Carbapenemase-encoding genes in critical gram-negative bacteria isolated from ICU patients with infections and/or gastrointestinal carriage, and environmental samples in the amhara National Regional state, Ethiopia

Effective infection control requires identifying and eliminating carbapenemase-producing (CP) Gram-negative bacteria (GNB) in high-risk groups like intensive care unit (ICU) patients and from contaminated environmental surfaces. This study aimed to describe the diversity of carbapenemase-encoding genes among critical GNB isolates from ICU patients with infection and/or gastrointestinal (GI) colonization, as well as from ICU environmental surfaces in the Amhara National Regional state, Ethiopia.A total of 169 carbapenem-resistant isolates were identified, including 26 from infections, 82 from GI colonization, and 61 from environmental samples. These comprised Klebsiellapneumoniae (n = 107), Escherichia coli (n = 16), Pseudomonas aeruginosa (n = 9), and Acinetobacter species (n = 37), of which 147 were analyzed.Singleplex and multiplex PCR were performed to detect predominant carbapenemase-encoding genes, including KPC (blaKPC), MBLs (blaIMP, blaVIM, and blaNDM), and OXA (blaOXA-48, blaOXA-23, and blaOXA-58). PCR analysis revealed that at least one carbapenemase-encoding gene was detected in 133 (78.7%) of the 169 carbapenem-resistant isolates from patients and environmental surfaces. They were detected in 22/133(16.5%), 70/133(52.6%), and 41/133(30.8%) isolates obtained from infection, GI colonization, and environmental samples, respectively. The most prevalent carbapenemase-encoding gene, blaNDM, was found in 101 (75.9%) of the 133 CP isolates. Other detected carbapenemase-encoding genes included blaOXA-23 in 5 (3.8%) isolates, blaVIM in 4 (3.0%), blaOXA-48 in 1 (0.8%), and blaOXA-58 in 1 (0.8%). K. pneumoniae and Acinetobacter spp. harbored all the gene types detected in this study. Co-harboring of two or more carbapenemase-encoding genes, in combination with blaNDM, was observed in 21 of 133 (15.8%) isolates, including 7 K. pneumoniae and 14 Acinetobacter spp. isolates. However, blaKPC and blaIMP were not identified in any of the tested isolates. This study highlights the presence of carbapenemase-encoding genes among critical GNB across all sample source types in the study area. Moreover, the detection of isolates harboring multiple carbapenemase-encoding genes underscores the need for enhanced infection control measures in ICU settings.