Clusters of imipenem-resistant Acinetobacter baumannii clones producing different carbapenemases in an intensive care
A Tsakris1, A Ikonomidis, A Poulou
1Department of Microbiology, Medical School, University of Athens, Athens, Greece. atsakris@med.uoa.gr
Abstract:
During a 2-year period (April 2005-March 2007), 31 intensive care unit (ICU) patients in a Greek hospital were infected or colonised with imipenem-resistant isolates of Acinetobacter baumannii. Twelve patients died, with imipenem-resistant A. baumannii infection contributing to the death of seven patients. The 31 representative A. baumannii isolates were multidrug-resistant and clustered in four distinct clones, each of which contained different carbapenemase genes: clone I was predominant and contained bla(VIM-1), bla(OXA-58) and the intrinsic bla(OXA-66) gene; clone II contained bla(VIM-4), bla(OXA-58) and the intrinsic bla(OXA-69) gene; clone III contained bla(OXA-58) and the intrinsic bla(OXA-69) gene; and clone IV contained only the intrinsic bla(OXA-66) gene. ISAba1 was not associated with the intrinsic bla(OXA-51-like) alleles, whereas ISAba3 was found upstream and downstream of bla(OXA-58) in isolates of clone I, and upstream of bla(OXA-58) in isolates of clone III, but was not detected in isolates of clone II. PCR, curing and hybridisation experiments indicated that the bla(VIM) alleles were chromosomally located, whereas the bla(OXA-58) alleles were plasmid-located. This study provides the first description of the clonal spread of multidrug-resistant A. baumannii isolates carrying bla(VIM-1) and bla(VIM-4) metallo-beta-lactamase genes, and revealed that distinct carbapenem-resistant A. baumannii clusters bearing different carbapenemase genes may emerge and cause severe infections, even in a well-defined regional hospital setting.
Insights
Multidrug-resistant Acinetobacter baumannii strains carrying carbapenemase genes caused severe infections in a Greek hospital. This study highlights the clonal spread of these resistant bacteria and their impact on patient mortality.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Genetics
Background:
- Acinetobacter baumannii is a significant cause of hospital-acquired infections, particularly in intensive care units (ICUs).
- The emergence of carbapenem resistance in A. baumannii poses a major threat to patient treatment and outcomes.
- Understanding the genetic basis and clonal dissemination of resistant strains is crucial for infection control.
Purpose of the Study:
- To investigate the characteristics of imipenem-resistant Acinetobacter baumannii isolates from ICU patients in a Greek hospital.
- To identify the carbapenemase genes and clonal types involved in infections and colonizations.
- To determine the genetic location and spread of resistance determinants.
Main Methods:
- Surveillance of ICU patients over a 2-year period for imipenem-resistant A. baumannii.
- Molecular typing to identify distinct clones.
- Detection and characterization of carbapenemase genes (blaVIM, blaOXA) using PCR, curing, and hybridization.
- Analysis of insertion sequences (ISAba1, ISAba3) associated with resistance genes.
Main Results:
- Thirty-one imipenem-resistant A. baumannii isolates were identified, with 7 patient deaths attributed to infection.
- Isolates belonged to four distinct multidrug-resistant clones.
- Different carbapenemase genes (blaVIM-1, blaVIM-4, blaOXA-58) were found in different clones.
- blaVIM genes were chromosomally located, while blaOXA-58 genes were plasmid-located.
Conclusions:
- This study is the first to describe the clonal spread of multidrug-resistant A. baumannii carrying blaVIM-1 and blaVIM-4.
- Distinct carbapenem-resistant A. baumannii clones with varying carbapenemase genes can emerge and cause severe infections.
- Effective infection control strategies are essential to manage the spread of carbapenem-resistant A. baumannii in healthcare settings.
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