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At least 739 records · Page 41Linked to original sources
PubMed2003

Biocontrol of Listeria monocytogenes on fresh-cut produce by treatment with lytic bacteriophages and a bacteriocin.

The fresh-cut produce industry has been the fastest-growing portion of the food retail market during the past 10 years, providing consumers with convenient and nutritious food. However, fresh-cut fruits and vegetables raise food safety concerns, because exposed tissue may be colonized more easily by pathogenic bacteria than intact produce. This is due to the higher availability of nutrients on cut surfaces and the greater potential for contamination because of the increased amount of handling. We found that applied Listeria monocytogenes populations survived and increased only slightly on fresh-cut Red Delicious apples stored at 10 degrees C but increased significantly on fresh-cut honeydew melons stored at 10 degrees C over 7 days. In addition, we examined the effect of lytic, L. monocytogenes-specific phages via two phage application methods, spraying and pipetting, on L. monocytogenes populations in artificially contaminated fresh-cut melons and apples. The phage mixture reduced L. monocytogenes populations by 2.0 to 4.6 log units over the control on honeydew melons. On apples, the reduction was below 0.4 log units. In combination with nisin (a bacteriocin), the phage mixture reduced L. monocytogenes populations by up to 5.7 log units on honeydew melon slices and by up to 2.3 log units on apple slices compared to the control. Nisin alone reduced L. monocytogenes populations by up to 3.2 log units on honeydew melon slices and by up to 2.0 log units on apple slices compared to the control. The phage titer was stable on melon slices, but declined rapidly on apple slices. The spray application of the phage and phage plus nisin reduced the bacterial numbers at least as much as the pipette application. The effectiveness of the phage treatment also depended on the initial concentration of L. monocytogenes.

Bacteriophages↗
PubMed1963

INACTIVATION OF THE RADIATION-RESISTANT SPOILAGE BACTERIUM MICROCOCCUS RADIODURANS. I. RADIATION INACTIVATION RATES IN THREE MEAT SUBSTRATES AND IN BUFFER.

A simplified technique permitting the pipetting of raw puréed meats for quantitative bacteriological study is described for use in determining survival of these non-sporing bacteria, which are exceptionally resistant to radiation. Survival curves, using gamma radiation as the sterilizing agent, were determined in raw beef with four strains of Micrococcus radiodurans. Survival curves of the R(1) strain in other meat substrates showed that survival was significantly greater in raw beef and raw chicken than in raw fish or in cooked beef. Resistance was lowest in the buffer. Cells grown in broth (an artificial growth medium) and resuspended in beef did not differ in resistance from cells that had been grown and irradiated in beef. Survival rate was statistically independent of the initial cell concentration, even though there appeared to be a correlation between lower death rate and lower initial cell concentrations. The initial viable count of this culture of the domesticated R(1) strain in beef was reduced by a factor of about 10(-5) by 3.0 megarad, and 4.0 megarad reduced the initial count by a factor of more than 10(-9). Data suggest that M. radiodurans R(1) is more resistant to radiation than spore-forming spoilage bacteria for which inactivation rates have been published.

Animals↗
PubMed1965

Increase in sensitivity for the assay of neomycin in milk.

A study was conducted to design a more sensitive and flexible technique for the assay of neomycin in milk. Sterile Antibiotic Assay medium (Difco; 15 ml) was poured into glass petri dishes with aluminum tops equipped with absorbent discs. Seed agar (4 ml; containing 1% sodium chloride) inoculated with standardized amounts of the test organism (Staphylococcus epidermidis ATCC 12228) was laid over the hardened base agar, and stainless-steel cylinders were placed equal distances apart in the agar. The plates were refrigerated for 30 min and the cups were removed in an atmosphere of minimal contamination. The resultant holes were sealed with melted agar. After preparation, the holes were used for assay procedures. Samples to be assayed were pipetted into the holes and the plates were refrigerated for 90 min at 4 C. Plates were incubated for 18 to 20 hr at 32 C. The zones of inhibition were recorded and compared with a standard curve. The approximate sensitivity of this method was 0.05 mug/ml.

Animals↗
PubMed1969

Micromethod for assaying serum levels of erythromycin.

