In recent times, an increase in the bloodstream cases of bloodstream infections (BSIs) has been reported, caused by Escherichia coli and Klebsiella pneumonia. Researchers conducted a population-level genomic record of bloodstream E.coli and Klebsiella pneumonia from 2008 to 2018 in the United Kingdom. According to the studies, 3478 E. coli (3278 passed quality control) and 556 K. pneumoniae (535 [K-antigen] and 549 [O-antigen] passed quality control). The 4 most similar E. coli O-antigens (O1/O2/O6/O25) were identified in 1499/3278 in total; the incidence of O-types increased over time (incidence rate ratio per year [IRRy] = 1.14, 95% confidence interval [CI]: 1.11–1.16). These O-types opted for 616/1434 multidrug-resistant (MDR) and 173/256 extended-spectrum beta-lactamase (ESBL)-resistant isolates in Oxfordshire but only 19/90 carbapenem-resistant isolates across all studies. For Klebsiella pneumoniae, the most similar O-antigens (O2v2/O1v1/O3b/O1v2) accounted for 410/549; the incidence of BSIs caused by these also increased annually (IRRy=1.09; 95% CI: 1.05–1.12). These O-types accounted for 122/148 MDR, and 106/123 ESBL isolates in Oxfordshire, and 557/734 carbapenem-resistant isolates across all studies. The study indicated substantial capsular antigen diversity. Analysis of 3678 isolates from global studies demonstrated the generalizability of these findings. For E. coli, based on serotyping, the ExPEC4V and ExPEC10V vaccines under investigation would cover 46% and 72% of Oxfordshire isolates, respectively, and 47% and 71% of MDR isolates. The study concluded that O- antigen targeted vaccines would result useful in decrease of morbidity, mortality, and antimicrobial resistance by E.coli and K.pneumoniae.