1,721,611 research outputs found
From Pneumococcus to Pseudomonas: the antibacterial behaviour through the time [Dallo pneumococco alla Pseudomonas: Il comportamento antibatterico negli anni]
No full textThe worldwide use of fluoroquinolones in community and hospital settings, due to their high efficacy and tolerability, to the wide antibacterial spectrum and to the availability of an oral formulation, has created a relevant selective pressure for the emergence of resistant bacterial strains towards this antimicrobial class. Nevertheless, twenty years after development of the first fluoroquinolones (e.g. norfloxacin and ciprofloxacin) and ten years after levofloxacin introduction, the antibacterial activity of these drugs remains overall high
Characterization of Tn5393d, a complex Tn5393 derivative carrying the PER-1 extended-spectrum beta-lactamase gene and other resistance determinants
No full textIn Alcaligenes faecalis FL-424/98, a clinical isolate that produces the PER-1 extended-spectrum β-lactamase, the blaPER-1 gene was found to be carried on a 44-kb nonconjugative plasmid, named pFL424, that was transferred to Escherichia coli by electroporation. Investigation of the genetic context of the blaPER-1 gene in pFL424 by means of a combined cloning and PCR mapping approach revealed that the gene is associated with a transposonlike element of the Tn3 family. This 14-kb element is a Tn5393 derivative of original structure, named Tn5393d, which contains the transposition module and the strAB genes typical of other members of the Tn5393 lineage plus additional resistance determinants, including the bla PER-1 gene and a new allelic variant of the aphA6 aminoglycoside phosphotransferase gene, named aphA6b, whose product is active against kanamycin, streptomycin, and amikacin. Tn5393d apparently originated from the consecutive insertion of two composite transposons into a Tn5393 backbone carrying the aphA6b and the blaPER-1 genes, respectively. The putative composite transposon carrying blaPER-1, named Tn4176, is made of two original and nonidentical insertion sequences of the IS4 family, named IS1387a and IS1387b, of which one is interrupted by the insertion of an original insertion sequence of the IS30 family, named IS1066. In pFL424, Tn5393d is inserted into a Tn501-like mercury resistance transposon. Transposition of Tn5393d or modules thereof containing the blaPER-1 gene from pFL424 to small multicopy plasmids or to a bacterial artificial chromosome was not detected in an E. coli host harboring both replicons. Copyright © 2005, American Society for Microbiology. All Rights Reserved
Etiology, resistance and diagnostic techniques inskin and skin structure infections [Eziologia, antibiotico-resistenza e diagnostica microbiologica delle infezioni della cute e dei tessuti molli]
No full textSkin and soft tissue infections (SSTI) are common and, generally, uncomplicated at the time of initial presentation. However, these infections can worsen quickly when there are delays in diagnosis and treatment. The clinical presentation of most SSTI is the culmination of a microbial three-step process as follow: 1) bacterial adherence to host cells; 2) invasion of tissue with evasion of host defences; 3) elaboration of toxins. Even if the microbiology of wounds has been actively investigated in recent years, there is still much to be learned about the microbial mechanisms that induce infection and prevent wound healing. There are also several means by which bacteria penetrate the skin barrier. The most common route is through a break in the barrier (lacerations, bite wounds, scratches, instrumentations, pre-existing skin conditions, wounds or ulcers, burns and surgery); other routes of penetration include contiguous spread from adjacent infections (e.g. osteomyelitis), entry of water into the skin pores, and, rarely, haematogenous seeding (i.e septic emboli). From what it was said, many microrganisms, above all from the normal skin microbiota, can be involved in these often polymicrobial infections, with Gram-positives such as Staphylococcus aureus, Streptococcus pyogenes, Staphylococcus epidermidis, Corynebacterium spp being predominant. Many other aerobic and anaerobic species, including Gram-negative bacilli, can also be involved. Even if the diagnosis of most SSTI is based on clinical examination, laboratory investigations, guided by clinical information, can help to confirm the diagnosis and elucidate the characteristics of specific pathogens. These microbiological investigations may include blood cultures, tissue swabs with culture, and needle aspiration. In rapidly progressing infections, empirical therapy is essential, although microbiological data are important in confirming subsequently that the chosen regimen is appropriate. Furthermore, the number of microrganisms becoming resistant to many usual drugs and the changing microbial epidemiology of these infections, such as the emergence of CA-MRSA, required a constant cooperation between the microbiology lab and the clinician in order to address microbiological aspects that can be critical to the successful management of SSTI
The Aeromonas hydrophila cphA gene: molecular heterogeneity among class B metallo-beta-lactamases
