History
Trauma
Elucidating a history of trauma, especially a puncture wound while gardening or a cat's scratch, can help make the correct diagnosis. Vehicular accidents are predisposing factors, particularly if significant exposure to soil occurred. [18] Trauma may have occurred several days to several months prior to clinical illness.
Occupational exposure
Rural laborers exposed to traumatic injuries while walking barefoot are at highest risk of mycetoma formation. Others at increased risk are farmers and gardeners.
Immunodeficiency
Immunosuppression is commonly a contributing factor in N asteroides infections but typically is not necessary for infections caused by N brasiliensis. N asteroides is primarily an opportunistic pathogen, while N brasiliensis causes skin infections in healthy hosts.
Additionally, with the advent of new immune-response modifying medications (eg, infliximab) for relatively common diseases such as rheumatoid arthritis, Crohn disease, and psoriasis, opportunistic nocardiosis may increase in prevalence. [19] A case report revealed Nocardia species as the causative organisms in a patient receiving infliximab and prednisone. Inquire about compliance with prophylactic antibiotics with certain underlying conditions, including HIV infection and certain cancers, including leukemia.
Given the sensitivity of Nocardia species to trimethoprim-sulfamethoxazole (TMP-SMZ), compliance with prophylaxis greatly decreases the likelihood of nocardiosis in these patients. [20]
Resistance to previous antibiotic therapy
Because many nocardial infections mimic infections caused by skin florae, standard antibiotic regimens for staphylococcal and streptococcal species often fail and the infection worsens while the patient is on empiric therapy.
History of fever
Fever is more common in patients with acute cellulitis and abscess.
Mild weight loss
Weight loss is more common in patients with the chronic mycetoma variant.
History of local recurrence
Cellulitis and abscesses caused by nocardial species require prolonged antibiotic therapy or they commonly recur.
Physical Examination
Superficial skin infection (eg, cellulitis, abscesses, ulcers)
This cannot be distinguished clinically from more common bacterial etiologies. Typically, no lymphadenopathy is noted. Fever is common. Superficial skin infection is often accompanied by a pyoderma, which is a purulent crusting lesion that heals with ulcer formation. In 1979, Satterwhite and Wallace [21] reported that 3 of 7 patients had associated pyoderma. Patients may have other less common superficial infections, including paronychia, posttraumatic keratitis and endophthalmitis, and wound infections secondary to compound fractures or sternotomy.
Lymphocutaneous infection
This manifests as an initial ulcerative papule or nodule at the inoculation site with secondary subcutaneous nodules along lymphatic vessels (chaining nodular lymphangitis). [22] It most commonly involves the upper extremities. The lymphocutaneous infection is more acute and inflammatory, with more painful, tender, erythematous lesions, than in infections caused by Sporothrix schenckii. Purulent drainage is noted. Macroscopic sulfur granules can be expressed from lesions, although this is a rare occurrence. Regional lymphadenopathy is common.
Mycetoma
This typically involves the dorsal foot, and it can be localized to the leg, arm, or hand. It is a progressively destructive infection of the skin and can extend to subcutaneous tissues, fascia, bone, and muscle. It appears as an area of localized tumorlike swelling with multiple sinus tracts; however, amazingly, it usually is not painful. Macroscopic sulfur granules commonly can be expressed from sinus tracts.
Complications
Recurrence of disease is the most frequent complication. A full course of appropriate antibiotics is essential for preventing recurrence.
At least three cases of dissemination of primary cutaneous nocardiosis have been reported. Despite the rarity of this occurrence, dissemination is associated with a much higher mortality rate.
If a patient remains ill or febrile despite seemingly adequate therapy, treatment failure may be a result of a sequestered abscess that requires drainage. Often, localization and drainage subsequently result in efficacious results.
Mycetoma, although rare in developed countries, is much more invasive and destructive than other forms of cutaneous nocardiosis. Because fascia, bone, and muscle are frequently involved in severe untreated mycetoma, wide debridement and amputation are known complications.
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Red nodules on a patient with disseminated nocardiosis.
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Ulcer on the arm of a patient with primary cutaneous nocardiosis.
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Gomori methenamine silver stain demonstrating black filamentous Nocardia species.