A micromethod for assaying serum levels of erythromycin is described. The assay had the following characteristics: detection of 0.03 to 0.035 mug/ml, a long-range curve which minimizes sample dilution, 0.04 ml for a single measurement (0.3 ml required for full coverage), and utility for a variety of body fluids. The method employs radial diffusion from small paper discs which were saturated by capillary action rather than by dipping or pipetting. Although the method was designed to handle serum in which the sample volume is limited, statistical analysis demonstrated that the method has satisfactory precision for routine use. A study of 10 consecutive assays indicates a precision of +/-12% at the 95% confidence limits. The method of least squares was used to calculate the line of best fit, and the statistics were developed on this basis. The assay method is applicable to a variety of antibiotics.

Anti-Bacterial Agents↗
PubMed1974

Rapid method for determining serum bactericidal activity.

To screen large numbers of sera, a method was devised which utilizes the Steers-Foltz replicator which is usually used to determine minimal inhibitory concentration for antibiotics. Each of the wells (9 by 15 mm) of the replicator is filled with 0.06 ml of serum, 0.02 ml of a 10(5) suspension of organisms, and 0.02 ml of diluent (tris(hydroxymethyl)aminomethane-hydrochloride buffer, pH 8.4). The mixtures are incubated for 3 h, and samples are taken at 0, 1, 2, and 3 h by stamping duplicate nutrient agar plates (approximately 0.04 ml from each well). Plates are incubated overnight, and bactericidal activity is estimated by visual inspection of bacterial growth at each site for each sampling time. Results obtained with 28 serum-organism pairs paralleled standard pipetting-pour plate methods. The replicator method for determining bactericidal activity allows for the testing of a large number of samples and requires negligible amounts of serum.

Blood Bactericidal Activity↗
PubMed1997

Evaluation of a method for counting absolute numbers of cells with a flow cytometer.

We evaluated a method for performing absolute cell counts of lymphocyte populations with a flow cytometer. In this method, TruCount, test tubes that contain a known number of brightly fluorescent polystyrene beads are provided by the manufacturer. Whole anticoagulated blood is accurately pipetted into the tubes and mixed with fluorochrome-labeled monoclonal antibodies, the erythrocytes are lysed, and this mixture is analyzed on the flow cytometer. Absolute counts of lymphocyte subsets are calculated by determining the ratio of beads to the cell population of interest and then multiplying this ratio by the number of beads in the tube. We found this method to be reproducible. The values we obtained by the TruCount method were 5 to 10% higher than those obtained by conventional methods (flow cytometry and automated hematology) used to determine absolute numbers of cells. We believe that these differences are due to the methods of determining absolute cell counts and not to faulty identification of lymphocyte subsets.

Adolescent↗
PubMed1982

Evaluation of Phadebact and Streptex Kits for rapid grouping of streptococci directly from blood cultures.

The Phadebact Streptococcus Test and the Streptex Test kits were evaluated for grouping streptococci directly from blood cultures. Pellets of bacteria obtained from centrifuged samples of positive blood cultures were inoculated into Todd-Hewitt broth for 2- and 4-h Phadebact tests and into pronase for Streptex tests. Hemolysis was determined after pipetting a portion of each pellet into cuts made in blood agar plates incubated anaerobically for 2 to 6 h. Serological groups were also determined from colonies of the 137 strains of streptococci used in the study by the Lancefield precipitin method. Of the 126 strains tested by the 4-h Phadebact method, 120 (95.2%) agreed with Lancefield groupings, and 133 (97.1%) of the 137 strains tested by Streptex were in agreement. In contrast, only 31 of 55 strains (56.4%) were correctly identified by the 2-h Phadebact method. Misidentifications were related to multiple agglutinations and weak agglutinations in homologous antisera. Group A isolates were most frequently misidentified by all of the test methods. Hemolysis was determined within 4 h for 92.7% of the isolates and within 6 h for the remaining strains. Although the 4-h Phadebact procedure and the Streptex procedure were comparable in overall accuracy, cost, and technologist time, Streptex was the method of choice for direct groups. Results were available within 75 min for the Streptex procedure compared with 4 h for the Phadebact method. Because few cross-reactions occurred, agglutination responses were clearer and easier to interpret. Results from 2-h Phadebact tests were not satisfactory, and this method is not recommended.

