Survival of Campylobacter jejuni on beef trimmings during freezing and frozen storage

AIMS: To investigate the survival of two animal isolates of Campylobacter jejuni on beef trimmings during freezing and frozen storage. METHODS AND RESULTS: Meat packs inoculated with 10(3) or 10(6) cfu g(-1) of either strain of C. jejuni were frozen to -18 degrees C, and sampled at regular intervals over 112 d storage to determine Campylobacter numbers and sublethal injury. For both strains and inoculation levels the numbers of Campylobacter decreased in the first 7 d of storage by ca. 0.6-2.2 log cfu g(-1) and then remaining constant over the remainder of the storage trial, with neither isolate exhibiting sublethal injury. CONCLUSIONS: Despite an initially significant decrease in number, these pathogens were able to survive standard freezing conditions in meat, but did not exhibit sublethal injury. SIGNIFICANCE AND IMPACT OF THE STUDY: Strict hygiene and/or the implementation of decontamination technologies are recommended as a means to assure the safety of meat with respect to this pathogen.     

Influence of interactions between temperature,ferric ammonium citrate and glycine betaine on the growth of Listeria monocytogenes in a defined medium

AIMS: To investigate interactions, if any, between temperature, ferric ammonium citrate and glycine betaine on the growth of Listeria monocytogenes in modified Pine's medium (Pine et al. 1989). METHODS AND RESULTS: Modified Pine's medium containing 0, 0.044, 0.088 or 0.176 g l(-1) ferric ammonium citrate, and 0 or 1 mM glycine betaine, was inoculated with each of two L. monocytogenes strains and incubated at 4, 25 or 37 degrees C. The optical density at 600 nm, and cell numbers, were determined at appropriate time intervals. At 4 degrees C, but not other temperatures, increasing ferric ammonium citrate resulted in improved growth in the absence, but not the presence, of glycine betaine. The presence of glycine betaine was inhibitory at 25 and 37 degrees C, but not at 4 degrees C. CONCLUSIONS: Interactions affecting the growth kinetics of L. monocytogenes were apparent between the parameters investigated. SIGNIFICANCE AND IMPACT OF THE STUDY: Limitations on the use of modified Pine's medium, and the significance of iron metabolism at lower temperatures, were revealed.     

Pyrethroid-Resistance and Presence of Two Knockdown Resistance (kdr) Mutations,F1534C and a Novel Mutation T1520I,in Indian Aedes aegypti

Background

Control of Aedes aegypti, the mosquito vector of dengue, chikungunya and yellow fever, is a challenging task. Pyrethroid insecticides have emerged as a preferred choice for vector control but are threatened by the emergence of resistance. The present study reports a focus of pyrethroid resistance and presence of two kdr mutations—F1534C and a novel mutation T1520I, in Ae. aegypti from Delhi, India.

Methodology/Principal Findings

Insecticide susceptibility status of adult-female Ae. aegypti against DDT (4%), deltamethrin (0.05%) and permethrin (0.75%) was determined using WHO''s standard insecticide susceptibility kit, which revealed resistance to DDT, deltamethrin and permethrin with corrected mortalities of 35%, 72% and 76% respectively. Mosquitoes were screened for the presence of kdr mutations including those reported earlier (I1011V/M, V1016G/I, F1534C, D1794Y and S989P), which revealed the presence of F1534C and a novel mutation T1520I. Highly specific PCR-RFLP assays were developed for genotyping of these two mutations. Genotyping using allele specific PCR and new PCR-RFLP assays revealed a high frequency of F1534C (0.41–0.79) and low frequency of novel mutation T1520I (0.13). The latter was observed to be tightly linked with F1534C and possibly serve as a compensatory mutation. A positive association of F1534C mutation with DDT and deltamethrin resistance in Ae. aegypti was established. However, F1534C-kdr did not show significant protection against permethrin.

