Table 2.

Key siderophores of hvKp, their genetic control, host interaction, and role in virulence.

Siderophore	Genetic control	Host interaction/Immune evasion	Virulence impact	References
Aerobactin	Encoded by iucABCD on virulence plasmid; often co-localized with rmpA	Not bound by lipocalin-2, not affected by low pH, enhances immune evasion	Considered the most important virulence factor in hvKp; strongly enhances growth in iron-poor environments	Liu et al. (2022) and Yeh et al. (2007)
Yersiniabactin	Encoded in the ybt locus in the chromosome with the ICEKp element; regulated by mobile elements	Some immune evasion, sensitive to oxidative stress and acidic pH, modulates the host stress response	Contributes to virulence; associated with serum survival, tissue dissemination	Abbas et al. (2024) and Hsieh et al. (2008)
Salmochelin	Found in the iroA locus on virulence plasmids; often near iuc genes	Modified form of enterobactin, which avoids binding by lipocalin-2, enhances immune evasion	Enhances survival in the host by bypassing lipocalin-2-mediated restriction	Fischbach et al. (2006)
Enterobactin	Core chromosomal siderophore; encoded by the entABCDEF genes	Sequestered by lipocalin-2, ineffective in the host iron competition	Primary siderophore in cKp; redundant in hvKp unless modified to salmochelin	Abbas et al. (2024)