comparison of different sampling techniques and enumeration methods

TITELBLATT UND INHALTSVERZEICHNIS Einleitung Literaturübersicht Eigene Untersuchungen ERGEBNISSE DISKUSSION SCHLUSSFOLGERUNGEN ZUSAMMENFASSUNG SUMMARY LITERATURVERZEICHNISUm Daten über die quantitative Belastung von Hähnchenfleisch zu erhalten und somit die Exposition im Zuge einer Risikoabschätzung für den Verbraucher näher charakterisieren zu können, beschäftigte sich die vorliegende Arbeit sowohl mit der qualitativen Erfassung als auch der Quantifizierung von Campylobacter auf der Oberfläche und im Muskel von Hähnchenschenkeln aus dem Handel sowie mit dem Nachweis eines möglichen saisonalen Einflusses. Im Rahmen der quantitativen Untersuchungen wurden verschiedene Probenarten (Haut- versus Spülprobe) zur Isolierung von Campylobacter, kombiniert mit verschiedenen Keimzählverfahren (MPN- versus Spateltechnik) miteinander verglichen, um eine geeignete Methode zur Isolierung und Quantifizierung des Erregers zu erarbeiten. Im Zeitraum von November 2003 bis Dezember 2004 wurden insgesamt 140 Handels-Packungen frischer Hähnchenschenkel, jeweils zehn pro Monat, aus Lebensmittelgeschäften des Berliner Einzelhandels erworben. Im Vorversuch wurde die Verteilung von Campylobacter auf der Oberfläche von Hähnchenschenkeln derselben Handels-Packung anhand von zehn Packungen mit jeweils 4-5 Schenkeln bestimmt, um eine Aussage über die Homogenität innerhalb der Probe treffen zu können. Die Ergebnisse zeigen, dass die oberflächlichen Campylobacter-Keimzahlen innerhalb einer Handels-Packung zwischen den als Unterproben dienenden Schenkeln nur mässig variieren und somit die Voraussetzung für den Methodenvergleich gegeben ist. Für die Gegenüberstellung verschiedener Probenahme- und Zähltechniken wurden bei insgesamt 90 Handels- Packungen die Oberfläche des einen Schenkels durch Homogenisieren der Haut (Hautprobe) und die des anderen Schenkels durch Spülen (Spülprobe) quantitativ und qualitativ auf Campylobacter untersucht. Die Keimzahlbestimmungen in den Haut- und Spülproben erfolgten bei 40 Handels-Packungen parallel mittels Spatelverfahren und MPN-Technik, um anschliessend die verschiedenen Keimzählmethoden anhand des jeweiligen quantitativen Resultats miteinander zu vergleichen. 70% (63/90) der Hautproben und 77% (69/90) der Spülproben fielen Campylobacter-positiv aus. Die Keimzahlbestimmung mittels Spatelverfahren ergab einen Medianwert von log 4,0 KbE/Schenkel (SD = 0,6) in den Hautproben bzw. log 4,3 KbE/Schenkel in den Spülproben (SD = 0,9). 73% (37/51) der Spülproben erbrachten höhere Keimzahlen als die Hautproben. Bezogen auf die Untersuchungstechnik lieferte das Spatelverfahren in 80% der untersuchten Spülproben mit einem Median von log 4,2 KbE/Schenkel einen höheres Keimzahlergebnis als die MPN-Technik, mit der ein Median von log 4,0 KbE/Schenkel ermittelt werden konnte. Der Unterschied erwies sich jedoch nicht als signifikant. Darüber hinaus zeigte sich eine sehr gute Korrelation der Ergebnisse beider Zählmethoden. Aufgrund der Ergebnisse der Vergleichsuntersuchung wurden die weiteren quantitativen Untersuchungen der Schenkeloberfläche mittels Hautprobe und Spatelverfahren fortgesetzt. Insgesamt zeigen die Ergebnisse der qualitativen und quantitativen Analyse, dass ein sehr hoher Prozentsatz oberflächlich kontaminierter Hähnchenschenkel an den Verbraucher abgegeben wird. Bei 66% der untersuchten Hähnchenschenkel konnten Campylobacter auf der Haut nachgewiesen werden und die Keimzahlen fallen mit einem Median von log 2,4 KbE/g beachtlich aus. Die Häufigkeit und die Anzahl der mittels MPN-Technik erfassten Campylobacter-Keime im Muskel waren vergleichsweise gering. Nur 27% der Muskelproben zeigten sich Campylobacter positiv bei einer Nachweisgrenze von >0,3 MPN Campylobacter/g. Die geringe Kontamination des Fleisches weist rohem Hähnchenfleisch eine weniger relevante Rolle in der Epidemiologie der humanen Campylobacteriose zu. Kreuzkontaminationen von verzehrsfertigen Lebensmitteln oder belasteten Oberflächen während der Zubereitung dürften hingegen ein höheres Gesundheitsrisiko darstellen als der Verzehr von unzureichend gegartem Hähnchenfleisch. Hinsichtlich der Speziesverteilung bestand sowohl auf der Schenkeloberfläche als auch in der Muskulatur eine Dominanz von C. jeuni (84% bzw. 97%), gefolgt von C. coli (16% bzw. 3%). Dabei ist die zunehmende Chinolonresistenz der aus dem Handel