Antibiotics And DFIs: What The Evidence Reveals

Anne Spichler, MD, PhD, and David G. Armstrong, DPM, MD, PhD

A Closer Look At The IDSA Antibiotic Recommendations For MRSA

We usually select antibiotics based on the severity of the infection, the likely etiologic agent(s) and the previous patient history of infection.

   The Infectious Diseases Society of America (IDSA) guideline, published in 2012, explained how to clinically identify and classify diabetic foot infections.7 The guideline also described the microbiology of diabetic foot infections and suggested that the selection of antibiotic therapy depended on various parameters. One must usually select the initial antibiotic regimen empirically and may modify it later on the basis of the availability of additional clinical and microbiological information.7

   According to the IDSA, the isolation of antibiotic-resistant organisms, particularly methicillin resistant Staphylococcus aureus (MRSA), is an increasing problem with diabetic foot infections in most settings.7 Prior long-term or inappropriate use of antibiotics, previous hospitalization, long duration of the foot wound, the presence of osteomyelitis and nasal carriage of MRSA are some factors that increase the risk for diabetic foot infection with MRSA. The most common predictor for MRSA is a previous history of this infection.

   All clinically infected foot wounds require antibiotic therapy. Infection with MRSA requires specifically targeted antibiotic therapy. When it comes to patients with diabetic foot infections, the IDSA recommends empiric treatment for MRSA in patients with a history of a previous MRSA infection or colonization within the past year; when there is a high local prevalence of MRSA; and in cases of severe infection when failing to cover MRSA, while waiting for definitive cultures, would pose a risk of treatment failure. For moderate or severe MRSA infection, the recommended antibiotics are vancomycin, linezolid (Zyvox, Pfizer) or daptomycin (Cubicin, Cubist Pharmaceuticals), according to the IDSA guideline.7

   Lipsky and colleagues compared IV and oral linezolid with IV ampicillin-sulbactam and oral amoxicillin-clavulanate in 371 patients with diabetic foot infections.8 The authors note that clinical cure rates associated with linezolid and the comparators were statistically equivalent overall, but were significantly higher for linezolid-treated patients with infected foot ulcers and for patients without osteomyelitis. In the linezolid group, 13 of the 18 patients who had MRSA experienced a cure.

   Arbeit and colleagues compared daptomycin with conventional antibiotics (cloxacillin, nafcillin, oxacillin, or flucloxacillin or vancomycin) in two trials involving a total of 1,092 patients ages 18 to 85.9 The primary inclusion criterion was a complicated skin and skin structure infection that was due, at least in part, to Gram-positive organisms and that required hospitalization and parenteral antimicrobial therapy for 96 hours or more. More than 80 percent of the patients had an infecting organism identified and the distribution of infecting organisms was similar in both groups. The authors noted that the safety and efficacy of daptomycin were comparable with the comparator groups in the study.

What You Should Know About New Antibiotic Agents

However, new antibiotics and new combinations of antibiotics are always welcome for the physician. Ceftaroline (Teflaro, Forest Laboratories) is a new parenteral cephalosporin with antimicrobial activity for multidrug-resistant Gram-positive bacteria, including S. aureus strains with reduced susceptibility to methicillin and vancomycin.

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