Abstract:
Hypervirulent Klebsiella pneumoniae (hvKp) is emerging worldwide. Hypermucoviscousity
is the characteristic trait that distinguishes it from classic K. pneumoniae (cKp), which enables Kp
to cause severe invasive infections. This research aimed to investigate the hypermucoviscous Kp
(hmvKp) phenotype among gut commensal Kp isolated from healthy individuals and attempted to
characterize the genes encoding virulence factors that may regulate the hypermucoviscosity trait.
Using the string test, 50 identified Kp isolates from healthy individuals’ stool samples were examined
for hypermucoviscosity and investigated by transmission electron microscopy (TEM). Antimicrobial
susceptibility profiles of Kp isolates were determined using the Kirby Bauer disc method. Kp isolates
were tested for genes encoding different virulence factors by PCR. Biofilm formation was assayed by
the microtiter plate method. All Kp isolates were multidrug-resistant (MDR). Phenotypically, 42% of
isolates were hmvKp. PCR-based genotypic testing revealed the hmvKp isolates belonged to capsular
serotype K2. All study Kp isolates harbored more than one virulence gene. The genes magA and rmpA
were not detected, while the terW gene was present in all isolates. The siderophores encoding genes
entB and irp2 were most prevalent in hmvKp isolates (90.5%) and non-hmvKp (96.6%), respectively.
hmvKp isolates harbored the genes wabG and uge with rates of 90.5% and 85.7%, respectively. The
outcomes of this research highlight the potential health risk of commensal Kp to cause severe invasive
diseases, owing to being hmvKp and MDR, and harboring multiple virulence genes. The absence
of essential genes related to hypermucoviscosity such as magA and rmpA in hmvKp phenotypes
suggests the multifactorial complexity of the hypermucoviscosity or hypervirulence traits. Thus,
further studies are warranted to verify the hypermucoviscosity-related virulence factors among
pathogenic and commensal Kp in different colonization niches.