isolierten Camplobacter-Stämme besorgniserregend und bei der antibiotischen Behandlung von Campylobacteriosen zu beachten. Die erhöhte Prävalenz und Anzahl von Campylobacter auf Hähnchenschenkeln in den wärmeren Monaten lässt eine saisonale Abhängigkeit der Campylobacter Belastung erkennen und spricht für ein erhöhtes Infektionsrisiko zu bestimmten Jahreszeiten.Quantification of Campylobacter spp. on the surface and in the muscle of chicken legs at retail; comparison of different sampling techniques and enumeration methods In order to collect data about the quantitative load of Campylobacter in chicken and thus defining the risk for consumers, the object of the present study was to determine the prevalence and number of Campylobacter on the surface and in the meat of chicken legs at retail level and to investigate seasonal influence on the prevalence and number of these pathogens. In the context of quantitative investigations, two different ways of sample preparation for the isolation of Campylobacter combined with two different enumeration methods were compared to develop an applicable method for the isolation and enumeration of these pathogens. From November 2003 to December 2004, 140 packages of raw chicken legs, 10 each month, were bought from different retail outlets in Berlin. At the beginning of the quantitative investigations, the distribution of Campylobacter-counts within the same package was examined in ten packages containing 4 to 5 legs to determine homogeneity within the sample. Results demonstrated that there is only a small difference between Campylobacter-counts on the surface of chicken legs within the same package which is a condition for the comparison of the sample preparation types. The comparison of the sample preparation types was carried out by rinsing one chicken leg (rinse sample) and homogenising the skin (skin sample) of the other leg of the same package with 90 packages. Both sample preparation types were examined by direct plating method and MPN technique in 40 packages and compared based on the colony forming units of Campylobacter per leg. 70% (63/90) of the skin samples and 77% (69/90) of the rinse samples were Campylobacter-positive. Enumeration of Campylobacter by direct plating method revealed a median of log 4.0 CFU/leg surface in skin samples (SD = 0.6) and a median of log 4.3 CFU/leg surface in rinse samples (SD = 0.9). 73% (37/51) of the rinse samples revealed higher numbers of Campylobacter than the skin samples. Concerning the sample preparation types, the direct plating method detected higher numbers of Campylobacter in 80% of the compared rinse samples with a median count of log 4.2 CFU/leg surface (SD = 1) than the MPN technique where a median of log 4.0 CFU/leg surface (SD = 1.1) was obtained. The difference was not significant. Furthermore, a highly significant positive correlation was observed between both methods. Due to the results achieved in the comparative examination, the further investigations were continued with skin samples and direct plating method. In total, results of the quantitative and qualitative investigation show that a high percentage of superficially contaminated chicken legs is sold to the consumer. 66% of the examined chicken legs were contaminated with Campylobacter on the surface and the numbers of Campylobacter with a median of log 2.4 CFU/g are remarkable. Incidence and number of Campylobacter detected by MPN technique in the muscle were comparatively low. Only 27% of the muscle samples were Campylobacter positiv with a detection limit of >0,3 MPN Campylobacter/g. The low contamination rate of meat allocates raw meat a minor role in the epidemiology of human campylobacteriosis. Cross contamination of ready to eat food or contaminated surfaces during food preparation may pose a higher health risk than the consumption of insufficient heated chicken meat. Regarding the species distribution, in both, skin and muscle samples, C. jejuni was isolated more frequently (84% and 97%, respectively) than C. coli (16% and 3%, respectively). The increasing quinolone-resistance of Campylobacter isolates from retail is alarming and should be considered when treating Campylobacter infection antibiotically. The increased prevalence and number of Campylobacter on chicken legs during warmer months shows a seasonal influence on Campylobacter contamination indicating a higher risk at certain seasons

