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Effekt av ulike desinfeksjonsstrategier mot Listeria monocytogenes
No full textKontroll med bakterier som Listeria utgjør en stor utfordring for mange matprodusenter. Listeria monocytogenes er hovedsakelig et produksjonshygienisk problem, forbedret hygiene kan derfor være tiltak for å redusere overlevelse og smitteoverføring av bakterien i produksjonsmiljø. Hensikten med forsøkene i oppgaven var å undersøke effekten av ulike desinfeksjonsstrategier på drap av L. monocytogenes, både når bakteriene var i biofilm og i suspensjon. Dette inkluderte bruk av tradisjonelle desinfeksjonsmidler etterfulgt av hypokloritt og klordioksid, i tillatte konsentrasjoner i drikkevann, i skyllevannet etter desinfeksjon.
Det ble benyttet en blanding av seks L. monocytogenes stammer isolert fra lakse- og kjøttindustrien. Biofilm ble dannet på stålkuponger over to døgn ved 20 °C. Biofilmen ble utsatt for desinfeksjon med hypokloritt, pereddiksyre og benzalkoniumklorid etterfulgt av hypokloritt og klordioksid i skyllevannet. L. monocytogenes i suspensjon ble eksponert for de samme konsentrasjonene av desinfeksjonsmiddel og antimikrobielle komponenter i skyllevannet. Det ble benyttet desinfeksjonsmiddelkonsentrasjoner som ga under to log drap i første desinfeksjonstrinn for å kunne måle drapseffekt og eventuelle samspillseffekter med de antimikrobielle komponentene i skyllevannet.
Klordioksid i skyllevannet var effektivt mot L. monocytogenes i biofilm, hvor det ledet til signifikant større totaldrap, på 2 log (2 x større drap), i kombinasjon med pereddiksyre (p=0,002) og 1 log i kombinasjon med benzalkoniumklorid (p=0,014). Hypokloritt som desinfeksjon var svært effektiv mot biofilm dannet av L. monocytogenes, hvilket gjorde det vanskelig å detektere ytterligere drap av de antimikrobielle komponentene i skyllevannet. Klordioksid, med konsentrasjonene 0,5 og 1 ppm, i skyllevannet var effektivt mot L. monocytogenes i suspensjon, hvor det ledet til signifikant større totaldrap, på over 3 log, i kombinasjon med pereddiksyre (p=0,000), over 4 log i kombinasjon med hypokloritt (p=0,000) og 1 ppm klordioksid ga et signifikant større totaldrap på 3 log i kombinasjon med benzalkoniumklorid (p=0,026).
Hypokloritt i skyllevannet førte til et signifikant større totaldrap, på 2 log, i kombinasjon med pereddiksyre både på L. monocytogenes i biofilm (p=0,002) og i suspensjon (p=0,050) samt i kombinasjon med benzalkoniumklorid på bakterier i biofilm (p=0,016). Hypokloritt i skyllevannet ga også et større totaldrap, på 1,5 log, i kombinasjon med hypokloritt som desinfeksjon på bakterier i suspensjon, men dette var ikke signifikant.
Pereddiksyre økte drapseffekten av klordioksid i skyllevannet både på L. monocytogenes i biofilm og i suspensjon. Hypokloritt som desinfeksjon førte til signifikant økt effekt av 0,5 ppm klordioksid i skyllevannet på bakterier i suspensjon. Pereddiksyre økte drapseffekten av hypokloritt i skyllevannet på bakterier i suspensjon.
Dette indikerer at bruk av hypokloritt og klordioksid i skyllevann etter desinfeksjon kan gi økt drap av L. monocytogenes både i biofilm og i suspensjon, hvor kombinasjon av desinfeksjonsmidler med samme virkningsmekanismer viste tendens til å gi størst totaldrap. ABSTRACT
Control of bacteria, as Listeria, is a major challenge in the food manufacturing industry. Listeria monocytogenes is mainly a hygienic problem, enhanced hygiene can therefore be used to reduce survival and transmission of the bacteria in the production environment. The purpose of this study was to evaluate different disinfection strategies on L. monocytogenes, both bacteria in biofilms and in suspension. This included the use of traditional disinfectants followed by hypochlorite and chlorine dioxide, in concentrations that is legally in drinking water, in rinsing water after disinfection.
