MRSA: Where Do We Go From Here?
- Volume 18 - Issue 3 - March 2005
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Patients with either type 1 and 2 diabetes have a high prevalence of macrovascular disease.22 Due to frequent vascular dysfunction in the lower extremities and the high-pressure distribution over ulcerated areas of the foot, infections in these patients often require other surgical interventions to promote healing. Surgery may be needed to drain deep pockets of pus, which otherwise could lead to a spread of infection. In ischemic cases, a revascularization procedure is usually indicated in order to save the foot.
One should attempt to treat limb-threatening infections with conservative modalities before resorting to amputation as the latter is associated with significant morbidity and mortality. In a five-year, retrospective cohort study, Pittet, et. al., evaluated outcomes of 105 patients who were admitted for foot lesions.23 Out of these patients, 74 percent had ulcers that were complicated by contiguous osteomyelitis, deep tissue involvement and/or gangrene. Although 14 patients (13 percent) required immediate amputation, researchers implemented conservative treatment in the remainder of the cohort. This consisted of daily wound dressing, debridement, bed rest, removing pressure from the affected area and parenteral antibiotics. This approach was successful in 63 percent of the remaining 91 patients. While cultures revealed the majority of infections in this cohort were polymicrobial, S. aureus was the predominant microorganism isolated.
When More Aggressive Surgery Is Warranted
When osteomyelitis is present in deep ulcers, aggressive debridement of devitalized bone is necessary. In a retrospective study, Bodegom et. al., analyzed the results of surgical treatment of chronic osteomyelitis in the toe of 47 patients with diabetes on antibiotic therapy.24 In all cases, they removed the metatarsophalangeal joint and 37 patients (79 percent) fully recovered after primary surgery. Seven patients required a second procedure and four patients eventually underwent an amputation. Results showed that a cure rate as high as 94 percent is possible with a combination of early surgical treatment and antibiotic therapy.
When infections become limb- or life-threatening, amputation is the modality of choice. Patients with diabetes have a rate of lower extremity amputation that is 15 to 46 times higher than that of the general population and about half of these procedures are performed at the level of the foot.25,26 Fejfarova, et. al., examined the role that resistant organisms, particularly MRSA, play in the incidence of amputation.16 Out of 191 patients treated at a foot clinic, 50 (26 percent) eventually underwent varying degrees of amputation. Those who had undergone amputations were more likely to have had infected ulcers caused by resistant pathogens. Researchers found resistant strains of S. aureus in 21 percent of all patients and in 43 percent of those who required amputations.
Obtaining intraoperative cultures can assist in antibiotic selection or modification. While both superficial swabbing and deep-culture biopsy yield similar results, intraoperative specimens run a lower risk of contamination. Pellizzer, et. al., found that swabbing and tissue biopsy sampling were relatively equal in reliability when comparing specimens in patients with severe polymicrobial infections.27 Both are useful for monitoring antimicrobial treatment, but deep tissue cultures appeared more sensitive for monitoring resistant pathogens.