SEARCH · PubMed Health

Results for “Microbial Viability”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources

PubMed2005

Antimicrobial activity of diterpenoids from hairy roots of Salvia sclarea L.: salvipisone as a potential anti-biofilm agent active against antibiotic resistant Staphylococci.

The antimicrobial activities of crude dichloromethane fractions from acetone extracts of Agrobacterium rhizogenes transformed roots and roots of field-grown plants of Salvia sclarea as well as four pure abietane diterpenoids isolated from the hairy root cultures were determined. The growth of Gram-positive bacteria (Staphylococcus aureus, S. epidermidis, Enterococcus faecalis) but not Gram-negative ones (Escherichia coli, Pseudomonas aeruginosa) or pathogenic fungi (Candida albicans) was inhibited by fractions tested at concentrations of 37.5-75.0 microgml(-1). Abietane diterpenoids: salvipisone, aethiopinone, 1-oxoaethiopinone and ferruginol were shown to be bacteriostatic as well as bacteriocidal for the cultures of S. aureus and S. epidermidis strains, regardless of their antibiotic susceptibility profile. This was demonstrated by using simultaneously the optical density measuring method and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide-reduction assay. The highest activity was shown by salvipisone which demonstrated also a very interesting activity when its effect on 24-h-old staphylococcal biofilm cells viability was examined. It limited the survival of biofilms formed by S. aureus as well as by S. epidermidis, putting this compound to the list of potential anti-biofilm agents, better than most of known antibiotics.

Anti-Bacterial Agents↗

PubMed2002

The survival and persistence of Lactobacillus acidophilus LF221 in different ecosystems.

Being a human isolate and bacterocin producer with wide antimicrobial spectrum, Lactobacillus acidophilus LF221 fulfills preliminary conditions as a potential probiotic strain. To investigate the LF221 strain with respect to its persistence in complex ecosystems, viable LF221 cells were orally administered to laboratory animals (mice and piglets) and added to cheese milk. During the 10-day feeding of mice with LF221 viable cells, 0.9% of lactobacilli isolated from faeces were identical with LF221 strain. Within the piglets' feeding trial, 920 lactobacilli colonies randomly selected from faecal samples were screened for the presence of LF221-like colonies. During the six times of sampling of piglets' faeces, LF221 colonies were always detected. Even the final sampling 10 days after the last LF221 cell suspension was dosed into piglets revealed the presence of LF221 strain at a concentration of about 3 x 10(8) cells/g of faeces. LF221 intake did not significantly influence the total count of lactobacilli in faecal samples and it had no negative health effects on animals. Analyses of cheese demonstrated that the LF221 strain maintained a high viability during ripening and that it could be detected for at least 6 weeks at a level of about 6.8 x 10(6) cells/g of cheese. According to these results, semihard cheese represents a suitable medium for introducing a potential probiotic LF221 into a diet.

Administration, Oral↗

PubMed2004

Segregation to non-dividing cells in recombinant Escherichia coli fed-batch fermentation processes.

In Escherichia coli fermentation processes, a drastic drop in viable cell count as measured by the number of colony forming units per ml (c.f.u. ml(-1)) is often observed. This phenomenon was investigated in a process for the production of the recombinant fusion protein, promegapoietin (PMP). After induction, the number of c.f.u. ml(-1) dropped to approximately 10% of its maximum though the biomass concentration continued to increase. Flow cytometric analysis of viability and intracellular concentration of PMP showed that almost all cells were alive and contributed to the production. Thus, the drop in the number of c.f.u. ml(-1) probably reflects a loss of cell division capability rather than cell death.

Apoptosis↗

PubMed2001

Endoplasmic reticulum chaperone gp96 is required for innate immunity but not cell viability.

Chaperone proteins are thought to promote the correct folding and assembly of newly synthesized proteins and to facilitate restoration of the folded state under environmental conditions that favour protein denaturation. They are among the most ubiquitous and highly conserved of all proteins. The eukaryotic endoplasmic reticulum (ER) chaperone gp96 in particular has long been thought to be indispensable for cell survival. Here we report that a screen for genes required for the immune response to bacterial endotoxins has identified a B-cell line deficient in gp96. Absence of gp96 is compatible with cellular survival even under stress conditions and causes a defect in the formation of only a small subset of cell surface receptors. Toll-like receptors are retained intracellularly in the absence of gp96, explaining the unresponsiveness of the mutant to microbial stimuli.

