Miniaturized oligonudeotide arrays

OBJECTIVE - We sought to evaluate the use of oligonucleotide arrays to discriminate colonization from infection due to Staphylococcus aureus in diabetic foot ulcers. RESEARCH DESIGN AND METHODS - We included diabetic patients hospitalized in a diabetic foot department for an episode of foot ulcer. Only patients who had no antibiotic treatment during the previous 6 months were included. At admission, ulcers were classified on clinical examination, according to the Infectious Diseases Society of America system. Seventy-two patients with a culture positive only for S. aureus as the sole pathogen were included. In individuals with a grade I ulcer, a second wound bacterial specimen was obtained I month later. Using oligonucleotide arrays, S. aureus resistance and virulence genes were compared between grade I and grades 2-4 ulcers. RESULTS - S. aureus was initially isolated from 22 grade I and 50 grade 2-4 ulcers: 35 were methicillin resistant and 37 methicillin sensitive. In 20 grade I ulcers (92%), no virulence genes were identified, whereas these genes were present in all but I grade 2-4 ulcers. During follow-up, the two grade I ulcers that were infected with strains carrying virulence genes rapidly deteriored: the array technology showed unchanged genotype profiles. On the contrary two grade 1 ulcers healed: the genotype profiles were different from those at inclusion but without appearance of virulence genes. CONCLUSIONS - The DNA array appears as a promising technique and is easy to perform. Our observational stud), suggests that it might help distinguish colonized grade I from infected grade 2 wounds, predict ulcer outcome, and contribute to a more adequate use of antibiotics.