Ensuring connectedness for the Maximum Quasi-clique and Densest kk-subgraph problems

Given an undirected graph $G$, a quasi-clique is a subgraph of $G$ whose density is at least $\gamma$ $(0 < \gamma \leq 1)$. Two optimization problems can be defined for quasi-cliques: the Maximum Quasi-Clique (MQC) Problem, which finds a quasi-clique with maximum vertex cardinality, and the Densest $k$-Subgraph (DKS) Problem, which finds the densest subgraph given a fixed cardinality constraint. Most existing approaches to solve both problems often disregard the requirement of connectedness, which may lead to solutions containing isolated components that are meaningless for many real-life applications. To address this issue, we propose two flow-based connectedness constraints to be integrated into known Mixed-Integer Linear Programming (MILP) formulations for either MQC or DKS problems. We compare the performance of MILP formulations enhanced with our connectedness constraints in terms of both running time and number of solved instances against existing approaches that ensure quasi-clique connectedness. Experimental results demonstrate that our constraints are quite competitive, making them valuable for practical applications requiring connectedness

Implementation of anaphylaxis management guidelines

Anaphylaxis management guidelines recommend the use of intramuscular adrenaline in severe reactions, complemented by antihistamines and corticoids; secondary prevention includes allergen avoidance and provision of self-applicable first aid drugs. Gaps between recommendations and their implementation have been reported, but only in confined settings. Hence, we analysed nation-wide data on the management of anaphylaxis, evaluating the implementation of guidelines. Within the anaphylaxis registry, allergy referral centres across Germany, Austria and Switzerland provided data on severe anaphylaxis cases. Based on patient records, details on reaction circumstances, diagnostic workup and treatment were collected via online questionnaire. Report of anaphylaxis through emergency physicians allowed for validation of registry data. 2114 severe anaphylaxis patients from 58 centres were included. 8% received adrenaline intravenously, 4% intramuscularly; 50% antihistamines, and 51% corticoids. Validation data indicated moderate underreporting of first aid drugs in the Registry. 20% received specific instructions at the time of the reaction; 81% were provided with prophylactic first aid drugs at any time. There is a distinct discrepancy between current anaphylaxis management guidelines and their implementation. To improve patient care, a revised approach for medical education and training on the management of severe anaphylaxis is warranted

Switchable Signaling Molecules for Media Modulation: Fundamentals, Applications, and Research Directions

Although visionary applications of molecular communication (MC), such as long-term continuous health monitoring by cooperative in-body nanomachines, have been proposed, MC is still in its infancy when it comes to practical implementation. In particular, long-term experiments and applications face issues such as depletion of signaling molecules (SMs) at the transmitter (TX) and inter-symbol interference (ISI) at the receiver (RX). To overcome these practical challenges, a new class of SMs with switchable states seems to be promising for future MC applications. In this work, we provide an overview of existing switchable SMs, and classify them according to their properties. Furthermore, we highlight how switchable SMs can be utilized as information carriers for media modulation. In addition, we present theoretical and experimental results for an end-to-end MC system employing the green fluorescent protein variant "Dreiklang" (GFPD) as switchable SM. Our experimental results show, for the first time, successful information transmission in a closed-loop pipe system using media modulation. Finally, we discuss media modulation specific challenges and opportunities.Comment: 7 pages, 6 figures. This work has been accepted for publication in IEEE Communications Magazin

Comparing validation of four ELISAsystems for detection of Salmonella Derby- and Salmonella Infantis-infected pigs

The objective of this study was the comparative evaluation of four indirect Salmonella ELISA tests at study time approved in Germany to detect Salmonella infection in pigs. Three tests are based on a LPS-antigen mix and directed against specific IgG antibodies. The fourth test is based on a purified S. Typhimurium whole-cell lysate antigen and discriminates between Salmonella- specific IgM-, IgA-, and IgG- antibodies. In a longitudinal study, two groups of six weeks old hybrid piglets were orally infected with a porcine S. Infantis or S. Derby strain. Clinical and bacteriological parameters were monitored weekly during an observation period of 130 days after infection and serum samples were investigated in parallel with the respective ELISAs. Apparently, the LPS-based ELISA systems used in this study failed to recognize S. Infantis-infected pigs although those animals shed the pathogen in high amounts throughout the study until day 81 post infection (p. i.). In contrast, the isotype-specific Salmonella Typhimurium whole-cell-lysate based ELISA was capable of detecting Salmonella-infected pigs from day ten p. i. at all tested serotypes and revealed the highest sensitivity in detection of S. Infantis- infected pigs. Furthermore, it became apparent that the often used surveillance cut-off value of 40 OD% is not appropriate for intra-vitam detection of S. Infantis- and S. Derbyinfected pigs. In contrast, the cut-off values of the ELISAs given by the suppliers result in considerable higher detection rates

