Incidence of toxigenic Escherichia coli in soft cheese made with raw or pasteurized milk

The role of cellular Na+ accumulation in acetylcholine-induced desensitization was investigated in guinea pig ileal longitudinal muscle. Desensitization was induced by the pretreatment with acetylcholine (10(-4) M, 30 min) and was expressed by the rightward shift in the concentration-response curve for acetylcholine after the treatment. The same treatment with acetylcholine caused accumulation of cellular Na+ that amounted to about 3.5-fold of the control level. To study the relationship between the gain of cellular Na+ and the development of desensitization, we treated the muscle strips with acetylcholine under the condition in which the external Na+ concentration ranged from zero to 149.2 mM. The result showed that cellular Na+ content is closely related to the extent of desensitization; that is, desensitization was at the lowest level when acetylcholine induced no increase in cellular Na+, while desensitization developed in proportion to the increase in cellular Na+ content. However, when cellular Na+ was increased by another method (by the treatment with ouabain), the inhibition of the acetylcholine response was far less than that observed in the case of desensitization. We concluded that both muscarinic stimulation and the accompanying accumulation of cellular Na+ are required for desensitization to occur in full. This desensitization could be the result of a muscarinic stimulated and cellular Na+-dependent mechanism.     

Sporadic case of listeriosis associated with the consumption of a Listeria monocytogenes-contaminated ''Camembert'' cheese

Listeria monocytogenes is an intracellular gram-positive organism responsible for severe infections in both humans and animals. Whereas the food-borne transmission of listeriosis was demonstrated in several outbreaks, most cases of listeriosis occur sporadically and are rarely linked with consumption of contaminated foods. In this paper a case of septicaemia with L. monocytogenes in a 73-year-old immunocompromised man is described. Evidence for the association of this case of listeriosis with the consumption of a contaminated 'Camembert' cheese is provided by serotyping, esterase typing, DNA macrorestriction patterns analysis and level of virulence of the isolated strains for mice.     

Quantitative microbiological risk assessment: principles applied to determining the comparative risk of salmonellosis from chicken products

Ensuring microbiological safety requires identification of realistic hazards and the means of controlling them. The risk assessment framework proposed by Codex Alimentarius allows the impact of raw materials and processes to be appreciated, and the output can be used for risk management and communication. Mathematical models allow numerical information to be processed by a computer and interpreted to give quantitative or comparative risk assessments. In this example, models have been put together according to the Codex. Alimentarius principles, providing a quantitative risk assessment (QRA) of salmonellosis from frozen poultry products. This model-based QRA takes into account three types of information: occurrence and distribution of the agent, sensitivity of populations to infection (e.g., normal or susceptible), and the effect of cooking (in the factory or home) on concentration of the agent and hence risks of infection after product consumption. It only demonstrates the impact of a single-process step (heating) and the effect of changes in population sensitivity, raw material quality, and cooking regime on the final risk. The effects of growth and recontamination are not considered. To aid risk communication, the models have been visualized by means of displays and slider controls on a computer screen because effective communication is essential to encourage manufacturers and their product designers to assess the effect of changes in processing or materials on risk.     

Effect of psychrotrophic bacteria from raw milk on milk proteins and stability of milk proteins to ultrahigh temperature treatment

The effects of psychrotroph growth in raw milk on proteins of mils and on the response of milk proteins to heat treatments with ultrahigh temperature were studied. Ten gram-negative psychrotrophs isolated from raw milk readily attacked raw milk proteins. Kappa- and beta-casein were most susceptible although some of the isolates also attacked the whey proteins. Detectable proteolysis did not require large psychrotroph populations. A 10 to 20% decrease in kappa-casein during 2 days at 5 C accompanied growth of one isolate to a population of only 10,000/ml. Growth of psychrotrophs in raw milk predisposed the proteins to deleterious effects of ultrahigh temperature treatments. Ultrahigh temperature treatment by direct steam injection had little effect on raw milk caseins and decreased alpha-lactalbumin and beta-lactoglobulin by 21% and 34%, respectively. Milk that had undergone proteolysis exhibited decreased detectable kappa-, beta-, and alphas-caseins and increased loss of beta-lactoglobulin as a result of ultrahigh temperature treatment. Milk suffering extensive kappa-casein degradation coagulated during ultrahigh temperature treatment. Coagulation during or shortly after heating increased with severity of heat treatment and size of psychrotroph population.     