Six L. monocytogenes strains isolated from salmon- and meatindustry were used in the research. The biofilms were initially formed on stainless steel coupons for two days at 20 °C. The biofilm was subjected to disinfection with hypochlorite, peracetic acid and benzalkonium chloride followed by hypochlorite and chlorine dioxide in the rinsing water. L. monocytogenes in suspension were exposed to the same concentrations of disinfectant and antimicrobial components in the rinse water. The concentrations of disinfectants that gave approximately two log reduction were selected in the first disinfection step, which made it possible to measure log reduction and possible interactions with the antimicrobial component in the rinsing water.
Chlorine dioxide in the rinsing water was effective against L. monocytogenes in biofilm. Chlorine dioxide increased total log reduction with 2 log (2 x greater reduction), in combination with peracetic acid (p=0,002) and with 1 log in combination with benzalkonium chloride (p=0,014) as the first disinfectants. Hypochlorite as disinfectant was very effective on L. monocytogenes in biofilm, which made it difficult to detect further reduction from antimicrobial components in the rinsing water. Chlorine dioxide, in concentrations of 0.5 and 1 ppm, in the rinse water was effective on L. monocytogenes in suspension. Where it led to significant greater log reduction, over 3 log, in combinations with peracetic acid (p=0,000), over 4 log in combination with hypochlorite (p=0,000) and 1 ppm chlorine dioxide gave 3 log greater reduction in combination with benzalkonium chloride (p=0,026).
Hypochlorite in the rinse water increased log reduction with 2 log in combinations with peracetic acid both on L. monocytogenes in biofilm (p=0,002) and in suspension (p=0,050), and in combination with benzalkonium chloride on bacteria in biofilm (p=0,016). Hypochlorite in the rinse water also led to 1.5 log reduction in combination with hypochlorite as disinfectant on bacteria in suspension, but this was not significant.
Peracetic acid as disinfectant increased the effect of chlorine dioxide in rinsing water both on L. monocytogenes in biofilm and in suspension. Hypochlorite as disinfectant increased the effect of 0.5 ppm chlorine dioxide in the rinsing water on bacteria in suspension. Peracetic acid increased the effect of hypochlorite in rinsing water on bacteria in suspension.
This indicates that antimicrobial components in the rinsing water after disinfection may increase reduction of L. monocytogenes, both in biofilm and in suspension. Combinations of disinfectants with the same mechanism of action showed greatest total log reduction
Effect of various disinfection strategies against Listeria monocytogenes
No full textKontroll med bakterier som Listeria utgjør en stor utfordring for mange matprodusenter. Listeria monocytogenes er hovedsakelig et produksjonshygienisk problem, forbedret hygiene kan derfor være tiltak for å redusere overlevelse og smitteoverføring av bakterien i produksjonsmiljø. Hensikten med forsøkene i oppgaven var å undersøke effekten av ulike desinfeksjonsstrategier på drap av L. monocytogenes, både når bakteriene var i biofilm og i suspensjon. Dette inkluderte bruk av tradisjonelle desinfeksjonsmidler etterfulgt av hypokloritt og klordioksid, i tillatte konsentrasjoner i drikkevann, i skyllevannet etter desinfeksjon.
Det ble benyttet en blanding av seks L. monocytogenes stammer isolert fra lakse- og kjøttindustrien. Biofilm ble dannet på stålkuponger over to døgn ved 20 °C. Biofilmen ble utsatt for desinfeksjon med hypokloritt, pereddiksyre og benzalkoniumklorid etterfulgt av hypokloritt og klordioksid i skyllevannet. L. monocytogenes i suspensjon ble eksponert for de samme konsentrasjonene av desinfeksjonsmiddel og antimikrobielle komponenter i skyllevannet. Det ble benyttet desinfeksjonsmiddelkonsentrasjoner som ga under to log drap i første desinfeksjonstrinn for å kunne måle drapseffekt og eventuelle samspillseffekter med de antimikrobielle komponentene i skyllevannet.