Conclusions/Significance

The Aedes aegypti population of Delhi is resistant to DDT, deltamethrin and permethrin. Two kdr mutations, F1534C and a novel mutation T1520I, were identified in this population. This is the first report of kdr mutations being present in the Indian Ae. aegypti population. Highly specific PCR-RFLP assays were developed for discrimination of alleles at both kdr loci. A positive association of F1534C mutation with DDT and deltamethrin resistance was confirmed.     

The 'human revolution' in lowland tropical Southeast Asia: the antiquity and behavior of anatomically modern humans at Niah Cave (Sarawak, Borneo)

Recent research in Europe, Africa, and Southeast Asia suggests that we can no longer assume a direct and exclusive link between anatomically modern humans and behavioral modernity (the 'human revolution'), and assume that the presence of either one implies the presence of the other: discussions of the emergence of cultural complexity have to proceed with greater scrutiny of the evidence on a site-by-site basis to establish secure associations between the archaeology present there and the hominins who created it. This paper presents one such case study: Niah Cave in Sarawak on the island of Borneo, famous for the discovery in 1958 in the West Mouth of the Great Cave of a modern human skull, the 'Deep Skull,' controversially associated with radiocarbon dates of ca. 40,000 years before the present. A new chronostratigraphy has been developed through a re-investigation of the lithostratigraphy left by the earlier excavations, AMS-dating using three different comparative pre-treatments including ABOX of charcoal, and U-series using the Diffusion-Absorption model applied to fragments of bones from the Deep Skull itself. Stratigraphic reasons for earlier uncertainties about the antiquity of the skull are examined, and it is shown not to be an 'intrusive' artifact. It was probably excavated from fluvial-pond-desiccation deposits that accumulated episodically in a shallow basin immediately behind the cave entrance lip, in a climate that ranged from times of comparative aridity with complete desiccation, to episodes of greater surface wetness, changes attributed to regional climatic fluctuations. Vegetation outside the cave varied significantly over time, including wet lowland forest, montane forest, savannah, and grassland. The new dates and the lithostratigraphy relate the Deep Skull to evidence of episodes of human activity that range in date from ca. 46,000 to ca. 34,000 years ago. Initial investigations of sediment scorching, pollen, palynomorphs, phytoliths, plant macrofossils, and starch grains recovered from existing exposures, and of vertebrates from the current and the earlier excavations, suggest that human foraging during these times was marked by habitat-tailored hunting technologies, the collection and processing of toxic plants for consumption, and, perhaps, the use of fire at some forest-edges. The Niah evidence demonstrates the sophisticated nature of the subsistence behavior developed by modern humans to exploit the tropical environments that they encountered in Southeast Asia, including rainforest.     

Feeding by numbers: an ethnographic study of how breastfeeding women understand their babies' weight charts

Background

Assisting mothers to breastfeed is not easy when babies experience difficulties. In a neonatal intensive care unit (NICU), nurses often help mothers by using hands-on-breast without their permission. Little is known about how mothers feel about this unusual body touching. To gain more knowledge from mothers who lived through this experience, this hands-on practice was studied in a NICU in Sweden.

Methods

Between January and June 2001, in-depth interviews were conducted with ten mothers of preterm or sick term infants and all of them experienced the hands-on approach. In this research, Radnitzky's seven principles of hermeneutic interpretation were applied in order to interpret the meaning of mothers' responses. This article presents results related to the period of initiation of breastfeeding. This qualitative study was based on a combination of the models of Gustafsson, Orem, and Aarts' Marte Meo.

Results

Five main themes were identified: Insult to integrity, Manipulating the baby, Understanding and adjustment, Breasts as objects, Alternatives to this practice. Hands-on help in the breastfeeding situation was experienced as unpleasant and the women experienced their breasts as objectified. The mothers accepted the hands-on help given by nursing staff, even though they considered it unpleasant. Most mothers expressed a need for assistance when starting breastfeeding, but could not suggest any alternative to hands-on help such as demonstrating with an artificial breast and a doll.

