The effects of wound fluid pH on bacterial persistence in diabetic foot ulcers

Abstract

This interdisciplinary study aimed to investigate interactions between diabetic foot ulcer (DFU) wound fluid pH and DFU bacteria, a currently under-investigated but clinically significant aspect of these difficult to resolve wounds, which are highly disruptive in terms of patient quality of life, mobility and mortality, as well as posing considerable and increasing pressures on health care resources.

The study was based on a structured literature review which confirmed the stark contrast between the overall importance of DFU infections, and the relatively small amount of previous research on the impact of pH on bacterial growth and metabolism in DFUs.

The planned programme of research involved a clinical investigation of the pH values in DFU wound fluid from patients with diabetes, along with visual clinical assessment of the presence or absence of infection in sampled wounds and the microbial analysis of DFU wound fluid. This was supported by a series of linked laboratory based studies to provide new information on the pH values in such wounds, and the impact of such conditions on the growth, resistance and virulence of DFU bacteria.

The clinical study developed and applied a novel, rapid, non-invasive, method for the successful recovery and analysis of DFU wound fluid and DFU bacteria, using Periopaper®, and confirmed the suitability of this method for the collection of wound fluid samples within the operational constraints of routine podiatry clinic activities. This clinical study established relationships between wound fluid pH and microbial analysis, and the visual assessment of infection.

The laboratory studies used broth based and agar based models to establish that pH conditions very significantly modulate a number of important DFU bacterial properties including growth rate, antimicrobial resistance and biofilm expression.

The findings of the doctoral studies provide evidence in relation to the factors that may link to “failure to heal”, and the incidence of infection with persistence of alkaline conditions within wounds. These results indicate that monitoring of wound fluid pH may provide a rapid, objective, clinic appropriate means of monitoring microbial loading and detecting infection within DFUs.

The thesis discusses the potential microbiological and clinical impacts of the overall findings of the doctoral studies with particular reference to future options in the real time monitoring and/or manipulation of DFU pH. It also discusses the clinically beneficial aspects such as the early detection of incipient infection, the disruption of bacterial growth within DFUs, the selection and application of more efficacious antibiotics, and the suppression of undesirable biofilm in DFUs.

Date of Award	Jun 2015
Original language	English
Sponsors	Department of Employment and Learning
Supervisor	Katie Lagan (Supervisor) & DAVID MCDOWELL (Supervisor)