Pseudomonas aeruginosa strains harbouring an unusual blaVIM-4 gene cassette isolated from hospitalized children in Poland (1998-2001).
OBJECTIVE
During 1997-2001, 151 isolates of imipenem-resistant Pseudomonas aeruginosa were obtained from clinical specimens taken from children hospitalized in Warsaw, Poland. These strains were investigated further to determine the mechanism of resistance.


METHODS
The strains were analysed by a combination of genotyping and PCR-based strategies.


RESULTS
Eleven of these strains were found to contain the metallo-beta-lactamase (M beta L) gene bla(VIM-4). The first strain appeared in 1998, and P. aeruginosa strains harbouring this M beta L have become endemic in this hospital since then. All P. aeruginosa strains belonged to serotype O:6, and PFGE analysis revealed four different patterns and three sub-types. All 11 M beta L-producing strains contained an identical class 1 integron with the usual 5' and 3' conserved sequences. The integron included two resistance cassettes, aacA4 in the first position and the bla(VIM-4) cassette in the second position. The bla(VIM-4) gene included an unusual direct repeat of 169 bp of the 3' portion of the bla(VIM-4) gene.


CONCLUSIONS
An unusual bla(VIM-4) M beta L has become endemic in P. aeruginosa isolates infecting Polish children hospitalized on surgical wards. The formation of this unusual bla(VIM-4) gene cassette could be explained by a mechanism involving deletion of a segment of an ancestral tandem repeat of bla(VIM-4) via slipped strand replication, mediated by a combination of polymerase and integrase.
Patzer
Jan
J
The Children's Memorial Health Institute, Warsaw, Poland.
Toleman
Mark A
MA
Deshpande
Lalitagauri M
LM
Kamińska
Wanda
W
Dzierzanowska
Danuta
D
Bennett
Peter M
PM
Jones
Ronald N
RN
Walsh
Timothy R
TR
D002648:Child; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D018014:Gene Transfer Techniques; D006760:Hospitalization; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D011044:Poland; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012703:Serotyping; D013845:Thienamycins / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics*
D013845:Thienamycins; D015378:Imipenem; D001618:beta-Lactamases; C477893:beta-lactamase bla(VIM-4), Pseudomonas aeruginosa