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Volume 45, Number 4, August 2012

 Changing trends in antimicrobial susceptibility of Streptococcus pneumoniae isolates in Taiwan, 2006-2007


Chien-Feng Li, Meei-Fang Liu, Zhi-Yuan Shi, Po-Ren Hsueh, Chun-Hsing Liao, Tsrang-Neng Jang, Shih-Ming Tsao, Hsiang-Chi Kung, Gwo-Jong Hsu, Yu-Jen Cheng, Hsiu-Chen Lin, Yung-Ching Liu, Yin-Ching Chuang, Lih-Shinn Wang, Chih-Ming Chen


Received: April 30, 2011    Revised: July 1, 2011    Accepted: August 22, 2011   

 

Corresponding author:
Zhi-Yuan Shi, Section of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, 160 Section 3, Chung-Kang Road, Taichung 40705, Taiwan. E-mail address: zyshi@vghtc.gov.tw (Z.-Y. Shi).


 

Background and purpose: 

 Multiple antibiotic-resistant clones of Streptococcus pneumoniae have spread throughout the world and continue to evolve under the selective pressure of antibiotics and vaccines. The aim of this study is to assess the susceptibility of S. pneumoniae isolates and to analyze the resistance trends in Taiwan. 



 

Methods:

 Antimicrobial susceptibility tests were performed on 152 nonmeningeal isolates of S. pneumoniae that were collected from 13 different hospitals around Taiwan from 2006e-2007. Tests were performed using the broth microdilution method according to recommendations of the Clinical and Laboratory Standards Institute.



 

Results:

 The minimal inhibitory concentrations (MIC50/MIC90) of penicillin, cefotaxime, vancomycin, and moxifloxacin were 0.5/1.0, 0.25/1.0, 0.25/0.5, and 0.06/0.12 mg/mL, respectively. The susceptibility rates of penicillin, cefotaxime, vancomycin, and moxifloxacin were 99.3%, 99.3%, 100%, and 98.7%, respectively. However, if the meningitis breakpoints were applied to these nonmeningeal isolates, the susceptibility rates of penicillin and cefotaxime were reduced to 18.4% and 76.3%, respectively.  Compared with the findings from previous studies in Taiwan, our results show that the percentage of S. pneumoniae isolates with a penicillin MIC of 0.12e1.0 mg/mL increased from 43.3% in 1996e1997 to 73.7% in 2006-2007 (p < 0.001). The percentage of S. pneumoniae isolates with a cefotaxime MIC of 1.0 mg/mL increased from 11.3% in 1996e1997 to 23.0% in 2006e2007 (p < 0.001). Regarding the serial

MIC intervals of the four antimicrobial agents, there was no significant difference between bacteremic and nonbacteremic isolates.


 

Conclusion:

 Although nonmeningeal S. pneumoniae isolates remained susceptible to penicillin, the proportion of isolates with a penicillin MIC of 0.12e1.0 mg/mL or cefotaxime MIC of 1.0 mg/mL increased during the past decade in Taiwan. The ever-increasing resistance of S. pneumoniae has a great impact on the treatment of meningitis.



 

Key words:

 Antimicrobial susceptibility; Streptococcus pneumoniae; Taiwan