Efficacy of Imipenem/Cilastatin/Relebactam in infections caused by Difficult-to-Treat Gram-Negative Bacteria: A Retrospective Analysis of Real-world data in Greece.

BACKGROUND

The escalating global crisis of antimicrobial resistance (AMR), particularly among multidrug-resistant (MDR) Gram-negative bacteria (GNB), presents a significant challenge to patient care. Newer β-lactam/β-lactamase inhibitor (BL/BLI) combinations, such as imipenem/cilastatin/relebactam (IMI/REL), have been developed to overcome key resistance mechanisms, including those mediated by KPC and AmpC enzymes, offering new hope for treating severe infections with limited therapeutic options.

PATIENTS AND

METHODS

This was a retrospective, single-center, observational study of 195 adult patients with GNB bacteraemia who received IMI/REL for at least 48 hours. The patient cohort was characterized by a high comorbidity burden (median Charlson Comorbidity Index of 4) and significant illness severity (median APACHE II score of 14). The most common pathogens were Pseudomonas aeruginosa (63.1%) and Klebsiella pneumoniae (24.6%), with a high proportion of isolates being carbapenem-non-susceptible (77.5%). The primary outcome was clinical success, and secondary outcomes included 30-day all-cause mortality and safety.

RESULTS

The overall clinical success rate was 72.82%, and the all-cause 30-day mortality rate was 11.3%. Microbiologic failure occurred in 12.3% of patients, and infection recurrence within 30 days was seen in 8.2%. The safety profile was favourable, with adverse drug reactions reported in 4.1% of patients, leading to treatment discontinuation in only two cases (1.02%).

CONCLUSIONS

The findings of this study reinforce the value of IMI/REL as an effective and well-tolerated treatment for severe GNB infections in a complex, real-world patient population. These outcomes compare favourably with published data for other new BL/BLI agents, supporting the targeted use of IMI/REL as a crucial component of modern antibiotic stewardship.