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Development of antibiotic resistance in Mycoplasma gallisepticum in vitro. Avian Pathology
No full textThe results of in vitro tests for induction of antibiotic resistance in some strains of Mycoplasma gallisepticum are reported. The number of passages required to induce resistance varied considerably between different antibiotics. In two groups of tests, with different strains of M. gallisepticum, resistance (>/= 1 mg/ml) to streptomycin appeared after two to three passages, to erythromycin and spiramycin after five to eight passages, to tylosin after nine to eleven and to enrofloxacin after eight to ten passages. With chlortetracycline the increase in resistance was very low (no more than ten times the starting minimal inhibitory concentration). Cross-sensitivity tests using strains with induced resistance to the different antibiotics demonstrated that those which were resistant to tylosin were also resistant to other macrolides ( > 1 mg/ml), whereas strains made resistant to erythromycin and spiramycin appeared only less sensitive (2 to 200 mug/ml) to tylosin in comparison with the original strains. Streptomycin, chlortetracycline and enrofloxacin induced very little or no cross-resistance
Diversity and antimicrobial resistance of pathogenic and non pathogenic Escherichia coli isolated in the broiler production chain
No full textAvian pathogenic Escherichia coli (APEC) causes extraintestinal diseases in broilers and
share common virulence factors with extraintestinal pathogenic E. coli (ExPEC) isolated
in humans suggesting the zoonotic potential of APEC [1]. APEC are characterised by a
high intra-population diversity in terms of serogroup, MLST and virulence genes [2].
The aim of the present study was to investigate the diversity and antimicrobial
resistance of E. coli isolated from lung, spleen, pericardium and brain of broilers
affected by colisepticemia and treated with enrofloxacin. In three different farms with
ongoing infections, at day 0 (before starting the treatment), day 5 (last day of
treatment), day 10 and day 20 (after treatment), 10 birds were humanly euthanized
and their organs investigated for E. coli isolation by standard microbiological
procedures. A total of 179 E. coli were isolated and submitted to pulsed field gel
electrophoresis (PFGE) and minimum inhibitory concentration (MIC) to gain insights
on their genetic diversity and antimicrobial susceptibility. Based on metadata as well
as MIC and PFGE data, 31 isolates were whole genome sequenced on MiSeq platform
(Illumina, 250 bp reads, paired ends). Genomic diversity by SNP calling and in silico
MLST as well as antimicrobial resistance and virulence-associated genes were analysed
with publicly available bioinformatics pipelines. According to PFGE results, in all three
farms the genetic diversity was overall low before the treatment and increases along
and after. At day 0, E. coli isolates can be gathered in 3 - 6 clusters at 95% similarity.
Whereas at day 5, 10 and 20 the number of clusters rises up to 10-16 with the
majority of single-isolate clusters. Similar results were confirmed by MLST and SNP
calling analyses on the sequenced genomes. MIC data showed a significant increase of
resistance to enrofloxacin and flumequine in E. coli isolates collected at day 5, 10 and
20 in comparison to day 0. Along with this drug, a significant increase of resistance to
trimethoprim/sulfametoxazole (SXT) was observed in one of the three farms. These
results suggest that the antibiotic was effective in eradicating the initial pathogen
strains responsible for the colibacillosis infections. In all farms, fluoroquinolone
resistant E. coli were collected after enrofloxacin treatment. In one farm, a high number
of SXT resistant strains arose, although their SXT resistance genes were genetically
unrelated to enrofloxacin resistance genes/mutations. Finally, the gross pathological
lesions encountered before the treatment on diseased birds disappeared after the
treatment in all organs except for lungs, suggesting the lower virulence of E. coli
isolates collected after the treatment from spleen, pericardium and brain
Survey on the presence of Salmonella gallinarum in Dermanyssus gallinae in intensive poultry farms
No full textSalmonella enterica subsp. enterica ser Gallinarum is the causative agent of fowl typhoid. The disease
represents a major concern among industrial poultry farms, causing heavy economic losses due to its
detrimental effects on productivity and animal welfare. The pathogen is highly persistent and its eradication
from an infected farm is often difficult. A possible cause of its survival may be the association with parasites,
such as the poultry red mite Dermanyssus gallinae. The latter is widespread among European poultry farm,
with infestation rates raising up to 90%.
