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Biomedical subjects

K R Schneider

Publications and source records attributed to K R Schneider.

13 recordsLinked to original sources
PubMed2006

Adaptation of Salmonella spp. in juice stored under refrigerated and room temperature enhances acid resistance to simulated gastric fluid.

The objective of this study was to evaluate the acid resistance of Salmonella spp. adapted in juices stored under refrigeration and room temperatures to simulated gastric fluid (SGF, pH 1.5). Five Salmonella serovars, Agona, Gaminara, Michigan, Montevideo, and Poona were used in this study. Apple, orange, and tomato juices inoculated with five serovars were stored at refrigeration (7 degrees C) and room temperature (20 degrees C) for 24 h for adaptation. Acid resistances of serovars adapted in juice were determined in SGF at 37 degrees C. All acid-adapted Salmonella serovars in juices displayed enhanced survival time compared to non-adapted controls. Among serovars, S. Poona adapted in apple at 20 degrees C and orange juices at 7 and 20 degrees C showed >2.0 log cfu/ml survivors, while the other serovars decreased to non-detectable level or <2.0 log cfu/ml for 100 s in SGF. Unlike apple and orange juices, all serovars adapted in tomato juice survived with >2.0 log cfu/ml for 100 s. For D-values, all Salmonella serovars adapted in apple and tomato juice enhanced their acid resistances compared to orange juices. S. Agona adapted in tomato juice at 7 degrees C and S. Poona in apple juice at 20 degrees C had the highest D-values with 82.9 and 82.5s, respectively. Results showed that the adaptation in juice increased acid resistance in SGF and varied by serovar, juice type, and adaptation temperature. Therefore, this study indicates that the introduction of Salmonella spp. to an acidic juice environment during processing can enhance their ability to survive in a human stomach, possibly increasing the risk of a Salmonella outbreak by juice.

Adaptation, Physiological↗
PubMed2006

Shigella as a foodborne pathogen and current methods for detection in food.

Shigella, the causative agent of shigellosis or "bacillary dysentery," has been increasingly involved in foodborne outbreaks. According to the Centers for Disease Control and Prevention's Emerging Infections Program, Foodborne Diseases Active Surveillance Network (FoodNet), Shigella was the third most reported foodborne bacterial pathogen in 2002. Foods are most commonly contaminated with Shigella by an infected food handler who practices poor personal hygiene. Shigella is acid resistant, salt tolerant, and can survive at infective levels in many types of foods such as fruits and vegetables, low pH foods, prepared foods, and foods held in modified atmosphere or vacuum packaging. Survival is often increased when food is held at refrigerated temperatures. Detection methods for Shigella include conventional culture methods, immunological methods, and molecular microbiological methods. Conventional culture of Shigella in foods is often problematic due to the lack of appropriate selective media. Immunological methods for Shigella have been researched, yet there is only one commercially available test kit. Molecular microbiological methods such as PCR, oligonucleotide microarrays, and rep-PCR have also been developed for the detection and identification of Shigella. This manuscript reviews the general characteristics, prevalence, growth and survival, and methods for detection of Shigella in food.

Dysentery, Bacillary↗
PubMed2005

Comparison of chromogenic Shigella spp. plating medium with standard media for the recovery of Shigella boydii and Shigella sonnei from tomato surfaces.

Isolation of Shigella spp. from food is difficult because of a lack of appropriate selective media and the presence of low numbers of shigellae relative to competitive microorganisms. Chromogenic Shigella spp. plating medium (CSPM) was evaluated for use with the U.S. Food and Drug Administration Bacteriological Analytical Manual (BAM) enrichment procedure for isolation of artificially contaminated Shigella boydii UI02 and Shigella sonnei UI05 from tomato surfaces. Tomatoes were inoculated with various concentrations of S. boydii UI02 or S. sonnei UI05 and rinsed using a shake-rub-shake procedure. Tomato rinses were enriched overnight according to the BAM procedure and streaked for isolation on CSPM, Salmonella-Shigella agar (SSA), and MacConkey agar (MAC). To access the isolation of S. boydii UI02 and S. sonnei UI05 without competition from natural tomato microflora, experiments were repeated using rifampin-adapted inocula and enrichments supplemented with 50 microg/ml rifampin. Isolation of S. boydii UI02 and S. sonnei UI05 with or without natural tomato microflora was not significantly different (P > 0.05) on CSPM, MAC, or SSA. Colony color enhancements created by CSPM may ease differentiation of Shigella colonies from those of closely related competitors.

