1,721,000 research outputs found
Rapid Molecular Diagnosis of Extra-Pulmonary Tuberculosis by Xpert/RIF Ultra
Full text linkRapid detection of Mycobacterium tuberculosis complex and determination of drug resistance are essential for early diagnosis and treatment of tuberculosis (TB). Xpert MTB/RIF Ultra (Xpert Ultra), a molecular test that can simultaneously identify M. tuberculosis complex and resistance to rifampicin directly on clinical samples, is currently used. Xpert Ultra represents a helpful tool for rapid pulmonary TB diagnosis, especially in patients with paucibacillary infection. The aim of this review is to provide an overview of the diagnostic performance of Xpert Ultra in detection of extra-pulmonary tuberculosis
Efflux pump inhibitors against nontuberculous mycobacteria
Full text linkOver the last years, nontuberculous mycobacteria (NTM) have emerged as important human pathogens. Infections caused by NTM are often difficult to treat due to an intrinsic multidrug resistance for the presence of a lipid-rich outer membrane, thus encouraging an urgent need for the development of new drugs for the treatment of mycobacterial infections. Efflux pumps (EPs) are important elements that are involved in drug resistance by preventing intracellular accumulation of antibiotics. A promising strategy to decrease drug resistance is the inhibition of EP activity by EP inhibitors (EPIs), compounds that are able to increase the intracellular concentration of antimicrobials. Recently, attention has been focused on identifying EPIs in mycobacteria that could be used in combination with drugs. The aim of the present review is to provide an overview of the current knowledge on EPs and EPIs in NTM and also, the effect of potential EPIs as well as their combined use with antimycobacterial drugs in various NTM species are described
Efficacia degli inibitori di pompe di efflusso in associazione alla claritromicina in isolati clinici di Mycobacterium avium subsp. hominissuis
Full text linkMycobacterium avium subsp. hominissuis (MAH) è uno dei micobatteri non tubercolari di maggiore rilevanza clinica, rappresentando quello più spesso isolato in soggetti con gravi patologie croniche dell’apparato respiratorio. Inoltre, MAH può causare infezioni polmonari o disseminate in pazienti con immunodeficienza acquisita (AIDS) e in altri soggetti immunodepressi. Recenti dati epidemiologici mostrano un considerevole incremento della prevalenza delle infezioni da MAH in Italia, come pure in molti altri paesi del resto del mondo. Le infezioni causate da MAH sono difficili da trattare, a causa dell’intrinseca multi-farmaco resistenza del microrganismo. La claritromicina (CLA) rappresenta il principale farmaco di prima linea impiegato nel trattamento delle infezioni da MAH, verso il quale però il micobatterio può sviluppare resistenza compromettendone l’efficacia. Uno dei principali meccanismi responsabili di tale resistenza è dato dalla presenza di pompe di efflusso che determinano l’estrusione del farmaco dall’interno della cellula micobatterica.
Lo scopo del presente studio è stato quello di valutare l’attività antimicrobica di inibitori delle pompe di efflusso (EPI) in associazione alla CLA su isolati clinici di MAH.
Materiali e Metodi
Sono stati selezionati 4 ceppi di MAH resistenti alla CLA e, come controllo, 6 ceppi sensibili. Tutti gli isolati provenivano dal laboratorio di micobatteriologia dell’Azienda Ospedaliera Universitaria Pisana. Tali ceppi sono stati esaminati mediante un saggio colorimetrico in microdiluizione su piastra denominato “REsazurin Microtiter Assay” (REMA) per valutare la minima concentrazione inibente (MIC) della CLA da sola e in presenza di diverse concentrazioni di ciascuno dei seguenti EPI: berberina (BER), piperina (PIP), tetrandrina (TET) e carbonil cianuro m-clorofenil idrazone (CCCP).
Risultati
I ceppi resistenti hanno mostrato per la CLA una MIC ≥ 256 g/ml e i ceppi sensibili una MIC compresa tra 1 e 4g/ml. L’utilizzo degli EPI in associazione alla CLA ha ridotto nella quasi totalità dei ceppi resistenti la MIC della CLA. Infatti, la BER e il CCCP hanno determinato una riduzione della MIC fino a 10 diluizioni scalari, la TET fino a 9 e la PIP fino a 6. In particolare, in un isolato resistente, l’impiego della CLA in combinazione con ciascuno dei quattro EPI ha evidenziato una riduzione della MIC tale da rendere il ceppo sensibile. Come atteso, anche in tutti i ceppi di controllo gli EPI hanno ridotto la MIC della CLA.
