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Generating Transposon Insertion Libraries in Gram-Negative Bacteria for High-Throughput Sequencing
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High-level gentamicin resistance mediated by a Tn4001-like transposon in seven nonclonal hospital isolates of

Viola C Y Chow1, Peter M Hawkey, Edward W C Chan

  • 1Department of Microbiology, The Chinese University of Hong Kong, The Prince of Wales Hospital, 30-32 Ngan Shing St., Shatin, New Territories, Hong Kong SAR, China. violachow@cuhk.edu.hk

Antimicrobial Agents and Chemotherapy
|March 21, 2007
PubMed

Insights

High-level gentamicin resistance was found in Streptococcus pasteurianus clinical isolates in Hong Kong. This resistance is linked to a specific gene, necessitating routine screening to prevent treatment failures and further resistance development.

Area of Science:

  • Microbiology
  • Genetics
  • Infectious Diseases

Background:

  • High-level gentamicin resistance (HLGR) is a significant concern in treating Gram-positive bacterial infections.
  • Streptococcus pasteurianus is an emerging pathogen, and its antimicrobial resistance patterns require investigation.

Purpose of the Study:

  • To report the first occurrence of HLGR in clinical isolates of Streptococcus pasteurianus.
  • To characterize the genetic basis and epidemiological relatedness of these resistant isolates.

Main Methods:

  • Species identification using sodA gene sequencing.
  • Molecular typing via pulse-field gel electrophoresis (PFGE).
  • Characterization of resistance genes and transposon structures.

Main Results:

  • Seven clinical isolates of Streptococcus pasteurianus from Hong Kong exhibited HLGR (MICs ≥ 512 μg/ml).
  • Isolates were confirmed as S. pasteurianus via sodA gene sequencing.
  • PFGE indicated isolates were not clonally related.
  • A chromosomal, transposon-borne gene [aac(6')Ie-aph(2'')Ia] encoding a bifunctional aminoglycoside-modifying enzyme was identified.
  • The transposon structure was similar to Tn4001.

Conclusions:

  • Routine screening for HLGR in clinically significant blood culture isolates is recommended.
  • This screening can prevent treatment failures in conditions like endocarditis.
  • It also helps avoid the selection of resistant strains and unnecessary gentamicin use.

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