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Analysis of ISO 11731:2017 method to assess Legionella pneumophila in water with high background : And how it differentiates from its earlier variant ISO 11731:1998
No full textLegionella pneumophila is a human pathogen commonly found in natural and artificial aquatic environments and can cause a condition called legionellosis. Monitoring for legionellae is therefore important for protecting public health and identifying its environmental sources is a way to prevent illness. This has resulted in development of several control strategies to identify these sources. One of these strategies is to construct a valid method to detect Legionella pneumophila and monitoring these methods is a way to ensure the method remain effective at tracing infection. The current version of standardized method is called ISO 11731:2017 and supersedes its former version called ISO 11731:1998. The former version uses a combination of heat and acid solution treatment to reduce interfering microorganisms in water with high background, whereas the current version separates the treatment by subdividing the sample in three parts. One part is subjected to heat treatment, one with acid solution treatment and one remains untreated. Therefore, the aim of this study is to analyse how this difference in method strategy will affect detection of Legionella pneumophila between the current and its former version of ISO 11731. To do this, this study divided the experiment into two parts: experiment A was aimed at evaluating the validity of the method and experiment B was designed to study repeatability in terms of dispersion and performance data range. For experiment A: 14 samples were tested using both ISO 11731:2017 and 11731:1998 to see how the results differentiated. Six are natural samples and was appointed based on their previous results that showed positive for Legionella. Four samples were spiked with different serotypes of Legionella and the remaining four were spiked with both Legionella and Legionella-inhibited bacteria. For experiment B, three certified reference material with different concentration of Legionella pneumophila serotype 1 was tested in repeatability conditions with each sample producing ten replicates. In conclusion, based on results assessed in this study ISO 11731:1998 was more suitable to analyse water with higher concentration of interfering microorganisms. By a combination of heat and acid solution treatment: it maximizes the reduction of interfering microorganisms which facilitates Legionella to cultivate on agar. ISO 11731:2017 was more efficient in recovering different serotypes of Legionella. Although, there were a significant increase in dispersion and performance data range results in ISO 11731:2017. This indicates that since there is an additional dilution step added in acid solution treatment: it increases the risk of human error and therefore a greater vulnerability to the method.
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
Inaccuracies of the ISO 11731 Method for Environmental Validation of Legionella in Building Water Systems: Opportunities to Improve Sensitivity and Detect Viable but Non-Culturable Legionella
No full textCurrent environmental diagnostics for the detection of Legionella fail to detect viable but non-culturable Legionella, have sensitivity limitations and are time-consuming (10–14 days to results). The objective of this study was to compare Legionella detection results between the standard ISO 11731 and an innovative Legionella detection method that utilizes a hybrid methodology of traditional microbiology and molecular detection. In this study, four hundred and seventy-six (476) potable building water samples were analyzed with ISO 11731 and the novel method in parallel. Of the 476 total samples that were tested, a discrepancy of 21% was observed when comparing the ISO 11731 method to the novel method. Separating the samples based on hazard control methods yielded a 15.4% discrepancy for chlorinated systems (n = 284) and a 29% discrepancy for monochloraminated systems (n = 192). The data presented here conclusively show inaccuracies in environmental validation for building water systems based on results returned by the standard ISO 11731 method. This is especially evident in systems primarily disinfected with monochloramines. Overall, these data highlight the need for new and innovative methods to overcome the inaccuracies of the traditional ISO 11731 spread plates to prevent disease and injury caused by Legionella
Falsos positivos na detecção de Legionella spp. seguindo a norma UNE ISO-11731:1998
No full textDissertação de Mestrado em Biologia Clínica LaboratorialAs infecções provocadas por Legionella spp. são consideradas actualmente, um problema emergente de saúde pública e estão associadas a altas taxa de mortalidade e morbilidade, quando não tratadas adequadamente.
