Virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers: a new paradigm.
OBJECTIVE
The purpose of this study was to assess the virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers and to discriminate noninfected from infected ulcers.


METHODS
Diabetic patients hospitalized in a diabetic foot department with a foot ulcer were prospectively enrolled if they had been free of antibiotic treatment over the previous 6 months. At admission, ulcers were classified as infected or noninfected on the basis of clinical examination, according to the International Working Group on the Diabetic Foot system. Only patients carrying S. aureus as the sole pathogen were included. In individuals with a grade 1 ulcer, a second bacterial specimen was obtained 1 month later. Using virulence genotyping markers, clonality tools, and an in vivo Caenorhabditis elegans model, we correlated the virulence of 132 S. aureus strains with grade, time of collection, and ulcer outcome.


RESULTS
Among virulence genes, the most relevant combination derived from the logistic regression was the association of cap8, sea, sei, lukE, and hlgv (area under the curve 0.958). These markers were useful to distinguish noninfected (grade 1) from infected (grades 2-4) ulcers and to predict wound status at the follow-up. With use of the nematode model, S. aureus strains isolated from grade 1 ulcers were found to be significantly less virulent than strains from ulcers at or above grade 2 (P < 0.001).


CONCLUSIONS
This study highlights the coexistence of two S. aureus populations on diabetic foot ulcers. A combination of five genes that may help distinguish colonized grade 1 from infected grade >or=2 wounds, predict ulcer outcome, and contribute to more appropriate use of antibiotics was discovered.
Sotto
Albert
A
Institut National de la Santé et de la Recherche Médicale, ESPRI 26, Université de Montpellier 1, Nîmes, France.
Lina
Gérard
G
Richard
Jean-Louis
JL
Combescure
Christophe
C
Bourg
Gisèle
G
Vidal
Laure
L
Jourdan
Nathalie
N
Etienne
Jérôme
J
Lavigne
Jean-Philippe
JP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D016523:Foot Ulcer / Q000382:microbiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification* / Q000472:pathogenicity*; D014774:Virulence