Management of an infection from NDM-1-producing Escherichia coli with susceptibility to aztreonam

Background Infections with New Delhi metallo-beta-lactamase (NDM)-producing Enterobacterales are increasingly reported in the United States, with some isolates being reported susceptible to aztreonam (ATM) alone. However, data for the use of ATM as monotherapy are lacking, and current guidelines recommend the use of cefiderocol (FDC) or ceftazidime-avibactam (CZA) plus ATM for severe infections due to concern for co-production of serine beta-lactamases. Case Summary Here, we report a case of necrotizing soft tissue and surgical hardware infection in an immunocompromised patient with NDM-1-producing Escherichia coli that was susceptible to ATM, who was successfully treated with ATM + CZA followed by transition to ATM and minocycline. Conclusion This case demonstrates the potential efficacy of ATM therapy, at least for part of the treatment course. Further studies are needed regarding treatment outcomes for ATM-susceptible NDM-producing Enterobacterales infections.