Metallo-b-lactamases type IMP associated with loss expression of OprD porins in nosocomial isolates of carbapenem-resistant Pseudomonas aeruginosa

Abstract number: P906

Gayosso-Vazquez C., Alcantar-Curiel D., Morfin-Otero R., Rodriguez-Noriega E., Mussaret Z., Cardiel L., Firo V., Justiniani N., Santos J.I., Alpuche-Aranda C.

Background: Carbapenem resistance (CBPR) in Pseudomonas aeruginosa (Psa) is associated with metallo-b-lactamases (MBLs) production or AmpC activity combined with loss of the porin OprD. In addition overexpression of efflux pumps could confer CBPR. In this study we investigated molecular mechanisms of CBPR in Psa causing bloodstream infections in Mexican hospitals.

Methods: We analysed eight Psa strains characterised in our laboratory. Antimicrobial susceptibility testing was performed by disk diffusion and dilution methods following CLSI standards. MBLs activity was detected by EDTA (0.5M)-disk synergy test with MEM (10 mg) or IPM (10 mg) and by E-test-MBL. The MBL genes were characterised by PCR using specific primers for IMP, GIM, SPM and VIM, and sequencing analysis. Production of OprD porin was performed by SDS-PAGE from outer membrane proteins. PFGE and endonuclease restriction analysis was used to characterise clonal dissemination.

Results: The eight Psa strains were isolated from three different hospitals in Mexico: Hospital Civil de Guadalajara (3), Hospital OHoran, (4) and Hospital General de Mexico (1). All strains were 100% resistant to AMK, CAZ, CIP, FEP, GEN, IMP, MEM and the MIC to IMP was >256 mg/mL in 6/8 strains. MBLs activity was confirmed in all strains, however by PCR and sequencing analysis only four strains were IMP type and negative to the other types. Three of these IMP-expressing strains failed to produce OprD porin. The PFGE profile demonstrated clonal variability.

Conclusions: Although isolates analysed are few, this is the first study that confirmed multiresistance, including CBPR in Psa strains causing serious nosocomial infections selected in different geographic areas in Mexico.

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:
Back to top