No full textAn Aeromonas hydrophila gene, named cphA, coding for a carbapenem-hydrolyzing metallo-beta-lactamase, was cloned in Escherichia coli by screening an Aeromonas genomic library for clones able to grow on imipenem-containing medium. From sequencing data, the cloned cphA gene appeared able to code for a polypeptide of 254 amino acids whose sequence includes a potential N-terminal leader sequence for targeting the protein to the periplasmic space. These data were in agreement with the molecular mass of the original Aeromonas enzyme and of the recombinant enzyme produced in E. coli, evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude beta-lactamase preparations followed by renaturation treatment for proteins separated in the gel and localization of protein bands showing carbapenem-hydrolyzing beta-lactamase activity by a modified iodometric technique. The deduced amino acid sequence of the CphA enzyme showed regions of partial homology with both the beta-lactamase II of Bacillus cereus and the CfiA beta-lactamase of Bacteroides fragilis. Sequence homologies were more pronounced in the regions encompassing the amino acid residues known in the enzyme of B. cereus to function as ligand-binding residues for the metal cofactor. The CphA enzyme, however, appeared to share a lower degree of similarity with the two other enzymes, which, in turn, seemed more closely related to each other. These results, therefore, suggest the existence of at least two molecular subclasses within molecular class B metallo-beta-lactamases
The Aeromonas hydrophyla cphA gene: molecular heterogeneity among class B metallo-β-lactamases
Full text linkAn Aeromonas hydrophila gene, named cphA, coding for a carbapenem-hydrolyzing metallo-beta-lactamase, was cloned in Escherichia coli by screening an Aeromonas genomic library for clones able to grow on imipenem-containing medium. From sequencing data, the cloned cphA gene appeared able to code for a polypeptide of 254 amino acids whose sequence includes a potential N-terminal leader sequence for targeting the protein to the periplasmic space. These data were in agreement with the molecular mass of the original Aeromonas enzyme and of the recombinant enzyme produced in E. coli, evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude beta-lactamase preparations followed by renaturation treatment for proteins separated in the gel and localization of protein bands showing carbapenem-hydrolyzing beta-lactamase activity by a modified iodometric technique. The deduced amino acid sequence of the CphA enzyme showed regions of partial homology with both the beta-lactamase II of Bacillus cereus and the CfiA beta-lactamase of Bacteroides fragilis. Sequence homologies were more pronounced in the regions encompassing the amino acid residues known in the enzyme of B. cereus to function as ligand-binding residues for the metal cofactor. The CphA enzyme, however, appeared to share a lower degree of similarity with the two other enzymes, which, in turn, seemed more closely related to each other. These results, therefore, suggest the existence of at least two molecular subclasses within molecular class B metallo-beta-lactamases
metodo per la valutazione della sinergia tra prodotti antibiotici, e relativo kit di prodotti per l'attuazione di tale metodo
No full textUnusual clustering of Alu repeats within the 5'-flanking region of the human lysozyme gene
No full textWe report the nucleotide sequence of the 2.2-kb 5'-flanking region of the human lysozyme gene. Four Alu repeats are located within this upstream region. Classification and dating of these four Alu elements, as well as of the four Alu elements present within the human lysozyme structural gene, were performed. Transposition of the eight Alu repeats found in the human lysozyme locus has apparently occurred at four different times during the primate genome evolution. Considering that Alu repeats are interspersed throughout human DNA with an average spacing of 4 kb, the presence of eight such repeats within the 8-kb lysozyme gene region and, in particular, of four of them in the 2.2-kb region upstream of the structural gene, appears quite unusual. © 1993 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted
Chromosome polymorphism among strains of Hansenula polymorpha (syn. Pichia angusta)
No full textContour-clamped homogeneous electrophoresis and an embedded-agarose method of sample preparation were combined to carry out an analysis of the chromosome sets of nine strains of Hansenula polymorpha (syn. Pichia angusta). Chromosomal DNA molecules could be separated into a series of bands ranging, approximately, from 650 up to 2,200 kb in size. Polymorphism of the electrophoretic pattern was demonstrated among the strains investigated in this study. Cross-hybridization between H. polymorpha and Saccharomyces cerevisiae ribosomal DNA was also observed
Evaluation of in vitro antimicrobial activity of lomefloxacin against staphylococci, enterococci, Enterobacteriaceae, and Pseudomonas aeruginosa
No full textIn vitro antimicrobial activity of lomefloxacin and other antibiotics (norfloxacin, β-lactams, cotrimoxazole, netilmicin, and miokamycin) was evaluated against 317 clinical isolates including Staphylococcus aureus, enterococci, Enterobacteriaceae, and Pseudomonas aeruginosa. Lomefloxacin showed a high in vitro activity against a wide variety of bacterial species. Against Enterobacteriaceae, lomefloxacin displayed the highest activity (MIC90s, ≤1 μg/ml), and it was usually more active than ampicillin and netilmicin, and often more active than cotrimoxazole. Lomefloxacin showed a good antimicrobial activity also against both methicillin-susceptible and methicillin-resistant S. aureus, as it was able to inhibit 90% of staphylococcal strains at a concentration ≤2 μg/ml. Against enterococci and P. aeruginosa, lomefloxacin was usually less active (MIC90s, 8 μg/ml). As compared to norfloxacin, lomefloxacin displayed an overall similar activity against staphylococci and enterococci, but appeared less active against Gram-negative bacteria. Bactericidal activity of lomefloxacin against E. coli, when assayed by a novel method, proved to be high, and results indicate that an oral dose of 200 mg of lomefloxacin should exert a very high bactericidal activity against E. coli in urinary tract infections, even in those sustained by large bacterial populations. © 1989
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