Testing of raw milk for tetracycline residues

A newly improved Bacillus calidolactis tube diffusion test and two postscreening test systems--a receptor assay (Charm HVS; Charm Sciences, Inc., Malden, MA) and a newly developed Bacillus cereus ATCC 11778 mycoides test system--were evaluated for the detection and identification of tetracycline residues using 973 samples of bulk milk taken at random in The Netherlands. All milk samples were assayed with the B. calidolactis tube and the receptor test. The milk samples testing as suspect or positive with one or both of the test systems were analyzed with HPLC (limit of detection, 10 ng/ml) and the recently developed B. cereus test system. The B. calidolactis tube diffusion test detected tetracycline residues > 45 ng/ml in milk. With the B. cereus test plate, residues of oxytetracycline and tetracycline of > 30 ng/ml milk were detected; for chlortetracycline and doxycycline, the detection limit was 10 ng/ml. Raw milk exhibiting inhibition diameters of < 20 mm on the B. cereus test plate fulfilled the European Union criterion for maximum residue level for tetracyclines of < 100 ng/ml (including their 4-epimer derivatives). The detection limits of the receptor assay depended on the type of milk used. The scintillation counts that were obtained for control samples of bulk milk were considerably lower than for the milks obtained from Charm Sciences, Inc. or processed using UHT pasteurization. One of 973 milk samples was suspect for tetracycline residues by means of the B. calidolactis tube test as well as by the receptor assay; 8 other samples were also considered to be positive using the receptor assay alone. The presence of tetracycline residues could not be proved for these 9 samples (residue concentration, < 10 ng/ml) with HPLC. We concluded that the receptor assay was not reliable to detect tetracycline residues in raw milk at < 150 ng/ml. The B. cereus test plate was determined to be an inexpensive, reliable alternative for the receptor assay for detection of tetracycline residues.     

The results of an experimental study of an anti-Opisthorchis preparation made from plant raw material

A device operating by the principle of local negative pressure has been developed and patented in Russia. Its trial in 122 patients with erectile insufficiency in combination with conservative treatment showed that positive effect may be reached in patients subjected to partial intracavernous restorative surgery of the penis with unsatisfactory outcome.     

Detection of Listeria in raw and pasteurized milk

We report the case of a 16-year-old adolescent with the onset of a panic disorder with agoraphobia after a first panic attack during marijuana intoxication. There was a good response to standard cognitive behavioural therapy for panic disorder.     

Evaluation of universal preenrichment broth for the recovery of foodborne pathogens from milk and cheese

The use of universal preenrichment broth for the recovery of verotoxigenic Escherichia coli, Salmonella spp., and Listeria monocytogenes from milk and cheese was examined. Universal preenrichment broth supported the growth of low inoculum levels (10 cfu/ml) of these organisms in pure cultures and in mixed cultures containing higher levels of other pathogens or bacterial flora from raw milk. This medium also supported the recovery and growth of heat-injured Salmonella spp., L. monocytogenes, and verotoxigenic E. coli at inoculum levels of 10(2) cfu/ml to yield cell levels of 10(8) cfu/ml in pure cultures and at least 10(5) cfu/ml in the presence of high levels of known competitive pathogens or microflora of cheese samples after 24 h of incubation. Universal preenrichment broth performed better than Listeria enrichment broth in supporting the recovery and growth of heat-injured L. monocytogenes and equally as well as buffered peptone water or trypticase soy broth in supporting the growth of uninjured L. monocytogenes, Salmonella spp., and verotoxigenic E. coli. Coenrichment of these pathogens in universal preenrichment broth reduced the quantity of milk or cheese samples that were required for analysis and also reduced the cost and labor involved in preparing and processing separate preenrichment media.     

Quantitative risk assessment: an emerging tool for emerging foodborne pathogens

New challenges to the safety of the food supply require new strategies for evaluating and managing food safety risks. Changes in pathogens, food preparation, distribution, and consumption, and population immunity have the potential to adversely affect human health. Risk assessment offers a framework for predicting the impact of changes and trends on the provision of safe food. Risk assessment models facilitate the evaluation of active or passive changes in how foods are produced, processed, distributed, and consumed.     

Development of probiotic cheese manufactured from goat milk: response surface analysis via technological manipulation

