E. coli ST11 (O157:H7) does not encode a functional AcrF efflux pump.

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Escherichia coli (E. coli) is a well-studied bacterium, but knowledge often relies on the laboratory strain E. coli K-12.
• Resistance-nodulation-division (RND) efflux pumps are crucial for antibiotic resistance in Gram-negative bacteria.
• E. coli K-12 possesses six RND pumps, a complement often assumed to be universal across all E. coli strains.

Purpose of the Study:

• To investigate the presence and function of the AcrF efflux pump in the virulent E. coli ST11 lineage.
• To determine if the RND efflux pump composition differs between laboratory and pathogenic E. coli strains.

Main Methods:

• Bioinformatic analysis of 1787 E. coli ST11 genome assemblies to identify the presence of the acrF gene.
• Genetic analysis to characterize a conserved insertion within the acrF gene in E. coli ST11.
• Laboratory experiments involving gene complementation in E. coli K-12 to assess AcrF function.

Main Results:

• The acrF gene is absent from the pangenome of the E. coli ST11 lineage.
• A conserved 13-amino acid insertion with two stop codons was identified within the acrF gene in 97.59% of ST11 genomes analyzed.
• Complementation experiments confirmed that the ST11-derived acrF gene cannot restore AcrF function in E. coli K-12.

Conclusions:

• The virulent E. coli ST11 lineage, including E. coli O157:H7, possesses a non-functional AcrF efflux pump due to a specific genetic insertion.
• The complement of RND efflux pumps in pathogenic E. coli strains can differ significantly from those found in laboratory strains.
• This divergence has implications for understanding antibiotic resistance and developing targeted therapies against bacterial pathogens.