Bacteriological Techniques↗
PubMed2001

Continuous online processing of fecal- and ingesta-contaminated poultry carcasses using an acidified sodium chlorite antimicrobial intervention.

The objective of this study was to determine the effectiveness of the combined use of an inside-outside-bird-washer for the removal of visible contamination and an online acidified sodium chlorite (ASC) spray system in reducing microbial levels on contaminated poultry carcasses. Specifically, we attempted to determine if this technique (referred to as continuous online processing [COP]) would (i) eliminate the need for offline reprocessing of contaminated carcasses, (ii) meet Zero Fecal Tolerance standards, and (iii) attain significant reductions in titers of some of the commonly found bacterial species. Carcasses were sampled for Ercherichia coli, Salmonella, and Campylobacter at five stations along the processing lines in a series of five commercial plant studies to compare the efficacy of the COP system to that of offline processing. The microbiological quality of fecally contaminated carcasses was found to be significantly better following COP treatment (E. coli, 0.59 log10 CFU/ml; Salmonella, 10.0% incidence) than after standard offline reprocessing (E. coli, 2.37 log10 CFU/ml; Salmonella, 31.6% incidence). Zero Fecal Tolerance requirements were met by all but 2 (0.2%) of the 1.127 carcasses following COP. COP also significantly reduced the titers of Campylobacter; residual titers were 1.14 log10 CFU/ml (49.1% incidence) following COP, compared to 2.89 log10 CFU/ml (73.2% incidence) in carcasses that underwent offline reprocessing. These results support the combined use of an inside-outside-bird-washer for the removal of visible contamination and an online ASC spray system to reduce microbial levels in commercially processed poultry.

Animals↗
PubMed2000

Model reduction by extended quasi-steady-state approximation.

We extend the quasi-steady-state approximation (QSSA) with respect to the class of differential systems as well as with respect to the order of approximation. We illustrate the first extension by an example which cannot be treated in the frame of the classical approach. As an application of the second extension we prove that the trimolecular autocatalator can be approximated by a fast bimolecular reaction system. Finally we describe a class of singularly perturbed systems for which a higher order QSSA can easily be obtained.

Enzymes↗
PubMed2000

Validation of thiosulfate for neutralization of acidified sodium chlorite in microbiological testing.

At low pH, acidified sodium chlorite (ASC) has antimicrobial activity against a variety of foodborne contaminants. To evaluate the antimicrobial efficacy of ASC at specific time points posttreatment, it is necessary to halt the action of the disinfectant by removing residual chlorite or by increasing the pH. In this study, thiosulfate was investigated at varying concentrations for its effect on microbial survival and was investigated at a concentration of 0.1% in the presence of ASC for its effect on the antimicrobial and chemical activity of the test solution. Additionally, sodium thiosulfate was tested in two buffering systems, buffered peptone water (BPW) and Butterfield's phopshate buffer (BPB), for its ability to inactivate ASC chemistry. The results of this study show that, at a concentration of 0.1%, sodium thiosulfate has no deleterious effect on Escherichia coli survival and is effective in halting the antimicrobial action of ASC by eliminating the production of residual chlorite. The BPW alone and BPB in combination with thiosulfate were found to be effective inactivators of ASC chemistry.

Bacteria↗
PubMed1998

A genetic study of signaling processes for repression of PHO5 transcription in Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, transcription of a secreted acid phosphatase, PHO5, is repressed in response to high concentrations of extracellular inorganic phosphate. To investigate the signal transduction pathway leading to transcriptional regulation of PHO5, we carried out a genetic selection for mutants that express PHO5 constitutively. We then screened for mutants whose phenotypes are also dependent on the function of PHO81, which encodes an inhibitor of the Pho80p-Pho85p cyclin/cyclin-dependent kinase complex. These mutations are therefore likely to impair upstream functions in the signaling pathway, and they define five complementation groups. Mutations were found in a gene encoding a plasma membrane ATPase (PMA1), in genes required for the in vivo function of the phosphate transport system (PHO84 and PHO86), in a gene involved in the fatty acid synthesis pathway (ACC1), and in a novel, nonessential gene (PHO23). These mutants can be classified into two groups: pho84, pho86, and pma1 are defective in high-affinity phosphate uptake, whereas acc1 and pho23 are not, indicating that the two groups of mutations cause constitutive expression of PHO5 by distinct mechanisms. Our observations suggest that these gene products affect different aspects of the signal transduction pathway for PHO5 repression.

