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At least 19 recordsLinked to original sources
PubMed2003

Microbial viability in preparations packaged for single use.

We evaluated microbial viability in preparations packaged for single use only which mandate that residual solution be discarded such as albumin and globulin preparations as blood products, preparations containing albumin (such as urokinase and interferon), fat emulsions, and a preparation containing fat emulsions (propofol). In most preparations, Serratia marcescens and Burkholderia cepacia proliferated rapidly at 30 degrees C. However, in globulin preparations containing 1-2.25% glycine to prevent protein degradation (Gamma-Venin P, Venilon-I, Globulin Injection, and Ahlbulin), no growth of S. marcescens and B. cepacia was detected over 24 h at 30 degrees C. For globulin preparations containing 1-2.25% glycine, the injunction to "Discard residual solution after the package has been used" in the package inserts can be revised to "It is possible to use residual solution within 24 h after the package has been used with storage in a cool place."

Bacteria↗
PubMed1993

Factors affecting the selection and use of tetrazolium salts as cytochemical indicators of microbial viability and activity.

The reduction of four tetrazolium cations (TCs), nitroblue tetrazolium (NBT), neotetrazolium (NT), methylthiazolyldiphenyltetrazolium (MTT) and iodonitrophenyltetrazolium (INT), by viable micro-organisms, immobilized on glass cover slips, was examined by light microscopy with a view to determining a systematic basis for applying these reagents as cytochemical indicators of microbial viability and activity. The potential value of histochemical information about TC reactions for developing their microbiological applications was also assessed. INT and MTT detected viable cells more readily than NBT and NT. In order to obtain cell-localized formazan, MTT required cobalt ions in the reaction mixture and INT reactions had to be assessed soon after mounting. In general, formazan deposition could be accelerated by the addition of glucose and an intermediate electron carrier (IEC) to the reaction mixture, although inhibitory effects of IECs were also detected. Cultures in exponential phase, in stationary phase and inhibited by chloramphenicol could be differentiated with MTT but not with INT. For some organisms, notably Candida albicans, Pseudomonas aeruginosa and Enterococcus faecalis. TC reactions proved to be a relatively insensitive means of demonstrating viability. Two parameters used in selecting TCs for histochemical reactions, lipophilicity and reducibility appeared to be predictive for the relative sensitivity of these reagents as indicators of cell viability. The concepts of substantivity, a measure of non-specific interactions between reagents and staining substrates, and TC oxygen sensitivity, the effect of competition between oxygen and TCs for electrons, were found to be relevant to formazan deposition in live microbes. These findings support the use of TCs as cytochemical probes of microbial activity in defined settings and the use of histochemical knowledge to support further development of these techniques.

Bacteria↗
PubMed2001

Confocal microscopy and microbial viability detection for food research.

Confocal microscopy offers several advantages over other conventional microscopic techniques as a tool for studying the interaction of bacteria with food and the role of food microstructure in product quality and safety. When using confocal microscopy, samples can be observed without extensive preparation processes, which allows for the evaluation of food without introducing artifacts. In addition, observations can be made in three dimensions without physically sectioning the specimen. The confocal microscope can be used to follow changes over a period of time, such as the development of the food structure or changes in microbial population during a process. Microbial attachment to and detachment from food and food contact surfaces with complex three-dimensional (3-D) structures can be observed in situ. The fate of microbial populations in food system depends on processing, distribution, and storage conditions as well as decontamination procedures that are applied to inactivate and remove them. The ability to determine the physiological status of microorganisms without disrupting their physical relationship with a food system can be useful for determining the means by which microorganisms survive decontamination treatments. Conventional culturing techniques can detect viable cells; however, these techniques lack the ability to locate viable cells in respect to the microscopic structures of food. Various microscopic methods take advantage of physiological changes in bacterial cells that are associated with the viability to assess the physiologic status of individual cells while retaining the ability to locate the cell within a food tissue system. This paper reviews the application of confocal microscopy in food research and direct observation of viable bacteria with emphasis on their use in food microbiology.

Bacteria↗
PubMed2006

Synbiotic microcapsules that enhance microbial viability during nonrefrigerated storage and gastrointestinal transit.

A Bifidobacterium infantis strain was microencapsulated within a film-forming protein-carbohydrate-oil emulsion. This novel encapsulant incorporated prebiotics and substantially protected the bacterium during nonrefrigerated storage and gastrointestinal transit. The dried microcapsules were small (15 to 20 microm), had low water activity (0.2 to 0.3), and rapidly released the bacteria in simulated intestinal fluid.

Bifidobacterium↗
PubMed1989

Myeloperoxidase-mediated inhibition of microbial respiration: damage to Escherichia coli ubiquinol oxidase.