Agglutination Tests↗
PubMed1975

Formalinized bacterial "antigens" as a potential infection hazard.

It is widely thought that after enteric bacteric have been "formalinized" (treated with an equal volume of 0.6% formalin) for 1 h, the bacteria become "antigens" and are no longer viable. None of the 27 cultures of Salmonella and other Enterobacteriaceae were entirely killed within 1 h after formalin was added, but all 27 were reduced from 10(9) viable cells per ml to less than 10(2) per ml within 7 h. Thus, mouth pipetting of cultures formalinized for only 1 h is a possible infection hazard.

Antigens, Bacterial↗
PubMed1996

Comparison of inoculation methods for testing enterococci by using vancomycin screening agar.

One hundred four recent clinical isolates of Enterococcus species were screened for vancomycin resistance by using inocula of 10(5) or 10(6) CFU dispensed by pipet and by use of a cotton swab dipped in a 0.5 McFarland standard organism suspension applied to the surface of brain heart infusion agar containing 6 micrograms of vancomycin per ml. The three inoculation methods were equivalent in the detection of nonsusceptible isolates. The use of swab inoculation was convenient and less costly than the use of micropipets.

Agar↗
PubMed2004

Use of the DNA flow-thru chip, a three-dimensional biochip, for typing and subtyping of influenza viruses.

Influenza A viruses, which are further subtyped on the basis of antigenic differences in external hemagglutinin and neuraminidase glycoproteins, and influenza B viruses are prominent among the viral causes of respiratory diseases and can cause a wide spectrum of illness. Each year these viruses are responsible for recurrent epidemics, frequently in association with genetic variation. There is a requirement for sensitive and rapid diagnostic techniques in order to improve both the diagnosis of infections and the quality of surveillance systems. A new three-dimensional biochip platform (Flow-Thru Chip; MetriGenix) was used to develop a rapid and reliable molecular method for the typing and subtyping of influenza viruses. Oligonucleotide probes immobilized in microchannels of a silicon wafer were selected to recognize multiple fragments of the influenza A virus matrix protein gene; the influenza B virus NS gene; the H1, H3, and H5 hemagglutinin genes; and the N1 and N2 neuraminidase genes. Biotinylated amplicons resulting from either multiplex or random reverse transcription-PCR were hybridized to arrayed oligonucleotides on the influenza virus chip before they were stained with horseradish peroxidase-streptavidin and were imaged by use of a chemiluminescent substrate. The chip analysis procedure, from the time of pipetting of the sample into the chip cartridge to the time of analysis of the results, was performed in less than 5 h. The random PCR exhibited a higher level of performance than the multiplex PCR in terms of the specificity of product hybridization to the influenza virus chip. Analysis of influenza A viruses (H1N1, H3N2, H1N2, and H5N1) and influenza B viruses showed that this microarray-based method is capable of the rapid and unambiguous identification of all types and subtypes of viruses by use of random PCR products. The redundancy of the probes designed for each gene selected yielded an additional criterion of confidence for the subtyping of viruses which are known for antigenic variations in some of their components.

Base Sequence↗
PubMed1978

Comparison of micro-ID, API 20E, and conventional media systems in identification of Enterobacteriaceae.

The Micro-ID, a new identification kit for Enterobacteriaceae, consists of 15 biochemical tests, with substrates and reagents impregnated in filter paper disks. A 0.2-ml amount of an organism suspension equal to a 0.5 McFarland standard is pipetted into each of the compartments. After 4 h of incubation and addition of potassium-hydroxide (KOH) to the Voges-Proskauer test, the color reactions are read according to the recommendations of the manufacturer. A five-digit octal code number is derived from each set of reactions from which an identification is derived by using a code book. In a single-blind, comparative study of the Micro-ID system with the API 20E system (Analytab Products Inc.) and conventional biochemical tube media, we found that the Micro-ID and the API 20E systems gave a 90% identification correlation when each was compared with the conventional tube media. A comparison of all three systems gave an 82% overall identification correlation. When the common tests of Micro-ID and API 20E were compared with conventional tube media, we found that the tests in the Micro-ID performed as well as or better than those of the API 20E. Certain groups of organisms, i.e., Citrobacter, Enterobacter, Proteus, Salmonella, and Serratia genera, were found to give low correlation on certain common tests. When using primary isolation MacConkey plates from the clinical laboratory, only 74% of the plates with Enterobacteriaceae had sufficient numbers of colonies of each enteric organism to produce the 0.5 McFarland inoculum density required. Problems concerning the misidentification of some organisms are discussed.

