Case report of peritoneal dialysis-associated peritonitis caused by Mycobacterium abscessus in a child, successfully treated with dual β-lactam combination therapy.

Background: Peritoneal dialysis-associated peritonitis caused by Mycobacterium abscessus is a rare and difficult-to-treat infection that frequently results in peritoneal dialysis failure. Since M. abscessus is intrinsically resistant to many antibiotics, therapeutic decisions are challenging. While data are limited, a prolonged course of antibiotics with at least two or three agents is recommended, guided by susceptibility testing. Many regimens use amikacin, which can worsen renal function and cause deafness. There is limited safety and efficacy data on newer antimycobacterial medications in children. Safe and well-tolerated options are needed for the treatment of infections caused by M. abscessus. Case Summary: Herein, we present the case of a toddler with dysplastic congenital renal disease, who developed peritoneal dialysis catheter-related M. abscessus peritonitis and was treated with a multidrug regimen including two β-lactam antibiotics. This resulted in clinical and microbiologic cure, despite peritoneal failure and transition to hemodialysis. Based on predicted synergy testing, the patient was treated with a combination that included meropenem and ceftaroline for the initial intensified intravenous phase, followed by a regimen that included amoxicillin combined with cefdinir for step-down therapy. This allowed the option of enteral therapy and limited the use of more toxic medications or agents with inadequate information for use in children. Conclusion: This case highlights the potential benefit of dual β-lactam therapy for the treatment of M. abscessus infection as a well-tolerated regimen for a difficult-to-treat infection. To our knowledge, this is the first report using this approach for the treatment of M. abscessus peritonitis.