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Trichophyton Species As The Cause of A Diabetic Deep Plantar Foot Abscess: A Case Report
Bacterial diabetic foot infections commonly present with Staphylococcus species involvement; however, Trichophyton species in a deep tissue abscess of the foot involving muscles and tendons is more rare. Dermatophytes predominantly invade the nails and hair, but not the deep tissue. Gardenier and colleagues in 2016 presented a case series of angioinvasive mold infections in burn patients.1 Toussaint and Sticherling in 2019 reported a case of an immunocompromised patient with several dermal abscesses caused by Trichophyton.2 As diabetic foot infections are usually polybacterial, patients are often treated only with antibacterial therapy. Clinicians often overlook the possibility of fungal infectious elements, and do not always order fungal cultures as part of the workup.3
When A Patient’s Infection Is Not Responding To Treatment
We present an unusual case of a 39-year-old male with poorly controlled type 2 diabetes, and status post-myocardial infarction, who presented to the ED with an infected chronic plantar right foot wound. There was no superficial dermatophytosis noted to the foot. He began empiric IV antibiotics, and a right foot MRI showed osteomyelitis of the bases of the fourth and fifth proximal phalanges as well as the head of the fourth metatarsal. He underwent initial irrigation and debridement of the wound with resection of the infected bone; however, on the first postoperative day he continued to have severe foot edema, erythema, and purulence from the operative foot. Computed tomography (CT) and repeat MRI showed no plantar abscess; however, clinically and intraoperatively noted purulence.
The patient underwent repeat incision and drainage with continued IV antibiotics; however, there was little-to-no clinical improvement. Bacterial cultures grew several species; thus, we administered more targeted IV antibiotics. He underwent several more debridements before a soft tissue culture identified mold from a specimen collected during the second incision and drainage. The fungal culture began growing mold 10 days after collection, and as a result, the patient began taking oral Cresemba® (isavuconazole sulfate, Pfizer) per the infectious disease team's recommendation. In addition, after culturing the mold, we included amphotericin B powder in the saline irrigation. We also placed cement beads impregnated with amphotericin B and vancomycin into the wound for several days before the final procedure, at which time we closed the wound with sutures. Discharge took place from the hospital after 16 days. The infectious disease team recommended a six-week course of IV antibiotics (Vancomycin with trough goal 15-20, cefepime 2g every 12 hours), oral metronidazole 500mg daily, and oral Cresemba for six weeks upon discharge. The culture identified the mold as a “Trichophyton species” with no further differentiation, and final results became available 21 days after collection. He continued with local wound care and offloading, making a full recovery several weeks later.
Taking A Closer Look At Deep Dermatophyte Infections
Dermatophyte infections commonly present superficially in hair, nails, and skin. Deeper dermatophyte infection is rare and typically occurs in patients with immunosuppressive conditions such as diabetes, organ transplantation, autoimmune diseases, or patients on immunosuppressive therapy.1 These patients typically present with a superficial fungal infection as well, however, not always. In cases of severe dermatophyte infection and no known immunosuppressive conditions, it may be helpful to screen patients for inherited immunodeficiencies.1,2 Deeper dermatophyte infections typically involve the lower extremities; however, they can occur anywhere in the body.4
In our case, the patient had diabetes with a history of myocardial infarction and with concurrent influenza A and RSV diagnoses. The patient had had a diabetic foot ulcer for several months prior to presentation. The most common pathogen for deep dermatophyte infections is T. rubrum, but other causative pathogens include T. violaceum, T. mentagrophytes, Microsporum canis, M. ferrugineum, and T. verrucosum. The portal of entry for this case of deep dermatophyte infection was possibly the chronic foot wound on the operative foot. These species of molds and fungus are ubiquitous on many surfaces, including the insides of shoes. T. rubrum and other dermatophytes thrive in shoes as they provide a dark, warm, moist environment. Individuals with diabetes are very likely to present with superficial dermatophyte infections like onychomycosis and tinea pedis. As deeper dermatophyte infections are so rare and can present in diverse ways, there is not yet a clear classification system.
One should consider the possibility of deep fungal infections in patients with immunosuppressive conditions, even without the presence of superficial fungus.2 Fungal and bacterial cultures should be routine in this patient population. These infections should also exist in the differential diganosis for situations where the wound or clinical picture is not improving despite appropriate antibiotic coverage, as in this case.5 Fungal cultures may take longer to result than bacterial cultures, so at times, there may be a delay in starting antifungal therapy. There is not an established standard treatment for deep dermal dermatophytosis, but systemic antifungal therapy is routinely used with or without oral therapy.2 In this case, we packed cement beads impregnated with Amphotericin B in the wound, and the wound was irrigated using Amphotericin B as well. Early and aggressive wound debridement is critically important. It is often necessary to debride the same wound multiple times. Other tenets of wound care must be followed as well, including glycemic control, edema control, nutrition, and protein intake, and proper offloading for diabetic foot ulcers.4
Concluding Thoughts
In addition to the typical bacterial aerobic and anaerobic culture and sensitivity, fungal cultures are a vital aspect of microbiological examination. In our case, this patient did not fully respond to antibiotic therapy and did not show improvement until we obtained fungal culture results. Once adding IV antifungal medication and Amphotericin B to the regimen, our patient’s systemic condition improved rapidly. The infection of the foot wound resolved in a matter of days; thus, fungal cultures should be part of a routine infection management protocol in immunosuppressed patients.
Dr. Schlesinger is in practice in Yuma and San Luis, Arizona.
Dr. Rottman is a clinical assistant professor with the Division of Vascular and Endovascular Surgery at the University of Arizona Department of Surgery.
1.Gardenier JC, Chopra VK, Filicori F, et al. Angioinvasive mold in the surgical and burn intensive care unit: a case series and review of the literature. Surg Infect Case Reports Volume 2016;1(1):72–78.
2.Toussaint F, Sticherling M. Multiple dermal abscesses by trichophyton rubrum in an immunocompromised patient. Front Med. 2019;6:97.
3.Park BJ, Pappas PG, Wannemuehler KA. Invasive non-aspergillus mold infections in transplant recipients, United States, 2001–2006. Emerg Infect Dis. 2011;17(10);1855-1864.
4.Dai Y, Xia X, Shen H. Multiple abscesses in the lower extremities caused by Trichophyton rubrum. BMC Infect Dis. 2019;19:271.
5. Özturk et al. A neglected causative agent in diabetic foot infection: a retrospective evaluation of 13 patients with fungal etiology. Turk J Med Sci. 2019;49(1):81-86.
Park BJ, Pappas PG, Wannemuehler KA. Invasive non-aspergillus mold infections in transplant recipients, United States, 2001–2006. Emerg Infect Dis. 2011;17(10);1855-1864.
6.Schaenman JM, DiGiuilio DB, Mirels LF, et al. Scedosporium apiospermum soft tissue infection successfully treated with voriconazole: potential pitfalls in the transition from intravenous to oral therapy. J Clin Microbiol. 2005;43(2):973–977.
