{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T22:45:44Z","timestamp":1769553944131,"version":"3.49.0"},"reference-count":25,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T00:00:00Z","timestamp":1769472000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004332","name":"Seoul National University Hospital Research Fund","doi-asserted-by":"publisher","award":["02-2022-0530"],"award-info":[{"award-number":["02-2022-0530"]}],"id":[{"id":"10.13039\/501100004332","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>This study investigated the clinical and genomic characteristics of Enterobacter cloacae complex (ECC) and Klebsiella aerogenes bloodstream infections (BSIs) in pediatric patients. A total of 115 BSI episodes (ECC: 86, K. aerogenes: 29) from 110 children hospitalized between 2011 and 2024 were retrospectively analyzed. Whole-genome sequencing was performed on available isolates to determine species, sequence types, and antimicrobial resistance (AMR) genes. Clinical characteristics, antibiotic usage, and outcomes were compared between groups. Patients with K. aerogenes BSI were younger and more likely to be preterm or diagnosed with urosepsis, while ECC infections were more frequently associated with hematologic malignancies. According to a multivariable analysis of the entire cohort (n = 115), K. aerogenes infection (OR [6.26], 95% CI [1.36\u201328.78]) and gentamicin resistance (OR [10.06], 95% CI [1.88\u201353.87]) were independently associated with 30-day mortality. Enterobacter hormaechei was the most common ECC species (68.4%) and exhibited the highest prevalence of AMR genes, particularly those conferring resistance to aminoglycosides, \u03b2-lactams, and trimethoprim\u2013sulfamethoxazole. In contrast, K. aerogenes harbored few resistance genes. Multi-locus sequence typing analysis revealed high genetic diversity in both ECC and K. aerogenes, without evidence of dominant clonal expansion. Despite similarities in clinical presentation, ECC and K. aerogenes exhibit distinct age distributions, resistance profiles, and genetic diversity in pediatric BSIs. These findings underscore the importance of species-level identification and continued genomic surveillance to inform empirical antibiotic strategies and prevent the spread of resistant strains.<\/jats:p>","DOI":"10.3390\/microorganisms14020292","type":"journal-article","created":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T09:05:27Z","timestamp":1769504727000},"page":"292","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Clinical and Genetic Characteristics of Enterobacter cloacae and Klebsiella aerogenes in Children"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0798-6779","authenticated-orcid":false,"given":"Ki Wook","family":"Yun","sequence":"first","affiliation":[{"name":"Department of Pediatrics, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea"},{"name":"Department of Pediatrics, Seoul National University Children\u2019s Hospital, Seoul 03080, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-5984-5309","authenticated-orcid":false,"given":"Ye Eun","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, College of Medicine, Seoul National University, Seoul 03080, Republic of Korea"},{"name":"Department of Pediatrics, Seoul National University Children\u2019s Hospital, Seoul 03080, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dayun","family":"Kang","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Seoul National University Children\u2019s Hospital, Seoul 03080, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7881-1343","authenticated-orcid":false,"given":"Hye Jeong","family":"Moon","sequence":"additional","affiliation":[{"name":"Department of Pediatrics, Seoul National University Children\u2019s Hospital, Seoul 03080, Republic of Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1016\/S0163-4453(03)00096-3","article-title":"Extended-spectrum beta-lactamases: Implications for the clinical microbiology laboratory, therapy, and infection control","volume":"47","author":"Sturenburg","year":"2003","journal-title":"J. Infect."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1389","DOI":"10.1093\/cid\/civ020","article-title":"Extended-spectrum beta-lactamase-producing Enterobacteriaceae in children: Old foe, emerging threat","volume":"60","author":"Lukac","year":"2015","journal-title":"Clin. Infect. Dis."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"593","DOI":"10.1016\/j.jinf.2019.09.012","article-title":"The global prevalence of multidrug-resistance among Acinetobacter baumannii causing hospital-acquired and ventilator-associated pneumonia and its associated mortality: A systematic review and meta-analysis","volume":"79","author":"Lim","year":"2019","journal-title":"J. Infect."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1446","DOI":"10.1093\/cid\/ciz173","article-title":"Antibacterial Resistance Leadership Group. A primer on AmpC beta-lactamases: Necessary knowledge for an increasingly multidrug-resistant world","volume":"69","author":"Tamma","year":"2019","journal-title":"Clin. Infect. Dis."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e02093-16","DOI":"10.1128\/mBio.02093-16","article-title":"Comprehensive genome analysis of carbapenemase-producing Enterobacter spp.: New insights into phylogeny, population structure, and resistance mechanisms","volume":"7","author":"Chavda","year":"2016","journal-title":"mBio"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"ofab390","DOI":"10.1093\/ofid\/ofab390","article-title":"Difference in the clinical outcome of bloodstream infections caused by Klebsiella aerogenes and Enterobacter cloacae complex","volume":"8","author":"Jeon","year":"2021","journal-title":"Open Forum Infect. Dis."