Emergence and persistence of integron structures harbouring VIM genes in the Children's Memorial Health Institute, Warsaw, Poland, 1998-2006.
OBJECTIVE
The aim was to perform a genetically detailed study of the emergence of metallo-beta-lactamase (MBL) genes in Pseudomonas spp. in the Children's Memorial Health Institute over a 9 year period.


METHODS
Carbapenem-resistant Pseudomonas spp. isolates were collected from 1998 to 2006 and screened for MBL production. MBL-positive isolates were further investigated by a combination of genetic techniques including PCR, genomic location experiments using pulsed-field gel electrophoresis (PFGE) of I-Ceu1, S1 and SpeI digests, and sequencing.


RESULTS
Of the 20 MBL-containing Pseudomonas isolates collected from 1998 to 2006, 16 Pseudomonas aeruginosa isolates contained an identical class 1 integron structure. Two P. aeruginosa isolates contained the bla(VIM-2) gene, and two Pseudomonas putida isolates harboured the bla(VIM-4) gene cassette in different integron structures. PFGE analysis indicated that all bla(VIM-4)-containing P. aeruginosa isolates were closely related, whereas the P. putida isolates were not. All MBL genes in this study were chromosomally encoded, and all isolates harboured only one class 1 integron. The bla(VIM-2) isolates were clonal, and the genetic structure supporting the bla(VIM-2) gene was found in an identical chromosomal position.


CONCLUSIONS
MBL gene emergence in this hospital has paralleled a 6-fold increase in carbapenem usage. We have found an increase in MBL gene diversity, MBL host organisms and MBL genetic support structures in the hospital over the 9 year study period. There is also compelling evidence of the persistence of individual strains in the hospital throughout the study period. This suggests that once MBL genes have emerged in a hospital environment, they are difficult to remove.
Patzer
Jan A
JA
Department of Clinical Microbiology and Immunology, The Children's Memorial Health Institute, Warsaw, Poland.
Walsh
Timothy R
TR
Weeks
Janis
J
Dzierzanowska
Danuta
D
Toleman
Mark A
MA
D001426:Bacterial Proteins / Q000235:genetics*; D015373:Bacterial Typing Techniques; D003428:Cross Infection / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006761:Hospitals; D006801:Humans; D032023:Integrons; D008969:Molecular Sequence Data; D011044:Poland; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D016958:Pseudomonas putida / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D001618:beta-Lactamases