Escherichia coli K1 strain (E. coli K1)

The **Escherichia coli K1 strain** is a pathogenic variant of the Gram-negative bacterium Escherichia coli distinguished by its K1 capsular polysaccharide antigen, which mimics host sialic acid structures to evade innate immunity and promote serum resistance. This capsule enables the strain to traverse the blood-brain barrier, invade endothelial cells without lysosomal fusion, and cause severe neonatal infections such as meningitis and sepsis, often originating from intestinal colonization. Common in phylogenetic groups B2, D, and A, it expresses virulence factors like outer membrane protein A, P-fimbriae, and toxins such as CNF1. K1 strains show distinct antibiotic susceptibility patterns, generally lower resistance to quinolones and trimethoprim-sulfamethoxazole compared to K1-negative strains, though beta-lactam resistance and rare ESBL production occur. No specific targeted therapies exist beyond broad-spectrum antibiotics, with challenges from phase-variable capsule modifications like O-acetylation via prophage-encoded neuO. Research highlights its role in global neonatal disease burden, particularly clones like O18:K1:H7.

Other names

E. coli K1 strainK1-positive E. colimeningitis-causing E. coli K1

Beta-lactam inhibition of cell wall synthesis; Quinolone interference with DNA gyrase; Sulfonamide-folate pathway inhibition; Aminoglycoside protein synthesis inhibition