Investigation of metallo-beta-lactamase producing strains of Pseudomonas aeruginosa and Acinetobacter baumannii by E-test, disk synergy and PCR

Scand J Infect Dis. 2008;40(4):320-5. doi: 10.1080/00365540701704698.

Abstract

Carbapenem non-susceptible Pseudomonas aeruginosa and Acinetobacter baumannii strains were tested for the presence of metallo-beta-lactamases (MBLs) by EDTA-synergy screening. Imipenem hydrolysis was investigated by a bioassay and IMP-/VIM-encoding genes by PCR. No bla(IMP/VIM) related genes or imipenemase activity were detected although E-test found all strains as MBL-positive. Disk synergy tests with 0.5 M EDTA determined 63.6-100%, while those with 0.1 M EDTA detected 0-7.7% of isolates as MBL producers. Most strains were susceptible to EDTA. In conclusion, for MBL-screening purposes, EDTA-synergy results change with molarity of EDTA, but even if some false positives are encountered, 0.1 M EDTA seems to be acceptable.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter Infections / epidemiology
  • Acinetobacter Infections / microbiology
  • Acinetobacter baumannii / drug effects*
  • Acinetobacter baumannii / enzymology
  • Acinetobacter baumannii / genetics
  • Adult
  • Anti-Bacterial Agents / pharmacology*
  • Child
  • Disk Diffusion Antimicrobial Tests
  • Drug Resistance, Bacterial
  • Edetic Acid / pharmacology
  • Genotype
  • Humans
  • Imipenem / pharmacology
  • Microbial Sensitivity Tests / methods*
  • Phenotype
  • Polymerase Chain Reaction / methods*
  • Pseudomonas Infections / epidemiology
  • Pseudomonas Infections / microbiology
  • Pseudomonas aeruginosa / drug effects*
  • Pseudomonas aeruginosa / enzymology
  • Pseudomonas aeruginosa / genetics
  • Turkey / epidemiology
  • beta-Lactamases / biosynthesis*
  • beta-Lactamases / genetics

Substances

  • Anti-Bacterial Agents
  • Imipenem
  • Edetic Acid
  • beta-Lactamases