A microbicidal system, mediated by neutrophil myeloperoxidase, inhibits succinate-dependent respiration in Escherichia coli at rates that correlate with loss of microbial viability. Succinate dehydrogenase, the initial enzyme of the succinate oxidase respiratory pathway, catalyzes the reduction of ubiquinone to ubiquinol, which is reoxidized by terminal oxidase complexes. The steady-state ratio of ubiquinol to total quinone (ubiquinol + ubiquinone) reflects the balance between dehydrogenase-dependent ubiquinone reduction and terminal oxidase-dependent ubiquinol oxidation. Myeloperoxidase had no effect on total quinone content of E. coli but altered the steady-state ratio of ubiquinol to total quinone. The ratio doubled for organisms incubated with the myeloperoxidase system for 10 min, suggesting decreased ubiquinol oxidase activity, which was confirmed by observation of a 50% decrease in oxidation of the ubiquinol analogue 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinol. Despite inhibition of ubiquinol oxidase, overall succinate oxidase activity remained unchanged, suggesting that succinate dehydrogenase activity was preserved and that the dehydrogenase was rate limiting. Microbial viability was unaffected by early changes in ubiquinol oxidase activity. Longer (60 min) exposure of E. coli to the myeloperoxidase system resulted in only modest further inhibition of the ubiquinol oxidase, but the ubiquinol to total quinone ratio fell to 0%, reflecting complete loss of succinate dehydrogenase activity. Succinate oxidase activity was abolished, and there was extensive loss of microbial viability. Early myeloperoxidase-mediated injury to ubiquinol oxidase appeared to be compensated for by higher steady-state levels of ubiquinol which sustained electron turnover by mass effect. Later myeloperoxidase-mediated injuries eliminated succinate-dependent ubiquinone reduction, through inhibition of succinate dehydrogenase, with loss of succinate oxidase activity, effects which were associated with, although not clearly causal for, microbicidal activity.

Animals↗
PubMed1999

Effect of compressed carbon dioxide on microbial cell viability.

In order to study the influence of compressed carbon dioxide, over a range of pressures (1.5 to 5.5 MPa) and exposure times (up to 7 h), on the survival of Escherichia coli, Saccharomyces cerevisiae, and Enterococcus faecalis, a new pressurizable reactor system was conceived. Microbial cells were inoculated onto a solid hydrophilic medium and treated at room temperature; their sensitivities to inactivation varied greatly. The CO2 treatment had an enhanced efficiency in cell destruction when the pressure and the duration of exposure were increased. The effects of these parameters on the loss of viability was also studied by response-surface methodology. This study showed that a linear correlation exists between microbial inactivation and CO2 pressure and exposure time, and in it models were proposed which were adequate to predict the experimental values. The end point acidity was measured for all the samples in order to understand the mechanism of microbial inactivation. The pHs of the treated samples did not vary, regardless of the experimental conditions. Other parameters, such as water content and pressure release time, were also investigated.

Carbon Dioxide↗
PubMed1994

Electrophoretic free mobility and viability of microbial cells: a preliminary study in preparation for space experiments.

Electrophoretic free mobilities (EFM) of four fungal spores and five bacterial cells were determined in 7 mM triethanolamine/acetate (TEA) buffer by means of microscopic electrophoresis (ME) and free flow electrophoresis (FFE). Spores of Aspergillus terreus, Penicillium citrinum, Gliocladium virens, and Rhizopus oryzae had similar EFM from 2.2 to 3.1 microns sec-1/V cm-1. The resolution of the spore mixture by FFE was therefore determined to be poor. Bacterial cells of Salmonella typhimurium LT2 mutants showed a distinctive EFM from 0 to 4.2 microns sec-1/V cm-1, which is a large enough difference to produce a clear separation of each mutant type from the mixture in FFE. The differences in the EFM of bacteria result from defective structures in the lipopolysaccharide of their outer membranes. The viability of bacteria in TEA buffer at 4 degrees C was investigated, and it was found to be stable for 14 days. This period is long enough to allow the performance of space experiments.

Aspergillus↗
PubMed2003

Water-in-oil macroemulsions sustain long-term viability of microbial cells in organic solvents.

Extremely stable water-in-oil macroemulsions have been obtained by dispersing water in isooctane in the presence of lecithin. Either prokaryotic (Escherichia coli) and eukaryotic (Saccharomyces cerevisiae and Rhodotorula minuta) cells hosted in these water-in-oil macroemulsions are viable for weeks despite the consistent excess of organic solvent (ranging from 70 to 84%, v/v) in these ternary systems. Conjugation occurs upon mixing macroemulsions containing F(+) or F(-) Escherichia coli strains, indicating consistent mass transfer between the water droplets. Populations of yeasts hosted in water-in-oil macroemulsion feature a higher frequency of cells aggregation when compared with the corresponding populations suspended in homogeneous aqueous media.

Cell Division↗
PubMed1999

Effect of hypergravitational stress on microbial cell viability.

