Molecular epidemiological characterization of invasive extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates from infants less than 3 months old in East Asia.

OBJECTIVES: Neonatal sepsis due to Gram-negative bacteria remains a clinical challenge. This study aimed to characterize the current epidemiology, genetic diversity, and antimicrobial resistance of invasive Escherichia coli and Klebsiella pneumoniae infections in infants under 90 days old in Taiwan and Korea.

METHODS: Culture-confirmed clinical isolates collected from 2020 to 2023 (Taiwan) and 2015-2023 (Korea) were analyzed. Multilocus sequence typing, antimicrobial susceptibility testing, and screening for β-lactamase-encoding genes were performed.

RESULTS: E. coli was the predominant pathogen in both regions, encompassing 29 sequence types (STs) across 23 clonal complexes. ST1193 and ST131 were predominant and linked to high mortality, whereas ST95 was linked to neonatal meningitis. K. pneumoniae exhibited regional diversity, with 15 unique STs. Ceftriaxone resistance was common, in approximately one-third of isolates in Taiwan and over 60% in Korea. Key resistance genes included blaCTX-M-3/15/55 (Taiwan E. coli), blaCTX-M-14/27/65 (Korea E. coli and K. pneumoniae), blaSHV (Taiwan K. pneumoniae and Korea K. pneumoniae), and blaDHA (Taiwan K. pneumoniae). Although less common, more E. coli ST131 carried blaCTX-M than ST1193.

CONCLUSION: High ceftriaxone resistance rates necessitate urgent, judicious antimicrobial selection for critically ill neonates. The diversity of STs and region-specific extended-spectrum β-lactamases patterns highlight the need for continuous surveillance and tailored empiric strategies.