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Virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers: a new paradigm.
Sotto A, Lina G, Richard JL, Combescure C, Bourg G, Vidal L, Jourdan N, Etienne J, Lavigne JP. Diabetes Care. 2008 Sep 22. [Epub ahead of print]
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Objective: To assess the virulence potential of Staphylococcus aureus isolated from diabetic foot ulcers and to discriminate non-infected from infected ulcers.
Research design and methods: Diabetic patients hospitalized in a diabetic foot department f with a foot ulcer were prospectively enrolled if they had been free of antibiotics treatment over the previous 6-months . At admission, ulcers were classified as infected or non-infected based on clinical examination, according to the IWGDF 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 one 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 (AUC 0.958). These markers were useful to distinguish non-infected (grade 1)/infected (grades 2-4) ulcers and to predict wound status at the follow-up. Using the nematode model, S. aureus strains isolated from grade 1 ulcers were found to be significantly less virulent than strains from grade >/=2 ulcers (P<0.001).
Conclusions: This study highlighted the coexistence of two S. aureus populations on diabetic foot ulcers. A combination of 5 genes was discovered that may help distinguish colonized grade 1 from infected grade >/=2 wounds, predict ulcer outcome and contribute to a more appropriate use of antibiotics
Re: Virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers: a new paradigm.
Polymicrobial nature of chronic diabetic foot ulcer biofilm infections determined using bacterial tag encoded FLX amplicon pyrosequencing (bTEFAP).
Dowd SE, Wolcott RD, Sun Y, McKeehan T, Smith E, Rhoads D. PLoS ONE. 2008 Oct 3;3(10):e3326.
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BACKGROUND: Diabetic extremity ulcers are associated with chronic infections. Such ulcer infections are too often followed by amputation because there is little or no understanding of the ecology of such infections or how to control or eliminate this type of chronic infection. A primary impediment to the healing of chronic wounds is biofilm phenotype infections. Diabetic foot ulcers are the most common, disabling, and costly complications of diabetes. Here we seek to derive a better understanding of the polymicrobial nature of chronic diabetic extremity ulcer infections.
METHODS AND FINDINGS: Using a new bacterial tag encoded FLX amplicon pyrosequencing (bTEFAP) approach we have evaluated the bacterial diversity of 40 chronic diabetic foot ulcers from different patients. The most prevalent bacterial genus associated with diabetic chronic wounds was Corynebacterium spp. Findings also show that obligate anaerobes including Bacteroides, Peptoniphilus, Fingoldia, Anaerococcus, and Peptostreptococcus spp. are ubiquitous in diabetic ulcers, comprising a significant portion of the wound biofilm communities. Other major components of the bacterial communities included commonly cultured genera such as Streptococcus, Serratia, Staphylococcus and Enterococcus spp.
CONCLUSIONS: In this article, we highlight the patterns of population diversity observed in the samples and introduce preliminary evidence to support the concept of functional equivalent pathogroups (FEP). Here we introduce FEP as consortia of genotypically distinct bacteria that symbiotically produce a pathogenic community. According to this hypothesis, individual members of these communities when they occur alone may not cause disease but when they coaggregate or consort together into a FEP the synergistic effect provides the functional equivalence of well-known pathogens, such as Staphylococcus aureus, giving the biofilm community the factors necessary to maintain chronic biofilm infections. Further work is definitely warranted and needed in order to prove whether the FEPs concept is a viable hypothesis. The findings here also suggest that traditional culturing methods may be extremely biased as a diagnostic tool as they select for easily cultured organisms such as Staphylococcus aureus and against difficult to culture bacteria such as anaerobes. While PCR methods also have bias, further work is now needed in comparing traditional culture results to high-resolution molecular diagnostic methods such as bTEFAP
Virulence potential of Staphylococcus aureus strains isolated from diabetic foot ulcers: a new paradigm.
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