*Purpose: Mycobacterium abscessus complex infections are associated with high rates of morbidity and mortality in immunocompromised hosts. Treatment can be challenging due to broad spectrum antimicrobial resistance that often requires prolonged and frequently toxic therapeutic regimens. Further, HSCT recipients are at increased risk for complications associated with prolonged parenteral and myelosuppressive antibiotic regimens. Tedizolid phosphate is an oral oxazolidinone with demonstrated efficacy against M. abscessus, and may be a safe treatment option in patients requiring prolonged therapy. We report two cases of M. abscessus infection in pediatric HSCT recipients treated with oral tedizolid phosphate.

*Methods: Patient 1, a 16 yo F with a history of relapsed Acute Lymphoblastic Leukemia (ALL) presented with erythema, exudate, and induration of a central venous line site on day + 15 following allogeneic HSCT. Blood and wound cultures were positive for M.abscessus and susceptibility testing demonstrated in vitro resistance to moxifloxacin, ciprofloxacin, doxycycline, minocycline, with intermediate susceptibility to cefoxitin and imipenem, and sensitivity to clarithromycin, linezolid and amikacin. Patient 2, a 14 yo M with relapsed ALL presented with fever and exudative skin and soft tissue infection with associated M. abscessus bacteremia on day +8 following allogeneic HSCT. Susceptibility testing of the isolate demonstrated in vitro resistance to moxifloxacin, ciprofloxacin and doxycycline, intermediate susceptibility to cefoxitin, minocycline and imipenem, and susceptibility to linezolid, amikacin, and clarithromycin.

*Results: Treatment induction regimens for both patients consisted imipenem, azithromycin and amikacin, with durations of 4 and 6 weeks, respectively. Patient WBC, Hgb, and platelet counts following induction were within anticipated range. In both patients, there was resolution of fevers, and clearance of bacteremia (days 2 and 5) with adequate source control. Continuation phase therapy consisted of oral tedizolid phosphate and azithromycin for an additional 16 and 12 weeks, respectively with no evidence of progression or rebound infection at 3 and 2 months respectively.

*Conclusions: Tedizolid phosphate is a novel oxazolidinone with demonstrated activity against M. abscessus and a favorable toxicity profile. We report the first 2 cases to our knowledge, of M. abscessus infection successfully treated with an oral tedizolid phosphate containing antimicrobial regimen in pediatric HSCT recipients. Incorporation of this agent into treatment regimens for M. abscessus infection may decrease superfluous parenteral and toxic antibiotic exposures among high risk HSCT recipients.

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