This study is aimed to evaluate the association among D. gallinae and S. gallinarum in the Italian intensive
poultry farms.
Seventy-four samples of mites were collected from 62 intensive poultry farms. Up to 100 mites per
sample underwent to homogenization and DNA extraction. The extracted DNA was used as template in a
seminested-PCR-based protocol, already proved to be sensitive and specific.
Four samples out of 74 (5.41%) resulted positive for the presence of S. gallinarum. Three positive samples
came from different laying hen farms, while the other came from a broiler parent farm.
Such data confirm the association between D. gallinae and S. gallinarum, once again evidencing the
potential vectorial role of the mite for the bacterial pathogen. Furthermore, they suggest that D. gallinae
may act as a reservoir of S. gallinarum, as it could be hosted by the mite even during the sanitary breaks,
which are carried out in order to eradicate fowl typhoid from an infected poultry far
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Study on selection and transfer of antimicrobial resistant Escherichia coli from broiler breeders to their progeny
No full textEscherichia coli is a normal inhabitant of the intestinal tract of chickens and is harmless as long as its growth and colonization is inhibited by other commensal intestinal microbial populations. When an imbalance in bacterial flora of the intestinal tract occurs, E. coli may grow and cause extraintestinal infections. E. coli disease outbreaks, manifested as septicaemia in both parent flocks and their progeny, are often due to clonal strains which can acquire multiple antibiotic resistance characters along the antimicrobial therapy and eventually transfer it to other intestinal bacteria circulating between birds. The aim of this study was to evaluate the transmission of E. coli clones and their antimicrobial resistant characters from broiler breeders to their progeny in absence or presence of an ongoing E. coli infection. Three groups of chicks (i.e., A1, B1, C1) characterised by omphalitis symptoms and originated from the same group of broiler breeders (R1) were chosen during the first week of life along with three groups (i.e., A2, B2, C2) of healthy chicks originated from the same group of broiler breeders (R2). Among each group 5-10 animals were picked out. Consistently from each group of birds 5-10 animals at 21 days and at the end of the productive cycle were selected. In particular, for sick birds (A1, B1, C1) 5-10 animals were collected before and 5-10 animals after the antimicrobial therapy at 21 days. In parallel, three pools of environmental dust were sampled. Two weeks after the collection of healthy and sick chicks, 5-10 animals of each of the corresponding broiler breeder group (R1 or R2) were also selected. All selected animals were humanely euthanized and from each of them different organs (i.e., liver, spleen, intestine, heart, lungs and tracheal mucus) were collected and tested for the presence of E. coli. In brief, 10 g of dust or sampled organ were diluted 1:10 in Ringer’s Solution (Oxoid, Hampshire, UK). An aliquot was plated on Eosin Methylene Blue agar (EMB) and incubated at 37 °C for 24h in duplicate. From each plate, two colonies showing characteristic E. coli morphology were selected for confirmation through biochemical tests. E. coli isolates were molecular characterised by Pulsed Field Gel Electrophoresis (PFGE), using the standard PulseNet protocol with XbaI as restriction enzyme, and automated ribotyping according to the manufacturer instructions with EcoRI as restriction enzyme (Oxoid, Hampshire, UK). The antimicrobial sensibility of E. coli isolates toward amoxicillin, tetracycline, spectinomycin, enrofloxacin and ciprofloxacin was investigated by the microdilution method following standard procedures reported in the document M31-A2 of the Clinical Laboratory Standard Institute (CLSI). Results on the selection and transfer of antimicrobial resistant E. coli isolates from broiler breeders to their progeny will be discussed at the conference
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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