Pseudomonas aeruginosa strains harbouring an unusual blaVIM-4 gene cassette isolated from hospitalized children in Poland (1998–2001)

• Published in: Journal of antimicrobial chemotherapy 2004-03, Vol.53 (3), p.451-456
• Main Authors: Patzer, Jan, Toleman, Mark A., Deshpande, Lalitagauri M., Kamińska, Wanda, Dzierżanowska, Danuta, Bennett, Peter M., Jones, Ronald N., Walsh, Timothy R.
• Format: Article
• Language: English
• Subjects: Antibiotics. Antiinfectious agents. Antiparasitic agents; beta-Lactamases - genetics; Biological and medical sciences; carbapenems; Child; Drug Resistance, Bacterial; Electrophoresis, Gel, Pulsed-Field; Gene Transfer Techniques; Hospitalization; Humans; Imipenem - pharmacology; Medical sciences; metallo-β-lactamases; Microbial Sensitivity Tests; Molecular Sequence Data; PFGE; Pharmacology. Drug treatments; Poland; Pseudomonas aeruginosa - genetics; Pseudomonas Infections - microbiology; Reverse Transcriptase Polymerase Chain Reaction; serotypes; Serotyping; Thienamycins - pharmacology; β-lactams
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/dkh095

Objectives: 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-β-lactamase (MβL) gene blaVIM-4. The first strain appeared in 1998, and P. aeruginosa strains harbouring this MβL 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 MβL-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 blaVIM-4 cassette in the second position. The blaVIM-4 gene included an unusual direct repeat of 169 bp of the 3′ portion of the blaVIM-4 gene. Conclusions: An unusual blaVIM-4 MβL has become endemic in P. aeruginosa isolates infecting Polish children hospitalized on surgical wards. The formation of this unusual blaVIM-4 gene cassette could be explained by a mechanism involving deletion of a segment of an ancestral tandem repeat of blaVIM-4 via slipped strand replication, mediated by a combination of polymerase and integrase.