2,111 research outputs found
Functional diversity among metallo-β-lactamases: characterization of the CAR-1 enzyme of Erwinia Carotovora
No full textMetallo-β-lactamases (MBLs) are zinc-dependent bacterial enzymes characterized by an efficient hydrolysis of carbapenems and a lack of sensitivity to commercially available β-lactamase inactivators. Apart from the acquired subclass B1 enzymes, which exhibit increasing clinical importance and whose evolutionary origin remains unclear, most MBLs are encoded by resident genes found in the genomes of organisms belonging to at least three distinct phyla. Using genome database mining, we identified an open reading frame (ORF) (ECA2849) encoding an MBL-like protein in the sequenced genome of Erwinia carotovora, an important plant pathogen. Although no detectable β-lactamase activity could be found in E. carotovora, a recombinant Escherichia coli strain in which the ECA2849 ORF was cloned showed decreased susceptibility to several β-lactams, while carbapenem MICs were surprisingly poorly affected. The enzyme, named CAR-1, was purified by means of ion-exchange chromatography steps, and its characterization revealed unique structural and functional features. This new MBL was able to efficiently hydrolyze cephalothin, cefuroxime, and cefotaxime and, to a lesser extent, penicillins and the other cephalosporins but only poorly hydrolyzed meropenem, while imipenem was not recognized. CAR-1 is the first example of a functional naturally occurring MBL in the family Enterobacteriaceae (order Enterobacteriales) and highlights the extraordinary structural and functional diversity exhibited by MBLs. Copyright © 2008, American Society for Microbiology. All Rights Reserved
Genetic and biochemical characterization of FUS-1 (OXA-85), a narrow-spectrum class D beta-lactamase from Fusobacterium nucleatum subsp. polymorphum
No full textPrevious studies have reported β-lactamase-mediated penicillin resistance in Fusobacterium nucleatum, but no β-lactamase gene has yet been identified in this species. An F. nucleatum subsp. polymorphum strain resistant to penicillin and amoxicillin was isolated from a human periodontitis sample. DNA cloning and sequencing revealed a 765-bp open reading frame encoding a new class D β-lactamase named FUS-1 (OXA-85). A recombinant Escherichia coli strain carrying the blaFUS-1 gene exhibited resistance to amoxicillin with a moderate decrease in the MICs with clavulanic acid. The bla FUS-1 gene was found in two additional clonally unrelated F. nucleatum subsp. polymorphum isolates. It was located on the chromosome in a peculiar genetic environment where a gene encoding a putative transposase-like protein is found, suggesting a possible acquisition of this class D β-lactamase gene. The FUS-1 enzyme showed the closest ancestral relationship with OXA-63 from Brachyspira pilosicoli (53% identity) and with putative chromosomal β-lactamases of Campylobacter spp. (40 to 42% identity). FUS-1 presents all of the conserved structural motifs of class D β-lactamases. Kinetic analysis revealed that FUS-1 exhibits a narrow substrate profile, efficiently hydrolyzing benzylpenicillin and oxacillin. FUS-1 was poorly inactivated by clavulanate and NaC1. FUS-1 is the first example of a class D β-lactamase produced by a gram-negative, anaerobic, rod-shaped bacterium to be characterized. Copyright © 2006, American Society for Microbiology. All Rights Reserved
IMP-12: A NEW PLASMID-ENCODED IMP VARIANT HIGHLY DIVERGENT FROM IMP-1. ABTRACTS: 42° INTERSCIENCE CONFERENCE ON ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, SAN DIEGO, CALIFORNIA, 27-30 SETTEMBRE 2002
No full textMetallo-beta-lactamase producers in environmental microbiota: New molecular class B enzyme in Janthinobacterium lividum
No full textNovel 3-N-aminoglycoside acetyltransferase gene, aac(3)-Ic, from a Pseudomonas aeruginosa integron