Production of caprine milk has been rising steadily, partially because of its good nutritional value; the possibility of improving nutritional benefits by adding probiotic species such as Bifidobacterium lactis and Lactobacillus acidophilus was assessed. The manufacturing process of a traditional semi-hard goat cheese was technologically modified to optimize the process. The amount of starter inoculum, the concentration of salt, the addition of a protein hydrolysate, and the ripening time were varied to improve the microbiological, biochemical, and sensory properties of the cheese. Bifidobacterium lactis was able to grow slightly (up to 3 x 10(8) cfu/g), but growth was dependent on the physicochemical characteristics of the cheese. Lactobacillus acidophilus did not grow substantially in any of the experimental cheeses, and maximum numbers did not exceed 6 x 10(7) cfu/g. Concentrations of lactic acid and acetic acid increased throughout cheese manufacture, indicating that production of these acids was uncoupled from growth. Viability of the probiotic strains during ripening was sufficient to yield numbers that were above the accepted threshold (10(6) cfu/g) for a probiotic effect. Both strains contributed significantly to ripening, especially in the formation of low molecular mass peptides and amino acids, but lipolysis was not greatly affected. Statistical analyses using response surface methodology indicated that the manufacture of goat cheese could be optimized by the addition of 0.30% (vol/wt) milk hydrolysate, 3 x 10(7) of viable B. lactis and 7 x 10(6) of viable L. acidophilus cells/ml of milk, respectively, 3.50% (wt/wt) salt, and ripening for 70 d.     

Prevalence of Listeria species in raw milk from farm bulk tanks in Nagano prefecture

The redox chemistry of Pyrococcus furiosus rubredoxin and ferredoxin has been studied as a function of temperature in direct voltammetry and in EPR monitored bulk titrations. The Ems of both proteins, measured with direct voltammetry, have a normal (linear) temperature dependence and show no pH dependence. EPR monitoring is not a reliable method to determine the temperature dependence of the Em: upon rapid freezing the proteins take their conformation corresponding to the freezing point of the solution.     

国产动态轻压下设备的应用

包头钢铁集团公司在2006年底投产的5号连铸机上成功安装国产动态轻压下设备,并对重轨钢进行了轻压下试验研究.1年多的试验结果表明:该轻压下设备在合理的工艺条件下可以显著提高重轨钢的质量,改善了重轨钢铸坯的碳元素平均偏差指数,钢轨的内伤率减少,并使普通钢轨的成分偏差达到了高速轨的要求.     

Quantitative assessment of pneumoencephalograms

In planimetric analysis of pneumoencephalograms the state of the brain ventricles can be assessed on the basis of planimetric coefficients--ratio of the sizes of individual parts of the ventricles and the width of the cerebral skull. Each of the calculated coefficients reflects the state of an individual portion of the ventricles. A summated coefficient Q is introduced which calculation permits to compose a digital characteristics of the state of the lateral ventricles as a whole. The ratio of the transverse size of the skull to the width of the III ventricle was also calculated, which reflects more objectively the state of the ventricle than the measurement of its absolute width value. The normal values of the coefficients were calculated on pneumoencephalograms with unchanged brain ventricles. In various degrees of ventricular dilatation the coefficients were determined on the pneumoencephalograms with a pathologically altered ventricular system.     

Gamma-glutamyltransferase as a marker for the pasteurization of raw milk

The degree and rate of inactivation of gamma-glutamyltransferase in raw cow's milk by heating at 50, 60, 70, and 80 degrees C for 1, 2, 3, 5, 10, 15, 20, 25, and 30 min were measured to evaluate the suitability of this enzyme as a marker for the pasteurization of milk. The enzymes alkaline phosphatase and lactate dehydrogenase were also measured under similar conditions for comparison. The patterns of heat inactivation of gamma-glutamyltransferase and alkaline phosphatase were similar, with only a minimal inactivation of the enzymes at 50 degrees C. The rate of inactivation increased as a result of increasing temperatures and time. A complete inactivation of both enzymes was seen at 70 degrees C after 10 min and at 80 degrees C after 1 min. Lactate dehydrogenase showed a higher heat resistance with almost complete inactivation at 70 degrees C for 30 min, and compete inactivation at 80 degrees C for 3 min. No activities of these enzymes were found in commercially pasteurized or heat-treated milk. The levels of gamma-glutamyltransferase in raw milk were between 8 and 10% higher than those of alkaline phosphatase and lactate dehydrogenase, making it more sensitive and accurate as a testing marker. It seems that gamma-glutamyltransferase may serve as a good pasteurization marker. Furthermore, the simplicity of testing and the availability of commercial kits for testing by both wet and dry chemistry make it an attractive choice, especially because dry chemistry procedures overcome the difficulties originating from the turbidity of milk, which interferes with spectrophotometric procedures.     

基于神经网络的水厂原水水质的综合评价

基于BP神经网络的改进算法,提出了以Matlab 7.0为平台的算法程序的人工神经网络水质评价模型。参照《地表水环境质量标准》(GB3838-2002),确定神经网络学习和训练的样本并确定了模型的相应参数。以连云港市海州水厂原水取水口水质数据为样本,进行水质综合评价分析。与单因子评价法和模糊综合评价法进行了比较,结果表明神经网络模型所获得的结果更加客观、合理。