Conclusion

The study provides information about how mothers experience unexpected hands-on help with breastfeeding in a NICU, which has not been described previously. Since most mothers in this study regarded this behavior as unpleasant and not helpful mostly because it was unexpected and unexplained, it would be important to either explain beforehand to mothers what type of physical approach could be attempted on their body or better, to avoid this type of approach completely.     

Characterisation of Curli Production, Cell Surface Hydrophobicity, Autoaggregation and Attachment Behaviour of Escherichia coli O157

Escherichia coli O157 are an important group of foodborne pathogens with the ability to attach to materials commonly used in food processing environments such as slightly hydrophilic stainless steel. The aim of this study was to characterise six E. coli isolates, including five E. coli O157, for curli production, autoaggregation, hydrophobicity and attachment to highly hydrophilic glass and hydrophobic Teflon^®. Curli production and autoaggregation were determined using absorbance assays; hydrophobicity by bacterial adherence to hydrocarbons, hydrophobic interaction chromatography and contact angle measurements; and attachment using epifluorescence microscopy. Curli production varied between strains and for some strains correlated with autoaggregation. Curli production correlated with decreased hydrophobicity for two strains. Four of the six isolates increased attachment to glass, but decreased attachment to Teflon^® with increased curli production. In contrast, one of the six isolates decreased attachment to glass, but increased attachment to Teflon^® with increasing curli production. Curli production by the remaining isolate did not correlate with hydrophobicity or attachment. Attachment of some E. coli, including E. coli O157, to abiotic surfaces may be influenced by curli production, autoaggregation and hydrophobicity. However, for other strains, a variety of factors may be of greater influence on these properties and ability to attach to abiotic surfaces. This study highlights the complexity of bacterial surface properties and their relationship with bacterial attachment.     

Thermal energy conduction in a honey bee comb due to cell-heating bees

Theoretical analysis and numerical calculations are performed to characterize the unsteady two-dimensional conduction of thermal energy in an idealized honey bee comb. The situation explored corresponds to a comb containing a number of brood cells occupied by pupae. These cells are surrounded by other cells containing pollen which, in turn, are surrounded (above) by cells containing honey and (below) by vacant cells containing air. Up to five vacant cells in the brood region can be occupied by cell-heating bees which, through the isometrical contraction of their flight muscles, can generate sufficient energy to raise their body temperatures by a few degrees. In this way, the cell-heating bees alter the heat flux and temperature distributions in the brood region so as to maintain conditions that benefit the pupae. The calculations show that the number of cell-heating bees significantly affects the magnitude, time rate of change, and spatial distribution of temperature throughout the comb. They also reveal a vertically aligned asymmetry in the spatial distribution of temperature that is due to the large heat capacity and thermal conductivity of honey relative to air, whereby air-filled cells experience larger temperature increases than honey-filled cells. Analysis shows that convection and radiation represent negligible modes of thermal energy transfer at all levels in the problem considered. Also, because of its small thickness, the wax wall of a comb cell simultaneously presents negligible resistance to conduction heat transfer normal to it and very large resistance along it. As a consequence the walls of a cell play no thermal role, but simply serve as mechanical supports for the materials they contain.     

Effects of long-term fixation on histological quality of undecalcified murine bones embedded in methylmethacrylate

While long-term fixation and storage of specimens is common and useful for many research projects, it is particularly important for space flight investigations where samples may not be returned to Earth for several months (International Space Station) or years (manned mission to Mars). We examined two critical challenges of space flight experimentation: the effect of long-term fixation on the quality of mouse bone preservation and the preservation of antigens and enzymes for both histochemical and immunohistochemical analyses, and how the animal/sample processing affects the preservation. We show that long-term fixation minimally affects standard histological staining, but that enzyme histochemistry and immunolabeling are greatly compromised. Further, we demonstrate that whole animal preservation is not as suitable as whole leg or stripped leg preservation for long-term fixation and all histological analyses. Overall, we recommend whole leg processing for long-term storage of bone specimens in fixative prior to embedding in plastic for histological examination.