Rhodococcus is an opportunistic pathogen that primarily affects horses. It presents as a pleomorphic, Gram-positive, aerobic, weakly acid-fast coccobacillus. Human infection is rare and occurs via inhalation or transcutaneous exposure, with immunosuppressed individuals being most vulnerable. It may manifest as pulmonary and/or extrapulmonary disease and has tuberculosis as its main differential diagnosis. A 42-year-old woman from rural Viamão, living near equine and cattle farms but without clear exposure, presented with hypertension, obesity, home oxygen therapy for idiopathic pulmonary hemosiderosis diagnosed in childhood, and immunosuppression due to cyclophosphamide, last used six months earlier. She was admitted with one week of fever, productive cough, hemoptysis, dyspnea and pleuritic chest pain. Initial blood gas showed significant hypocapnia and hypoxemia, improving with nasal oxygen. Initial labs showed leukocytosis without left shift, CRP 78 mg/dL and LDH 525 U/L. Blood cultures were collected promptly, and methylprednisolone plus broad-spectrum meropenem were started. Chest CT revealed diffuse ground-glass opacities suggesting exacerbation of underlying disease and/or alveolar hemorrhage. During hospitalization, the patient improved clinically and laboratorially. Peripheral blood cultures grew Rhodococcus hoagii at 69 hours. Carbapenem was discontinued, and levofloxacin plus azithromycin was started. She continued to improve and was discharged with combined antibiotic therapy for 4–6 weeks. This case illustrates how MALDI-TOF is an important diagnostic tool for rapid identification, as this pathogen is commonly isolated in peripheral blood. Although uncommon, Rhodococcus infection should be suspected in patients with pulmonary disease, risk factors and epidemiologic exposure, particularly when immunosuppressed.
Modesti et al. (2026) studied this question.