Conclusioni
I risultati ottenuti in questo studio, se pur relativi a un numero limitato di ceppi, confermano che gli EPI testati (BER, PIP, TET e CCCP), in associazione con la CLA, aumentano l’efficacia del farmaco; in particolare, è emerso che la BER ed il CCCP sono gli EPI più efficaci. Tali dati suggeriscono quindi l’importanza del ruolo degli EPI nel trattamento delle infezioni causate da MAH
Short-term stability of rocky intertidal biofilm to nitrogen and phosphorus pulses
No full textCoastal environments experience both natural and anthropogenic inputs of nitrogen (N) and phosphorus (P). Agricultural fertilisers, organic run-offs, and edaphic characteristics of coastal environments may generate mosaics of nutrient concentrations that ultimately influence the coastal primary productivity. Here, we experimentally assessed the effects of repeated pulses of N and P on multiple components of ecological stability (sensitivity, resilience, temporal stability and recovery) of phototrophic rocky intertidal biofilm. We performed a repeated-pulses factorial experiment crossing increasing N and P concentrations chosen to reflect a range of nutrient enrichment conditions, from oligotrophic to eutrophic. N and P, regardless of concentration or whether they occurred in isolation or combination, enhanced biofilm's sensitivity (increased biomass or physiological performance compared to controls) without altering resilience. Our experiment illustrates how the stability of an essential coastal primary producer responds to increasing N and P supply levels. Furthermore, notwithstanding the importance of decomposing the multiple dimensions of stability, the transitory increase of the sole sensitivity indicated that rocky shore biofilm is robust against a wide range of nutrient enrichment
Experimental evidence of spatial signatures of approaching regime shifts in macroalgal canopies
Full text linkDeveloping early warning signals to predict regime shifts in ecosystems is a central issue in current ecological research. While there are many studies addressing temporal early warning indicators, research into spatial indicators is far behind, with field experiments even more rare. Here, we tested the performance of spatial early warning signals in an intertidal macroalgal system, where removal of algal canopies pushed the system toward a tipping point (corresponding to approximately 75% of canopy loss), marking the transition between a canopy- to a turf-dominated state. We performed a two-year experiment where spatial early warning indicators were assessed in transects where the canopy was differentially removed (from 0 to 100%). Unlike Moran correlation coefficient at lag-1, spatial variance, skewness, and spatial spectra at low frequency increased along the gradient of canopy degradation and dropped, or did not show any further increase beyond the transition point from a canopy- to a turf-dominated state (100% canopy removal). Our study provides direct evidence of the suitability of spatial early warning signals to anticipate regime shifts in natural ecosystems, emphasizing the importance of field experiments as a powerful tool to establish causal relationships between environmental stressors and early warning indicators
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Exogenous disturbances and endogenous self-organized processes are not mutually exclusive drivers of spatial patterns in macroalgal assemblages
No full textComplex spatial patterns are common in coastal marine systems, but mechanisms underlying their formation are disputed. Most empirical work has focused on exogenous spatially structured disturbances as the leading cause of pattern formation in species assemblages. However, theoretical and observational studies suggest that complex spatial patterns, such as power laws in gap-size distribution, may result from endogenous self-organized processes involving local-scale interactions. The lack of studies simultaneously assessing the influence of spatially variable disturbances and local-scale interactions has fuelled the idea that exogenous and endogenous processes are mutually exclusive explanations of spatial patterns in marine ecosystems. To assess the relative contribution of endogenous and exogenous processes in the emergence of spatial patterns, an intertidal assemblage of algae was exposed for two years to various combinations of intensity and spatial patterns of disturbance. Localized disturbances impinging at the margins of previously disturbed clearings and homogenous disturbances without any spatial pattern generated heterogeneous distributions of disturbed gaps and macroalgal patches, characterized by a power-law scaling. Spatially varying disturbances produced a spatial gradient in the distribution of algal patches and, to a lesser extent, also a power-law scaling in both patch- and gap-size distributions. These results suggest that exogenous and endogenous processes are not mutually exclusive forces that can lead to the formation of similar spatial patterns in species assemblages
Evaluation of Xpert MTB/RIF Ultra assay for rapid diagnosis of pulmonary and extra-pulmonary tuberculosis in an Italian center
Full text linkAbstract not availabl
The Obligate Symbiont “Candidatus Megaira polyxenophila” Has Variable Effects on the Growth of Different Host Species
Full text link“Candidatus Megaira polyxenophila” is a recently described member of Rickettsiaceae which comprises exclusively obligate intracellular bacteria. Interestingly, these bacteria can be found in a huge diversity of eukaryotic hosts (protist, green algae, metazoa) living in marine, brackish or freshwater habitats. Screening of amplicon datasets revealed a high frequency of these bacteria especially in freshwater environments, most likely associated to eukaryotic hosts. The relationship of “Ca. Megaira polyxenophila” with their hosts and their impact on host fitness have not been studied so far. Even less is known regarding the responses of these intracellular bacteria to potential stressors. In this study, we used two phylogenetically close species of the freshwater ciliate Paramecium, Paramecium primaurelia and Paramecium pentaurelia (Ciliophora, Oligohymenophorea) naturally infected by “Ca. Megaira polyxenophila”. In order to analyze the effect of the symbiont on the fitness of these two species, we compared the growth performance of both infected and aposymbiotic paramecia at different salinity levels in the range of freshwater and oligohaline brackish water i.e., at 0, 2, and 4.5 ppt. For the elimination of “Ca. Megaira polyxenophila” we established an antibiotic treatment to obtain symbiont-free lines and confirmed its success by fluorescence in situ hybridization (FISH). The population and infection dynamics during the growth experiment were observed by cell density counts and FISH. Paramecia fitness was compared applying generalized additive mixed models. Surprisingly, both infected Paramecium species showed higher densities under all salinity concentrations. The tested salinity concentrations did not significantly affect the growth of any of the two species directly, but we observed the loss of the endosymbiont after prolonged exposure to higher salinity levels. This experimental data might explain the higher frequency of “Ca. M. polyxenophila” in freshwater habitats as observed from amplicon data
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