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"acmi000421","DOI":"10.1099\/acmi.0.000421","article-title":"Mortality difference from Klebsiella aerogenes vs Enterobacter cloacae bloodstream infections","volume":"5","author":"Chou","year":"2023","journal-title":"Access Microbiol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1445","DOI":"10.1007\/s15010-023-02010-1","article-title":"Significant clinical differences but not outcomes between Klebsiella aerogenes and Enterobacter cloacae bloodstream infections: A comparative cohort study","volume":"51","author":"Laupland","year":"2023","journal-title":"Infection"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1186\/s12941-024-00700-8","article-title":"Differences in clinical outcomes of bloodstream infections caused by Klebsiella aerogenes, Klebsiella pneumoniae and Enterobacter cloacae: A multicentre cohort study","volume":"23","author":"Guedes","year":"2024","journal-title":"Ann. Clin. Microbiol. Antimicrob."},{"key":"ref_10","unstructured":"CLSI (2020). Performance Standards for Antimicrobial Susceptibility Testing, CLSI. [30th ed.]."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"585","DOI":"10.7326\/0003-4819-115-8-585","article-title":"Enterobacter bacteremia: Clinical features and emergence of antibiotic resistance during therapy","volume":"115","author":"Chow","year":"1991","journal-title":"Ann. Intern. Med."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"995","DOI":"10.1128\/AAC.01083-07","article-title":"Emergence of antibiotic resistance during therapy for infections caused by Enterobacteriaceae producing AmpC beta-lactamase: Implications for antibiotic use","volume":"52","author":"Choi","year":"2008","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/j.jinf.2019.09.017","article-title":"A prospective, multicenter case control study of risk factors for acquisition and mortality in Enterobacter species bacteremia","volume":"80","year":"2020","journal-title":"J. Infect."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3159","DOI":"10.1128\/AAC.48.8.3159-3161.2004","article-title":"High prevalence of extended-spectrum beta-lactamase-producing strains among blood isolates of Enterobacter spp. collected in a tertiary hospital during an 8-year period and their antimicrobial susceptibility patterns","volume":"48","author":"Pai","year":"2004","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"e00582-20","DOI":"10.1128\/JCM.00582-20","article-title":"Newly named Klebsiella aerogenes (formerly Enterobacter aerogenes) is associated with poor clinical outcomes relative to other Enterobacter species in patients with bloodstream infection","volume":"58","author":"Wesevich","year":"2020","journal-title":"J. Clin. Microbiol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"436","DOI":"10.1016\/j.diagmicrobio.2009.11.007","article-title":"Comparison of the clinical and microbiologic characteristics of patients with Enterobacter cloacae and Enterobacter aerogenes bacteremia: A prospective observation study","volume":"66","author":"Song","year":"2010","journal-title":"Diagn. Microbiol. Infect. Dis."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"351","DOI":"10.1016\/j.jgar.2021.04.008","article-title":"Clinical characteristics and outcome of bacteraemia caused by Enterobacter cloacae and Klebsiella aerogenes: More similarities than differences","volume":"25","author":"Lepe","year":"2021","journal-title":"J. Glob. Antimicrob. Resist."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"161","DOI":"10.3201\/eid2701.190154","article-title":"Precise species identification by whole-genome sequencing of Enterobacter bloodstream infection, China","volume":"27","author":"Wu","year":"2021","journal-title":"Emerg. Infect. Dis."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"41","DOI":"10.7883\/yoken.JJID.2021.141","article-title":"Molecular epidemiology of Enterobacter cloacae Complex isolates with reduced carbapenem susceptibility recovered by blood culture","volume":"75","author":"Sarangi","year":"2022","journal-title":"Jpn. J. Infect. Dis."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"944","DOI":"10.1093\/jac\/dkab471","article-title":"Emergence of VIM-producing Enterobacter cloacae complex in France between 2015 and 2018","volume":"77","author":"Emeraud","year":"2022","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"e0216022","DOI":"10.1128\/spectrum.02160-22","article-title":"Whole-genome sequencing-based species classification, multilocus sequence typing, and antimicrobial resistance mechanism analysis of the Enterobacter cloacae complex in southern China","volume":"10","author":"Dong","year":"2022","journal-title":"Microbiol. Spectr."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1093\/jac\/dku359","article-title":"MLST reveals potentially high-risk international clones of Enterobacter cloacae","volume":"70","author":"Izdebski","year":"2015","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Davin-Regli, A., and Pages, J.M. (2015). Enterobacter aerogenes and Enterobacter cloacae; versatile bacterial pathogens confronting antibiotic treatment. Front. Microbiol., 6.","DOI":"10.3389\/fmicb.2015.00392"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1093\/jac\/48.suppl_1.59","article-title":"Detection of beta-lactamase-mediated resistance","volume":"48","author":"Livermore","year":"2001","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1093\/cid\/ciae160","article-title":"Mutation rate of AmpC beta-lactamase-producing enterobacterales and treatment in clinical practice: A word of caution","volume":"79","author":"Maillard","year":"2024","journal-title":"Clin. Infect. 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