Sources of diversity of carbapenem resistance levels in Klebsiella pneumoniae carrying blaVIM-1.
J Antimicrob Chemother
; 58(3): 669-72, 2006 Sep.
Article
em En
| MEDLINE
| ID: mdl-16870645
ABSTRACT
OBJECTIVES:
To elucidate the mechanisms responsible for the diversity of beta-lactam resistance phenotypes among isolates of a VIM-1-producing Klebsiella pneumoniae (VPKP) strain that is endemic in Greek hospitals.METHODS:
Five VPKP clinical isolates were studied. MICs of beta-lactams were determined by agar dilution. PFGE of XbaI-digested genomic DNA was used for typing. Profiles of outer membrane proteins (OMPs) were determined by SDS-PAGE. Selected isolates were transformed with a plasmid encoding the Omp36K porin. beta-Lactamase activities were analysed by IEF and imipenem hydrolysis was assessed by spectrophotometry. VIM-1-encoding, self-transmissible plasmids were characterized by replicon typing, RFLP and hybridization with bla(VIM)- and IS26-specific probes. Characterization of integrons was performed by PCR, cloning and sequencing.RESULTS:
Isolates exhibited highly similar PFGE patterns. Imipenem MICs were 2, 4, 16, 32 and 64 mg/L. The isolate with the highest imipenem MIC (Vipm-64) lacked a 36 kDa OMP. Expression of a cloned OmpK36 in this isolate reduced the imipenem MIC to susceptibility levels. Imipenem-hydrolysing activity was significantly higher in Vipm-16 as compared with the other isolates that expressed similar amounts of VIM-1. All isolates transferred beta-lactam resistance to Escherichia coli through conjugative, IncN plasmids that exhibited differences in the RFLP and hybridization patterns with bla(VIM)- and IS26-specific probes. The Vipm-16 plasmid, mediating the higher imipenem MICs among transconjugants, carried two copies of bla(VIM-1). Cloning and sequencing showed In-e541-like integrons truncated at the 5'CS by insertion of IS26 elements at two different positions.CONCLUSIONS:
A VIM-1-producing strain of K. pneumoniae has evolved through OMP alterations and rearrangements in the bla(VIM-1)-carrying plasmid probably mediated by IS26, generating isolates with imipenem MICs ranging from susceptibility to resistance.
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Coleções:
01-internacional
Contexto em Saúde:
3_ND
Base de dados:
MEDLINE
Assunto principal:
Proteínas da Membrana Bacteriana Externa
/
Beta-Lactamases
/
Carbapenêmicos
/
Resistência beta-Lactâmica
/
Genes Bacterianos
/
Klebsiella pneumoniae
/
Antibacterianos
Idioma:
En
Revista:
J Antimicrob Chemother
Ano de publicação:
2006
Tipo de documento:
Article