Klebsiella pneumoniae (Kp) causes 10% of nosocomial infections in the U.S and Europe. Multidrug resistant strains are a major problem due to limited treatment options and are associated with high morbidity and mortality. The most common clone associated with carbapenem-resistance is ST258. Our goal was to perform an unbiased characterization of Kp isolates at Stony Brook University Hospital (SBUH) to assess the prevalence of ST258 clones and characterize the capsule types in Kp clinical isolates. We also assessed clinical characteristics of patients with ST258 vs. non-ST258 clones.
We used molecular typing to characterize the genetic backgrounds and capsular polysaccharides. The waxworm model, Galleria mellonella was used to demonstrate differences in virulence. We performed retrospective chart reviews on the patients harboring Kp to assess comorbidities, ICU stay, antibiotic usage, sensitivity to carbapenems, and mortality.
A total of 156 Kp clinical isolates were isolated at SBUH from September 2014 to April 2015. 70% of the isolates were obtained from urine samples and 17% from sputum. Of the 84 isolates typed, 19% were ST258 clones, which is the major Kp Carbapenemase (KPC) producing strain worldwide. However, we found that 25% of our ST258 strains were actually carbapenem sensitive and lacked the KPC gene. Capsule typing based on wzi gene sequencing identified both clade I- and clade II-capsular polysaccharides among the ST258 strains. A K1 hypermucoid strain that causes invasive infections was also found. The 156 isolates of Kp were obtained from 140 patients. Retrospective chart review of 61 consecutive patients revealed 8 patients with ST258 strains and 53 patients with other strains. ST258 strain recovery was associated with higher rates of prior antibiotic use (100 vs. 62%), carbapenem resistance (75 vs. 9.4%) and mortality rate (37.5 vs. 7.5%). Galleria experiments confirmed wide variability in virulence among Kp strains.
Klebsiella pneumoniae strains exhibit extensive variability with respect to their capsular polysaccharide and virulence. The ST258 strain infection in our patients was associated with higher antibiotic exposure, carbapenem resistance, and mortality rate. Carbapenem sensitive ST258 strains were detected that lacked the KPC gene.
B. Fries, None
E. Spitzer, None
E. Diago-Navarro, None