The accuracy of a diagnostic test is often expressed using a pair of measures: sensitivity (proportion of test positives among all individuals with target condition) and specificity (proportion of test negatives among all individuals without target condition). If the outcome of a diagnostic test is binary, results from different studies can easily be summarized in a meta-analysis. However, if the diagnostic test is based on a discrete or continuous measure (e.g., a biomarker), several cut-offs within one study as well as among different studies are published. Instead of taking all information of the cut-offs into account in the meta-analysis, a single cut-off per study is often selected arbitrarily for the analysis, even though there are statistical methods for the incorporation of several cut-offs. For these methods, distributional assumptions have to be met and/or the models may not converge when specific data structures occur. We propose a semiparametric approach to overcome both problems. Our simulation study shows that the diagnostic accuracy is under-estimated, although this underestimation in sensitivity and specificity is relatively small. The comparative approach of Steinhauser et al. is better in terms of coverage probability, but may lead to convergence problems. In addition to the simulation results, we illustrate the application of the semiparametric approach using a published meta-analysis for a diagnostic test differentiating between bacterial and viral meningitis in children.

Methods for standard meta-analysis of diagnostic test accuracy studies are well established and understood. For the more complex case in which studies report test accuracy across multiple thresholds, several approaches have recently been proposed. These are based on similar ideas, but make different assumptions. In this article, we apply four different approaches to data from a recent systematic review in the area of nephrology and compare the results. The four approaches use: a linear mixed effects model, a Bayesian multinomial random effects model, a time-to-event model and a nonparametric model, respectively. In the case study data, the accuracy of neutrophil gelatinase-associated lipocalin for the diagnosis of acute kidney injury was assessed in different scenarios, with sensitivity and specificity estimates available for three thresholds in each primary study. All approaches led to plausible and mostly similar summary results. However, we found considerable differences in results for some scenarios, for example, differences in the area under the receiver operating characteristic curve (AUC) of up to 0.13. The Bayesian approach tended to lead to the highest values of the AUC, and the nonparametric approach tended to produce the lowest values across the different scenarios. Though we recommend using these approaches, our findings motivate the need for a simulation study to explore optimal choice of method in various scenarios.

BACKGROUND:In the past years, it became apparent that health status and performance differ considerably within dairy farms in Northern Germany. In order to obtain clues with respect to possible causes of these differences, a case-control study was performed. Case farms, which showed signs of health and performance problems, and control farms, which had none of these signs, were compared. Risk factors from different areas such as health management, housing, hygiene and nutrition were investigated as these are known to be highly influential. The aim of this study was to identify major factors within these areas that have the strongest association with health and performance problems of dairy herds in Northern Germany.RESULTS:In the final model, a lower energy density in the roughage fraction of the diet, more pens with dirty lying areas and a low ratio of cows per watering spaces were associated with a higher risk for herd health problems. Moreover, case farms were affected by infections with intestinal parasites, lungworms, liver flukes and Johne's Disease numerically more often than control farms. Case farms more often had pens with raised cubicles compared to the deep bedded stalls or straw yards found in control farms. In general, the hygiene of the floors and beddings was worse in case farms. Concerning nutrition, the microbiological and sensory quality of the provided silages was often insufficient, even in control farms. Less roughage was provided to early lactating cows and the feed was pushed to the feeding fence less frequently in case farms than in control farms.CONCLUSIONS:The results show that milk yield and health status were associated with various factors from different areas stressing the importance of all aspects of management for good animal health and performance. Moreover, this study confirmed well-known risk factors for health problems and performance losses. These should better be taken heed of in herd health management.

Erratum zu: Bundesgesundheitsbl 2019 https://doi.org/10.1007/s00103-019-02947-5 In der Originalfassung des Artikels finden sich Bezüge auf Rechtsverordnungen, die während des Reviewprozesses außer Kraft gesetzt wurden, sowie zwei sprachliche Inkorrektheiten. Im Abschnitt „Freie Studien und ihre …

