Diabetic Foot Ulcer (DFU)

A diabetic foot ulcer (DFU) is a chronic wound that is a common complication among patients who have diabetes mellitus that is not well controlled. It is usually the result of poor glycemic control, underlying neuropathy, peripheral vascular disease, or poor foot care. It is also a common cause of osteomyelitis of the foot – infection and inflammation of the bones of the foot – and can result in amputation. These ulcers are typically located on the bottom of the foot, usually in an area that experiences repetitive trauma and pressure.

Diabetic foot ulcers occur in 15% of patients with diabetes. Native Americans, African Americans, Hispanics, and older men are the patient groups most likely to develop DFUs. People who use insulin are at a higher risk of developing a foot ulcer, as are patients with diabetes-related kidney, eye, and heart disease, and patients who are overweight and use alcohol and tobacco.

Of those who develop a foot ulcer, 6% will be hospitalized due to infection or other ulcer-related complication. Staphylococcus is the most common infective organism, but DFU infections can be caused by both bacteria and fungi. Approximately 14% - 24% of patients with diabetes who develop a foot ulcer will have an amputation as a result of a DFU that does not heal.

DFU Infection Symptoms

Common symptoms include:

  • Drainage on a patient’s socks
  • Redness and swelling
  • Odor

Pain is not a common symptom because many people who develop foot ulcers lose the ability to feel pain, a consequence of nerve damage called “peripheral neuropathy” that is also a common complication of poorly controlled diabetes.

MicroGenDX Tests Used in Diagnosing DFU Infections

An evaluation and culture (growing microbes from your sample in a lab) are often used to diagnose foot ulcer infections. However, standard cultures might come back negative even when you actually do have an infection, and that means your infection won’t be treated. A MicroGenDX test detects the DNA of all microbes in your sample along with how much of each microbe is present and uses that information to identify causes of your infection and the drugs that can best treat it. Because of the many factors contributing to the formation of diabetic foot ulcers, DFUs can take long time to heal even when an infection is cured. However, MicroGenDX testing can assist with healing when an infection slowed or “stalled” your DFU.

You can order that WoundKEY test and get complete instructions here: https://microgendx.com/product/woundkey-test-service-dm-intl/

Providing Samples for the DFU Infection Test

Your doctor will use one of two methods to provide a sample for this test: the swab method or debridement, which is the surgical removal of dead or contaminated tissue. Both methods start by using gauze and saline to lightly wipe the surface area to remove dead skin and tissue.

For the swab method, your doctor will roll the swab over entire surface area of the wound, applying pressure as it moves across the wound. As much material as possible needs to be gathered on the swab to ensure a conclusive sample. Then the swab will be inserted into the specimen tube.

For the debridement method, your doctor might use a numbing agent such as injectable Lidocaine for your comfort. Then your doctor will collect the sample by scraping the entire surface of the wound. There might be a little bit of bleeding. If possible, your doctor will collect samples from all areas of the wound to ensure a full and accurate sample, and then transfer the sample into a specimen vial.

Everything you need to know about how chronic wound samples are taken is included with the WoundKEY test and is also available online on the product page. The instructions included with your test contain illustrations that will help you to help your doctor collect a sample without contaminating it. It is always important to obtain a proper sample by following the instructions for collecting the sample, as well as when packaging and shipping it. For example, with either method, be sure not to contaminate the sample by touching it with your hands. For best results, you must be off all antibiotics for two days before the sample is collected. However, if this is not possible, the test can still be run.

Medical Specialties That Treat DFU Infections

The recommended approach for treatment combines an interprofessional team including a primary care physician, podiatrist, endocrinologist, vascular surgeon, and infectious disease specialist.

How DFU Infections are Treated

DFU infections are treated with antibiotics that may be taken orally, applied topically on the surface of the wound, or both. How long and how often you take an oral antibiotic or apply a topical antibiotic depends on what your doctor prescribes. If a fungus is the cause of your DFU infection, you will be prescribed an anti-fungal instead of an antibiotic.

DFU infections can take a long time to resolve – and the underlying foot ulcer can require additional weeks or months to fully heal – so carefully following the instructions and duration for using the antibiotics or antifungals your doctor prescribes is very important. Some bacteria that cause DFU infections can also develop resistance to specific antibiotics, so that the infection cannot be effectively treated with those antibiotics. This is why all MicroGenDX diagnostic tests include detection of antibiotic resistance genes in your sample, and then provide alternative antibiotics for your doctor to consider prescribing to you.

References

  1. Oliver TI, Mutluoglu M. Diabetic Foot Ulcer. [Updated 2021 Aug 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537328/
  2. American Podiatric Medical Association (APMA) website: https://www.apma.org/diabeticwoundcare
  3. van Asten, S.A.V., La Fontaine, J., Peters, E.J.G. et al. The microbiome of diabetic foot osteomyelitis. Eur J Clin Microbiol Infect Dis 35, 293–298 (2016). https://doi.org/10.1007/s10096-015-2544-1
  4. https://www.idcmjournal.org/evaluation-of-diabetic-foot-infections

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