ATLANTA — Diabetes appears to be a predictor for identifying which patients with Staphylococcus aureus-infected wounds will develop severe complications or even die as a result, according to a study presented at the annual meeting of the Wound Healing Society.
“The presence of diabetes was the strongest predictor of severe outcome,” said Lisa Tibor, M.D., of the University of California, San Francisco.
To assess potential clinical predictors of outcome, the researchers reviewed charts of patients identified with S. aureus infection during routine care. Investigators studied wound type and location, relevant comorbidities (diabetes and peripheral arterial disease), antibiotic resistance as reported for treatment protocol, and outcome. Severe outcomes were defined as amputation, sepsis, or death.
Overall, 38 strains of S. aureus were identified from wounds of patients at the University of Tübingen (Germany) hospital, from September to November 2001.
Almost 60% of diabetic patients had severe outcomes. In comparison, no nondiabetic patients with peripheral arterial disease had severe outcomes.
The researchers also looked at possible bacterial markers for poor outcomes. In particular, they evaluated antibiotic resistance and a molecular marker called the S. aureus repeat (STAR) element. The STAR elements are variable-length nucleotide regions on the bacterial chromosome. Select STAR element groups were used as markers for methicillin resistance in this study.
The researchers hypothesized that infections caused by methicillin-resistant S. aureus strains (identified by STAR group) are bacterial indicators of poor patient outcome.
Antibiotic resistance of each strain was tested by plating the strains on antibiotic-coated agar. Polymerase chain reaction was used to identify STAR element groups for each strain.
There was a trend suggesting methicillin resistance was associated with severe outcome. About 40% of patients with methicillin-resistant S. aureus strains and 20% of patients with methicillin-susceptible strains that were resistant to other antibiotics had severe outcomes. Dr. Tibor noted that one patient with an apparently nonresistant strain had a severe outcome. However, there was no clear association between STAR group and severe outcome.
This study was part of a larger one to characterize strains of S. aureus at the molecular level.