No full textA novel gene, aac(3)-Ic, encoding an AAC(3)-I aminoglycoside 3-N-acetyltransferase, was identified on a gene cassette inserted into a Pseudomonas aeruginosa integron that also carries a blaVIM-2 and a cmlA7 gene cassette. The aac(3)-Ic gene product is 59 and 57% identical to AAC(3)-Ia and AAC(3)-Ib, respectively, and confers resistance to gentamicin and sisomicin
Prevalenza di metallo-beta-lattamasi in isolati clinici di Pseudomonas aeruginosa. 30° CONGRESSO NAZIONALE SIM, CATANIA 6-9 OTTOBRE 2002
No full textBEL-2, an extended-spectrum beta-lactamase with increased activity toward expanded-spectrum cephalosporins in Pseudomonas aeruginosa
No full textA Pseudomonas aeruginosa isolate recovered in Belgium produced a novel extended-spectrum ß-lactamase, BEL-2, differing from BEL-1 by a single Leu162Phe substitution. That modification significantly altered the kinetic properties of the enzyme, increasing its affinity for expanded-spectrum cephalosporins. The blaBEL-2 gene was identified from a P. aeruginosa isolate clonally related to another blaBEL-1-positive isolate. Copyright © 2010, American Society for Microbiology. All Rights Reserved
Biochemical characterization of the THIN-B metallo-beta-lactamase of Janthinobacterium lividum
No full textThe THIN-B metallo-β-lactamase, a subclass B3 enzyme produced by the environmental species Janthinobacterium lividum, was overproduced in Escherichia coli by means of a T7-based expression system. The enzyme was purified (>95%) by two ion-exchange chromatography steps and subjected to biochemical analysis. The native THIN-B enzyme is a monomeric protein of 31 kDa. It exhibits the highest catalytic efficiencies with carbapenem substrates and cephalosporins, except for cephaloridine, which acts as a poor inactivator. Individual rate constants for inactivation by chelators were measured, suggesting that inactivation occurred by a mechanism involving formation of a ternary complex
Regulation of neuraminidase expression in Streptococcus pneumoniae
No full textThe electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2180/12/200 Extent: 12p.BackgroundSialic acid (N-acetylneuraminic acid; NeuNAc) is one of the most important carbohydrates for Streptococcus pneumoniae due of its role as a carbon and energy source, receptor for adhesion and invasion and molecular signal for promotion of biofilm formation, nasopharyngeal carriage and invasion of the lung.ResultsIn this work, NeuNAc and its metabolic derivative N-acetyl mannosamine (ManNAc) were used to analyze regulatory mechanisms of the neuraminidase locus expression. Genomic and metabolic comparison to Streptococcus mitis, Streptococcus oralis, Streptococcus gordonii and Streptococcus sanguinis elucidates the metabolic association of the two amino sugars to different parts of the locus coding for the two main pneumococcal neuraminidases and confirms the substrate specificity of the respective ABC transporters. Quantitative gene expression analysis shows repression of the locus by glucose and induction of all predicted transcriptional units by ManNAc and NeuNAc, each inducing with higher efficiency the operon encoding for the transporter with higher specificity for the respective amino sugar. Cytofluorimetric analysis demonstrated enhanced surface exposure of NanA on pneumococci grown in NeuNAc and ManNAc and an activity assay allowed to quantify approximately twelve times as much neuraminidase activity on induced cells as opposed to glucose grown cells.ConclusionsThe present data increase the understanding of metabolic regulation of the nanAB locus and indicate that experiments aimed at the elucidation of the relevance of neuraminidases in pneumococcal virulence should possibly not be carried out on bacteria grown in glucose containing media.Luciana Gualdi, Jasvinder Kaur Hayre, Alice Gerlini, Alessandro Bidossi, Leonarda Colomba, Claudia Trappetti, Gianni Pozzi, Jean-Denis Docquier, Peter Andrew, Susanna Ricci and Marco R Oggion
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