Objectives To develop a standard reference broth microdilution method for antimicrobial susceptibility testing (AST) of Arcobacter butzleri. The protocol was subsequently applied to a collection of A. butzleri isolates from different sources. Methods Broth microdilution susceptibility testing was performed on eight A. butzleri isolates in three media: non-supplemented CAMHB, CAMHB + 2% FBS and CAMHB + 5% FBS. The MIC values were read after 24 and 48 h of incubation at 35 ± 2 °C in ambient air. A logistic regression model was used to determine the combination of medium and incubation time yielding the most homogeneous results. Subsequently, the protocol was applied to 65 A. butzleri isolates to determine their MICs of 31 antimicrobial agents. Results The statistical analysis revealed that the most homogeneous MIC values were obtained with CAMHB + 5% FBS and reading of MIC values after 24 h of incubation. The standardized method was successful for AST of all 65 A. butzleri isolates. MIC values were distributed unimodally for most antimicrobial agents. However, one field isolate showed elevated MIC values of gentamicin, streptomycin, tetracycline and trimethoprim/sulfamethoxazole. Conclusions This study presents a new protocol for AST of A. butzleri by broth microdilution and shows the distribution of MIC values of 31 antimicrobial agents for a collection of A. butzleri isolates from different origins.

Antimicrobial resistance in livestock is a matter of general concern. To develop hygiene measures and methods for resistance prevention and control, epidemiological studies on a population level are needed to detect factors associated with antimicrobial resistance in livestock holdings. In general, regression models are used to describe these relationships between environmental factors and resistance outcome. Besides the study design, the correlation structures of the different outcomes of antibiotic resistance and structural zero measurements on the resistance outcome as well as on the exposure side are challenges for the epidemiological model building process. The use of appropriate regression models that acknowledge these complexities is essential to assure valid epidemiological interpretations. The aims of this paper are (i) to explain the model building process comparing several competing models for count data (negative binomial model, quasi-Poisson model, zero-inflated model, and hurdle model) and (ii) to compare these models using data from a cross-sectional study on antibiotic resistance in animal husbandry. These goals are essential to evaluate which model is most suitable to identify potential prevention measures. The dataset used as an example in our analyses was generated initially to study the prevalence and associated factors for the appearance of cefotaxime-resistant Escherichia coli in 48 German fattening pig farms. For each farm, the outcome was the count of samples with resistant bacteria. There was almost no overdispersion and only moderate evidence of excess zeros in the data. Our analyses show that it is essential to evaluate regression models in studies analyzing the relationship between environmental factors and antibiotic resistances in livestock. After model comparison based on evaluation of model predictions, Akaike information criterion, and Pearson residuals, here the hurdle model was judged to be the most appropriate model.

In the last two decades, an increase in chronic herd health problems of hitherto unknown causes was reported in northwest Germany. For further aetiological clarification, the objective of this project was to reveal differences between herds with good and chronically depressed herd health statuses regarding the symptoms at the herd Ievel.Therefore, a case-control study was conducted. The case farms (case 1 farms: no vaccination against clostridia, n = 45; case 2 farms: multi-clostridia vaccination applied, n = 47) must have fulfilled at least three of the following five criteria: decreased milk yield, increased mortality, increased culling rate, increased number of downer cows, and farmers' impressions of having herd health problems. The control farms (n = 47) did not fulfil any of these criteria. Multifactorial logistic regression modelling revealed that both types of case farms had fewer overconditioned cows, more cows with skin lesions on their legs, and a lower cow comfort quotient than the control farms. Moreover, the case 1 farms had a longer calving interval, and the cows had more frequently a soiled udder compared to control farms. The case 2 farms had a lower cud chewing index than the control farms. The intraherd prevalences of lameness, cachectic cows and skin lesions were very high compared to recommendations, even on most control farms. These results indicate that different factors, e.g. the housing conditions and management, may play an important role in the presumably multifactorial chronic herd health problems. Therefore, additional aetiological research and veterinary services should consider additional information from all areas of herd management.

In this investigation the farm prevalence of cefotaxime-resistant Escherichia coli (CREC) in German broiler farms was evaluated. In total, 59 flocks on 34 broiler farms were sampled in four agricultural regions of Germany. Per broiler flock, three faecal samples, a pair of boot swabs and one dust sample were taken and examined for the presence of CREC. After pre-enrichment of sample material in Luria-Bertani-broth, the broth was streaked onto MacConkey agar containing 1mg/l cefotaxime (CTX). CREC isolates were detected in at least one sample from each flock resulting in a farm prevalence of 100%. The proportion of positive samples was high in all three sample types. Of 177 collective faecal samples 81.9% were positive, of 59 boot swabs and 59 dust samples 79.7% and 62.7% were positive. In conclusion, the prevalence of broiler farms with cefotaxime-resistant E. coli in Germany is very high. We suggest that the analysis of collective faecal samples is sufficient to determine the CREC farm status. In addition to other studies our study supports the finding that cefotaxime resistance is a good proxy for the presence of ESBL- or plasmidic AmpC-beta-lactamases.

