Distinguishing colonization from infection with Staphylococcus aureus in diabetic foot ulcers with miniaturized oligonucleotide arrays: a French multicenter study

Abstract

Objective: To extend our previous work on evaluating the use of oligonucleotide arrays to discriminate colonization from infection owing to Staphylococcus aureus in diabetic foot ulcers (DFUs).

Research design and methods: Patients admitted to 14 French diabetic foot departments for a DFU were screened for entry into the study. At admission, ulcers were classified based on clinical examination according to the Infectious Diseases Society of America system. Only patients with monomicrobial culture for S. aureus were included. In persons with an uninfected ulcer, a second wound bacterial specimen was obtained 1 month later. Using oligonucleotide arrays, S. aureus resistance and virulence genes were determined, and each isolate was affiliated to a clonal complex (CC).

Results: S. aureus was initially isolated from 75 uninfected and 120 infected ulcers; 35 were methicillin resistant. A total of 44 (59%) strains from uninfected DFUs belonged to CC5/CC8 clones vs. 6 (5%) from infected DFUs (P < 0.001). During follow-up, 57 (76%) of uninfected DFUs healed or had a favorable outcome; the strain in 49 (86%) of them belonged to CC5/CC8. Conversely, 18 (24%) had a poor outcome but not a single strain belonged to CC5/CC8 clone. Moreover, lukDE was significantly associated with a favorable outcome of the wound.

Conclusions: As suggested by our previous study, the use of DNA arrays appears to be a promising technique that might help distinguishing uninfected from infected wounds, predicting ulcer outcome and then contributing to a more adequate use of antibiotics.

Figure 1

Flow of patients through the study and results of CC8-MSSA/CC5-MSSA obtained of grade 1–4 inclusion and during follow-up of uninfected ulcers. *Grades according to the IDSA/ IWGDF classification system (4,5): grade 2, n = 38; grade 3, n = 70; grade 4, n = 12.