Clinical Outcomes in Bloodstream Infections Due to New Species, Klebsiella aerogenes

Bacteria Klebsiella
Bacteria Klebsiella
Patients with bloodstream infection due to Klebsiella aerogenes had poor clinical outcomes relative to Enterobacter cloacae complex.

Patients with bloodstream infection (BSI) due to Klebsiella aerogenes had poor clinical outcomes relative to Enterobacter cloacae complex, according to research presented at IDWeek 2019, held October 2 to October 6, 2019, in Washington, DC.

While whole genome-based comparative bacterial phylogenetics has led to Enterobacter aerogenes being renamed K aerogenes, the mechanism of infections with K aerogenes differ from E cloacae complex remains unclear. Thus, in this prospective study, researchers evaluated data from 150 adult patients with K aerogenes (n=104) or E cloacae complex (n=46) BSI enrolled at Duke University Medical Center in Durham, North Carolina, from 2002 to 2015. The investigators compared clinical characteristics, antibiotic resistance, patient outcomes, and bacterial virulence genes.

A pan-genome ortholog clustering tool identified flexible genomic islands. Multidrug resistance was defined as resistance to ≥3 drug classes, and poor clinical outcome was defined as death before discharge and/or BSI complication such as septic shock, acute kidney injury, acute lung injury/acute respiratory distress syndrome, or disseminated intravascular coagulation.

Multidrug resistance was similar with E cloacae complex and K aerogenes infection. In addition, total and attributable in-hospital mortality did not differ between the 2 genera. Researchers did observe that patients with E cloacae complex BSI more often required hemodialysis (23% vs 9%; P =.04).

Poor clinical outcome was more common with K aerogenes BSI; this association remained significant after adjusting for age, source of BSI, site of acquisition, days to appropriate antibiotic treatment initiation, and chronic Acute Physiology and Chronic Health Evaluation (APACHE) II score (odds ratio, 2.8; 95% CI, 1.2-6.4; P =.001).

E cloacae complex and K aerogenes isolates formed 14 and 3 phylogenetic clades, respectively. K aerogenes contained 983 core genes, grouped within 324 flexible genomic islands, which were not present in E cloacae complex. “These included homologs to virulence genes involved in iron acquisition, flagella synthesis, and fimbriae production,” noted the researchers.

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“Multiple unique K aerogenes genes homologous to virulence factors may contribute” to the poorer clinical outcomes with K aerogenes BSI, concluded the researchers.

Disclosure: Vance G. Fowler, Jr., MD, MHS, declared affiliations with several pharmaceutical companies. Please see the original reference for a full list of his disclosure.


Wesevich A, Sutton G, Fouts D, Fowler VG, Thaden J. Newly-named Klebsiella aerogenes is associated with poor clinical outcomes relative to Enterobacter cloacae complex in patients with bloodstream infection. Presented at: IDWeek 2019; October 2-6, 2019; Washington, DC, MD. Poster 221.