The objective was to establish and standardise a broth microdilution susceptibility testing method for porcine Bordetella (B.) bronchiseptica. B. bronchiseptica isolates from different geographical regions and farms were genotyped by macrorestriction analysis and subsequent pulsed-field gel electrophoresis. One reference and one type strain plus two field isolates of B. bronchiseptica were chosen to analyse growth curves in four different media: cation-adjusted Mueller-Hinton broth (CAMHB) with and without 2% lysed horse blood, Brain-Heart-Infusion (BHI), and Caso broth. The growth rate of each test strain in each medium was determined by culture enumeration and the suitability of CAMHB was confirmed by comparative statistical analysis. Thereafter, reference and type strain and eight epidemiologically unrelated field isolates of B. bronchiseptica were used to test the suitability of a broth microdilution susceptibility testing method following CLSI-approved performance standards given in document VET01-A4. Susceptibility tests, using 20 antimicrobial agents, were performed in five replicates, and data were collected after 20 and 24 hours incubation and statistically analysed. Due to the low growth rate of B. bronchiseptica, an incubation time of 24 hours resulted in significantly more homogeneous minimum inhibitory concentrations after five replications compared to a 20-hour incubation. An interlaboratory comparison trial including susceptibility testing of 24 antimicrobial agents revealed a high mean level of reproducibility (97.9%) of the modified method. Hence, in a harmonization for broth microdilution susceptibility testing of B. bronchiseptica, an incubation time of 24 hours in CAMHB medium with an incubation temperature of 35°C and an inoculum concentration of approximately 5 x 105 cfu/ml was proposed.

Purpose We investigated different evaluation strategies for bioequivalence trials with highly variable drugs on their resulting empirical type I error and empirical power. The classical ‘unscaled’ crossover design with average bioequivalence evaluation, the Add-on concept of the Japanese guideline, and the current ‘scaling’ approach of EMA were compared. Methods Simulation studies were performed based on the assumption of a single dose drug administration while changing the underlying intra-individual variability. Results Inclusion of Add-on subjects following the Japanese concept led to slight increases of the empirical α-error (≈7.5%). For the approach of EMA we noted an unexpected tremendous increase of the rejection rate at a geometric mean ratio of 1.25. Moreover, we detected error rates slightly above the pre-set limit of 5% even at the proposed ‘scaled’ bioequivalence limits. Conclusions With the classical ‘unscaled’ approach and the Japanese guideline concept the goal of reduced subject numbers in bioequivalence trials of HVDs cannot be achieved. On the other hand, widening the acceptance range comes at the price that quite a number of products will be accepted bioequivalent that had not been accepted in the past. A two-stage design with control of the global α therefore seems the better alternative.

The European Union ban on conventional battery cages had far-reaching consequences for animal welfare and the economic success of egg production. The aim of this study was to identify the main influences on economic success of farms keeping laying hens in aviaries or small-group housing systems. The results confirmed the importance of productivity measures (i.e. conversion rate), whereas farm size was of consequence for small-group housing systems, only. Dependent on the housing system, management decisions (i.e. daily inspection time, feeding of self-mixed feed) accounted for a considerable part of economic effectiveness. Furthermore, the number of years of experience of the farmer with the housing system seemed to influence economic productivity. Positive effects of selling graded eggs (instead of bulk-ware) showed the relevance of market outlets on economic profitability. The study indicated that small group housing systems might profit from selling their products directly to the consumer. The results show that decisions of politics and the retail sector as well as consumer choices have an influential effect on the economic success of egg production.

Epidemiological and experimental studies suggest that exposure to ultrafine particles (UFP) might aggravate the allergic inflammation of the lung in asthmatics.

After kidney transplantation, immunosuppressive therapy causes impaired cellular immune defense leading to an increased risk of viral complications. Trough level monitoring of immunosuppressants is insufficient to estimate the individual intensity of immunosuppression. We have already shown that virus-specific T cells (Tvis) correlate with control of virus replication as well as with the intensity of immunosuppression. The multicentre IVIST01-trial should prove that additional steering of immunosuppressive and antiviral therapy by Tvis levels leads to better graft function by avoidance of over-immunosuppression (for example, viral infections) and drug toxicity (for example, nephrotoxicity).

