Use of TaqMan array to investigate infection in diabetic foot wounds

S. Johnson-Lynn, M. Curran, C. Allen, K. Webber, M. Maes, D. Enoch, A.H. Robinson, A.P. Coll

Introduction: Diabetic foot disease is a major public health problem with an annual NHS expenditure in excess of £1 billion. Infection increases risk of major amputation fivefold. Due to the polymicrobial nature of diabetic foot infections, it is often difficult to isolate the correct organism with conventional culture techniques, to deliver appropriate narrow spectrum antibiotics. Rapid DNA-based technology using multi-channel arrays presents a quicker alternative and has previously been used effectively in intensive care and respiratory medicine.

Methods: We gained institutional and Local Ethics Committee approval for a prospective cohort study of patients with clinically infected diabetic foot wounds. They all had deep tissue samples taken in clinic processed with conventional culture and real-time PCR TaqMan array.

Results: 50 samples were taken from 39 patients between October 2020 and March 2022. 84% of patient were male, 88% had type 2 diabetes. The ulcers were of variable chronicity prior to sampling (range 1-113 weeks) and mean HbA1c was 67.2mmol/mol. Ulcers were on the heel (3), midfoot (6) and forefoot (41). Minimum follow up was 3 months. 6 ulcers healed, 24 patients were admitted due to foot disease, there were 2 major amputations and 4 deaths. TaqMan array results were available a mean of 4.3 days earlier than culture results. 9 patients had negative conventional cultures and 8 were negative onarray testing. 17 patients had the same organisms detected on culture and array. 16 of these 17 had additional organisms detected by array. The most frequent organisms detected on array that were not detected by culture were Staphylococcus spp., Enterobacter, Pseudomonas and fungi.

Conclusions: TaqMan array shows promise in detecting infecting organisms from diabetic foot wounds and providing earlier and more detailed results than standard culture, which may facilitate specific and timely antibiotic therapy.