Novel transferable extended-spectrum beta-lactamase (SHV-6) from Klebsiella pneumoniae conferring selective resistance to ceftazidime.
ABSTRACT A clinical isolate of Klebsiella pneumoniae sensu lato isolated from throat and a blood culture taken from a neutropenic patient treated for 2 weeks with ceftazidime and vancomycin was resistant to ceftazidime (MIC: 32 micrograms/ml) and moderately susceptible to aztreonam (MIC: 4 micrograms/ml). The isolate contained a plasmid of 180 kb which, when transferred to Escherichia coli by conjugation, conferred resistance to ceftazidime and tetracycline. The transconjugant had decreased susceptibility to ceftazidime (128-fold) and aztreonam (8-fold). Clavulanic acid and sulbactam each inhibited the resistance and clavulanic acid showed a synergistic effect when associated with ceftazidime and aztreonam. An extended-spectrum beta-lactamase with an isoelectric point of 7.6 was detected in the clinical isolates from blood and its transconjugant. This beta-lactamase showed similar substrate and inhibition profiles to SHV-1. In particular it did not hydrolyse ceftazidime. Hybridization with an intragenic probe for SHV-3 indicates that this beta-lactamase is an SHV-type enzyme. We propose that this novel CAZ-type extended-spectrum beta-lactamase be named SHV-6.
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ABSTRACT: Antibiotic disks with and without clavulanic acid, 3-aminophenylboronic acid, or EDTA were tested with a set of 55 Klebsiella pneumoniae and Escherichia coli strains producing well-characterized extended-spectrum, AmpC, or carbapenem-hydrolyzing beta-lactamases. A relatively simple scheme was devised for distinguishing beta-lactamase types in clinical isolates with or without intact outer membrane porins.Journal of Clinical Microbiology 07/2006; 44(6):1971-6. · 4.07 Impact Factor
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ABSTRACT: A new SHV-derived extended-spectrum beta-lactamase, SHV-57, that confers high-level resistance to ceftazidime but not cefotaxime or cefazolin was identified from a national surveillance study conducted in Taiwan in 1998. An Escherichia coli isolate resistant to ampicillin, cephalothin, and ceftazidime but sensitive to cefoxitin, ceftriaxone, cefotaxime, imipenem, and a narrow-spectrum cephem (cefazolin) was isolated from the urine of a patient treated with beta-lactam antibiotics. Resistance to beta-lactams was conjugatively transferred with a plasmid of about 50 kbp. The pI of this enzyme was 8.3. The sequence of the gene was determined, and the open reading frame of the gene was found to consist of 861 bases (GenBank accession number AY223863). Kinetic parameters showed that SHV-57 had a poor affinity to cefazolin. The K(m) value toward cefazolin (5.57 x 10(3) muM) was extremely high in comparison to those toward ceftazidime (30.9 muM) and penicillin G (67 muM), indicating its low affinity to cefazolin. Although the K(m) value of the beta-lactamase inhibitor was too high for the study of catalytic activity (k(cat)), indicating the low k(cat) of SHV-57, the SHV-57 carrier was highly susceptible to a beta-lactam-beta-lactamase inhibitor combination. Comparison of the three-dimensional molecular model of SHV-57 with that of the SHV-1 beta-lactamase suggests that the substitution of arginine for leucine-169 in the Omega loop is important for the substrate specificity.Antimicrobial Agents and Chemotherapy 03/2005; 49(2):600-5. · 4.57 Impact Factor
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ABSTRACT: A technically simple method-the MAST double disc (MDD) test-for the detection of extended-spectrum beta-lactamase (ESBL) production by bacteria is described. A wide range of ESBL, non-ESBL and Class 1 beta-lactamase-producing isolates was examined. The MDD test, which uses discs containing ceftazidime and a complementary disc containing ceftazidime and clavulanate and a second pair containing cefotaxime and cefotaxime and clavulanate was compared with the standard double disc diffusion test and an Etest method. Both the Etest and the MDD correctly identified 93% of ESBL producers. The MDD is an inexpensive alternative to current methods for the detection of ESBL production.Journal of Antimicrobial Chemotherapy 07/2000; 45(6):881-5. · 5.34 Impact Factor