Carriage and infections by multi-carbapenemases producing Enterobacterales.

Introduction: Multi-carbapenemases producing Enterobacterales (MCP-EB) represents a new public health challenge due to their ability to display complex resistance phenotypes.

Methods: MCP-EB isolates identified from patients admitted to an Italian Center in the period 2020-2024 were included. Clinical features were collected.

Results: Among 3,117 carbapenemase-producing Enterobacterales clinical strains, 31 (1 %) were MCP-EB and were detected from 28 patients. The most common MCP-EB species was Klebsiella pneumoniae (78.6 %; n = 22). Six combinations of two different carbapenemases were observed: KPC+VIM (75 %; n = 21), KPC+NDM (10.7 %; n=3), VIM+NDM (10.7 %; n = 3), KPC+OXA-48-like (3.6 %; n = 1), VIM+OXA-48-like (7.1 %; n = 2), and NDM+OXA-48-like (3.6 %; n = 1). Patients with MCP-EB had a median age of 67 years [IQR 59-73], were predominantly men (57.1 %; n = 16), and a median Charlson Comorbidity Index of 5 [IQR 4-6]. The comorbidities mainly observed were cardiovascular disease (53.6 %; n = 15), chronic respiratory disease (39.3 %; n = 11), and chronic kidney disease (32.1 %; n = 9). Fifty per cent (n = 14) of patients had been hospitalized in the previous 180 days and 75 % (n = 21) had been exposed to antibiotics in the previous 30 days. Median time from admission to MCP-EB specimen collection was 16 days [IQR 10-24] and 28.6 % (n = 8) of patients showed to carry MCP-EB in more than two body districts. Fourteen-day, 30-day, and in-hospital mortality were 10.7 %, 25 %, and 32.1 %, respectively. MCP-EB showed high rates of resistance to all antibiotics tested except aztreonam/avibactam. Patients with MCP-EB infection (35.7 %; n = 10) were treated with combination regimens, mainly including aztreonam plus ceftazidime/avibactam or cefiderocol. Two patients (20 %) had a recurrence of MCP-EB infection and four (40 %) patients did not survive hospitalisation.

Conclusion: Clinical features of patients with MCP-EB are common in the hospital population with chronic diseases and showed high mortality rates both in infected and carriers-only patients. Aztreonam/avibactam and cefiderocol could be promising treatment options against MCP-EB infections.