ACO1 and Respiratory tract infection: The simultaneous high expression of the iron uptake genes entB, irp1, irp2, ybtS, and fyuA by some of the strains after infection of A549 and A431 cell lines highlights the virulence of the strains to cause acute infections because entB (enterobactin) and irp-1 (yersiniabactin) expression increases biofilm formation in Klebsiella pneumoniae, causing liver abscess [30]; ybtS (yersiniabactin) promotes respiratory tract infection [31], while irp and fyuA (yersiniabactin) reduce the bactericidal capacity of innate immune cells [32].