Bacteriological Techniques↗
PubMed2000

Enhancement of dedifferentiation and myoid differentiation of retinal pigment epithelial cells by platelet derived growth factor.

AIMS: To clarify factor(s) involved in morphological dedifferentiation of retinal pigment epithelial (RPE) cells in vitro from mitotically quiescent hexagonal cells to flattened cells that lack epithelial characteristics and concurrent myoid differentiation. METHODS: RPE cells which retained their differentiated hexagonal morphology were isolated from bovine eyes by mechanical pipetting. Dedifferentiation and myoid differentiation of RPE cells were examined by microscopic observation and immunohistochemical analysis using antibodies against cytokeratin, an epithelial marker, and alpha smooth muscle actin, a marker of myoid differentiation. The contractile ability of RPE cells was evaluated by collagen gel contraction assay. RESULTS: Platelet derived growth factor (PDGF) enhanced morphological changes in the RPE from hexagonal-shaped cells to flattened cells. Coincident with this morphological alteration, the expression of cytokeratin in RPE cells decreased and expression of alpha smooth muscle actin began and was increased in a time dependent manner. These alterations were completely blocked by collagen synthesis inhibitors. Interleukin 1beta, transforming growth factor beta1, insulin-like growth factor I, and basic fibroblast growth factor had little or no effect on the dedifferentiation. PDGF also potentiated the RPE induced collagen gel contraction. CONCLUSIONS: These results demonstrate that PDGF enhanced the dedifferentiation of RPE cells, the initial step of proliferative vitreoretinopathy (PVR), as well as myoid differentiation and collagen gel contraction. PDGF may have a versatile role in the pathogenesis of PVR involving collagen synthesis.

Actins↗
PubMed1977

Survey of safety and health care in British medical laboratories.

A retrospective postal survey of 24 000 medical laboratory workers in England, Wales, and Scotland showed highly variable standards of safety and health care. Pre-employment health screening was offered to two-thirds of employees, the physicians being the least likely to be examined (15%). Scottish laboratories provided better safety control than English and Welsh laboratories, while Public Health Service Laboratories had a better record than National Health Service establishments. Mouth pipetting is still practised in 65% of English and Welsh laboratories, and the use of protective clothing is rarely compulsory. The servicing of safety cabinets is often inadequate. Known and suspected carcinogens are still apparently used in a few laboratories (2-10%). In view of the wide variation in standards among laboratories, urgent consideration should be given to establishing regulations for codes of safe practice rather than relying merely on recommendations as at present.

Accident Prevention↗
PubMed1982

Evaluation of the Lumac kit for the detection of bacteriuria by bioluminescence.

Four hundred and twenty-two urine samples were screened for significant bacteriuria using bioluminescence and microscopy of uncentrifuged urine. A smaller number of false-negatives were seen with bioluminescence (10%) than with microscopy (40%) while both techniques gave a similar number of false-positives (18%). The kit required a large amount of manual preparation, largely pipetting. With this and the short shelf-life of the reconstituted reagents, it is not suitable for small numbers of urines. At 45p per urine, the cost of bioluminescence is too high.

Adenosine Triphosphate↗
PubMed1997

Rapid identification of multiple supernumerary ring chromosomes with a new FISH technique.

