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Title: Biofilms and chronic equine wound healing
Author: Westgate, Samantha Jane
ISNI:       0000 0004 2734 1526
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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Biofilms in human wounds are considered responsible for the non-healing nature of some chronic wounds. Recent advancements in chronic wound healing have resulted from an increased understanding and awareness of biofilms. These findings led to the hypothesis that bacterial biofilms were also present within the wound bed of non- healing equine wounds and could be responsible for the unexplained retardation of some chronic equine wounds. This study aimed to collect and present information regarding the microbiological composition of equine wounds and to present evidence supporting the presence of bacterial biofilms within these wounds. The objectives were firstly to gain an understanding of the common bacterial microflora in horse wounds and on horse skin. To achieve this, the study utilised culture and molecular techniques, where molecular techniques included denaturing gradient gel electrophoresis (DGGE) and gene sequencing. Secondly, the study examined chronic wounds for in-vivo evidence of biofilm material. In-vitro experiments such as the crystal violet microtitre plate assay and a CDC biofilm reactor were used to quantify biofilm formation. Genotypic and phenotypic methods including the Kirby Bauer disc diffusion assay and PCR-gel electrophoresis, were used to investigate the correlation between antibiotic resistance and bacterial biofilm formation. The latter stages of the study investigated the effect that mixing bacterial populations had on in-vitro biofilm formation and the role of silver as a possible treatment option for biofilm infected wounds. Microbiological and molecular analysis of wound samples revealed that bacteria were present in all wound types. The most commonly recovered wound isolates were Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis and Escherichia coli. Histological staining of chronic wound tissue revealed discrete clusters of bacteria and the ability of equine wound isolates to form a biofilm was further supported by scanning electron microscopy studies. According to data obtained using the crystal violet microtitre plate assay, the biofilm forming potential (BFP) of wound isolated bacteria was greater than that of skin isolated bacteria. Biofilm forming isolates demonstrated an increased phenotypic tolerance to antimicrobial treatments, and silver impregnated dressings, compared to non-biofilm forming isolates. Screening for known genetic resistance regions such as the mecA cassette revealed the presence of resistant isolates including Type IV MRSA. Despite finding multidrug resistant bacteria such as MRSA in some of the chronic wounds, treatments including; repeated debridement, thorough cleansing and appropriate antibiotics, resulted in the successful healing of 49 of the 51 cases enrolled in this study. This work has contributed to the field of equine wound microbiology by presenting and comparing the bacterial compositions of equine skin and equine wounds. Furthermore, it has contributed to the field of biofilm microbiology by quantifying the BFP of each of the cultured isolates and' it has enhanced the clinical understanding of biofilms within veterinary wounds. This work supports the hypothesis that biofilms exist within chronic equine wounds and provides a sound basis for future work that can be used to guide and enhance the successful healing of chronic equine wounds.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available