Genomic and Molecular Analysis of Multidrug-Resistant Gram-Negative Bacteria Causing Bloodstream Infections in Hospitalized Patients

Bloodstream infections caused by multidrug-resistant and extensively drug-resistant Gram-negative bacteria represent a major global health concern, particularly among hospitalized and critically ill patients. This study aimed to characterize the molecular profiles, antimicrobial resistance patterns, and phylogenetic relationships of Gram-negative isolates obtained from bloodstream infections in hospitalized patients. A cross-sectional study was conducted between September 2024 and May 2025. Bacterial identification and antimicrobial susceptibility testing were performed using the BD Phoenix M50 and BD BACTEC FX40 automated systems, and extended-spectrum β-lactamase production was confirmed by the Combined Disk Test. Resistance genes, including bla _SHV , bla _CTX−M , bla _IMP , bla _NDM , bla _TEM , OqxA, OqxB, aac(1)A , and aac(1)B were detected via PCR, and the RpoB gene was sequenced for phylogenetic analysis. Among 30 isolates, Klebsiella pneumoniae (70%) was the predominant species. The highest resistance was observed to Ceftriaxone (96.7%), while Tigecycline showed the greatest activity (66.7% susceptibility). The bla _SHV and bla _IMP genes were detected in all isolates, and OqxB (93.3%) and bla _CTX−M (80%) were highly prevalent. Phylogenetic analysis revealed close clustering of clinical isolates with the reference XDR strain K. pneumoniae CP008827.1, suggesting intra-hospital transmission. These findings highlight the urgent need for continuous molecular surveillance, strict infection control, and rational antibiotic stewardship programs.