Animals↗

PubMedDate not supplied

Inhibition of human immunodeficiency virus type-1 (HIV-1) replication by immunor (IM28), a new analog of dehydroepiandrosterone.

The inhibition of HIV-1 replication in vitro by Immunor 28 (IM28), an analog of dehydroepiandrosterone (DHEA), was monitored using the HIV-1 laboratory wild-type strain IIIB. Evaluation of the 50% inhibitory dose (IC50) revealed a decrease in HIV-1 replication giving an IC50 value around 22 microM. The toxicity of the drug has been determined also, in MT2 cells and PBMCs. 60 microM of IM28 provoked a 50% decrease in cell viability while DHEA caused the same decrease at 75 microM in MT2 cells. These values are 125 microM for IM28 in PBMCs and 135 microM for DHEA. Thus, DHEA is less toxic than IM28, but IM28 has a higher antiviral activity.

Anti-HIV Agents↗

PubMed1987

Effect of alternating current exposure on the resistivity of resting Escherichia coli B cells to crystal violet and other basic dyes.

Phosphate buffer suspensions of resting Escherichia coli B cells at pH 7.0 were anaerobically exposed to alternating current (a.c.) of 50 Hz at a current density of 600 +/- 60 mA/cm2 and 34 degrees +/- 3 degrees C. The minimum inhibitory concentrations of eight basic dyes: crystal violet, malachite green, brilliant green, fuchsin, methylene blue, toluidine blue, safranin and acriflavine for exposed cells were decreased to about the half values of those for unexposed ones when both cells were grown in the minimal medium including one of the dyes. The integrated viabilities of exposed cells tended to decline with increasing concentration of the dyes markedly more than those of unexposed ones, whereas the exposed cells took up the dyes less readily than the unexposed cells. These results suggested that a.c. exposure may serve as an agent which renders E. coli cells susceptible to the basic dyes.

Coloring Agents↗

PubMed1995

The antimicrobial activity of hexapeptides derived from synthetic combinatorial libraries.

A series of peptides identified through the use of synthetic hexapeptide combinatorial libraries (represented by the formula Ac-RRWWCO-NH2) were examined for their antimicrobial activity against five different micro-organisms. Their toxicity was also evaluated in an in vitro haemolytic assay. The peptides showed activity against the five micro-organisms, although higher activities were found against Gram-positive bacteria. Both growth inhibition and cell viability assays were carried out to demonstrate the bactericidal activities of these peptides against two of the micro-organisms tested. The dimeric cystine forms of these peptides were shown to have biological activities identical to the monomeric forms.

Amino Acid Sequence↗

PubMed2002

[Mode of action of ciclopiroxolamine on Candida albicans].

Candida albicans is a common pathogen causing both superficial and invasive mycoses. The hydroxypyridone ciclopiroxolamine belongs to antimycotic drugs used for treatment of superficial mycoses. Whereas the mode of action of other antimycotics, for example the azoles, is well known, the specific action of ciclopiroxolamine is poorly understood. There are hints, that ciclopiroxolamine acts as a potential chelating agent and influences some cellular processes by chelating metal ions. Consequently, the antimycotic effectiveness of ciclopiroxolamine could be due to a general reduced viability of the fungus, or due to a higher sensitivity of a fungus against the human immune system as well as due to a reduced capability to produce some specific virulence factors that are indispensable for infection. Nevertheless, iron metabolism seems to play a major role in its effect.

Candida albicans↗

PubMed2006

Intrinsic properties of so-called dormant probiotic bacteria, determined by flow cytometric viability assays.

Plate counting and four culture-independent flow cytometric assays were used to determine the viability and intrinsic properties of three probiotic strains during storage. The strains showed reduction in plate counts but were able to maintain esterase activity, intact cytoplasmic membrane, and pH gradient. The apparently uncultivable probiotic cells were active and stress resistant.

Animals↗

PubMed1999

Interactions between cationic liposomes and bacteria: the physical-chemistry of the bactericidal action.

