MRSA: Where Do We Go From Here?

By David G. Armstrong, DPM, MSc, PhD

   Foot ulcers are a major predictor of future lower limb amputations. Fourteen to 24 percent of patients with diabetes with foot ulcers eventually require an amputation and more than 60 percent of nontraumatic lower extremity amputations occur in those with diabetes.1,2 Although risk factors may vary, the majority of diabetes-related amputations result from peripheral arterial disease, peripheral neuropathy or infection.3

   The healthcare costs associated with diabetic foot infections are staggering. In an analysis of medical and pharmacy insurance claims filed by more than 7 million people during a two-year period, Holzer, et. al., reported that the direct medical expenditures associated with lower extremity ulcers in patients with diabetes exceeded $16 million and 80.7 percent of those costs were hospital-related.4

   Overall, 6 percent of diabetic patients with foot ulcers require hospitalization.3 According to data from the 1983-1990 National Hospital Discharge Surveys (NHDS), chronic ulcers were present in 2.7 percent of all hospitalized patients with diabetes.5 The average hospital length of stay for patients with an extremity ulcer was 59 percent longer than for those without an ulcer. Patients without ulcers remained in the hospital about 10 days whereas those with ulcers stayed approximately 15 days.

   Although up to 90 percent of ulcers will heal when they are treated aggressively with a comprehensive approach, recovery can be slow.6 Ulcers may take weeks or months to heal, and patients remain at high risk for ulcer recurrences.7 Ramsey, et. al., reported that diabetic foot ulcers are predictive of increased mortality.8 Among 8,905 patients with either type 1 or type 2 diabetes, the cumulative three-year survival rate was 72 percent for patients with a foot ulcer versus 87 percent for those without ulcers.

   While not all diabetic foot ulcers become infected, delayed or inadequate treatment can result in an infection that may lead to gangrene, osteomyelitis or even limb amputation. The risk of infection remains high in these cases even when lesions are treated quickly and appropriately.

What The Literature Reveals About The Rise Of MRSA

   Antibiotic resistance is a growing problem in diabetic foot infections. In particular, methicillin-resistant Staphylococcus aureus (MRSA) pathogens have been isolated with increasing frequency from wound and skin infections that commonly affect the lower extremities of patients with diabetes. For these individuals, foot infections caused by MRSA organisms have been associated with poorer outcomes related to an increased risk of amputations and infection-related mortality.

   Wheat, et. al., collected 54 specimens from infected foot ulcers in diabetic patients and identified Staphylococcus isolates in 34 (64 percent) specimens and Streptococcus isolates in 16 (30 percent) specimens.9 In another study involving 111 patients with diabetic foot infections, El-Tahawy reported that S. aureus was identified in 28 percent of cases and was the most common pathogen isolated.10 Other isolated organisms included Pseudomonas aeruginosa (22 percent), Proteus mirabilis (18 percent) and anaerobic gram-negative bacteria (11 percent). Enterococci have frequently been cultured from infections in patients who have been previously treated with cephalosporins whereas Pseudomonas species are often identified in patients whose ulcers have been soaked or treated with wet dressings.11

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