Raw and processed fish show identical Listeria monocytogenes genotypes with pulsed-field gel electrophoresis

A total of 257 raw fish samples at two different sites were examined for the presence of Listeria monocytogenes. The prevalence of L. monocytogenes was 4%. From 11 positive samples, nine different L. monocytogenes pulsed-field gel electrophoresis genotypes were recovered. From nine pulsotypes recovered from raw fish and 32 pulsotypes shown by 101 fish product isolates, two raw fish and fish product pulsotypes were indistinguishable from each other. Although the prevalence of L. monocytogenes in raw fish is low, the range of L. monocytogenes strains entering the processing plant in large amounts of raw material is wide. This indicates that the raw material is an important initial contamination source of L. monocytogenes in fish processing plants. This postulation is supported by the identical pulsotypes recovered from both raw and processed fish. Some L. monocytogenes strains entering a plant may thus contaminate and persist in the processing environment, causing recurrent contamination of the final products via processing machines.     

Prevalence and genetic diversity of Listeria monocytogenes in the tonsils of pigs

This study was set up to establish the prevalence of Listeria monocytogenes in the tonsils of sows and fattening pigs from five Finnish slaughterhouses and to evaluate the genetic similarity of L. monocytogenes strains isolated from the tonsils. A total of 271 pig tonsils (132 tonsils from fattening pigs and 139 from sows) from five different slaughterhouses in various parts of Finland were studied from June 1999 to March 2000. Overall, 14 and 4% of pig tonsils harbored L. monocytogenes and Listeria innocua, respectively. The prevalence of L. monocytogenes in tonsils of fattening pigs (22%) was significantly higher than in sows (6%). The isolates (n = 38) recovered from tonsils showed a wide genetic diversity by means of 24 different pulsed-field gel electrophoresis (PFGE) types presented by the strains. Moreover, in numerical analyses of restriction patterns, no association was found between the clustering of strains and the slaughterhouses, and strains showing a similar PFGE type were recovered from pigs of different slaughterhouses. The high prevalence of L. monocytogenes showing various PFGE types in the tonsils of pigs could indicate a potential source of contamination of pluck sets, carcasses, and the slaughterhouse environment and of subsequent processing steps.     

Prevalence of Listeria monocytogenes in, and microbiological and sensory quality of, rainbow trout, whitefish, and vendace roes from Finnish retail markets

The prevalence of Listeria monocytogenes in retail roe, as well as the microbiological and sensory qualities of the roe, were studied for three fish species under three different storage conditions. A total of 147 Finnish rainbow trout (Oncorhynchus mykiss), whitefish (Coregonus lavaretus), vendace (Coregonus albula), and burbot (Lota lota) roe samples were bought fresh, frozen, or frozen-thawed from Finnish retail markets. The overall prevalence of L. monocytogenes was 5%; however, the prevalence of the pathogen in fresh roe was 18%. Fresh-bought roe tested positive for Listeria spp. and for L. monocytogenes, respectively, 5 and 20 times as often as did frozen and frozen-thawed roe products combined. The microbiological quality (analyzed as total aerobic heterotrophic bacteria and coliform bacteria) of 78% of the roe samples was unacceptable. Frozen roe samples were found to have the best microbiological quality. According to the results of a sensory evaluation, at least one sensory attribute (appearance, odor freshness, texture, and freshness of taste) was unacceptable for 29% of the roe samples studied. The sensory quality of roe samples bought fresh was better than that of roe samples bought frozen or frozen-thawed. From the results of this study, it is concluded that both the microbiological and the sensory qualities of roe at the retail level need to be improved.     

Surgical smoke simulation study: Physical characterization and respiratory protection

Exposure of operating room (OR) personnel to surgical smoke, a unique aerosol generated from the common use of electrocautery during surgical procedures, is an increasing health risk concern. The main objective of this simulation study was to characterize the surgical smoke exposure in terms of the particle number concentration and size distribution in a human breathing zone. Additionally, the performance of respiratory protective devices designed for ORs was examined using two commercially available N95 facepiece filtering respirators (FFRs) as well as the same FFRs modified with new faceseal technology. The tests were conducted in an OR-simulating exposure chamber with the surgical smoke generated by electrocautery equipment applied to animal tissue and measured in the breathing zone with four aerosol spectrometers. The simulated workplace protection factor of each tested respirator was determined for ten subjects by measuring the total aerosol concentrations inside and outside of a respirator. The peak of the particle size distribution was in a range of 60–150 nm. The concentration of particles generated during the simulated surgical procedure significantly exceeded the background concentration under all tested air exchange conditions. The data suggest that wearing N95 filtering facepiece respirators significantly decreased the human exposure to surgical smoke. The new faceseal technology provided significantly higher respiratory protection than the commercial N95 FFRs.

