Key Insights On Managing Infected Diabetic Ulcers

Clinical Editor: Lawrence Karlock, DPM
Brill concurs, noting that rapidly progressing cellulitis would warrant hospital admission. One should also consider the possibility of a vascular problem as a comorbid concern, notes Dr. Cutrona. Dr. Karlock says the general health status of the patient also comes into play. For example, he would want to admit patients who are on renal dialysis for more aggressive treatment. The patient’s social structure (specifically the availability of a caregiver) plays a role in making the decision to treat patients as outpatients or admitting them to the hospital. “If the patient has a good support system at home to treat this wound, we’ll try to treat on an outpatient basis,” explains Dr. Karlock. “However, if the patient has a poor social structure at home, admission into the hospital is usually more appropriate.” Q: How do you approach the MRSA infected wound? A: Dr. Brill says MRSA and vancomycin resistant Staph aureus (VRSA) are becoming “alarmingly increasing” problems in the community he serves. More specifically, Dr. Karlock says MRSA accounts for upward of 40 percent of all Staph aureus isolates at one of the local hospitals in his area. Dr. Cutrona says 65 percent of the Staph aureus cases at his facility are MRSA. Dr. Brill says one should have a strong index of suspicion for MRSA when assessing patients who have diabetic wounds of long duration and a long history of single or multiple oral and/or topical antibiotic use. For these patients, Dr. Brill will pursue empiric treatment with vancomycin in the hospital and trimethoprim/sulphamethoxazole for outpatients. If the patients are allergic to sulphamethoxazole, Dr. Brill says he will substitute a tetracycline instead. Due to increasing resistance, Dr. Brill says he reserves daptomycin and linezolid for resistant cases. In these cases, he always obtains an infectious disease consult. MRSA strains are more prevalent in the hospital, according to Dr. Cutrona. He says these strains are resistant to most oral antibiotics and are sensitive to vancomycin, linezolid and rifampin. Dr. Cutrona says outpatient MRSA tends to be sensitive to the aforementioned antibiotics as well as doxycycline, clindamycin and trimethoprimsulfa. He emphasizes that treating MRSA is no different than treating penicillin- or methicillin-sensitive Staph aureus. If the wound involves deep structures, such as tendon, ligament or bone, Dr. Cutrona says IV antibiotics are necessary as well as aggressive surgical debridement. He emphasizes that clean surgical margins are key to facilitating the effectiveness of the antibiotics. The length of antibiotic therapy depends upon the depth of the wound infection, notes Dr. Cutrona. When there is extension to the bone, he says one will need to proceed with six to eight weeks of IV antibiotics. Q: In the workup of possible pedal osteomyelitis, what imaging modalities do you prefer to use and why? A: Drs. Brill and Karlock prefer magnetic resonance imaging (MRI) when they suspect osteomyelitis. Unless plain radiographs unequivocally demonstrate osteomyelitis, Dr. Brill says he prefers MRI because it is noninvasive and “has a fairly reliable sensitivity and specificity.” However, he warns there is a 10 to 20 percent false positive finding with MRIs, which he says is most likely due to neuropathic changes in bone. For the majority of pedal osteomyelitis, Dr. Karlock says he “usually relies” on standard radiographs as well as probe to bone tests. Dr. Cutrona agrees, noting that changes in serial plain X-rays should enable one to make the diagnosis. Dr. Karlock says he occasionally uses the Tc99 bone scan to rule out osteomyelitis. If he is dealing with a deep wound and wants to determine whether it is a soft tissue infection or osteomyelitis, Dr. Karlock says he will order the Tc99 to confirm there is no bony infection in the foot. He emphasizes this is not commonplace in his practice. Bone scans and the white blood cell tag in the scans seem to be unreliable in assessing patients with diabetes, according to Dr. Cutrona, who cites false positive and negatives in the range of 60 percent. He says these tests are “very expensive,” and for about the the same cost, one can obtain good anatomical resolution either by CT scan or MRI. Dr. Karlock agrees, noting that he usually does not order multiple tests and/or scans in this clinical setting.

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