Molecular characterization of carbapenemase-producing Gram-negative bacilli isolated from clinical samples in Senegal

Background: Antimicrobial resistance (AMR) is a major threat to global public health. In Senegal, the emergence of carbapenem resistance among Gram-negative bacilli (GNB) is a growing concern. Methods: This retrospective study aimed to characterize carbapenemase genes in 50 GNB isolates resistant to ertapenem and/or imipenem, recovered from clinical samples at the University Hospital Center (CHNU) of Fann between October 2022 and March 2024. Bacterial identification was performed using VITEK 2 and MALDI-TOF MS, and antibiotic susceptibility testing was conducted by agar disk diffusion. Whole-genome sequencing (WGS), followed by bioinformatics analyses, enabled the detection of resistance genes. Results: Among the 50 isolates, E. coli (n=21; 42%) was the most frequent species, followed by K. pneumoniae (n=12; 24%), Proteus mirabilis (n=5; 10%), and Enterobacter hormaechei (n=5; 10%). Carbapenemase genes were identified in 35 isolates, with blaNDM-5 (n=12; 34.3%) and blaNDM-1 (n=5; 14.3%) being the most prevalent. Other detected genes included blaOXA-181 (n=4; 11.4%) and blaOXA-484 (n=4; 11.4%), as well as co-occurrences such as blaNDM-5 + blaOXA-181 (n=3; 8.6%). We also report, for the first time in Senegal, the identification of blaNDM-15, blaOXA-68, blaOXA-70, blaOXA-420, and blaOXA-484 variants. Conclusion: These findings highlight the alarming dissemination of carbapenemases including newly reported variants in Senegal among clinical GNB isolates. They underscore the urgent need to strengthen surveillance strategies targeting multidrug-resistant bacteria in Senegal.