Carbapenem-resistant Enterobacterales (CRE) represent a major global public health threat, particularly in bloodstream infections, where limited treatment options and high mortality rates pose significant challenges. Understanding regional epidemiological trends and resistance mechanisms is essential for effective infection control and antimicrobial stewardship. This study investigated the species distribution, antimicrobial resistance patterns, and carbapenemase genotypes of CRE isolates from bloodstream infections in Busan, South Korea, between 2018 and 2024. A total of 609 non-duplicate CRE isolates collected from 51 healthcare institutions were analyzed. Species identification was performed using the Vitek 2 Compact system, and antimicrobial susceptibility to four carbapenems was determined by broth microdilution. Carbapenemase genes were identified using multiplex PCR targeting ten major carbapenemase types.

Klebsiella pneumoniae was the predominant species (81.8%), followed by Escherichia coli (11.7%) and Enterobacter spp. (4.6%). Ertapenem resistance was observed in 99.3% of isolates, with high-level resistance across all carbapenems. Carbapenemase-producing Enterobacterales (CPE) accounted for 98.2% of isolates. KPC-type carbapenemases were dominant (88.2%), with KPC-2 as the most prevalent subtype (84.9%). These findings indicate that KPC-2-producing K. pneumoniae is the primary driver of CRE bloodstream infections in Busan. The widespread distribution of carbapenemase genes suggests ongoing regional dissemination and possible clonal expansion, highlighting the need for targeted infection control and strengthened antimicrobial stewardship.

Sohyun Park, PhD, is a public health researcher at the Busan Metropolitan City Institute of Health and Environment, Republic of Korea. She specializes in infectious disease surveillance and antimicrobial resistance. Her work integrates laboratory diagnostics with epidemiological analysis to support rapid public health responses and strengthen regional surveillance systems.