The bactericidal effect of dioctadecyldimethylammonium bromide (DODAB), a liposome forming synthetic amphiphile, is further evaluated for Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Staphylococcus aureus in order to establish susceptibilities of different bacteria species towards DODAB at a fixed viable bacteria concentration (2.5 x 10(7) viable bacteria/mL). For the four species, susceptibility towards DODAB increases from E. coli to S. aureus in the order above. Typically, cell viability decreases to 5% over 1 h of interaction time at DODAB concentrations equal to 50 and 5 microm for E. coli and S. aureus, respectively. At charge neutralization of the bacterial cell, bacteria flocculation by DODAB vesicles is shown to be a diffusion-controlled process. Bacteria flocculation does not yield underestimated counts of colony forming units possibly because dilution procedures done before plating cause deflocculation. The effect of vesicle size on cell viability demonstrates that large vesicles, due to their higher affinity constant for the bacteria (45.20 m(-)) relative to the small vesicles (0.14 m(-)), kill E. coli at smaller DODAB concentrations. For E. coli and S. aureus, simultaneous determination of cell viability and electrophoretic mobility as a function of DODAB concentration yields a very good correlation between cell surface charge and cell viability. Negatively charged cells are 100% viable whereas positively charged cells do not survive. The results show a clear correlation between simple adsorption of entire vesicles generating a positive charge on the cell surfaces and cell death.

Anti-Bacterial Agents↗

PubMed1999

Cell surface analysis techniques: What do cell preparation protocols do to cell surface properties?

Cell surface analysis often requires manipulation of cells prior to examination. The most commonly employed procedures are centrifugation at different speeds, changes of media during washing or final resuspension, desiccation (either air drying for contact angle measurements or freeze-drying for sensitive spectroscopic analysis, such as X-ray photoelectron spectroscopy), and contact with hydrocarbon (hydrophobicity assays). The effects of these procedures on electrophoretic mobility, adhesion to solid substrata, affinity to a number of Sepharose columns, structural integrity, and cell viability were systematically investigated for a range of model organisms, including carbon- and nitrogen-limited Psychrobacter sp. strain SW8 (glycocalyx-bearing cells), Escherichia coli (gram-negative cells without a glycocalyx), and Staphylococcus epidermidis (gram-positive cells without a glycocalyx). All of the cell manipulation procedures severely modified the physicochemical properties of cells, but with each procedure some organisms were more susceptible than others. Considerable disruption of cell surfaces occurred when organisms were placed in contact with a hydrocarbon (hexadecane). The majority of cells became nonculturable after air drying and freeze-drying. Centrifugation at a high speed (15,000 x g) modified many cell surface parameters significantly, although cell viability was considerably affected only in E. coli. The type of washing or resuspension medium had a strong influence on the values of cell surface parameters, particularly when high-salt solutions were compared with low-salt buffers. The values for parameters obtained with different methods that allegedly measure similar cell surface properties did not correlate for most cells. These results demonstrate that the methods used to prepare cells for cell surface analysis need to be critically investigated for each microorganism so that the final results obtained reflect the nature of the in situ microbial cell surface as closely as possible. There is an urgent need for new, reliable, nondestructive, minimally manipulative cell surface analysis techniques that can be used in situ.

Bacterial Adhesion↗

PubMed2006

Effects of the pathogenic Vibrio tapetis on defence factors of susceptible and non-susceptible bivalve species: I. Haemocyte changes following in vitro challenge.

In microbial infections, the interaction between microorganisms and phagocytic cells is a crucial determinant in the outcome of the disease process. We used flow cytometry to study the in vitro interactions between Vibrio tapetis, the bacterium responsible for Brown Ring Disease (BRD) in the Manila clam Ruditapes philippinarum, and haemocytes from three bivalve species: the Manila clam (susceptible to BRD), the hard clam Mercenaria mercenaria and the eastern oyster Crassostrea virginica (both non-susceptible to BRD). Results demonstrated that V. tapetis cells and extracellular products elicit major changes in the haemocytes of R. philippinarum, including decreased viability and phagocytic activity, and altered size and internal structure. V. tapetis was able to kill haemocytes from M. mercenaria and C. virginica but to a far lesser extent than those of R. philippinarum. These results suggest that disease resistance is not solely dependent on a host activity against the pathogen, but is also a function and magnitude of the injury to the host cell by a given pathogen.

Analysis of Variance↗

PubMed2006

Mesocosm experiments for evaluating the biological efficacy of ozone treatment of marine ballast water.

