AUTHOR=Ganbold Michidmaral , Seo Jungyu , Wi Yu Mi , Kwon Ki Tae , Ko Kwan Soo 

TITLE=Species identification, antibiotic resistance, and virulence in Enterobacter cloacae complex clinical isolates from South Korea

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1122691

DOI=10.3389/fmicb.2023.1122691

ISSN=1664-302X

ABSTRACT=<p>This study aimed to identify the species of <italic>Enterobacter cloacae</italic> complex (ECC) isolates and compare the genotype, antibiotic resistance, and virulence among them. A total of 183 ECC isolates were collected from patients in eight hospitals in South Korea. Based on partial sequences of <italic>hsp60</italic> and phylogenetic analysis, all ECC isolates were identified as nine species and six subspecies. <italic>Enterobacter hormaechei</italic> was the predominant species (47.0%), followed by <italic>Enterobacter kobei</italic>, <italic>Enterobacter asburiae</italic>, <italic>Enterobacter ludiwigii</italic>, and <italic>Enterobacter roggenkampii</italic>. Multilocus sequence typing analysis revealed that dissemination was not limited to a few clones, but <italic>E. hormaechei</italic> subsp. <italic>xiangfangensis</italic>, <italic>E. hormaechei</italic> subsp. <italic>steigerwaltii</italic>, and <italic>E. ludwigii</italic> formed large clonal complexes. Antibiotic resistance rates were different between the ECC species. In particular, <italic>E. asburiae</italic>, <italic>E. kobei</italic>, <italic>E. roggenkampii</italic>, and <italic>E. cloacae</italic> isolates were highly resistant to colistin, whereas most <italic>E. hormaechei</italic> and <italic>E. ludwigii</italic> isolates were susceptible to colistin. Virulence was evaluated through serum bactericidal assay and the <italic>Galleria mellonella</italic> larvae infection model. Consistency in the results between the serum resistance and the <italic>G. mellonella</italic> larvae infection assay was observed. Serum bactericidal assay showed that <italic>E. hormaechei</italic>, <italic>E. kobei</italic>, and <italic>E. ludwigii</italic> were significantly more virulent than <italic>E. asburiae</italic> and <italic>E. roggenkampii</italic>. In this study, we identified the predominant ECC species in South Korea and observed the differences in antibiotic resistance and virulence between the species. Our findings suggest that correct species identification, as well as continuous monitoring is crucial in clinical settings.</p>