Klordioksid i skyllevannet var effektivt mot L. monocytogenes i biofilm, hvor det ledet til signifikant større totaldrap, på 2 log (2 x større drap), i kombinasjon med pereddiksyre (p=0,002) og 1 log i kombinasjon med benzalkoniumklorid (p=0,014). Hypokloritt som desinfeksjon var svært effektiv mot biofilm dannet av L. monocytogenes, hvilket gjorde det vanskelig å detektere ytterligere drap av de antimikrobielle komponentene i skyllevannet. Klordioksid, med konsentrasjonene 0,5 og 1 ppm, i skyllevannet var effektivt mot L. monocytogenes i suspensjon, hvor det ledet til signifikant større totaldrap, på over 3 log, i kombinasjon med pereddiksyre (p=0,000), over 4 log i kombinasjon med hypokloritt (p=0,000) og 1 ppm klordioksid ga et signifikant større totaldrap på 3 log i kombinasjon med benzalkoniumklorid (p=0,026).
Hypokloritt i skyllevannet førte til et signifikant større totaldrap, på 2 log, i kombinasjon med pereddiksyre både på L. monocytogenes i biofilm (p=0,002) og i suspensjon (p=0,050) samt i kombinasjon med benzalkoniumklorid på bakterier i biofilm (p=0,016). Hypokloritt i skyllevannet ga også et større totaldrap, på 1,5 log, i kombinasjon med hypokloritt som desinfeksjon på bakterier i suspensjon, men dette var ikke signifikant.
Pereddiksyre økte drapseffekten av klordioksid i skyllevannet både på L. monocytogenes i biofilm og i suspensjon. Hypokloritt som desinfeksjon førte til signifikant økt effekt av 0,5 ppm klordioksid i skyllevannet på bakterier i suspensjon. Pereddiksyre økte drapseffekten av hypokloritt i skyllevannet på bakterier i suspensjon.
Dette indikerer at bruk av hypokloritt og klordioksid i skyllevann etter desinfeksjon kan gi økt drap av L. monocytogenes både i biofilm og i suspensjon, hvor kombinasjon av desinfeksjonsmidler med samme virkningsmekanismer viste tendens til å gi størst totaldrap. ABSTRACT
Control of bacteria, as Listeria, is a major challenge in the food manufacturing industry. Listeria monocytogenes is mainly a hygienic problem, enhanced hygiene can therefore be used to reduce survival and transmission of the bacteria in the production environment. The purpose of this study was to evaluate different disinfection strategies on L. monocytogenes, both bacteria in biofilms and in suspension. This included the use of traditional disinfectants followed by hypochlorite and chlorine dioxide, in concentrations that is legally in drinking water, in rinsing water after disinfection.
Six L. monocytogenes strains isolated from salmon- and meatindustry were used in the research. The biofilms were initially formed on stainless steel coupons for two days at 20 °C. The biofilm was subjected to disinfection with hypochlorite, peracetic acid and benzalkonium chloride followed by hypochlorite and chlorine dioxide in the rinsing water. L. monocytogenes in suspension were exposed to the same concentrations of disinfectant and antimicrobial components in the rinse water. The concentrations of disinfectants that gave approximately two log reduction were selected in the first disinfection step, which made it possible to measure log reduction and possible interactions with the antimicrobial component in the rinsing water.
Chlorine dioxide in the rinsing water was effective against L. monocytogenes in biofilm. Chlorine dioxide increased total log reduction with 2 log (2 x greater reduction), in combination with peracetic acid (p=0,002) and with 1 log in combination with benzalkonium chloride (p=0,014) as the first disinfectants. Hypochlorite as disinfectant was very effective on L. monocytogenes in biofilm, which made it difficult to detect further reduction from antimicrobial components in the rinsing water. Chlorine dioxide, in concentrations of 0.5 and 1 ppm, in the rinse water was effective on L. monocytogenes in suspension. Where it led to significant greater log reduction, over 3 log, in combinations with peracetic acid (p=0,000), over 4 log in combination with hypochlorite (p=0,000) and 1 ppm chlorine dioxide gave 3 log greater reduction in combination with benzalkonium chloride (p=0,026).
