Keys To Addressing MRSA In The Diabetic Foot
Quinupristin/dalfopristin (Synercid, Pfizer). Both of these drug components have a synergistic effect in protein synthesis at the 50S ribosomal subunit. While both components are bacteriostatic, the combination of the two demonstrates bactericidal properties to the bacterial wall. There are no renal or hepatic adjustments with the dosing of Synercid but one should still monitor patients with these comorbid risks.
Clinicians commonly use this drug for vancomycin-resistant Staph aureus (VRSA) and as a combination agent for severe MRSA infections. Risks of the medication include arthralgia, myalgia and nausea. Cautious use and prescribing of this agent are recommended in an attempt to avoid the future risks of resistance.
Tigecycline (Tygacil, Pfizer). Tigecycline, a glycylcycline bacteriostatic agent, demonstrates excellent soft tissue penetration and researchers have shown it to be effective against many resistant organisms, including MRSA.7 One advantage is its efficacy against gram-negative bacteria, giving clinicians a broad spectrum coverage option. Researchers have shown tigecycline to be equivalent to vancomycin in battling skin and soft tissue infections.7
However, clinicians should use caution in regard to monitoring sensitivities in the presence of polymicrobial infections involving Pseudomonas. There is no required renal or hepatic adjustment in adults but again, monitoring in high-risk populations is recommended.
Daptomycin (Cubicin, Cubist Pharmaceuticals). Daptomycin is a lipopetide that acts by disrupting cell membrane function via calcium dependent binding. It is bacteriostatic and concentration dependent. There is required renal adjustment to dosing with CrCl levels 8 Daptomycin is approved by the FDA for SSTI and is active against MRSA and VRE.
Case Study One: When A Patient With Diabetes Presents With A Recurrent Ulcer
A 59-year-old African-American male with a history of diabetes for 15 years presented to the clinic with a recurrence of an ulcer to the plantar aspect of his left foot at the level of the fifth metatarsal base. He has had the ulcer on and off for the past year as the ulcer would heal fully but then recur. For the last month, the patient had been self-treating the wound with antibiotic ointment (bacitracin) that he had left over from previous prescriptions. He has not had any pain in the area but is concerned that the ulcer is worse than before as it is “blowing out” of the top and side as well. The patient did notice a creamy discharge when it blew out but that has ceased since then.
The patient’s past medical history is positive for type 2 diabetes, hypertension and peripheral vascular disease. He has a history of a partial hallux amputation on the left foot and partial second and third toe amputations on the right foot, which were well healed. The patient also had a femoral to popliteal bypass on the right extremity. He is married and denies tobacco and alcohol use. The patient cares for his wife, who is also a below-knee amputee and has diabetes. His last HgA1c was 7.2 and he monitors his blood glucose levels regularly. He denies fever and chills.
Upon examination, the patient has palpable dorsalis pedis and posterior tibial pulses on the right and decreased posterior tibial and dorsalis pedis pulses on the left (1+). He has palpable popliteal bilateral with absent pedal and lower extremity hair growth. Protective sensation is absent to both feet proximal to the ankle with the Semmes Weinstein monofilament. Nails are intact bilaterally. He has a 1.5 cm ulceration to the plantar left fifth metatarsal base, which probes to the bone and tracks laterally to exit the ulcer site at the lateral fifth metatarsal base. There are surrounding macerated tissue margins to the ulcer sites. Seropurulent drainage is present. We irrigated the wound and took deep soft tissue cultures. Radiographs of the left foot did not demonstrate any osseous involvement and cortices were intact.