Acetyltransferases↗
PubMed1994

Phosphate-regulated inactivation of the kinase PHO80-PHO85 by the CDK inhibitor PHO81.

A complex consisting of the cyclin-dependent kinase (CDK) PHO85 and the cyclin PHO80 phosphorylates and is thought to inactivate the transcription factor PHO4 when yeast cells are grown in medium containing high concentrations of phosphate. The CDK inhibitor PHO81 inhibits the kinase activity of the PHO80-PHO85 complex when Saccharomyces cerevisiae cells are grown in medium depleted of phosphate. A region of PHO81 with similarity to the mammalian CDK inhibitor p16INK4 is sufficient for inhibition in vitro. These studies demonstrate that CDK inhibitors are used to regulate kinases involved in processes other than cell cycle control and suggest that the ankyrin repeat motif may be commonly used for interaction with cyclin-CDK complexes.

Amino Acid Sequence↗
PubMed1991

Ozone depuration of Vibrio vulnificus from the southern quahog clam, Mercenaria campechiensis.

Southern quahog clams, Mercenaria campechiensis, were dosed with Vibrio vulnificus and placed in a pilot-scale depuration system using ozonated recirculated artificial seawater. Twenty-four hours of treatment with ozone-treated recirculating artificial seawater reduced the numbers of V. vulnificus in the shellfish meats by an average of 2 log units when compared to natural die-off in control clams. The oxidant levels (up to 3 mg/liter) did not adversely affect shellfish pumping during the depuration process.

Animals↗
PubMed1990

Marking snails with numbered, colored discs: a technique for identifying individual specimens.

Numbered, colored discs, measuring 2.5 mm in diameter, were evaluated under laboratory conditions as tags for marking and identifying individual snails. Discs were affixed to the shells of specimens of Helisoma duryi (Pulmonata: Planorbidae) with an adhesive supplied with the discs and with waterproof epoxy. All snails survived the initial tagging procedure and showed no observable behavioral responses to the tagging. The supplied adhesive, intended for use with terrestrial insects, was inadequate for securing the tags for prolonged periods under aquatic conditions. Use of waterproof epoxy, however, resulted in 100% tag retention for over 5 months without significant mortality. The permanence of the marks, their coding of individuals, the rapidity and ease with which the tags can be applied without causing behavioral changes or snail mortality suggest that this technique will be useful in studies requiring identification of individual aquatic snails.

Adhesives↗
PubMed1978

[Comparative studies of growth hormone secretion in acromegaly after isolated and combined application of insulin hypoglycemia, LH-RH- and TRH tests (author's transl)].

Growth hormone (GH) release was measured in 17 patients with active acromegaly following the administration of insulin, LH-RH and TRH given intravenously either combined or each separately. The simultaneous application of insulin and the hypothalamic releasing hormones resulted in a striking increase of plasma GH in 15 out of 17 patients. Inappropriate stimulation of GH release was found in 9 out of the 17 patients with acromegaly, when TRH was given as the only hormone; conversely this phenomenon due to LH-RH application was observed in 4 cases. In insulin-induced hypoglycemia GH release could be stimulated in 5 patients. After selective, transsphenoidal hypophysectomy, 4 of 13 patients still showed a definite stimulation of GH release after the combined use of test substances. Two of these also exhibited a comparable stimulation of GH after TRH, indicating adenoma cells remaining active after operation. The combined insulin-induced hypoglycemia/LH-RH/TRH-test is therefore advisable for patients with acromegaly, since GH release as well as other hypophyseal partial functions can be tested. The performance of individual tests is essential for evaluating selective stimulation of GH release.

Acromegaly↗