1,721,021 research outputs found
Nuove strategie antimicrobiche contro rilevanti patogeni umani
No full textDespite a century of often successful prevention and treatment efforts, infectious diseases remain an important global problem in public health, causing over 13 million deaths each year. This work has been developed on two areas of major concern nowadays: HIV-1 infection and emerging antimicrobial resistance.
The first part of this thesis focused on the definition of the biological role of the dimerization of Nef, HIV-1 accessory protein. This function has been reported to take place in vivo, neveretheless it hasn’t been well characterized yet. We believe that the inihibition of Nef oligomerization may become an innovative and successful antiviral therapy. For this reason, we screened two different libraries of small molecules and peptides, to discover compounds hindering Nef-Nef interaction in vitro. The characterization of the viral protein aminoacidic residues taking part in the interaction with the compounds will provide precise indications about the dimerization surface. This region has not been identified unambiguously yet. Moreover, the administration of small molecules to HIV-1 infected cells will shed light on the effects of Nef dimerization inhibition on the viral life and infectious cycle.
The second part of this work, aimed at determining the prevalence of fluoroquinolone resistance in Enterobacteriaceae samples, within our region. We focused our attention on the recently discovered plasmid-mediated mechanisms (PMQR). In the recent years, PMQR have spread rapidly all over the world, causing serious health concern, as they are often linked to both quinolone resistance and ESBL, giving rise to multi-resistant strains. Our study proved the large diffusion of these resistance determinants in the North East Italy. Furthermore, as the identification of new effective antimicrobial drugs is gaining more and more importance recently, we analysed the pharmacological activity and the mechanism of action of simocyclinone (SD8), a new antibiotic. SD8 has been demonstrated to have a broad spectrum of action, affecting both Gram positive and Gram negative bacterial species, so SD8 is likely to become a new antitopoisomerase drug.Nonostante l’ultimo secolo sia stato caratterizzato da un’intensa ed efficace attività di prevenzione e trattamento farmacologico, l’incidenza delle patologie di origine infettiva, che causano la morte di 13 milioni di individui ogni anno, continua a destare forte preoccupazione, rimanendo uno dei problemi maggiori per la sanità pubblica mondiale. Il lavoro svolto in questa tesi è stato sviluppato su due argomenti di rilevante interesse in questo periodo, le infezioni da HIV-1 e la diffusione della resistenza ai farmaci antimicrobici.
La prima parte del lavoro ha analizzato il ruolo biologico della dimerizzazione di Nef, proteina accessoria di HIV-1, funzione già dimostrata avvenire in vivo, ma finora non approfonditamente caratterizzata. Ritenendo che l’inibizione della formazione di oligomeri possa essere un’innovativa e promettente strategia antivirale, sono stati selezionati composti chimici e piccoli peptidi, che interferiscono con l’interazione Nef-Nef in vitro. L’analisi dei residui amminoacidici della proteina oggetto di studio, coinvolti nel legame ai composti, darà precise indicazioni sulla regione coinvolta nella formazione degli oligomeri, regione ancora non definita dai precedenti lavori presenti in letteratura. Inoltre, la somministrazione delle molecole a cellule infettate dal virus HIV-1, rivelerà quali siano le conseguenze dell’inibizione della dimerizzazione di Nef sul ciclo infettivo virale.
La seconda parte del lavoro ha, invece, riguardato la determinazione della prevalenza della resistenza ai fluorochinoloni negli isolati di Enterobacteriaceae all’interno della nostra regione. Sono stati presi in considerazione i meccanismi di resistenza mediati da plasmide (PMQR). Si tratta di tipologie di resistenza recentemente descritte, ad ampia e rapida diffusione in tutto il mondo, spesso in correlazione con ESBL (Extended Spectrum Beta Lactamase), che stanno destando notevole preoccupazione in ambito clinico. Lo studio svolto ha rivelato che si tratta di plasmidi largamente diffusi anche nella nostra regione, che in molti casi veicolano resistenza a più classi di antibiotici, ad esempio chinoloni e beta-lattamici. Vista, inoltre, l’importanza di individuare nuove efficaci molecole ad attività antimicrobica, è stata analizzata l’attività farmacologica e il meccanismo d’azione dell’antibatterico simociclinone (SD8). È stato dimostrato che SD8 abbia un ampio spettro d’azione, agendo sia su ceppi batterici Gram positivi che Gram negativi, e sia un buon candidato per lo sviluppo di un nuovo farmaco antitopoisomerasico
Strategies for inhibiting function of HIV-1 accessory proteins: a necessary route to AIDS therapy?
No full textThe Human Immunodeficiency Virus (HIV) genome encodes three major structural proteins common to all retroviruses (Gag, Pol and Env), two regulatory proteins (Tat and Rev) that are essential for viral replication, and four accessory proteins (Nef, Vif, Vpu, Vpr). While accessory proteins were initially reported to be unnecessary for viral growth, their importance as virulence factors is now being more and more appreciated: they can dramatically alter the course and severity of viral infection, replication and disease progression. None of the HIV accessory proteins display enzymatic activity: they rather act altering cellular pathways via multiple protein-protein interactions with a number of host cell factors. All currently approved anti-HIV drugs target pol and env encoded proteins. Therefore, widening the molecular targets of HIV therapy by additionally targeting accessory proteins may expand treatment options, resulting in high impact effective new therapy. In this review we present the state of the art of compounds that target HIV accessory proteins. Most of the research has focused on the inhibition of specific accessory proteins/host cell partner interactions. Promising compounds have been found within different classes of molecules: small natural and synthetic molecules, peptides and proteins, oligonucleotides, in particular those used as RNA interference (RNAi) tools. With the assortment of compounds available, especially against Nef and Vif functions, the demonstration of the clinical efficacy of the new anti-HIV-1 drugs targeting accessory proteins is next challenge
Basso Livello di resistenza ai fluochinoloni mediato dai geni qnr in ceppi produttori di ESBL
No full textEmerging resistance mechanisms in ESBL-producing strains
No full textObjective: ESBL producing strains are increasingly reported to present
additional resistance mechanisms. These multidrug resistant strains
should be detected early to rationalize drug treatment and avoid increased
selection of resistance. The aim of this study was to detect the
presence of AmpC, carbapenemases and plasmid-mediated quinolone
resistance (PMQR) (qnr, aac(6)-Ib-cr and qepA) mechanisms in ESBLproducing
strains by genotypic assays and compare their efficiency
versus phenotypic methods.
