The diagnosis of diabetic foot infections is difficult due to limitations of conventional culture-based techniques. The objective of this study was to evaluate the contribution of denaturing gradient gel electrophoresis (DGGE) in the microbiological diagnosis of diabetic foot ulcers in comparison to conventional techniques, and also to evaluate the need to perform a biopsy sample for this diagnosis.

Twenty diabetic patients (types 1 and 2) with foot ulcers (grades 1–4) were included. After debridement of their wounds, samples were taken in duplicate by surface swabbing and deep-tissue biopsy. The samples were analyzed by conventional culture and by a new molecular biology tool, DGGE technology.

Polymerase chain reaction (PCR)–DGGE led to the identification of more bacteria than did conventional cultures (mean: 2.35 vs 0.80, respectively). In 11 cases, the technology detected pathogenic species not isolated by classical cultures. PCR–DGGE also identified significantly more pathogenic species at deep levels compared with species detected at superficial levels (87% vs 58%, respectively; P=0.03). In 9/20 cases, pathogenic bacteria were detected only in deep samples, revealing the need to perform tissue biopsy sampling.

DGGE, achievable in 48h, could be a useful technique for the bacteriological diagnosis of diabetic foot infections. It may help to identify pathogenic bacteria in deeply infected ulcers, thereby contributing to a more appropriate use of antibiotics.