Should multidrug resistant Klebsiella pneumoniae strains displaying hypervirulent traits be reclassified as either ultravirulent or supervirulent?

Abstract

Historically, Klebsiella pneumoniae isolates were described either as hypervirulent or classical. While hypervirulent strains display a precise phenotype (thicker capsule, hypermucoviscosity, absence of antibiotic resistance markers, several siderophores, etc.), classical strains can relate to all other K. pneumoniae strains, including virulent multidrug-resistant clinical isolates. Recently, many surveillance studies reported virulent K. pneumoniae nosocomial strains resistant to all antibiotic classes which also contain genetic markers associated with hypervirulence. Due to their higher virulence and clinical importance, here it is proposed reclassify them as ultravirulent and as supervirulent, to distinguish them from each other and from those with either hypervirulent or virulent phenotypes.

Keywords: Antimicrobial resistance; Hypervirulence; Klebsiella pneumoniae; Nocosomial infections; Ultravirulence; Virulence.