BACKGROUND:Maintenance of metal homeostasis is crucial in bacterial pathogenicity as metal starvation is the most important mechanism in the nutritional immunity strategy of host cells. Thus, pathogenic bacteria have evolved sensitive metal scavenging systems to overcome this particular host defence mechanism. The ruminant pathogen Mycobacterium avium ssp. paratuberculosis (MAP) displays a unique gut tropism and causes a chronic progressive intestinal inflammation. MAP possesses eight conserved lineage specific large sequence polymorphisms (LSP), which distinguish MAP from its ancestral M. avium ssp. hominissuis or other M. avium subspecies. LSP14 and LSP15 harbour many genes proposed to be involved in metal homeostasis and have been suggested to substitute for a MAP specific, impaired mycobactin synthesis.RESULTS:In the present study, we found that a LSP14 located putative IrtAB-like iron transporter encoded by mptABC was induced by zinc but not by iron starvation. Heterologous reporter gene assays with the lacZ gene under control of the mptABC promoter in M. smegmatis (MSMEG) and in a MSMEG∆furB deletion mutant revealed a zinc dependent, metalloregulator FurB mediated expression of mptABC via a conserved mycobacterial FurB recognition site. Deep sequencing of RNA from MAP cultures treated with the zinc chelator TPEN revealed that 70 genes responded to zinc limitation. Remarkably, 45 of these genes were located on a large genomic island of approximately 90 kb which harboured LSP14 and LSP15. Thirty-five of these genes were predicted to be controlled by FurB, due to the presence of putative binding sites. This clustering of zinc responsive genes was exclusively found in MAP and not in other mycobacteria.CONCLUSIONS:Our data revealed a particular genomic signature for MAP given by a unique zinc specific locus, thereby suggesting an exceptional relevance of zinc for the metabolism of MAP. MAP seems to be well adapted to maintain zinc homeostasis which might contribute to the peculiarity of MAP pathogenicity.

A cross-sectional study concerning farm prevalence and risk factors for the count of cefotaxime resistant Escherichia coli (E. coli) (CREC) positive samples per sampling group on German fattening pig farms was performed in 2011 and 2012. Altogether 48 farms in four agricultural regions in the whole of Germany were investigated. Faecal samples, boot swabs and dust samples from two sampling groups per farm were taken and supplemental data were collected using a questionnaire. On 85% of the farms, at least one sample contained cefotaxime resistant E. coli colonies. Positive samples were more frequent in faeces (61%) and boot swabs (54%) than in dust samples (11%). Relevant variables from the questionnaire were analysed in a univariable mixed effect Poisson regression model. Variables that were related to the number (risk) of positive samples per sampling group with a p-value <0.2 were entered in a multivariable model. This model was reduced to statistically significant variables via backward selection. Factors that increased the risk for positive samples involved farm management and hygienic aspects. Farms that had a separate pen for diseased pigs had a 2.8 higher mean count of positive samples (95%-CI [1.71; 4.58], p=0.001) than farms without an extra pen. The mean count was increased on farms with under-floor exhaust ventilation compared to farms with over floor ventilation (2.22 [1.43; 3.46], p=0.001) and more positive samples were observed on farms that controlled flies with toxin compared to farms that did not (1.86 [1.24; 2.78], p=0.003). It can be concluded, that CREC are wide spread on German fattening pig farms. In addition the explorative approach of the present study suggests an influence of management strategies on the occurrence of cefotaxime resistant E. coli.

Purpose The objective was to study the association of different timings of intrapartum interventions with labour duration and mode of birth. Methods A longitudinal cohort study of 2,090 nulliparae and 1,873 multiparae with a singleton in cephalic presentation was conducted. We assessed the association between, on the one hand, the timing of augmentation with oxytocin, neuraxial analgesia and amniotomy, and, on the other hand, the time to complete dilatation, spontaneous or operative vaginal delivery or caesarean delivery, using a Cox regression model accounting for standard confounders. Results From amniotomy onwards labour was accelerated. In multiparae, amniotomy was associated with an initial 6.6-fold acceleration, decreasing first stage duration until the hazard ratio reached around 3.5, where the intervention was performed 5 h after labour onset; thereafter, acceleration continued with a hazard ratio of around 3. In nulliparae, neuraxial analgesia was associated with a shorter first stage when administered between 7 and 11 h after labour onset; the later it was performed, the less likely was spontaneous birth and the more likely an operative vaginal birth in nulliparae or a caesarean section in multiparae. The start of oxytocin augmentation was associated with acceleration towards both full dilatation and caesarean section during first stage and an increased risk of operative vaginal birth during second stage. The later oxytocin augmentation started, the more likely it was that spontaneous birth would be retarded in multiparous women. Conclusions Applying amniotomy, oxytocin and neuraxial analgesia at their optimal timing may improve the progress and outcome of labour.