Copyright © 2018 American Association for Aerosol Research     

Mathematical models of plant-soil interaction

In this paper, we set out to illustrate and discuss how mathematical modelling could and should be applied to aid our understanding of plants and, in particular, plant-soil interactions. Our aim is to persuade members of both the biological and mathematical communities of the need to collaborate in developing quantitative mechanistic models. We believe that such models will lead to a more profound understanding of the fundamental science of plants and may help us with managing real-world problems such as food shortages and global warming. We start the paper by reviewing mathematical models that have been developed to describe nutrient and water uptake by a single root. We discuss briefly the mathematical techniques involved in analysing these models and present some of the analytical results of these models. Then, we describe how the information gained from the single-root scale models can be translated to root system and field scales. We discuss the advantages and disadvantages of different mathematical approaches and make a case that mechanistic rather than phenomenological models will in the end be more trustworthy. We also discuss the need for a considerable amount of effort on the fundamental mathematics of upscaling and homogenization methods specialized for branched networks such as roots. Finally, we discuss different future avenues of research and how we believe these should be approached so that in the long term it will be possible to develop a valid, quantitative whole-plant model.     

Analysis of airborne actinomycete spores with fluorogenic substrates

The reactions between seven fluorogenic substrates and different groups of enzymes, esterases, lipases, phosphatases, and dehydrogenases, were studied in a search for a new method for the detection of actinomycete spores. Fluorescence measurement was chosen as a fast and sensitive method for microbial analysis. The focus of the research was on the spores of important air contaminants: Streptomyces albus and Thermoactinomyces vulgaris. For the measurement of the enzymatic activity, the chosen fluorogenic substrate was added to a mixture of spores and nutrient media, and the resulting fluorescence was measured with a spectrofluorometer. Fluorogenic substrates were found to show enzymatic activities even for dormant spores. Comparison of the enzymatic activities of dormant spores with those of vegetative cells showed similarity of the enzymatic profiles but higher activity for vegetative cells. The increase of enzymatic activity from dormant spores to vegetative cells was not linear but fluctuating. The largest fluctuations were found after 4 to 5 h of incubation. The enzymatic activities of S. albus were 10 to 50 times lower than those of T. vulgaris, except for the dehydrogenase activity, which was seven times higher. These results indicate that analysis with fluorogenic substrates has the potential for becoming a fast and sensitive method for the enumeration and identification of airborne actinomycete spores.     

The role of task-avoidant and task-focused behaviors in the development of reading and mathematical skills during the first school year: A cross-lagged longitudinal study.

The aim of the study was to examine whether children's achievement strategies would prospectively predict their improvement in reading and mathematical skills during the 1st school year, or whether it is rather the skills that predict the change in their achievement strategies. One hundred five 6- to 7-year-old children were investigated 3 times during the 1st school year. Each time, their reading and mathematical skills were tested, and their task-avoidant versus task-focused behaviors were rated by their classroom teacher. In addition, their overall cognitive competence was measured before entry into school. The maladaptive strategies children deployed in the classroom and their reading skills formed a cumulative developmental cycle. On the one hand, task-avoidant behaviors decreased subsequent improvement in reading skills, and on the other hand, a low level of reading skills increased subsequent task-avoidant behaviors. Although a low level of mathematical skills increased subsequent task avoidance, the mathematical skills were not influenced by it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fully microfabricated and integrated SU-8-based capillary electrophoresis-electrospray ionization microchips for mass spectrometry

We present a fully microfabricated and monolithically integrated capillary electrophoresis (CE)-electrospray ionization (ESI) chip for coupling with high-throughput mass spectrometric (MS) analysis. The chips are fabricated fully of a negative photoresist SU-8 by a standard lithographic process which enables straightforward batch fabrication of multiple chips with precisely controlled dimensions and, thus, reproducible analytical performance from chip to chip. As the coaxial sheath flow interface is patterned as an integral part of the SU-8 chip, the fluidic design is dead-volume-free. No significant peak broadening occurs so that very narrow peak widths (down to 2-3 s) are obtained. The sheath flow interface also enables comprehensive optimization of both the CE and the ESI conditions separately so that the same chip design is adaptable to diverse analytical conditions. Plate numbers of the order of 105 m-1 and good resolution are routinely reached for small molecules and peptides within a 2 cm separation length and a typical cycle time of only 30-90 s per sample. In addition, a limit of detection of 100 nM corresponding to a total amount of only 4.5 amol (per injection volume of 45 pL) and excellent quantitative linearity (R2 = 0.9999; 100 nM to 100 microM) were obtained in small-molecule analysis using verapamil as a test compound. The quantitative repeatability was proven good (8.5-21.4% relative standard deviation, peak area) also for the other drug substances and peptides tested.