Time course study of delayed wound healing in a biofilm‐challenged diabetic mouse model

Abstract

Bacterial biofilm has been shown to play a role in delaying wound healing of chronic wounds, a major medical problem that results in significant healthcare burden. A reproducible animal model could be very valuable for studying the mechanism and management of chronic wounds. Our previous work demonstrated that Pseudomonas aeruginosa (PAO1) biofilmchallenge on wounds in diabetic (db/db) mice significantly delayed wound healing. In this wound time course study, we further characterize the bacterial burden, delayed wound healing and certain aspects of the host inflammatory response in the PAO1 biofilm-challenged db/db mouse model. PAO1 biofilms were transferred onto 2 day old wounds created on the dorsal surface of db/db mice. Control wounds without biofilm-challenge healed by 4 weeks, consistent with previous studies; none of the biofilm-challenged wounds healed by 4 weeks; 64% of the biofilm-challenged wounds healed by 6 weeks; and all of the biofilm-challenged wounds healed by 8 weeks. During the wound healing process, P. aeruginosa were gradually cleared from the wounds while the presence of S. aureus (part of the normal mouse skin flora) increased. Scabs from all unhealed wounds contained 107 P. aeruginosa, which was 100 fold higher than the counts isolated from wound beds (i.e. 99% of the P. aeruginosa was in the scab). Histology and genetic analysis showed proliferative epidermis, deficient vascularization and increased inflammatory cytokines. Hypoxia inducible factor (HIF) expression increased 3 fold in 4 week wounds. In summary, our study demonstrates that biofilm-challenged wounds typically heal in approximately 6 weeks, at least 2 weeks longer than non biofilm-challenged normal wounds. These data suggest that this delayed wound healing model enables the in vivo study of bacterial biofilm responses to host defenses and the effects of biofilms on host wound healing pathways. It may also be used to test anti-biofilm strategies the treatment of chronic wounds.

Prevalence and antibiotic susceptibility of bacteria from acute and chronic wounds in Malaysian subjects

“…Virulence factors, including lipopolysaccharide (LPS), enterotoxin A, and ADP ribosylating enzymes excreted by P. aeruginosa have proven to be cytotoxic and have potent inhibitory effects on the proliferation of human granulocytes and macrophage progenitor cells during the wound healing process [36,37]. In vivo studies of mice and rabbits have further confirmed that S. aureus and P. aeruginosa evade host immunity and establish persistent infections via biofilm formation [38][39][40]. When compared to planktonic cells, bacteria in biofilm promote higher resistance towards antibiotics and other antimicrobial agents [6,41].…”

Biofilm Models of Polymicrobial Infection

“…[115]. The microbes developed biofilms on the wound and notably impaired wound healing compared with the noninfected mice, thus creating a chronic infection [116].…”

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.…”