Infected tissues in the feet of people with diabetes in the form of a diabetic foot ulcer (DFU) present a complex pathology for clinicians to manage. This is partly attributed to the multi-factorial nature of the disease, which may include; altered foot architecture leading to excessive plantar pressures and frictional forces peripheral arterial disease and loss of protective sensation. In addition, to the above comorbid variables, it is understood that a delayed wound healing state may be perpetuated by the presence of microorganisms residing in the wound tissue. The microbiology of chronic DFUs has often been reported as being polymicrobial. Of growing interest is the presence and potential role of anaerobic microorganisms in the pathology of DFUs and how they may contribute to the infective process or delayed healing. The presence of anaerobes in DFUs has been greatly underestimated, largely due to the limitations of conventional culture methods in identifying them from samples. Advancements in molecular and microscopy techniques have extended our view of the wound microbiome in addition to observing the growth and behaviour (planktonic or biofilm) of microorganisms in situ. This review paper will reflect on the evidence for the role and significance of anaerobes in DFUs and infection. A focus of this review will be to explore recent advancements in molecular genomics and microscopy techniques in order to better assess the roles of anaerobic bacteria in chronic DFUs and in biofilm-based wound care.
1 | INTRODUCTION
The causality of a diabetic foot ulcer (DFU) is considered multi-factorial in origin. Such factors can include peripheral vascular disease, peripheral neuropathy and some form of trauma which may inflict damage to the skin. Once the skin is breached underlying structures of the skin and soft tissue are exposed to planktonic commensal microorganisms or opportunistic pathogens. DFUs present an ideal environment for harbouring microorganisms as they offer a warm, moist and nutritive home especially if devitalized tissue is present in the wound bed. When this is combined with several aspects of altered immunologic function,1 it may explain why some bacterial infections in people with diabetes persist despite optimal care.
2 | CONCLUSION
Whilst the presence of microorganisms of a polymicrobial nature in DFUs is clearly evident there is still a large gap in knowledge over the distinct effect of anaerobic bacteria in the chronicity of DFUs and chronic wounds in general. This in part may be due to the varying methods of anaerobic microbiological isolation and evaluation and the models which are employed. What is intriguing is the evidence that supports the synergistic interactions between anaerobes and aerobes within in vitro biofilms. However, despite there being a small number of papers that identify the presence of biofilms within chronic wounds basic microbiological methods and even some molecular methods do not give us insight into the structure of a polymicrobial biofilm within these DFUs. The traditional physical architecture of a biofilm observed within in vitro biofilms, that is, mushroom structures are not considered to be found within in vivo biofilms. Consequently, studying and investigating the physical and chemical characteristics of “true to life” biofilms still remains a significant challenge. Despite this, our interpretations and extrapolations from in vitro biofilms has helped significantly to begin to develop information that is assisting with the management and study of biofilms of public health significance.
