ExPEC

ExPEC, or extraintestinal pathogenic Escherichia coli, is a broad pathotype of E. coli that causes disease outside the intestinal tract. ExPEC strains are responsible for many community- and hospital-acquired infections, including urinary tract infections, sepsis, meningitis in neonates, and pneumonia. They are distinguished by their capacity to survive and prosper in extraintestinal environments and by virulence gene content rather than a single serotype.

Subgroups commonly included in ExPEC are uropathogenic E. coli (UPEC), which causes most urinary tract infections; neonatal meningitis E. coli (NMEC), a leading cause of bacterial meningitis in newborns; and avian pathogenic E. coli (APEC), which affects birds and has been studied for cross-species virulence potential. Phylogenetically, ExPEC often belongs to communities such as groups B2 and D, and particular lineages like sequence type 131 (ST131) have been associated with widespread virulence and antimicrobial resistance.

Key virulence factors of ExPEC include adhesins (such as P fimbriae and type 1 fimbriae) that promote attachment to host tissues, siderophores (e.g., aerobactin, enterobactin) for iron acquisition, toxins (including hemolysin), and capsule polysaccharides that aid in immune evasion. These factors support colonization of the gut as a reservoir and subsequent infection of extraintestinal sites, including the urinary tract and, in neonates, the meninges.

Diagnosis typically involves culture of the affected sterile site (urine, blood, cerebrospinal fluid) with antibiotic susceptibility testing. Treatment depends on susceptibility profiling and may require agents such as carbapenems for resistant strains; resistance is a growing concern, particularly among ST131 lineages.

Prevention focuses on infection control and prudent antibiotic use; in animals, measures such as vaccination against APEC can reduce disease burden in poultry.