Purpose
Klebsiella pneumoniae
(
K. pneumoniae
) is a Gram-negative bacterium that is predominantly associated with liver abscesses in global diabetic patients. High levels of glucose in the surrounding of
K. pneumonia
increase its pathogenicity including capsular polysaccharide (CPS) and fimbriae. Other important virulent factors include outer membrane protein A (ompA) and regulator mucoid phenotype A (rmpA). The objective of this investigation was to elucidate the effects of high glucose on
rmpA
and
ompA
gene expression and serum resistance of
K. pneumoniae
causing liver abscess.
Patients and Methods
The clinical history of 57 patients suffering from
K. pneumoniae
-caused liver abscesses (KLA) was acquired and their clinical and laboratory manifestations in the presence or absence of diabetes were analyzed. The antimicrobial susceptibility, serotypes, and virulence genes were tested. Clinical isolates of 3 serotype-K1 hypervirulent
K. pneumoniae
(hvKP) were used to detect the effect of exogenous high glucose on
rmpA, ompA
, and
clbB
genes expression, and bacterial serum resistance.
Results
KLA patients with diabetes showed higher C-reactive protein (CRP) compared to non-diabetic KLA patients. Furthermore, the diabetic group showed increased incidences of sepsis and invasive infections, and their length of hospital stay was also prolonged. Pre-incubation of
K. pneumoniae
in high glucose (0.5%) concentration up-regulated
rmpA, ompA
, and
clbB
genes expression. However, cAMP supplementation, which was inhibited by environmental glucose, reversed the increase of
rmpA
and
ompA
in a cAMP-dependent manner. Moreover, hvKP strains incubated in high glucose also exhibited enhanced protection from serum killing.
Conclusion
High glucose levels reflected by poor glycemic control has increased gene expression of
rmpA
and
ompA
in hvKP by the cAMP signaling pathway and enhanced its resistance to serum killing, thus providing a new and reasonable explanation for the high incidences of sepsis and invasive infections in KLA patients with diabetes.