Hypochlorite in the rinse water increased log reduction with 2 log in combinations with peracetic acid both on L. monocytogenes in biofilm (p=0,002) and in suspension (p=0,050), and in combination with benzalkonium chloride on bacteria in biofilm (p=0,016). Hypochlorite in the rinse water also led to 1.5 log reduction in combination with hypochlorite as disinfectant on bacteria in suspension, but this was not significant.
Peracetic acid as disinfectant increased the effect of chlorine dioxide in rinsing water both on L. monocytogenes in biofilm and in suspension. Hypochlorite as disinfectant increased the effect of 0.5 ppm chlorine dioxide in the rinsing water on bacteria in suspension. Peracetic acid increased the effect of hypochlorite in rinsing water on bacteria in suspension.
This indicates that antimicrobial components in the rinsing water after disinfection may increase reduction of L. monocytogenes, both in biofilm and in suspension. Combinations of disinfectants with the same mechanism of action showed greatest total log reduction.Control of bacteria, as Listeria, is a major challenge in the food manufacturing industry. Listeria monocytogenes is mainly a hygienic problem, enhanced hygiene can therefore be used to reduce survival and transmission of the bacteria in the production environment. The purpose of this study was to evaluate different disinfection strategies on L. monocytogenes, both bacteria in biofilms and in suspension. This included the use of traditional disinfectants followed by hypochlorite and chlorine dioxide, in concentrations that is legally in drinking water, in rinsing water after disinfection.
Six L. monocytogenes strains isolated from salmon- and meatindustry were used in the research. The biofilms were initially formed on stainless steel coupons for two days at 20 °C. The biofilm was subjected to disinfection with hypochlorite, peracetic acid and benzalkonium chloride followed by hypochlorite and chlorine dioxide in the rinsing water. L. monocytogenes in suspension were exposed to the same concentrations of disinfectant and antimicrobial components in the rinse water. The concentrations of disinfectants that gave approximately two log reduction were selected in the first disinfection step, which made it possible to measure log reduction and possible interactions with the antimicrobial component in the rinsing water.
Chlorine dioxide in the rinsing water was effective against L. monocytogenes in biofilm. Chlorine dioxide increased total log reduction with 2 log (2 x greater reduction), in combination with peracetic acid (p=0,002) and with 1 log in combination with benzalkonium chloride (p=0,014) as the first disinfectants. Hypochlorite as disinfectant was very effective on L. monocytogenes in biofilm, which made it difficult to detect further reduction from antimicrobial components in the rinsing water. Chlorine dioxide, in concentrations of 0.5 and 1 ppm, in the rinse water was effective on L. monocytogenes in suspension. Where it led to significant greater log reduction, over 3 log, in combinations with peracetic acid (p=0,000), over 4 log in combination with hypochlorite (p=0,000) and 1 ppm chlorine dioxide gave 3 log greater reduction in combination with benzalkonium chloride (p=0,026).
Hypochlorite in the rinse water increased log reduction with 2 log in combinations with peracetic acid both on L. monocytogenes in biofilm (p=0,002) and in suspension (p=0,050), and in combination with benzalkonium chloride on bacteria in biofilm (p=0,016).
Hypochlorite in the rinse water also led to 1.5 log reduction in combination with hypochlorite as disinfectant on bacteria in suspension, but this was not significant.
Peracetic acid as disinfectant increased the effect of chlorine dioxide in rinsing water both on L. monocytogenes in biofilm and in suspension. Hypochlorite as disinfectant increased the effect of 0.5 ppm chlorine dioxide in the rinsing water on bacteria in suspension. Peracetic acid increased the effect of hypochlorite in rinsing water on bacteria in suspension.
This indicates that antimicrobial components in the rinsing water after disinfection may increase reduction of L. monocytogenes, both in biofilm and in suspension. Combinations of disinfectants with the same mechanism of action showed greatest total log reduction.2018-05-1
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
Variations 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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