Use of TaqMan array card to investigate bacterial isolates in diabetic foot ulcers

Diabetic foot disease is a major public health problem, with an annual National Health Service (NHS) expenditure exceeding £1 billion. Infection increases the risk of major amputation fivefold. Due to the polymicrobial nature of diabetic foot infections, it is often difficult to correctly and rapidly isolate pathological organisms with conventional culture techniques and deliver appropriate narrow-spectrum antimicrobials. Rapid DNA-based technology, using multi-channel arrays, offers a quicker alternative and has previously been used effectively in other settings. We undertook a prospective cohort study of deep tissue samples taken from diabetic foot ulcers (DFUs), comparing samples processed by conventional culture and real-time PCR TaqMan array card (TAC). Fifty samples were taken from 39 patients. The ulcers were of variable chronicity prior to sampling (range: 1-113 weeks) and were sited on the heel (3), midfoot (6) and forefoot (41). TAC results were available an average of 4.3 days earlier than culture results. Seventeen samples had the same organisms detected on culture and TAC. Sixteen of these 17 had additional organisms detected by TAC. The most frequent organisms detected by TAC that were not detected by culture were staphylococci, Enterobacter spp., Pseudomonas spp. and fungi. TAC rapidly and accurately detects clinically relevant organisms from DFUs, providing earlier results than standard culture. This may enable earlier rationalization of antimicrobials and infection control interventions.