From colonization to invasion: genomic and phenotypic comparison of faecal and bloodstream isolates from the same patients

Khanijau, A, Allman, E, Pulmones, R, Goodman, RN, Cantillon, D, McGalliard, R, Parry, CM, Carrol, ED ORCID: 0000-0001-8357-7726 and Roberts, AP (2026) From colonization to invasion: genomic and phenotypic comparison of faecal and bloodstream isolates from the same patients Journal of Medical Microbiology, 75 (4). 002147-. ISSN 0022-2615, 1473-5644

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Abstract

Introduction. Gram-negative bloodstream infections (GNBSIs) carry a significant global health burden. Escherichia coli and Klebsiella pneumoniae are the two most common causes of healthcare-associated GNBSI, which may arise from gastrointestinal tract (GIT) colonization. Gap Statement. We do not fully understand how GNBSIs arise from GIT colonization. Aim. To understand E. coli and K. pneumoniae genomic and phenotypic adaptations that underpin transition from GIT colonization to invasive bloodstream infection. Methodology. This study identified ‘linked’ faecal and blood isolates from children with healthcare-associated GNBSI caused by E. coli and K. pneumoniae. Linked pairs were compared for antimicrobial resistance and biofilm formation and underwent comparative genomic analysis via whole-genome sequencing, comparative average nucleotide identity and core genome single nucleotide polymorphism (SNP) analysis. Results. Five isolate pairs (three E. coli, two K. pneumoniae) showed high relatedness, supporting the GIT origin of bloodstream infection. Isolates within pairs had identical virulence genes, whereas phenotypic assays revealed changes in antimicrobial susceptibility, with one pair undergoing changes in resistance gene profiles and increased biofilm formation in four out of five isolates. Conclusion. This study provides insight into within-host evolution from gastrointestinal colonization to bloodstream invasion in Gram-negative pathogens. Convergence on metabolic adaptation and biofilm formation suggests that these traits may be advantageous in healthcare-associated GNBSI. Further studies involving larger cohorts alongside functional validation of mutations are needed to better understand GNBSI pathogenesis.

Item Type:	Article
Uncontrolled Keywords:	Feces, Humans, Biofilms, Escherichia coli, Klebsiella pneumoniae, Bacteremia, Escherichia coli Infections, Klebsiella Infections, Anti-Bacterial Agents, Microbial Sensitivity Tests, Drug Resistance, Bacterial, Phenotype, Polymorphism, Single Nucleotide, Genome, Bacterial, Child, Child, Preschool, Infant, Female, Male, Whole Genome Sequencing
Divisions:	Faculty of Health & Life Sciences Faculty of Health & Life Sciences > Inst. Infection, Vet & Ecological Sciences Faculty of Health & Life Sciences > Inst. Infection, Vet & Ecological Sciences > Inst. Infection, Vet & Ecological Sciences (T&R Staff) Faculty of Health & Life Sciences > Inst. Infection, Vet & Ecological Sciences > Clinical Infection, Microbiology & Immunology
Depositing User:	Symplectic Admin
Date Deposited:	13 Apr 2026 07:51
Last Modified:	01 May 2026 16:38
DOI:	10.1099/jmm.0.002147
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3197938
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