Multiple supernumerary ring chromosomes are a rare cytogenetic finding which is poorly understood. With the introduction of FISH techniques, their chromosomal origin can now be defined clearly. The techniques described previously are complicated and time consuming. We report a new rapid technique which has been used to investigate two new cases. Multiple probes were hybridised to a single slide by means of marking the underside with a diamond pen to form a grid of squares, pipetting fixed cell suspension into the centre of each square, forming a rubber solution grid on the denatured, dehydrated slide following the lines on the underside, adding a mixture of probes into each square, and sealing the slide with a silicone rubber rim and a covering slide. The type of probe and the size, dimensions, and number of squares in the grid can be tailored to individual cases. The two new cases examined here are mosaic for three (case 1) and four (case 2) supernumerary ring chromosomes derived from different chromosomes. Normal cell lines were also present. The karyotypes were established as 47,XY,+r(4)/47,XY,+r(17)/.../48,XY,+r(17),+r(20)/ 49,XY,+r(4),+r(17),+r(20)/46,XY for case 1 and 47,XX,+r(4)/47,XX,+r(8)/47,XX,+r (10)/48,XX,+r(X),+r(4)/... /49,XX,+r(X),+r (8),+r(10)/46,XX for case 2. Our findings suggest that the ring chromosomes were formed during meiosis, perhaps involving complex rearrangements, resulting in a germ cell containing all markers, with subsequent loss of markers during cell division. Our second case also shows that the outcome is not invariably mental or physical handicap.

Child, Preschool↗
PubMed2001

Glutathione in induced sputum of healthy individuals and patients with asthma.

BACKGROUND: Glutathione is central to the antioxidant defences of the lung. The aim of this study was to determine whether sputum induction can be used for the measurement of glutathione in the respiratory tract. METHODS: Saliva and induced sputum (3% NaCl, 20 minutes) samples were collected from 10 healthy individuals and 10 patients with stable asthma receiving treatment with inhaled corticosteroids. Samples were chilled on ice and dispersed by dilution with ice cold phosphate buffered saline and pipetting. Cell-free supernatants were obtained by centrifugation of samples and filtration of supernatants and analysed for total glutathione, glutathione disulfide, and albumin content. The cells were treated with dithiothreitol and cell numbers, cell viability, and differential cell patterns were determined. RESULTS: As judged by cell viability and percentage of non-squamous cells, adequate sputum samples were obtained from nine healthy and nine asthmatic subjects. The salivary total glutathione content was low (median concentration 1.2 microM (range 0.8-1.5) in healthy subjects and 0.9 microM (0.7-1. 2) in asthmatic subjects). The sputum total glutathione content of both healthy and asthmatic subjects was within the same range (3.9 (1.0-12.3) microM and 6.4 (1.3-19.2) microM, respectively; p=0.35). Surprisingly, and in marked contrast to results obtained with bronchoalveolar lavage, sputum levels of glutathione disulfide represented more than 50% of the total glutathione in both groups (50.9% (range 24.6-83.1) and 72.3% (range 36.5-97.4), respectively; p=0.2). CONCLUSIONS: The results of this study indicate that sputum induction can be used to measure the glutathione content of bronchial secretions. Sputum glutathione levels of stable asthmatic patients did not differ significantly from healthy controls.

Adolescent↗
PubMed1981

Voltage dependence of digitalis afterpotentials, aftercontractions, and inotropy.

The effects of membrane potential on digitalis-induced oscillatory afterpotentials (OAP) and aftercontractions (AC) were investigated in isolated canine false tendons and canine and feline papillary muscles. Transmembrane potential and contractions were measured simultaneously. Membrane potential was varied by current applied through an extracellular pipet. The amplitudes of OAP and AC induced by acetylstrophanthidin (0.5-1.0 X 10(-7) g/ml) or actodigin (0.5-1.0 X 10(-6) g/ml) were increased by depolarization and decreased or abolished by hyperpolarization in all tissues. Prior to the appearance of OAP and AC in preparations exposed to the drugs, depolarization caused both phenomena to appear. As in muscle, the strength of beats superimposed on the ascending limb of AC was potentiated, and the strength of beats superimposed on the relaxation phase was depotentiated. When the amplitude of AC was decreased by hyperpolarization, both potentiation and depotentiation were diminished. This effect was accompanied by a partial reversal of the changes induced by acetylstrophanthidin in the course of restitution of contractility and the configuration of the force-frequency relation.

Animals↗