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Microbes & Immunity A case of cutaneous Nocardia farcinica

Table 1. Isolate’s antimicrobial susceptibility
AM K AM C CRO CIP DOX LZD MIN MFX TOB TMP‑ SMX
MIC (µg/mL) 1 (S) 16 (I) 64 (R) 0.25 (S) 4 (I) 2 (S) 4 (I) 0.06 (S) 64 (R) 1 (S)
Note: These results are derived from post-operative week 12.
Abbreviations: MIC: Minimum inhibitory concentration; AMC: Amoxicillin- clavulanate; AMK: Amikacin; CIP: Ciprofloxacin; CRO: Ceftriaxone;
DOX: Doxycycline; I: Intermediate; LZD: Linezolid; MFX: Moxifloxacin; MIN: Minocycline; R: Resistant; S: Susceptible; TOB: Tobramycin; TMP-SMX:
Trimethoprim/sulfamethoxazole.

pulmonary source. Alternatively, patients can have direct N. farcinica, 19 patients were immunosuppressed (Table 2).
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exposure by inoculation from the environment, which is It is relatively rare to detect infected individuals with intact
most likely caused by N. farcinica. First described in 1888 immune systems; more details are discussed in Table 3.
by Edward Nocard in his discovery of bovine farcy, this All three immunocompetent cases we reviewed had
pathogen was initially named Streptothrix farcinica. One documented culture data about N. farcinica growth as well
year later, it was re-characterized by Trevisan who named as obvious environmental exposures to this pathogenic
it “Nocardia farcinica.” 1 organism. The treatment regimens varied based on extent
Primary cutaneous nocardiosis due to N. farcinica of subcutaneous infection as well as tolerance to the chosen
in particular is known for preferentially infecting antibiotics, but the gold standard of treatment, TMP-SMX
immunocompetent individuals. The presentation differs was attempted in each of the cases. There was resolution
between immunocompromised and immunocompetent of infection documented in each case as demonstrated in
patients. The criteria to be considered immunocompromised Table 3. Our case presents a woman with several risk factors,
for the purpose of this discussion includes primary including uncontrolled diabetes, smoking, and recent
immunodeficiency, untreated or advanced HIV, active surgery, who had a persistent abscess growing N. farcinica.
malignancy receiving chemotherapy, status post-solid This patient was not a gardener and denied contact with soil
organ transplant (SOT), or hematopoietic stem cell or decomposing organic matter. On detailed history, it was
transplant (HCT) with concurrent immunosuppressive discovered that she went for camping soon after a surgical
medications, chronic use of corticosteroids, and treatment procedure, she had and washed her hands with well water.
with immunomodulating therapy such as biologics. This was hypothesized to be an environmental exposure to
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Immunocompromised patients have greater morbidity N. farcinica. The proposed treatment was 3 – 6 months of
and mortality with Nocardia infections due to higher rates TMP- SMX while evaluating for resolution of the cutaneous
of dissemination. In a retrospective chart review, Nocardia lesion. There was consideration of her other risk factors as
infection-related mortality was 71% and 32% in HCT and mentioned above playing a role in delayed wound healing;
SOT patients, respectively. The article did not specify however, the lack of involvement of post-operative wound
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which of these patients were infected with N. farcinica over healing in two of three cases reviewed in literature argue
other subspecies of Nocardia, but N. farcinica was listed against that. Nevertheless, more investigations regarding
as one of the top three isolated subspecies. N. farcinica diabetes, smoking, and surgical site infection as risk factors
has been isolated in brain abscess pathology, which is for non- healing wounds implicated in Nocardia species-
also more common in immunocompromised patients. related infections are warranted, as they were not the
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Nocardia brain abscesses are considered the most severe primary inclusion criteria for immunosuppressed states
form of dissemination and mortality rates among patients based on the literature review for this paper.
with disseminated disease are 20% for immunocompetent There are several challenges in treating N. farcinica, one
patients and 55% for immunocompromised patients. of which is choosing the proper antibiotics. Treatment is
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Immunocompetent patients with nocardiosis tend to based on susceptibility of the organism; however, empiric
have indolent courses and the infection is more likely to therapy is often required as receiving antimicrobial
be limited to the skin. The lesions caused by cutaneous susceptibility results takes time. Historically, TMP-SMX
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nocardial infection vary and can present as ulcerations, has been used as monotherapy of choice, but there are
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papules, nodules, and abscesses. The spectrum of no official guidelines in place. Linezolid (LZD) is another
presentations and indolent course could lead to option. Treatment depends on whether a patient is
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underdiagnosis in immunocompetent patients, especially immunocompetent or immunocompromised, as well as
if the empiric antibiotics were in the class that N. farcinica the location of infection. A review done in 2021 aimed to
is susceptible to. Among the 15 case reports reviewed and create a potential algorithm for treatment of nocardiosis
one retrospective review of transplant patients of cutaneous based on these criteria. Using this algorithm, an
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Volume 2 Issue 4 (2025) 146 doi: 10.36922/mi.5189