1,721,164 research outputs found
Inhibition of poly(ADP-ribosyl)ation introduces an anomalous methylation pattern in trasfected foreign DNA
No full textPrevalence of extended spectrum β-lactamases among Enterobacteriaceae: an Italian survey
No full textThe prevalence of extended-spectrum β-lactamase (ESBL) production by consecutive non-repeated isolates of Enterobacteriaceae was determined over a 6-month period. A total of 8015 strains were isolated from ten Italian laboratories and 509 (6.3%) of these were designated ESBL producers from the results of a double-disk synergy test. Escherichia coli was the most isolated microrganism, followed by Klebsiella pneumoniae and Proteus mirabilis. Providencia stuartii (28.1%) was the most frequently isolated ESBL producer, followed by K. pneumoniae and Enterobacter aerogenes (20.5%). However, amongst all ESBL producers, K. pneumoniae (38.2%) was the most represented followed by P. mirabilis (25.7%). All the strains positive to DD tests were confirmed for the carriage of TEM and SHV genes using colony-blot hybridisation (CH). A total of 447 strains (88.0%) were CH-positive, of which 42.3% hybridised with the TEM-type probe, 30.1% with the SHV-type probe and 15.6% with both probes. In conclusion, our findings indicate that 6.3% of all Enterobacteriaceae tested produced ESBLs, 42.3% of which were TEM-derived enzymes. More than 20% of P. stuartii, K. pneumoniae and E. aerogenes harbour these enzymes. The double-disk test seems to be a useful test to identify ESBL producing strains. Copyright © 2002 Elsevier Science B.V. and International Society of Chemotherapy
Extended-spectrum TEM- and SHV-type β-lactamase-producing Klebsiella pneumoniae strains causing outbreaks in intensive care units in Italy
No full textThe aim of the present study was to investigate the production of extended-spectrum β-lactamases (ES βLs) and the epidemiological correlations in a total of 107 Klebsiella pneumoniae strains resistant to third- and fourth-generation cephalosporins. The strains were collected from patients in four intensive care units (3 neonatal and 1 general) in three hospitals in Italy between March 1996 and July 1997. All strains were found to produce ESβLs. Phenotypic (antibiotyping and ESβL patterns) and genotypic (plasmid profile and pulsed-field gel electrophoresis) analyses showed that a single strain had been responsible for each outbreak in each of the four intensive care units. Isoelectric focusing, activity on substrates and gene sequencing showed that the strains produced SHV-5, SHV-2a, SHV-12 and TEM-52 β-lactamases. This is not only the first time that ESβL-producing Klebsiella pneumoniae strains have been reported as causing epidemics in Italian hospitals, it is also, to the best of our knowledge, the first time that an outbreak caused by a TEM-52 ESβL-producing Klebsiella pneumoniae strain has been reported. The data presented here illustrate the complexity of determining the epidemiological pattern of ESβL producers in large hospitals that do not have an ESβL-monitoring program
The β-Lactamases of citrobacter diversus and their hydrolysis kinetics for some structurally-related cephalosporins
No full textCefotaxime, des-cefotaxime and ceftazidime: In vitro activity and stability to hydrolysis from TEM-derived extended spectrum β-lactamases
No full textβ-lactams represent one of the most important class of antibiotics for the treatment of infectious diseases due to pathogenic bacteria. The selective pressure exerted from the wide spread use of third generation cephalosporins generated mutant β-lactamases belonging mainly to the TEM or SHV family that are able to extend the activity spectrum of hydrolysis. Moreover, extended spectrum cephalosporins are often a good choice in clinical practice towards Enterobacteriaceae. Here we report a comparative analysis of stability between cefotaxime, desacetyl-cefotaxime and ceftazidime with some common TEM-derivatives extended spectrum β-lactamases
β-Lactamases as major mechanism of resi stance in Gram-negative bacteria.
No full textβ-lactamases are the major mechanism of resistance against β-lactam antibiotics among Gram-negative bacteria. On the basis of their amino acid sequence, β-lactamases are divided into four classes: A, B, C and D. This classification was first proposed by Ambler. The classes A, C and D include enzymes that hydrolyse their substrates by forming an acyl enzyme through an active site, whereas class B β-lactamases are metallo-enzymes which utilise one or two ions in their active sites. The massive use of expanded-spectrum cephalosporins, since the 1980s, has been conducive for the emergence of extended-spectrum β-lactamases (ESBLs) in the clinical setting, a group of enzymes capable of hydrolysing a wide range of expanded-spectrum β-lactams, including the oxyiminocephalosporins, but they are inactive against cephamicins and carbapenems. The emergence and widespread of ESBLs compromised the usefulness of carbapenems in clinical therapy leading to the emergence and diffusion of carbapenemases and in particular metallo-β-lactamases. © 2012 Bentham Science Publishers. All rights reserved
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
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