Molecular analysis of carbapenem-resistant strains of Pseudomonas aeruginosa isolated from patients hospitalized in various transplantation wards between 2008 and 2011.
BACKGROUND
Recent years have seen a concerning increase in the number of carbapenem-resistant Pseudomonas aeruginosa strains. P aeruginosa is one of the most dangerous factors causing nosocomial infections, and immunosuppressed patients constitute a special risk group. The purpose of our study was to conduct a molecular analysis of 22 clinical isolates of carbapenem-resistant P aeruginosa obtained between 2008 and 2011.


METHODS
Metallo-beta-lactamase (MBL) phenotype tests were conducted. A polymerase chain reaction technique was used to detect VIM, IMP, NDM, and GIM carbapenemase-encoding genes. The minimum inhibitory concentrations were determined for imipenem, meropenem, and doripenem. Molecular typing was conducted with the use of restriction fragment length polymorphism/pulsed-field gel electrophoresis (RFLP-PFGE).


RESULTS
Of the 22 strains initially resistant to at least one carbapenem, we selected 18 that exhibited the MBL phenotype. Of those 18, we identified 15 strains expressing VIM carbapenemase-encoding genes. None of the other evaluated genes were detected. VIM-positive isolates exhibited higher levels of resistance than the other ones. The RFLP technique revealed 10 different PFGE types and 6 epidemic foci. Identical strains were isolated over the period of up to 3 years.


CONCLUSIONS
The reason for resistance to carbapenems in the majority (68%) of P aeruginosa strains isolated at the evaluated hospital was the presence of VIM carbapenemase. It is safe to say that the VIM carbapenemase is responsible for a higher level of resistance than unidentified mechanisms. Carbapenem-resistant strains of P aeruginosa spread clonally within individual wards and are likely to be of hospital origin.
Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland.
E
E
Kosykowska
Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland.
K
K
Szymanek-Majchrzak
Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland.
S
S
Walter de Walthoffen
Division of Clinical Microbiology and Infection Prevention, National Medicines Institute, Warsaw, Poland.
R
R
Izdebski
Department of Dental Microbiology, Medical University of Warsaw, Warsaw, Poland.
A
A
Mlynarczyk
Department of Immunology, Transplantology and Internal Diseases, Transplantology Institute, Medical University of Warsaw, Warsaw, Poland.
M
M
Ciszek
Department of General and Transplantation Surgery, Transplantology Institute, Medical University of Warsaw, Warsaw, Poland.
A
A
Chmura
Department of Transplant Medicine and Nephrology, Transplantology Institute, Medical University of Warsaw, Warsaw, Poland.
M
M
Durlik
Department of Immunology, Transplantology and Internal Diseases, Transplantology Institute, Medical University of Warsaw, Warsaw, Poland.
L
L
Paczek
Department of Transplant Medicine and Nephrology, Transplantology Institute, Medical University of Warsaw, Warsaw, Poland.
D
D
Deborska-Materkowska
Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland.
A
A
Sawicka-Grzelak
Department of Medical Microbiology, Medical University of Warsaw, Warsaw, Poland. Electronic address: grazyna.mlynarczyk@wum.edu.pl.
G
G
Mlynarczyk
D000328:Adult; D015780:Carbapenems / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016377:Organ Transplantation; D012150:Polymorphism, Restriction Fragment Length; D011552:Pseudomonas Infections / Q000453:epidemiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D001618:beta-Lactamases / Q000235:genetics*
D015780:Carbapenems; C533914:metallo-beta-lactamase (VIM-13), Pseudomonas aeruginosa; D001618:beta-Lactamases