Methods: ESBL- and AmpC-producing strains were identified by
the double-disk test and double disk synergy test, respectively.
Carbapenemases were phenotypically detected by the Hodge test. MIC
of fluoroquinolones was detected by Etest. AmpC, carbapenemase, qnr,
aac(6)-Ib-cr and qepA genes were identified by multiplex PCR and
sequencing. Topoisomerase II mutations were detected by sequencing
of the quinolone-resistant determining region.
Results: In 2009, 200 ESBL-producing Enterobacteriaceae isolates
were collected at the Microbiology Unit of the Padua Hospital. ESBL
belonging to different classes (TEM, SHV, CTX-M and OXA) were
characterized by genotypic analysis. Qnr and aac(6)-Ib-cr genes were
found in 26% and 8% isolates, respectively. Qnr was mostly present
in Klebsiella pneumoniae, while aac(6)-Ib-cr was found exclusively
in Escherichia coli. QepA was not found. Both genes were localized
on plasmids and could be both transformed and trans-conjugated in
acceptor strains. MIC of fluoroquinolones on these acceptor strains
indicated a 20–100 increased resistance due to the plasmid-mediated
mechanism. However, high-level resistance to fluoroquinolone in the
wild-type strains was due to the additional presence of topoisomerase
mutations in strains presenting both ESBL and PMQR. AmpC were
detected on 5.5% isolates of Enterobacter spp. and Proteus mirabilis.
Carbapenemases were found in 3% isolates of E. aerogenes, E. coli
and K. pneumoniae. Carbapenemases were subsequently genotypically
characterized as IMP, VIM, OXA, KPC CMY or SME types.
Conclusions: Emerging resistance mechanisms were found in ESBLproducing
strains, with PMQR being the most frequent. While genotypic
assays implement phenotypic testing of AmpC and carbapenemases, they
are the only methods available up to date for detection of PMQR. Hence,
both phenotypic and genotypic methods should be employed to rationally
direct the pharmacological treatment
Diffusione della resistenza mediata da plasmide di tipo qnr, aac(6')-Ib-cr e qepA nel Nord-Est Italia
No full textSimocyclinone D8 turns on against Gram-negative bacteria in a clinical setting
No full textSimocyclinone D8 (SD8) is known to affect Gram-positive bacteria only. By testing SD8 against several clinical isolates, we showed that SD8 resulted very active against Gram-negative bacteria from clinical specimens, while it was shown inactive against laboratory strains. The activity against the former was in part due to enhanced drug entry. In addition, SD8 appears to share chromosome- and plasmid-mediated resistance mechanisms with fluoroquinolones
Presence, Location and Conservation of Putative G-Quadruplex Forming Sequences in Arboviruses Infecting Humans
Full text linkGuanine quadruplexes (G4s) are non-canonical nucleic acid structures formed by guanine (G)-rich tracts that assemble into a core of stacked planar tetrads. G4s are found in the human genome and in the genomes of human pathogens, where they are involved in the regulation of gene expression and genome replication. G4s have been proposed as novel pharmacological targets in humans and their exploitation for antiviral therapy is an emerging research topic. Here, we report on the presence, conservation and localization of putative G4-forming sequences (PQSs) in human arboviruses. The prediction of PQSs was performed on more than twelve thousand viral genomes, belonging to forty different arboviruses that infect humans, and revealed that the abundance of PQSs in arboviruses is not related to the genomic GC content, but depends on the type of nucleic acid that constitutes the viral genome. Positive-strand ssRNA arboviruses, especially Flaviviruses, are significantly enriched in highly conserved PQSs, located in coding sequences (CDSs) or untranslated regions (UTRs). In contrast, negative-strand ssRNA and dsRNA arboviruses contain few conserved PQSs. Our analyses also revealed the presence of bulged PQSs, accounting for 17-26% of the total predicted PQSs. The data presented highlight the presence of highly conserved PQS in human arboviruses and present non-canonical nucleic acid-structures as promising therapeutic targets in arbovirus infections
Prevalence of <it>aac(6')-Ib-cr </it>plasmid-mediated and chromosome-encoded fluoroquinolone resistance in <it>Enterobacteriaceae </it>in Italy
Full text linkAbstract The spread of aac(6')-Ib-cr plasmid-mediated quinolone resistance determinants was evaluated in 197 enterobacterial isolates recovered in an Italian teaching hospital. The aac(6')-Ib-cr gene was found exclusively in Escherichia coli strains. The gene was located on a plasmid which presented additional ESBL genes. Most of the clinical strains were clonally related and displayed three point mutations at the topoisomerase level which conferred high resistance to fluoroquinolones.</p
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