The dissemination of OXA-23 harbouring VIM-2 among Acinetobacter baumannii isolates in two major Saudi Arabia hospitals

Abstract number: P1506

Al-Sultan A.A., Hamouda A., Amyes S.G.B.

Objectives: Carbapenems have become the drugs of choice for serious Acinetobacter baumannii infections, however, they are being compromised by the emergence of carbapenem-hydrolysing b-lactamases of molecular class B and D. The IMP and VIM are more prevalent in the Far East, however, OXA carbapenemases are more reported in Europe. In addition, the genes encoding OXA-23-like and OXA-51-like enzymes have been found to be linked to insertion element ISAba-1, with the OXA-58-like encoding gene adjacent to ISAba-2, ISAba-3 and IS18. The aim of this work was to investigate the dissemination of these b-lactamases and to reveal if they are spread clonally.

Methods: A total of 28 nonrepetitive, A. baumannii strains collected between January 2006 and April 2007 from different specimens. Isolates were identified to the species level by restriction analysis of the 16S-23S rRNA intergenic spacer sequences. The (MIC) of antibiotics was determined by the agar dilution method following the BSAC Guidelines. The potency of tigecycline was tested by Disk diffusion test. The metallo-b-lactamases and the IS genes were detected by multiplex polymerase chain reaction (MPCR) and PCR respectively, and their identities were confirmed by sequencing. Pulsed-field gel electrophoresis (PFGE) typing was performed using ApaI restriction endonuclease.

Results: Out of 28 isolates, 11 were resistant to imipenem (MIC > 8 mg/L), of which 4 were highly resistant (MIC = 64 mg/L). Most of these isolates were also multi-drug resistant, they were resistant to meropenem, ciprofloxacin, gentamicin and many b-lactam antibiotics, but were all sensitive to tigecycline. Six imipenem-resistant isolates (MIC 16–64 mg/L) had OXA-23, of which 4 contained ISAba-1 and ISAba-2 and two with only ISAba-1. Only one isolate (MIC 16 mg/L) had OXA-24 and ISAba-1. One imipenem-sensitive isolate (MIC 0.25 mg/L) harboured ISAba-2, ISAba-3 and IS18. A mixture of 21 imipenem-sensitive and imipenem-resistant isolates had ISAba-1 upstream of blaOXA-51 gene. All imipenem-resistant isolates were positive by PCR for blaVIM gene, and sequencing confirmed that the PCR products were 100% identical to the VIM-2. The PFGE showed that, in one hospital, 4 imipenem-resistant isolates clustered in one big group. The rest were either clustered in two or grouped with imipenem sensitive isolates.

Conclusion: Both Oxacillinases and metallo-lactamase, are now prevalent in imipenem-resistant A. baumannii in Saudi Arabia hospitals.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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