Cell of Escherichia coli B, Thiobacillus intermedius 13-1, Bacillus amyloliquefaciens IFO14141, Staphylococcus aureus IID975, and Saccharomyces cerevisiae Kyokai no. 7 cultivated in nutrient media were subjected to hypergravitational stress for a period of between 1 and 24 h at 450,000 x g. The E. coli, B. amyloliquefaciens and S. cerevisiae cells showed survival rates of 38.5%, 0.005%, and 14.7%, respectively, after gravity treatment for 24 h as determined by their ability for colony formation, whereas a survival rate of S. cerevisiae cells of almost 100% was observed as determined using the methylene blue reduction test. E. coli cells, either in the logarithmic growth phase or cultivated in minimum media, were more sensitive to gravitational stress than those either in the stationary phase or cultivated in nutrient media.

Journal Article↗
PubMed1995

Microbiological assessment of an improved stannous fluoride dentifrice.

Recently, a new stabilized stannous fluoride (SnF2) dentifrice (SSF) has been developed. The aim of the present work was to examine the antimicrobial activity of SnF2, and to assess the long-term microbial safety of this dentifrice in a series of in vitro and clinical evaluations. Results of in vitro time-kill experiments with representative oral bacteria demonstrated that SnF2 exerts broad antimicrobial activity against both Gram-positives and Gram-negatives and, in particular, has potent activity against Streptococcus mutans. Sixty-eight subjects participated in a nine-day plaque regrowth clinical study to assess the short-term antiplaque effect of SSF. The results revealed no significant differences from the negative control, suggesting that SnF2 does not detectably or directly alter plaque microbial viability or composition. Separately, evaluation of microbial safety in a subgroup of 120 subjects participating in a six-month clinical efficacy and safety trial found no significant ecological shifts between SSF and the negative (NaF dentifrice) control among 11 supragingival microbial populations examined. The potential for development of bacterial resistance to SnF2 was assessed under both in vitro and clinical conditions. In a rigorous assessment of the ability of bacterial populations to develop either phenotypic or genotypic resistance to SnF2, representative bacteria were exposed to continuous sub-lethal concentrations of SnF2 in a laboratory chemostat for at least 9 days. Results of time-kill experiments on exposed populations revealed no significant changes in susceptibility despite exposure of over 10(12) bacteria. Based on typical spontaneous mutation rates of 10(-6) to 10(-8), these results suggested that the potential for bacteria to develop resistance to SnF2 is low. Evaluation of susceptibility to SnF2 to over 800 bacterial isolates obtained over the course of the six-month clinical trial corroborate the in vitro findings, revealing no changes in susceptibility suggestive of development of resistance to SnF2 is a microbiologically safe agent for oral use and support separate clinical observations demonstrating the safety and efficacy of this stabilized SnF2 dentifrice.

Actinomyces↗
PubMed1992

Rapid assessment of bacterial viability by flow cytometry.

The ability of a flow cytometer to rapidly assess microbial viability was investigated using three vital stains: rhodamine 123 (Rh123); 3,3'-dihexyloxacarbocyanine iodide [DiOC6(3)] and fluorescein diacetate (FDA). Rh123 was found to clearly differentiate viable from non-viable bacteria. The methodology for staining bacteria with this dye was optimised. Rh123 was shown to stain and discriminate several different species of viable bacteria although this was not universal. Viable cells of Bacillus subtilis were found to stain better with FDA than with Rh123. The results demonstrate the ability of flow cytometry to rapidly detect and estimate the viability of bacterial populations.

Bacterial Physiological Phenomena↗
PubMed1996

In vivo bioluminescence to detect the attachment of L-forms of Listeria monocytogenes to food and clinical contact surfaces.

A bioluminescent phenotype of Listeria monocytogenes was employed to study the adhesion and biofilm formation of both classical and L-forms to relevant food and clinical contact surfaces. Attachment of both parental (cell-walled) and L-forms to intravenous tubing and stainless steel was compared using viable counts and bioluminescence. Both cell types attached themselves to intravenous tubing and stainless steel. Parental cell numbers attached to intravenous tubing were 1 log higher than L-form numbers, and on stainless steel, attached L-form numbers were 1 log higher. Bioluminescence measurements yielded a pattern similar to viable count measurements. There was a clear relationship between light output of attached bacteria and their viability and, thus, a bioluminescent phenotype provides a rapid monitor of both microbial viability and biofilm formation by L-forms.

Bacterial Adhesion↗
PubMed1990

Root canal dentinal tubule disinfection.

Dentinal tubules of the root canal walls of human teeth were infected in vitro with a known bacterial isolate. The roots were exposed to either calcium hydroxide or iodine potassium-iodide for various periods of time and the viability of microorganisms was determined by incubation of entire root samples in a culture medium. The effects of the two agents on microbial viability were evaluated and compared. Iodine potassium-iodide disinfected dentin effectively. In contrast, bacteria remained viable in the dentin after relatively extended periods of calcium hydroxide treatment.

Calcium Hydroxide↗