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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 54 (1998), S. 341-346 
    ISSN: 1420-9071
    Keywords: Key words.β-lactamases; penicillins; cephalosporins; regulation; classification.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. β-Lactamase production is responsible for the appearance of a large number of pathogenic bacterial strains exhibiting a high degree of resistance to β-lactam antibiotics. A large number of enzymes have been described with very diverse primary structures and catalytic profiles. Nevertheless, all known three-dimensional structures of active-site serine β-lactamases exhibit a high degree of similarity with apparently equivalent chemical functionalities in the same strategic positions. These groups might not, however, play identical roles in the various classes of enzymes. Structural data have also been recently obtained for the zinc metallo-β-lactamases, but the detailed catalytic mechanisms might also differ widely, depending on the enzyme studied. Similarly, the induction of the synthesis of β-lactamases is now better understood, but many questions remain to be answered.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1238
    Keywords: Intensive care unit ; Antibiotic susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective Evaluation of the distribution and antibiotic susceptibility of the aerobic gramnegative bacilli (AGNB) isolated from patients in intensive care units (ICU study). Design and setting Microbiological study carried out in 1991 in 39 teaching hospitals. A standardized method was used to determine the minimum inhibitory concentrations of 12 antibiotics against 3366 strains of AGNB (close to 100 strains per hospital) during a period of 3 months. Results The 2773 initial strains (i.e., the first AGNB isolate for a given species and a given patient) were mainly isolated from the respiratory tract (34.4%), urinary tract (23%), or blood (9.6%) and were mainlyPseudomonas aeruginosa (22.9%),Escherichia coli (22%), Acinetobacter (9.7%), andKlebsiella pneumoniae (8.3%).E. coli was prominent in urine and blood andP. aeruginosa in the respiratory tract. Overall, the rate of susceptibility of AGNB was 58 to 65% to piperacillin, cefotaxime, and gentamicin; 69 to 75% to aztreonam, tobramycin, and ciprofloxacin; 83% to ceftazidime; and 91% to imipenem. The overall rates of susceptibility were higher for the initial strains isolated from blood than for those from the urinary or respiratory tracts, mostly reflecting differences in species distribution. Susceptibility rates were lower for the 593 repeat strains (i.e., all the subsequent isolates for a given species and a given patient) than for the initial strains, mostly due to the higher proportion of resistant species (P. aeruginosa 45.9%) but also due to the difference in susceptibility rates for some species-antibiotic combinations. Concomitant resistance (i.e., resistance to several antibiotics due to independent mechanisms of resistance) was marked between β-lactams and aminoglycosides or quinolones, particularly inP. aeruginosa andK. pneumoniae. Conclusions Rates of resistance in AGNB as a whole and in particular species (P. aeruginosa, Klebsiella), as well as frequency of concomitant resistance found in the French ICU study, were higher than those found in ICU studies conducted with the same methodology in Belgium, The Netherlands, and Germany, which may reflect differences in case mix.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1238
    Keywords: Key words Intensive care unit ; Antibiotic susceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: Evaluation of the distribution and antibiotic susceptibility of the aerobic gram-negative bacilli (AGNB) isolated from patients in intensive care units (ICU study). Design and setting: Microbiological study carried out in 1991 in 39 teaching hospitals. A standardized method was used to determine the minimum inhibitory concentrations of 12 antibiotics against 3366 strains of AGNB (close to 100 strains per hospital) during a period of 3 months. Results: The 2773 initial strains (i.e., the first AGNB isolate for a given species and a given patient) were mainly isolated from the respiratory tract (34.4%), urinary tract (23%), or blood (9.6%) and were mainly Pseudomonas aeruginosa (22.9%), Escherichia coli (22%), Acinetobacter (9.7%), and Klebsiella pneumoniae (8.3%). E. coli was prominent in urine and blood and P. aeruginosa in the respiratory tract. Overall, the rate of susceptibility of AGNB was 58 to 65% to piperacillin, cefotaxime, and gentamicin; 69 to 75% to aztreonam, tobramycin, and ciprofloxacin; 83% to ceftazidime; and 91% to imipenem. The overall rates of susceptibility were higher for the initial strains isolated from blood than for those from the urinary or respiratory tracts, mostly reflecting differences in species distribution. Susceptibility rates were lower for the 593 repeat strains (i.e., all the subsequent isolates for a given species and a given patient) than for the initial strains, mostly due to the higher proportion of resistant species (P. aeruginosa 45.9%) but also due to the difference in susceptibility rates for some species-antibiotic combinations. Concomitant resistance (i.e., resistance to several antibiotics due to independent mechanisms of resistance) was marked between β-lactams and aminoglycosides or quinolones, particularly in P. aeruginosa and K. pneumoniae. Conclusions: Rates of resistance in AGNB as a whole and in particular species (P. aeruginosa, Klebsiella), as well as frequency of concomitant resistance found in the French ICU study, were higher than those found in ICU studies conducted with the same methodology in Belgium, The Netherlands, and Germany, which may reflect differences in case mix.