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Indagine sulla patogenicità di ceppi mobili di aeromonas spp. isolati da specie ittiche
No full textLo studio della patogenicità di Aeromonas spp. è caratterizzato da notevole complessità, sviluppandosi in genere su più livelli e comprendendo saggi biologici in vitro (linee cellulari) ed in vivo (modelli animali), esami molecolari ed analisi delle proprietà fenotipiche degli isolati.
Nell’ambito di una tesi di specialità (Allevamento, Igiene, Patologia delle Specie Acquatiche e Controllo dei Prodotti Derivati) sulla caratterizzazione in vitro della virulenza di questi microrganismi, sono stati esaminati 101 ceppi di Aeromonas mobili, provenienti da specie ittiche selvatiche (69), allevate (26), ed ornamentali (6). L’isolamento è avvenuto da pesci setticemici (27) e apparentemente sani (74). Per ciascuno degli isolati, identificati biochimicamente a livello di complex, sono state analizzate le proprietà citotossiche su tre diverse linee cellulari (EPC, BF2, Vero) ed una serie di caratteristiche colturali (crescita a 37°C, emolisi), biochimiche (test VP, decarbossilazione della lisina, fenomeno del suicidio) ed enzimatiche (lipasi, gelatinasi) indicate in letteratura come potenziali fattori di virulenza di Aeromonas spp. In particolare, si è indagato sulla correlazione fra questi fattori, la fenospecie dei ceppi (A. hydrophila, A. sobria, A. caviae), la provenienza (selvatica, allevata) ed il quadro clinico delle specie ittiche d’isolamento.
In generale, lo studio ha registrato alte prevalenze (54.5-99.0%) dei potenziali indicatori di patogenicità all’interno del campione testato. La produzione di lipasi (98.0%) e gelatinasi (99.0%) è stata il fattore più frequentemente riscontrato. Anche le caratteristiche colturali/biochimiche hanno mostrato un’ampia diffusione fra i ceppi esaminati, con prevalenze variabili dal 70.3% (crescita a 37°C) al 94.1% (fenomeno del suicidio: attività non suicida). L’attività citotossica ha rappresentato il fattore di virulenza meno prevalente (54.5%).
Dai risultati è emersa una correlazione della capacità di crescita a 37°C, attività emolitica e citotossica con la fenospecie dei ceppi, in particolare con i complex A. caviae (crescita a 37°C) ed A. hydrophila (attività emolitica e citotossica). Ad esclusione dell’azione decarbossilasica sulla lisina, prevalente negli isolati selvatici, nessuno dei markers di virulenza è risultato associato all’origine dei ceppi. Solamente la crescita a 37°C è stata correlata con presenza di patologia nei pesci, indicando una scarsa significatività dei fattori fenotipici analizzati nella caratterizzazione in vitro in tal senso della patogenicità di Aeromonas spp.
Dei sistemi cellulari testati, le cellule Vero si sono dimostrate le più sensibili alle citotossine prodotte da Aeromonas spp. Si ritiene comunque che l’importanza di utilizzare le cellule Vero sia legata, oltre ad una migliore visualizzazione dell’effetto citopatico, anche alla possibilità di individuare ceppi in grado di esprimere il loro potenziale patogeno nei mammiferi e nell’uomo, il quale andrebbe però confermato mediante l’impiego dei tradizionali modelli animali.
Ulteriori studi si rendono necessari per meglio definire il significato clinico dei fattori di virulenza di Aeromonas spp. nei pesci, da eseguirsi su un maggior numero di isolati ed associando l’esame dei caratteri fenotipici dei ceppi alle analisi molecolari e, soprattutto, alle prove biologiche in vivo
Mycoplasma bovis infection in respiratory disease of dairy calves less than one month old
Full text linkMycoplasma bovis is an important cause of bovine respiratory disease, especially in young calves where it can also cause arthritis, tenosynovitis and otitis. During 2009 and 2010 a survey was carried out on carcasses of calves less than one month old sent to the Diagnostic Laboratory of the Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna in Brescia, regardless of the presence of lung lesions, to detect this pathogen. PCR tests for Mycoplasma spp. and M. bovis were applied. 83 out of 224 (37%) lung tissue samples examined were positive at PCR test for Mycoplasma spp.; in 64 cases of these we observed typical respiratory lesions (P< 0.001). M. bovis was identified in 26 out of 83 (31%) lung tissue samples positive at PCR test for Mycoplasma spp.; in 24 cases of these we observed typical respiratory lesions (P= 0.039). Our data demonstrate that presence of Mycoplasma spp. and M. bovis positively correlates with pneumonic lung lesions in young dairy calve
Motile aeromonads from farmed and wild freshwater fish in northern Italy: an evaluation of antimicrobial activity and multidrug resistance during 2013 and 2016
Full text linkBackground: Antimicrobial resistant bacteria are emerging biological contaminants of the environment. In aquatic ecosystems, they originate mainly from hospitals, livestock manure and private households sewage water, which could contain antimicrobial agents and resistant microorganisms. Aeromonas spp. occur ubiquitously in aquatic environments and they cause disease in fish. Motile aeromonads are also associated with human gastrointestinal and wound infections and fish can act as a transmission route of antimicrobial resistance (AMR) aeromonads to humans. The environmental ubiquity, the natural susceptibility to antimicrobials and the zoonotic potential of Aeromonas spp. make them optimal candidates for studying the AMR in aquatic ecosystems. Results: The AMR patterns of 95 motile aeromonads isolated from freshwater fish during 2013 and 2016 were analyzed. All samples from fish came from farms and natural water bodies located in northern Italy, which is an area characterized by high anthropic impact on the environment. The isolates were biochemically identified as Aeromonas hydrophila, Aeromonas sobria or Aeromonas caviae and AMR was determined by the standard disk diffusion method. All isolates were resistant to cloxacillin, spiramycin and tilmicosin. High AMR frequencies (> 95%) were detected for tylosin, penicillin and sulfadiazine. AMR to danofloxacin, enrofloxacin, flumequine, ceftiofur, aminosidine, colistin, doxycycline, gentamicin, marbocyl and florfenicol was observed at low levels (< 10%). No AMR to cefquinome was found. Logistic regression showed several differences in antimicrobial activity between complexes. According to the source of aeromonads, only few differences in AMR between isolates from farmed and wild fish were observed. Conclusions: Our data revealed an increasing trend of AMR to neomycin and apramycin among Aeromonas isolates during the study period, while resistance to erythromycin, tetracycline and thiamphenicol decreased. All isolates were multidrug resistance (MDR), but A. caviae showed the highest number of MDR per isolate. In most isolates, various degrees of MDR were detected to macrolides, quinolones, fluoroquinolones, polymyxins and cephalosporins (third and fourth generations), which are listed, by the World Health Organisation, to be among the highest priority and critically important antimicrobials in human medicine. Our findings underlined that freshwater fish can act as potential source of MDR motile aeromonads. Due to their zoonotic potential, this can pose serious threat to human health
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
COMPARATIVE STUDY AND VIROLOGICAL INVESTIGATIONS ON PMWS SUSPECTED AND NON SUSPECTED FARMS IN ITALY
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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