Predicting the influence of a p2-symmetric substrate on molecular self-organization with an interaction-site model

An interaction-site model can a priori predict molecular selforganisation on a new substrate in Monte Carlo simulations. This is experimentally confirmed with scanning tunnelling microscopy on Fre´chet dendrons of a pentacontane template. Local and global ordering motifs, inclusion molecules and a rotated unit cell are correctly predicted

The historical development of zoo elephant survivorship

In the discussion about zoo elephant husbandry, the report of Clubb et al. (2008, Science 322: 1649) that zoo elephants had a “compromised survivorship” compared to certain non-zoo populations is a grave argument, and was possibly one of the triggers of a large variety of investigations into zoo elephant welfare, and changes in zoo elephant management. A side observation of that report was that whereas survivorship in African elephants (Loxodonta africana) improved since 1960, this was not the case in Asian elephants (Elephas maximus). We used historical data (based on the Species360 database) to revisit this aspect, including recent developments since 2008. Assessing the North American and European populations from 1910 until today, there were significant improvements of adult (≥10 years) survivorship in both species. For the period from 1960 until today, survivorship improvement was significant for African elephants and close to a significant improvement in Asian elephants; Asian elephants generally had a higher survivorship than Africans. Juvenile (<10 years) survivorship did not change significantly since 1960 and was higher in African elephants, most likely due to the effect of elephant herpes virus on Asian elephants. Current zoo elephant survivorship is higher than some, and lower than some other non-zoo populations. We discuss that in our view, the shape of the survivorship curve, and its change over time, are more relevant than comparisons with specific populations. Zoo elephant survivorship should be monitored continuously, and the expectation of a continuous trend towards improvement should be met

Anticancer phototherapy using activation of E-combretastatins by two-photon–induced isomerization

The photoisomerization of relatively nontoxic E-combretastatins to clinically active Z-isomers is shown to occur in solution through both one- and two-photon excitations at 340 and 625 nm, respectively. The photoisomerization is also demonstrated to induce mammalian cell death by a two-photon absorption process at 625 nm. Unlike conventional photodynamic therapy (PDT), the mechanism of photoisomerization is oxygen- independent and active in hypoxic environments such as in tumors. The use of red or near-infrared (NIR) light for two-photon excitation allows greater tissue penetration than conventional UV one-photon excitation. The results provide a baseline for the development of a novel phototherapy that overcomes nondiscriminative systemic toxicity of Z-combretastatins and the limitations of PDT drugs that require the presence of oxygen to promote their activity, with the added benefits of two-photon red or NIR excitation for deeper tissue penetration

Do self-reported hearing and visual impairments predict longitudinal dementia in older adults?

Background Sensory impairments have been associated with dementia in older adults. However, the contribution of different impairments and how they interact in the development of dementia is not clear. We examined the independent and interaction effects of hearing impairment (HI) and visual impairment (VI) on incident dementia. Design Multi-centric population-based prospective cohort study. Setting Data were taken from the AgeDifferent.de platform, pooling participants aged 75 and older from the German LEILA75+ and AgeCoDe/AgeQualiDe cohorts. Participants Older adults (N = 3497) with mean age 79.8 years, 67.2% female. Measurements Standardized interviews and questionnaires were used to assess self-reported HI and VI at baseline and all-cause dementia in 9 follow-ups, spanning over 20 years. Methods Competing risk regression models were conducted to test the main and interaction effects of HI and VI on dementia incidence, adjusting for established risk factors of dementia and accumulated mortality. Results HI and VI at baseline were reported by 30.3% and 16.6% of individuals, respectively. Adjusting for baseline information on sociodemographics, substance use, cognitive functioning and morbidity, and controlling for accumulated mortality risk, HI (sHR 1.16, 95% CI 1.04–1.30, p = 0.011) but not VI (sHR 1.07, 95% CI 0.90–1.28, p = 0.462) was significantly associated with incident dementia. There was no interaction between HI and VI (sHR 1.09, 95% CI 0.81–1.46, p = 0.567). Conclusions Hearing impairment is associated with an increased incidence of all-cause dementia in older adults. There is no excess risk or risk compensation through the additional presence or absence of visual impairment. Early prevention measures for hearing impairment might help to reduce the long-term risk of dementia