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Evidence-Based Complementary and Alternative Medicine
Volume 2013, Article ID 621701, 10 pages
Research Article

Inhibition of Klebsiella pneumoniae Growth and Capsular Polysaccharide Biosynthesis by Fructus mume

1School of Chinese Medicine, China Medical University, No. 91 Hsueh-Shih Road, Taichung 40402, Taiwan
2Division of Urology, Department of Surgery, Taichung Branch, Buddhist Tzu Chi General Hospital, Taichung 40402, Taiwan
3Department of Biotechnology, Asia University, Taichung 41354, Taiwan
4Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 11221, Taiwan
5Research Institute of Biotechnology, Hungkuang University, Taichung 43302, Taiwan

Received 10 May 2013; Accepted 17 July 2013

Academic Editor: Seung-Heon Hong

Copyright © 2013 Tien-Huang Lin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Klebsiella pneumoniae is the predominant pathogen isolated from liver abscess of diabetic patients in Asian countries. With the spread of multiple-drug-resistant K. pneumoniae, there is an increasing need for the development of alternative bactericides and approaches to block the production of bacterial virulence factors. Capsular polysaccharide (CPS), especially from the K1 and K2 serotypes, is considered the major determinant for K. pneumoniae virulence. We found that extracts of the traditional Chinese medicine Fructus mume inhibited the growth of K. pneumoniae strains of both serotypes. Furthermore, Fructus mume decreased the mucoviscosity, and the CPS produced in a dose-dependent manner, thus reducing bacterial resistance to serum killing. Quantitative reverse transcription polymerase chain reaction analyses showed that Fructus mume downregulated the mRNA levels of cps biosynthesis genes in both serotypes, possibly by increasing the intracellular iron concentration in K. pneumoniae. Moreover, citric acid, a major organic acid in Fructus mume extracts, was found to have an inhibitory effect on growth and CPS biosynthesis in K. pneumoniae. Taken together, our results indicate that Fructus mume not only possesses antibacterial activity against highly virulent K. pneumoniae strains but also inhibits bacterial CPS biosynthesis, thereby facilitating pathogen clearance by the host immune system.