In Vitro Efficacy of Imipenem/Relebactam Against Imipenem Resistant Gram-Negative Strains Isolated from a Tertiary Care Hospital

Abstract

Objective: To determine in vitro efficacy of Imipenem/Relebactam against multi-drug resistant strains. Study Design: Cross-sectional study. Place and Duration of Study: Department of Microbiology, Fauji Foundation Hospital (FFH) Rawalpindi, Pakistan from Jul to Dec 2022. Methodology: All specimens from indoor and outdoor patients with infection due to Gram-negative organisms showing resistance to Imipenem disc (10μg) were included. Cultures were inoculated on Blood and MacConkey’s agar. Imipenemresistant Gram-negative species identification was made by Gram stain, Oxidase test and commercially available identification strips Analytical profile index 10S (API-10S) (from bioMerieux, Inc.).Imipenem-resistant species were identified, showing a zone diameter of less than 23mm against10µg Imipenem disc for Enterobacterale and Non-Enterobacterales, and for Pseudomonas species, zone size is ≤19mm. These resistant organisms were tested for sensitivity against Imipenem/Relebactam by E-strip (MTSTM –MIC Test Strip) (Liofilchem, Inc., Waltham, MA). Results: Out of 160 Carbapenem-resistant Enterobacterale and Non-Enterobacterales specimens, only 14 isolates (including 02 Pseudomonas spp.) showed susceptibility to Imipenem/Relebactam combination of drug. US-FDA Imipenem/Relebactam susceptibility interpretive criteria (STIC) was used. Conclusion: In our setup, only 8.75% isolates showed sensitivity to this newer drug combination Imipenem/Relebactum. This highlights the importance of evaluating newer drugs in our population before using them empirically.

Keywords

• Carbapenems
• Imipenem
• Anti-bacterial agents
• Drug resistance
• Bacterial drug resistance
• Multiple drug resistance