Successful treatment of an NDM-5-producing, carbapenem-resistant Salmonella Kentucky ST198 infection with aztreonam and ceftazidime-avibactam in a patient with acute erythroid leukemia: a case report

Salmonella enterica serotype Kentucky (S. Kentucky) is a globally distributed food-borne zoonotic pathogen. It is increasingly associated with multi-drug resistance (MDR), notably to ciprofloxacin, a trend largely attributed to antibiotic overuse in humans and livestock.

An acute erythroid leukemia (AML-M6) man was found to be infected with carbapenem-resistant (CR) Salmonella enterica after chemotherapy. Salmonella serum agglutination test showed that the strain belonged to S. Kentucky. Antimicrobial susceptibility test showed that this strain is an MDR strain (resistant to carbapenems, ciprofloxacin, third-generation cephalosporins). Carbapenemase production was assessed via a colloidal gold immunochromatography assay and indicated expression of an NDM enzyme. Whole genome sequencing (WGS) revealed that this strain carried blaNDM-5, blaCTXM-55, and blaTEM-1 genes. Based on the identification of an NDM carbapenemase, in vitro synergy testing was performed, which demonstrated a synergistic effect between aztreonam and ceftazidime-avibactam. The patient was successfully treated with this combination regimen and recovered.

This report describes an unusual infection caused by an NDM-5-producing S. Kentucky in an immunocompromised host. It underscores the necessity of employing combined phenotypic, immunologic, and molecular diagnostics to rapidly elucidate resistance mechanisms in such complex cases. Guided by this comprehensive analysis, the combination of aztreonam and ceftazidime-avibactam proved to be an effective, mechanism-based therapeutic strategy, highlighting its value in managing challenging infections in patients with hematological malignancies.

Not applicable.