1,720,992 research outputs found
Ceftaroline in vitro activity against methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococci: a short report from Italy
No full textHigh specificity of cphA-encoded metallo-β-lactamase from Aeromonas hydrophila AE036 for carbapenems and its contribution to β-lactam resistance
No full textThe Aeromonas hydrophila AE036 chromosome contains a cphA gene encoding a metallo-β-lactamase highly active against carbapenem antibiotics. This enzyme was induced in strain AE036 to the same extent by both benzylpenicillin and imipenem. When the cphA gene was inserted into plasmid pACYC184, used to transform Escherichia coli DH5α, the MICs of imipenem, meropenem, and penem HRE664 for recombinant clone DH5α(pAA20R), expressing the Aeromonas metallo-β-lactamase, were significantly increased, but those of penicillins and cephalosporins were not. When the metallo-β-lactamase purified from E. coli DH5α(pAA20R) was assayed with several β-lactam substrates, it hydrolyzed carbapenems but not penicillins or cephalosporins efficiently. These results demonstrate that this metallo-β-lactamase possesses an unusual spectrum of activity compared with all the other class B enzymes identified so far, being active on penems and carbapenems only. This enzyme may thus contribute to the development of resistance to penems and carbapenems but not other β-lactams
The β-Lactamases of citrobacter diversus and their hydrolysis kinetics for some structurally-related cephalosporins
No full textMeropenem stability to β-lactamase hydrolysis and comparative in vitro activity against several β-lactamase-producing Gram-negative strains
No full textThe interaction between meropenem and class A, B, C and D β-lactamases was studied by a spectrophotometric method. Class A, C and D β-lactamases were unable to confer in vitro resistance to carbapenems. Surprisingly, several class B metallo-β-lactamases expressed in Escherichia coli failed to confer resistance when a conventional inoculum (105 cfu/mL) was used
Spread of blaCTX-M-type and blaPER-2 β-lactamase genes in clinical isolates from Bolivian hospitals
No full textObjectives: To assess the prevalence and types of genes encoding extended-spectrum β-lactamases (ESBLs) in clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp. from Bolivia. Methods: A total of 642 clinical isolates were collected consecutively during a 4 month period (September to December 2004). Resistance or reduced susceptibility to cefotaxime and/or ceftazidime and/or aztreonam was assessed using double disc synergy tests using clavulanic acid, cefotaxime, ceftazidime and aztreonam to identify putative ESBL-producing isolates. The ESBL determinants were characterized by colony blot hybridization, PCR and DNA sequencing. Results: Of the 642 isolates, 220 (34.3%) showed resistance or reduced susceptibility to cefotaxime and/or ceftazidime and/or aztreonam, and 150 (23.4%) were putative ESBL producers. A total of 106 ESBL-producing isolates contained the blaCTX-M-2 gene, and 32 isolates had a novel allele, blaCTX-M-43. blaCTX-M alleles were detected in all P. aeruginosa and Acinetobacter spp. studied. In contrast, only 12 ESBL-producing isolates had blaPER-2, mainly Enterobacteriaceae, although it was also found in a strain of P. eruginosa. Conclusions: This is the first study on ESBL-producing strains in Bolivia and it reveals a high prevalence of blaCTX-M genes. The PER-2 enzyme was less prevalent, but its gene was detected in several species, including P. aeruginosa, which is consistent with horizontal transfer. © 2006 Oxford University Press
On the kinetic interaction between ceftriaxone and some β-lactamases
No full textThe activity of β-lactamases from Citrobacter diversus ULA-27 on ceftriaxone, a widely recognized third-generation cephalosporin, has been examined and compared to the activity of various other β-lactamases from different sources. Ceftriaxone (Roche S.p.A. Milan) was found to be resistant to hydrolysis by β-lactamases from Enterobacter cloacae and Bacillus cereus, but susceptible to β-lactamases from Mycobacterium fortuitum strain Cow 18 and, mostly, to β-lactamases from various strains of Citrobacter diversus. Derivatives with substituents in the 3-position of ceftriaxone, namely cefotaxime (Roussel Maestretti S.p.A., Milan) and ceftizoxime (Farmitalia Carlo Erba, Milan), were much less susceptible to hydrolysis by C. diversus ULA-27 enzymes (22 and 6% of ceftriaxone hydrolysis, respectively), the hydrolysis rate being paralleled by differences in MIC values. Ceftriaxone inhibited the activity of E. cloacae β-lactamases toward cefazolin as substrate, but the inhibition was totally abolished by preincubation of ceftriaxone with the enzyme before addition of the substrate. Overall, the data point to a relevance of C. diversus ULA-27 β-lactamases in the mechanism of resistance of this strain to the various third-generation cephalosporins
Broad spectrum β-lactamases of citrobacter diversus
No full textCitrobacter diversus NF85 produced a chromosomal β-lactamase that was induced by a variety of β-lactam antibiotics. Two major forms of the enzyme, with isoelectric points (pI's) of 5·7 and 6·2, were found in crude cell extracts. Derepressed mutants of NF85, generated by nitrosoguanidine treatment, displayed different levels of β-lactamase expression to the parent strain and had different patterns of resistance to a range of β-lactam antibiotics. Those mutants of NF85 that were totally derepressed, expressing high, constitutive levels of enzyme, were found to have an additional β-lactamase activity with a pI of 6·8. © 1990 by The British Society for Antimicrobial Chemotherapy
Biochemical characterization of laboratory mutants of extended-spectrum β-lactamase TEM-60
No full textThree mutants of the extended-spectrum -lactamase TEM-60, the P51L, K104E, and S164R mutants, were
constructed by site-directed mutagenesis. The kinetic parameters of the mutated enzymes and interactions of
inhibitors were significantly different from those of TEM-60, revealing that the L51P mutation plays an
important role in enzyme activity and stability in the TEM-60 background.Three mutants of the extended-spectrum β-lactamase TEM-60, the P51L, K104E, and S164R mutants, were constructed by site-directed mutagenesis. The kinetic parameters of the mutated enzymes and interactions of inhibitors were significantly different from those of TEM-60, revealing that the L51P mutation plays an important role in enzyme activity and stability in the TEM-60 background
BlaB-15, a new BlaB metallo-β-lactamase variant found in an Elizabethkingia miricola clinical isolate
Full text linkA multidrug-resistant strain of Elizabethkingia miricola was isolated from the urine of a 2-year-old boy hospitalized for severe clinical conditions. The strain produces 2 metallo-β-lactamases belonging to subclasses B1 and B3: a new BlaB variant (BlaB-15) and a GOB-7–like enzyme
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