Primary cutaneous nocardiosis in an immune-competent patient

ARTICLE

A carbuncle is a purulent bacterial inflammation originating from a hair follicle. Often an accompanying lymphadenitis and, in an advanced stage, systemic fever can be found. In the natural course of the lesion the draining of pus or, rarely, resorption can be observed. Septic thromboses of the sinus cavities are a known complication of carbuncles in the facial area.

The therapy for a carbuncle is incision and drainage, and local antiseptic or antibiotic treatment. In the case of a lymphogenic or hematogenic dissemination of bacteria a systemic antibacterial therapy must be initiated.

The most often isolated bacterium is Staphylococcus aureus. We recently observed a patient with a carbuncle in the area of the paranasal crease. A primary cutaneous nocardiosis was the final diagnosis. The case presented demonstrates the importance as well as the difficulties of obtaining a correct diagnosis in an apparently typical illness.

Case report

An otherwise healthy 59-year-old Swiss woman was referred to the hospital by her family doctor with a purulent skin lesion on the face. Two days prior to admission the patient noticed for the first time a slightly elevated skin lesion close to the nose on the right side. Over the next two days the lesion became more swollen, was surrounded by a red area and was warm compared to other skin areas. The morning of the day of admission, the patient awoke with a frontal headache and noticed a new swelling of the right lower eyelid. Her family doctor suspected a paranasal abscess and referred her to the hospital. Up to this time the patient had had no systemic symptoms.

The physical examination revealed multiple purulent skin lesions in the region of the right paranasal crease. These lesions were surrounded by an erythematous and indurated skin area (Fig. A) and of a swelling of the right lower eyelid. Slightly enlarged and painful lymph nodes were palpated in the neck on the right side. Laboratory investigations documented an elevation of the ESR (29 mm/1 h, limit < 10 mm/1 h) and of the C-reactive protein (126 mg/l, limit < 9 mg/l). The leukocyte count and the differential were within normal limits.

Based on these findings the presumptive diagnosis of a carbuncle caused by an infection with Staphylococcus aureus was made. Microbiological cultures of pus as well as material for herpes cell cultures were taken and an intravenous antibiotic therapy with amoxicillin and clavulanic acid was started. A surgical debridement was planned for the following day.

The second day in hospital the patient was febrile up to 39.6° C. Examination revealed an increase in the size of the skin lesion and a new central ulcer. The swelling of the right lower eyelid progressed and an additional edema of the upper eyelid was found. Surgical debridement showed no abscess formation and the macroscopic appearance corresponded to a cellulitis. A biopsy for histological examination and additional material for microbiological testing were taken.

The third day of hospitilization a central ulcer with a two centimeter diameter and with necrotic borders had developed in the area of the surgical debridement. The surrounding area showed an erythematous induration with multiple pustules (Fig. B). Based upon these findings the diagnosis of a pyoderma gangrenosum or a fasciitis, as well as of a Morbus Wegener was also considered. As a direct consequence a PCR assay against mycobacteria, the search for sporotrichosis and actinomycosis as well as the assessment of the ANCA were initiated. The antibiotic therapy was extended by clindamycin because of the possible differential diagnosis of a fasciitis.

The histology of the skin biopsy showed a dense inflammatory infiltrate with beginning of abscess formation and focal ulceration. In some places the Brown and Brenn stain (an equivalent to the Gram stain that is used in histology) revealed bacterial filaments (Fig. C). A Gram stain of purulent material that was collected during the debridement demonstrated delicate branching gram-positive rods (Fig. D) and in culture a Nocardia species could be identified (Fig. E). The antibiotic sensitivity testing determined susceptibility to penicillin, amoxicillin, trimethoprim-sulfamethoxazole and tetracycline. Identification using the sequencing of the 16S-rDNA identified Nocardia brasiliensis.

Based on the antibiotic susceptibly testing the therapy was reduced again to amoxicillin and clavulanic acid for a total of 28 days and an additional topical treatment with mupirocin ointment three times a day was started. The patient was discharged from the hospital after nine days. A follow-up evaluation three months later showed a complete clinical resolution of the skin lesion (Fig. F).

Discussion

Nocardia brasiliensis belongs with Nocardia asteroides and other Nocardia species to the genus Nocardia. These bacteria are found widespread in the soil and are necessarily aerobic. Nocardia species enter the human organism either by skin lesions or by the respiratory tract. Infections are seen most often in patients with an immunosuppressive disease as for example HIV infection, leukemia, lymphoma, dysgammaglobulinaemia but also in patients suffering from a chronic pulmonary disease or patients treated with immunosuppressive drugs [1-6]. Typically a purulent inflammation with central necrosis is found. Pulmonary, cutaneous and also systemic manifestations of Nocardia infections are known. However, a rare form of infection is the so-called actinomycetoma that is seen as tumor-like formations in the region of the extremities with involvement of the bone, as for example, the Madura foot.

The identification of Nocardia from other bacteria such as species of Mycobacteria, Corynebacteria, Rhodococcus, Gordona, Tsukamurella and others is difficult and is mostly not possible with commercial assays. The traditional way of identification consists of susceptibly testing, chromatographic analysis of components of the cell wall, ribotyping, DNA amplification and the use of endonucleases. Because of very slow growth, cultures have to be held for at least one week. In contrast, the sequencing of the 16S-rRNA (respectively of the coding DNA) is a fast method that allows an identification within 48 hrs.

In the literature several case reports of cutaneous Nocardiosis exist. In most cases a skin injury, as for example a skin abrasion [8], occurred prior to the infection. There are also cases documented after insect bites or cat scratch. Some weeks after the initial skin lesion the first symptoms are detected. The cutaneous Nocardia infection typically consists of a superficial skin lesion (pustule, ulcer, abscess) and of accompanying local lymphadenopathy. Often a cutaneous nocardiosis is a sign of a disseminated Nocardia infection [11-15]. An isolated primary cutaneous Nocardiosis as reported is rare [16, 17].

CONCLUSION

In conclusion, this case report is unique for several reasons: First, the patient presented suffered from a primary cutaneous Nocardia infection. Second, no prior skin injury occurred and third, the patient was not immune compromised. Therefore, in a case of an atypical carbuncle it is important to consider a Nocardia infection in the differential diagnosis and to initiate the necessary microbiological tests.

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