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 116 (1994), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Aztreonam-resistant Klebsiella oxytoca strain SL7811 was selected on agar containing 1 μg of aztreonam per ml from a susceptible strain SL781. The MICs for the resistant mutant towards penicillins, aztreonam and ceftriaxone were much higher, to cefotaxime slightly higher and to ceftazidime unchanged. Synthesis of β-lactamase was 223-fold greater in the mutant compared with the susceptible strain. SL781 and its resistant mutant SL7811 produced β-lactamase with the same isoelectric point and substrate profile. The β-lactamase genes from SL781 and SL7811 were cloned in plasmid pBGS18 giving pBOF-1 and pBOF-4 respectively. The sequences of the two putative promoters indicated two modifications in the resistant plasmid pBOF-4: a transversion (G → T) in the first base of the − 10 consensus sequence and a deletion of one C residue four base pairs upstream of the − 10 hexamer.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 67 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two novel β-lactamases conferring multiresistance to antibiotics including oxyimino β-lactams have been identified in two nosocomial K. pneumoniae strains isolated in Tunis in 1986 and 1988. Both enzymes were encoded by ca. 150-kilobase plasmids. Donor and transconjugant strains producing these enzymes exhibited highly similar pattern of resistance (CTX phenotype) to β-lactams including penicillins and oxyimino β-lactams e.g. cefotaxime, ceftriaxone, ceftazidime, and aztreonam. High and variable synergy (16 to 1066-fold) was obtained when combined to 0.1 μg/ml of clavulance (β-lactamase inhibitor). The isoelectric points of these two enzymes were 5.4 and 6.4. These β-lactamases differed from TEM types by hydrolysis for cefotaxime or ceftriaxone but were inhibited by clavulanate and cloxacillin. DNA hybridization studies suggested that the genes of these enzymes may be derived from genes encoding TEM-type enzymes.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 59 (1989), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A strain of Acinetobacter calcoaceticus var. anitratus highly resistant to ticarcillin but susceptible to ticarcillin in combination with clavulanic acid (2 mg/l) was found to produce a constitutive β-lactamase. This enzyme was periplasmic with a characteristic substrate profile of a carbenicillin-hydrolyzing enzyme. Enzyme inhibition was detected with antiserum (anti-CARB-3), pCMB, cloxacillin, clavulanic acid and sulbactam. This novel enzyme with a molecular mass of 28 000 resembles other plasmid-mediated carbenicillinases (CARB) but differs in its apparent isoelectric point estimated as 6.3 and has been designated CARB-5 on this basis.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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 μg/ml) and moderately susceptible to aztreonam (MIC: 4 μg/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 β-lactamase with an isoelectric point of 7.6 was detected in the clinical isolates from blood and its transconjugant. This β-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 β-lactamase is an SHV-type enzyme. We propose that this novel CAZ-type extended-spectrum β-lactamase be named SHV-6.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 8 (1980), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 134 (1995), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract To rapidly characterise TEM-derived extended-spectrum β-lactamases a fast and easy method using polymerase chain reaction-restriction fragment length polymorphism was developed. This method was validated with ten reference TEM-type extended-spectrum β-lactamases. The mutations involved in TEM-20 and TEM-21, which were previously reported only with biochemical analysis, were then characterised. TEM-20 differed from TEM-19 by a silent mutation at position 925 (A for G), and TEM-21 differed from TEM-3 and TEM-14 by a single mutation (G for A) in an unreported position 660, involving an amino acid substitution, arginine for histidine, at position 153. Moreover, a new extended-spectrum β-lactamase conferring low resistance to ceftazidime (TEM-29), was described. TEM-29 derived from TEM-1, with an amino acid substitution, his-164. Finally, the combination of polymerase chain reaction-restriction fragment length polymorphism and plasmid analysis allowed us to investigate nosocomial outbreaks due to clinical isolates of multi-resistant Klebsiella pneumoniae in three hospitals.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 82 (1991), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Intragenic DNA probes were synthesized by polymerase chain reaction using fragments of the genes of three major types of β-lactamases (TEM, SHV, CARB) as templates. The TEM probe hybridized with the genes encoding TEM-1, TEM-2 and six extended-spectrum related enzymes (TEM-3 to TEM-7, TEM-20) in colony hybridizations and Southern-blot analysis. The SHV probe hybridized with the genes for SHV-1, OHIO-1 and four derived extended-spectrum β-lactamases (SHV-2, SHV-3, SHV-4 and SHV-5). The CARB probe hybridized with the genes for PSE-1 (CARB-2), PSE-4 (CARB-1), CARB-3 and CARB-4. None of the probes hybridized with genes for any of eight oxacillin-hydrolysing enzymes, PSE-2, OXA-1 to OXA-7, ROB-1 and chromosomal β-lactamases of various Enterobacteriaceae (except Klebsiella pneumoniae) and Pseudomonas aeruginosa. Investigations of Escherichia coli clinical isolates using these probes indicate the presence of a novel type of extended-spectrum, transferable β-lactamase.
    Type of Medium: Electronic Resource
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