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Volume 49, Number 1, February 2016

Quantification and comparison of virulence and characteristics of different variants of carbapenemase-producing Klebsiella pneumoniae clinical isolates from Taiwan and the United States 


Tsung-Ta Chiang, Ya-Sung Yang, Kuo-Ming Yeh, Sun-Kang Chiu, Ning-Chi Wang, Te-Yu Lin, Li-Yueh Huang, Feng-Yee Chang, L.K. Siu, Jung-Chung Lin, Jiun-Han Chen


 

Corresponding author:

Jiun-Han Chen
Corresponding author. Department of Medical Laboratory Science and Biotechnology, Yuanpei University of Medical Technology, Number 306, Yuanpei Street, Hsinchu 30015, Taiwan. 



 

Background and purpose: 

The emergence of Klebsiella pneumoniae carbapenemase (KPC)-producing strains is a challenge for clinicians. The characteristics and virulence of variants of KPC-producing K. pneumoniae isolates were evaluated. 



 

Methods:

Five clinical isolates—three KPC subtypes from Taiwan (KPC2-TW, KPC3-TW, and KPC17-TW) and two clinical strains from the United States (US; KPC2-US, KPC3-US)—were included. Virulent traits and capsular serotypes were analyzed by Polymerase Chain Reaction (PCR). Serum killing, neutrophil phagocytosis, and mice lethargy studies were performed to evaluate virulence. 



 

Results:

Multilocus sequence typing (MLST) demonstrated that KPC2-TW and KPC17-TW belonged to sequence type (ST)11, and KPC2-US, KPC3-US, and KPC3-TW to ST258. KPC3-TW expressed capsular serotype K1, whereas the others were non-K1/K2/K5 isolates. MLST analysis indicated that ST11 strains were serum resistant, whereas ST258 isolates were serum sensitive. ST11 isolates exhibited significantly higher 15-minute phagocytic rates than ST258 isolates (70.28 ± 16.68% vs. 34.88 ± 10.52%, p < 0.001). The capsular serotype K1 strain was more resistant to neutrophil phagocytosis than non-K1/K2/K5 isolates (27.1 ± 10.23% vs. 54.46 ± 20.94%, p = 0.050). All KPC-producing strain variants from Taiwan and the US demonstrated less virulence in a mouse lethality study, where the LD50 ranged from approximately 106 colony-forming units (CFU) to >107 CFU. Immunological responses were not significantly correlated with KPC subtype; however, responses were associated with MLST and capsular serotype.
 



 

Conclusion:

Production of KPC itself was not associated with increased virulence despite different variants of KPC. The ST11 KPC-producing strain was resistant to serum killing, whereas capsular ss K1 was associated with resistance to neutrophil phagocytosis. 



 

Key words:

Klebsiella pneumoniae, KPC variants, virulence