Neste estudo foram analisadas 54 amostras de água provenientes de 8 concelhos da região Norte de Portugal, com a finalidade de obter uma colecção de estirpes do género Legionella e caracteriza-las tanto fenotipicamente como geneticamente. Sendo também objectivo deste trabalho, avaliar a eficácia da técnica de cultivo, método padrão de referência de acordo com a norma International Organization for Standardization 11731 (1998), na detecção de espécies de Legionella. O processamento laboratorial das amostras foi realizado segundo a metodologia recomendada pela ISO-11731:1998. Após filtração das amostras (1 litro), o colectado foi ressuspendido em 5 ml de água destilada estéril. Posteriormente, retirou-se 100 μl da suspensão e semeou-se em um meio selectivo, agar GVPC (BD BBL 257007), incubando-se 7 a 10 dias, a 37 ºC em condições aeróbias. Colónias morfologicamente características do género foram subcultivadas em agar BCYE (BD BBL 221808) e agar sangue, para confirmação. Somente as colónias que cresceram em agar BCYE e não em agar sangue foram consideradas presuntivas de Legionella, segundo a ISO 11731. A identificação das mesmas foi realizada por sequenciação do gene 16S rRNA, tendo-se verificado que nenhum dos isolados foi identificado como pertencente ao género Legionella. No entanto, mediante a ISO 11731 estes foram interpretados como positivos, correspondendo portanto, a resultados falsos positivos. Embora a técnica de cultura, seja o método recomendado pela norma ISO 11731 para a detecção de Legionella spp., neste trabalho esta técnica demonstrou-se muito morosa e de baixa sensibilidade, verificando-se inclusivamente a ocorrência de falsos positivos, o que evidência a importância da utilização de métodos genéticos para a correcta identificação dos microrganismos. A metodologia utilizada neste estudo permitiu ainda o isolamento de um conjunto de isolados (n=40), que formam um grupo independente de todos os géneros da família Chitinophagaceae descritos até ao momento e que pela sua distância filogenética poderá corresponder a um género ainda não descrito e portanto a uma nova espécie. Da avaliação do perfil de susceptibilidade, verificou-se que à excepção de três isolados, todas as estirpes testadas apresentaram um perfil de multiresistência aos antibióticos utilizados, entre os quais, os β-lactâmicos, os aminoglicosídeos e as quinolonas, sendo os menos eficazes a amoxicilina (penicilina) e a eritromicina.Infections caused by Legionella spp. are considered at present, an emerging public health problem and are linked to high rates of mortality and morbidity, if not properly treated.
This study analyzed 54 samples of water from 8 counties from Northern Portugal, with the aim of obtaining a collection of strains of the genus Legionella and to characterize them genetically and phenotypically. Another objective of this study was to evaluate the effectiveness of the technique of cultivation, the standard method according to International Organization for Standardization 11731 (1998), for the detection of species of Legionella. The laboratory processing of samples was performed according to procedure recommended by ISO-11731:1998. After filtration of samples (1 L), the filtrate was re-suspended in 5 ml of sterile distilled water. Subsequently, 100 μl of the suspension was spread in GVPC selective agar medium (BD 257007 BBL), and incubated for 7 to 10 days at 37 ºC, under aerobic conditions. Colonies that were morphologically characteristic of the genus were sub-cultured onto BCYE agar (BD 221808 BBL) and blood agar for verification. Only the colonies which grew in BCYE agar and not on blood agar were considered presumptive of Legionella, according to ISO 11731. The identification of these initially selected colonies was performed by sequencing the 16S rRNA gene, which revealed that none of the isolates were identified as belonging to the genus Legionella. However, through the ISO 11731 they were interpreted as positive, corresponding therefore to false-positive results. While the technique of culture is the method recommended by ISO 11731 for the detection of Legionella spp. in this work it was clearly shown that this technique is very slow and has low sensitivity, there is even the occurrence of false-positives, which highlighted the importance of using genetic methods for the proper identification of microorganisms. The methodology used in this study allowed the isolation of a number of isolates (n=40), which form an independent group of all genus of the family Chitinophagaceae written so far and that by their phylogenetic distance may be a genus not yet described and therefore a new species. Assessing the profile of susceptibility, it was found that with the exception of three strains, all strains tested showed a profile of multi-resistance to antibiotics used, including the β-lactams, aminoglycosides and the quinolones, and the least effective were amoxicillin (penicillin) and erythromycin
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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