Carbapenem-resistant (CR) Klebsiella pneumoniae (Kp) infections account for up to 10% of all nosocomial bacterial infections. The most common CR-Kp clone is ST258, which belongs to clonal group 258 (CG258) and can be identified by gene and capsular polysaccharide (CPS) typing. We performed an unbiased characterization of Kp-isolates at Stony Brook University Hospital (SBUH) to assess the prevalence of CG258 that remain carbapenem-sensitive (CS). Clinical characteristics of patients with CR vs. CS ST258 infections were assessed.
Kp-strains identified by SBUH microbiology laboratory were characterized by Multilocus Sequence typing (MLST) and molecular-based CPS typing based on wzi gene-sequencing to identify CG258 strains. Virulence of these CS CG258-strains was assessed in the Galleria mellonella and murine infection model. We performed retrospective chart reviews of CG258 infected patients to record comorbidities, ICU stay, antibiotic usage, and mortality and compare patients infected with CR vs. CS CG258 strains including 3 other CS ST258 strains from a previously published study from Montefiore Medical Center.
300 Kp-strains were isolated at SBUH during 2015. 83% were derived from urine, the remainder from sputum and wound. Typing has been completed on the first 156 isolates. Based on MLST 30 strains (19%) belonged to the CG258. CPS typing identified a wide diversity of CPS types among Kp-strains, and 83.3% were assigned to clade 1 and 2 in CG258. Of those, 4 (13%) were CS and lacked blaKPC gene. Including previous CSCG258 strains 4/7 were clade 1, 2/7 wzi18 and 1/7 clade 2. All CS-Kp-strains were virulent in Galleria (median 5d, range 1-11d). Three strains (2 clade 1, 1 wzi18) were tested in murine models and killed mice in 1-2d. These are the first non-clade 2 strains that are virulent in mice. Chart review showed 67% of CS-Kp-strains colonized patients with less co-morbidities whereas CR-Kp-strains caused disease in patients with co-morbidities.
Within the CG258 we found 13% of these Kp-strains were CS and lacked blaKPC gene. These strains more commonly colonize patients but were virulent in both models used. Further studies should be done to assess their capacity to acquire multidrug-resistant genes.
A. Khan, None
M. Adnan, None
H. A. Yoon, None
E. Spitzer, None
B. Fries, None