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Volume 44, Number 5, October 2011

Difference in imipenem, meropenem, sulbactam, and colistin nonsusceptibility trends among three phenotypically undifferentiated Acinetobacter baumannii complex in a medical center in Taiwan, 1997–2007


Chen Liang-Yu, Shu-Chen Kuo, Chun-Yu Liu, Bin-Syun Luo, Ling-Ju Huang, Yi-Tzu Lee, Chien-Pei Chen, Te-Li Chen, Chang-Phone Fung


Received: May 30, 2010    Revised: July 8, 2010    Accepted: August 12, 2010   

 

Corresponding author:

Te-Li Chen, Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
School of Medicine, National Yang-Ming University, Taiwan
Institute of Clinical Medicine, National Yang-Ming University, Taiwan



 

Background and purpose: 

To determine whether the susceptibilities and the trends of nonsusceptibility of imipenem, meropenem, sulbactam, and colistin differed among Acinetobacter baumannii, Acinetobacter genomic species 3 (AGS 3), and Acinetobacter genomic species 13TU (AGS 13TU) over 11 years.



 

Methods:

A total of 1,039 nonduplicate blood isolates of A baumannii complex from bacteremic patients between 1997 and 2007 were collected at Taipei Veterans General Hospital and were identified to the species level using a multiplex polymerase chain reaction method and sequence analysis of 16S–23S intergenic spacer. The minimal inhibitory concentrations of antibiotics were determined by the agar dilution method.



 

Results:

The nonsusceptibility rates of carbepenems and sulbactam were highest in A baumannii, which also showed a trend toward increasing rate of carbapenems nonsusceptibility over the 11-year period of the study. AGS 13TU had the highest nonsusceptible rate to colistin, comparably increasing trend of carbapenem nonsusceptiblity as that of A baumannii, and is the only species with increasing sulbactam nonsusceptibility. AGS 3 had the lowest rate of nonsusceptibility to all four antimicrobial agents.



 

Conclusion:

Although A baumannii had the highest nonsusceptibility rate to imipenem, meropenem, and sulbactam over the years, the higher rate of colistin nonsusceptibility and the emergence of nonsusceptibility of carbapenems and sulbactam in AGS 13TU suggested that this species might cause a great problem in the near future.



 

Key words:

Acinetobacter baumannii complex, Antimicrobial susceptibility, Resistance, Trend