Title : Carbapenem resistance and carbapenemases in bloodstream Enterobacterales, Busan, South Korea, 2018–2024

Abstract:

Carbapenem-resistant Enterobacterales (CRE) have emerged as a major global public health threat due to limited therapeutic options and high mortality rates, particularly in bloodstream infections. Regional epidemiological data are essential for understanding the dissemination of resistance mechanisms and for guiding infection-control strategies and antimicrobial stewardship.

This study aimed to investigate the distribution of species, antimicrobial resistance patterns, and carbapenemase genotypes among CRE isolates recovered from bloodstream infections in Busan, South Korea, from 2018 to 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 (bioMérieux, France). Antimicrobial susceptibility testing for four carbapenems (ertapenem, imipenem, meropenem, and doripenem) was conducted using broth microdilution. Carbapenemase genes were detected 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 (MIC ≥ 2 µg/mL) was observed in 99.3% of isolates, and high-level resistance (MIC ≥ 8 µg/mL) was frequently identified across all carbapenems. Carbapenemase-producing Enterobacterales (CPE) accounted for 98.2% of isolates. Among these, KPC-type carbapenemases were the most prevalent (88.2%), with KPC-2 being the dominant subtype (84.9%). In contrast, NDM- and OXA-type carbapenemases were detected sporadically.

These findings indicate that KPC-2-producing K. pneumoniae remains the principal driver of CRE bloodstream infections in Busan. The presence of multiple carbapenemase genotypes across healthcare institutions suggests ongoing regional dissemination of resistance determinants. Furthermore, the sustained dominance of KPC-2 suggests possible clonal dissemination within regional healthcare settings, highlighting the need for targeted infection-control interventions. These findings provide valuable regional evidence to inform antimicrobial stewardship policies and strengthen preparedness against emerging multidrug-resistant pathogens.

Biography:

Sohyun Park, PhD, is a public health researcher at the Busan Metropolitan City Institute of Health and Environment, Republic of Korea. She plays a leading role in regional surveillance of infectious diseases, antimicrobial resistance, and foodborne pathogens, contributing to national public health monitoring systems. Her work integrates laboratory-based diagnostics with epidemiological analysis to support rapid and evidence-based responses. She has conducted key surveillance programs, including norovirus monitoring and antimicrobial resistance studies. Her research on carbapenem-resistant-Enterobacterales CRE)has provided important insights into regional resistance trends and supports strengthening infectious disease response capacity.