Carbapenem Resistance and Carbapenemases in Bloodstream Enterobacterales, Busan, 2018-2024

Background: Carbapenem-resistant Enterobacterales(CRE) have emerged as a majorglobal health concern because of limited therapeutic options and high mortality in bloodstream infections.Regional epidemiologic data on bloodstream CRE infections are essential for guidinginfection-control strategies and antimicrobial stewardship.Methods: A total of 609 non-duplicate CRE isolates recovered from blood cultures at healthcare institutions in Busan, South Korea, between 2018 and 2024 were analyzed.Species identification was performed using the Vitek 2 Compact system(bioMrieux, France).Antimicrobial susceptibility testing for four carbapenems was determined by broth microdilution, and ten carbapenemase genes were detected by PCR.Results: Klebsiella pneumoniae predominated (81.8%), followed by Escherichia coli (11.7%) and Enterobacter spp.(4.6%).Ertapenem resistance (MIC 2 g/mL) was observed in 99.3% of isolates, and elevated MIC values ( 8 g/mL) were frequently observed across all carbapenems.Carbapenemase-producing Enterobacterales (CPE) accounted for 98.2% of isolates.KPC-type carbapenemases were most frequent (88.2%), predominantly KPC-2 (84.9%), whereas NDM-and OXA-type carbapenemases were detected sporadically.Conclusion: KPC-2-producing K. pneumoniae remains the principal cause of CRE bloodstream infections in Busan.The presence of diverse carbapenemase genotypes across healthcare institutions indicates ongoing regional disseminationof resistance determinants, underscoring the need for sustained molecular surveillance and coordinated infection-control efforts.