Hold your Horses! An Uncommon Cause of Bacteremia in HCT Recipients

Abstract

Abstract Background Diagnosis and management of bloodstream infections due to uncommon microorganisms in immunocompromised hosts (ICH) are challenging. Removing central venous catheters (CVC) and combination antimicrobial therapy may be necessary. Case A 2-year-old female with Mucopolysaccharidosis type I on day +125 after matched unrelated donor allogenic transplant presented with 2 days of decreased activity. Two days prior, she had completed 4 weeks of ciprofloxacin and clarithromycin for treatment of Mycobacterium cosmeticum catheter-related bacteremia (CRBSI). The CVC was removed. The patient lived in a rural area but had no direct animal exposure, except for an indoor vaccinated dog. Household contacts were healthy and immunized. The patient was febrile and tachycardic with no evidence of infection around CVL or G-tube. Laboratory results showed pancytopenia and elevated C-reactive protein Blood cultures grew diphtheroid gram-positive bacilli (GPB) and gram-positive cocci (GPC) in clusters, the later identified as S. epidermidis. The GPB could not be identified from the liquid media and was sent to an outside lab. The report was corrected to GPC after growing on solid medium culture. The patient was started on meropenem and vancomycin and the CVC was removed. The GPB was identified as Rhodococcus equi. A chest CT showed new ground glass nodules in the left lower lobe. The patient defervesced and was discharged on a 10-day course of oral linezolid for S. epidermidis, clarithromycin and levofloxacin. She completed one month of clarithromycin and levofloxacin. Chest CT at end of treatment confirmed resolution. Discussion and conclusions Rhodococcus equi is a pleomorphic gram-positive bacteria that presents as cocci in solid media and as a diphtheroid gram-positive rod in liquid media. Horses are the primary hosts, but most herbivores are fecal carriers. Transmission occurs through inhalation of dust from contaminated soil. R.equi frequently presents as pulmonary infection with cavitated nodules. Over half of ICH develop secondary bacteremia. Extrapulmonary infection secondary to dissemination of pulmonary disease can occur but isolated extrapulmonary disease is rare. R.equi can be easily dismissed as a contaminant requiring a high level of suspicion and communication with lab personnel. When isolated from an extrapulmonary location, chest imagining is essential to guide treatment. Treatment should combine two antibiotics, at least one of them with intracellular activity, with fluoroquinolones and macrolides among the preferred options. For device-related infections, removal is recommended. Treatment duration for uncomplicated infections is 10 to 14 days, but cavitary lesions require longer treatment based on the resolution of lesions