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Canadian Journal of Infectious Diseases and Medical Microbiology
Volume 2016 (2016), Article ID 4379686, 7 pages
Research Article

Diversity of Molecular Mechanisms Conferring Carbapenem Resistance to Pseudomonas aeruginosa Isolates from Saudi Arabia

1Pharmaceutics Department, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
2Microbiology and Immunology Department, Faculty of Pharmacy, Al-Azhar University, Cairo, Egypt
3Laboratoire de Bactériologie, Centre National de Référence de la Résistance aux Antibiotiques, Besançon, France
4Unité des Agents Antimicrobiens, Institut Pasteur, Paris, France
5Microbiology and Immunology Department, Faculty of Pharmacy, Helwan University, Cairo, Egypt
6College of Pharmacy, Al Baha University, Al Baha, Saudi Arabia
7College of Medicine, Alfaisal University, Riyadh, Saudi Arabia

Received 17 May 2016; Accepted 19 July 2016

Academic Editor: Maria De Francesco

Copyright © 2016 Mohamed H. Al-Agamy et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. This study described various molecular and epidemiological characters determining antibiotic resistance patterns in Pseudomonas aeruginosa isolates. Methods. A total of 34 carbapenem-resistant P. aeruginosa clinical isolates were isolated from samples collected at a tertiary hospital in Riyadh, Saudi Arabia, from January to December 2011. Susceptibility testing, serotyping, molecular characterization of carbapenem resistance, and pulsed-field gel electrophoresis (PFGE) were performed. Results. All isolates were resistant to ceftazidime, and more than half were highly resistant (minimum inhibitory concentration (MIC) > 256 mg/L). Fifteen isolates had MIC values ≥64 mg/L for any of the carbapenems examined. Vietnamese extended-spectrum β-lactamase (VEB-1) () and oxacillinase (OXA-10) () were the most prevalent extended-spectrum β-lactamase and penicillinase, respectively. Verona imipenemase (VIM-1, VIM-2, VIM-4, VIM-11, and VIM-28) and imipenemase (IMP-7) variants were found in metallo-β-lactamase producers. A decrease in outer membrane porin gene (oprD) expression was seen in nine isolates, and an increase in efflux pump gene (MexAB) expression was detected in five isolates. Six serotypes (O:1, O:4, O:7, O:10, O:11, and O:15) were found among the 34 isolates. The predominant serotype was O:11 (16 isolates), followed by O:15 (nine isolates). PFGE analysis of the 34 carbapenem-resistant P. aeruginosa isolates revealed 14 different pulsotypes. Conclusions. These results revealed diverse mechanisms conferring carbapenem resistance to P. aeruginosa isolates from Saudi Arabia.