting. More recently, preliminary criteria for defining biofilm associated diseases have been proposed and the purpose of this study was to create a biofilm-associated wound model based on these criteria. Using a porcine model, partial thickness wounds were inoculated with a wound isolate Staphylococcus aureus strain. Wounds were then treated with either one of two topical antimicrobial agents (mupriocin cream or triple antibiotic ointment) within 15 minutes to represent planktonic bacteria or 48 hours after initial inoculation to represent biofilm-associated wound infection. Using light microscopy, scanning electron microscopy and epifluorescence microscopy, we were able to observe biofilm-like structures in wounds after 48 hours of inoculation and occlusion. The in vivo antimicrobial assay was used to demonstrate that both mupirocin cream and the triple antibiotic ointment were effective in reducing planktonic S. aureus but had reduced efficacy against biofilm-embedded S. aureus. Our results demonstrated that S. aureus form firmly attached microcolonies and colonies of bacteria encased in an extracellular matrix on the surface of the wounds. These biofilm-like communities also demonstrated increased antimicrobial resistance when compared with their planktonic phenotype in vivo. The structural and physiological results support the hypothesis that bacterial biofilms play a role in wound colonization and infection.

Reactive oxygen: A novel antimicrobial mechanism for targeting biofilm-associated infection

“…Moreover, it has been shown that in 45 of 915 samples, Fusarium spp. formed biofilms in chronic wound infections [26].…”

“…[22]. It was also reported that as a result of low metabolic activities of biofilms, micro-organisms in biofilm forms are more difficult to eliminate with conventional antimicrobial agents than planktonic forms [26].…”

Chronic Wound Biofilm Model

“…24 Studies on animals, including rats, mice, rabbits, and pigs, have mostly addressed short-term acute-phase processes ranging between 2 and 26 days of infection (Table 1). 7,10,[25][26][27][28][29] Such approaches are of limited value as they fail to capture the long-term interplay between the host and biofilm, which has a significant bearing of the wound microenvironment at the site of the infection. 17 This article aims to concisely and critically review the various in vitro and in vivo models used for the study of biofilm infections of wounds with specific emphasis on the preclinical porcine model of chronic infections (duration of 8 weeks) recently reported by our laboratory.…”

“…45 Additionally and importantly, the human immune system has a higher similarity to the porcine immune system compared to rats or mice, making it a better suited model for studies on the host interactions that are integral to the complexities of the pathological biofilm in wound infections. 46 Davis et al 25 developed a porcine wound biofilm model, where partial-thickness wounds in pigs were infected with S. aureus. Using electron microscopy, the presence of biofilm matrix was established.…”

Antibiofilm efficacy of honey and bee-derived defensin-1 on multispecies wound biofilm

“…Together, these micro-organisms form a multispecies biofilm construct that protects them from antimicrobial therapy and the patient's immune system (Price et al, 2009;Attinger & Wolcott, 2012). Biofilm growth and its persistence within wounds have recently been suggested as contributing factors to impaired healing (Rhoads et al, 2007;Bjarnsholt et al, 2008;Davis et al, 2008).…”