Ballast water is a major pathway for the transfer of non-indigenous species in aquatic environments. The objectives of this study were to determine the ability of ozone to reduce the numbers of a spectrum of marine organisms collected from Puget Sound, Washington in replicated mesocosm (280 l) experiments, and estimate the minimum ozone concentrations as measured by total residual oxidant (TRO) required to reduce organism densities. Ozone treatment was effective in removing bacteria, phytoplankton, and mesozooplankton with initial TRO concentrations of 2-5 mg l(-1) as Br(2). Persistence of TRO resulted in an extended period of toxicity and cumulative mortality. TRO decay allowed bacteria populations to multiply when TRO levels fell below 0.5-1.0 mg l(-1) as Br(2). Phytoplankton chlorophyll a concentrations were rapidly reduced by ozone treatment and did not increase in any treatments or controls because of lack of light. Overall mesozooplankton viability was rapidly reduced by 90-99% in treatment TRO levels above 1.85 mg l(-1) as Br(2). Our study outlines novel protocols that can be used for testing different potential ballast water treatment systems in replicated and controlled mesocosm experiments.

Animals↗

PubMed2000

Effects of Streptococcus crista and human saliva on the viability of Fusobacterium nucleatum ATCC 10953.

Associations with facultative species might help planktonic oral anaerobes survive when they traverse saliva. This study investigated whether co-aggregation with Streptococcus crista ATCC 51110 enhanced the viability of Fusobacterium nucleatum ATCC 10953. Two tubes each of co-aggregates and Fus. nucleatum ATCC 10953 alone were prepared. One of each set was resuspended in buffer, and the other in clarified saliva from each of 20 donors. After 1 h, cells were stained for viability. The median percentage of viable Fus. nucleatum ATCC 10953 in buffer with Strep. crista (86%) was significantly higher (p=0.04) than in buffer alone (77%). A similar trend was observed for saliva with Strep. crista (81%) and saliva alone (74%), although that difference was not significant (p=0.41). The median percentage of Fus. nucleatum co-aggregated in buffer (44%) was significantly reduced after incubation in saliva (16%) (p<0.0002). No such change was seen when saliva was replaced with purified salivary proline-rich glycoprotein, which can bind both species. For co-aggregate suspensions, there was no difference in the viability of fusobacteria that were or were not in direct contact with Strep. crista. In both cases, viability was significantly reduced in saliva relative to buffer. Strep. crista may enhance the viability of planktonic Fus. nucleatum ATCC 10953, but it is not yet clear whether that requires co-aggregation. Transmission of fusobacteria through saliva could depend on the interplay between protective factors, such as the presence of streptococci, and antimicrobial factors, which kill cells or disassociate co-aggregates.

Anti-Bacterial Agents↗

PubMed2001

Biofilm culture of Pseudomonas aeruginosa expressing lux genes as a model to study susceptibility to antimicrobials.

A simple in vitro model for culture of biofilm populations of self-bioluminescent Pseudomonas aeruginosa was used for real-time monitoring of the effects of ciprofloxacin. Biofilms of these organisms were established within Sorbarod filters, perfused with a chemically defined simple salts medium. The biofilm population was shown to achieve a pseudo-steady state which was reproducible and stable over several days. The viability of membrane-associated and eluted cells was assessed by spread plate viable counts and by monitoring bioluminescence as a measure of metabolic activity. Pseudo-steady state biofilms were exposed to 5x MIC ciprofloxacin (0.3 mg x l(-1)) in the perfusing medium for 1 h. Whilst both methods for viability assessment indicated an immediate reduction in viable cell numbers, the decline recorded with bioluminescence was greater. The use of bioluminescent bacteria proved to be a rapid and sensitive method for the measurement of real-time antibacterial effects on a bacterial biofilm.

Anti-Infective Agents↗

PubMed1994

Intracellular activity of azithromycin against bacterial enteric pathogens.

Azithromycin, a new azalide antibiotic, is active in vitro against a variety of enteric bacterial pathogens. Since it is concentrated inside human neutrophils and other cells, it might be particularly useful in the treatment of infections caused by enteropathogens that invade host tissues. The intracellular activity of azithromycin against several enteric pathogens that had been phagocytosed by neutrophils was determined. Azithromycin was effective in reducing the intracellular viabilities of almost all strains tested, including representative strains of Salmonella, Shigella, and enteroinvasive, enteropathogenic, enterotoxigenic, and enterohemorrhagic Escherichia coli. Erythromycin was also effective in this model system, although azithromycin was generally more effective than erythromycin against strains of invasive enteric pathogens. Cefotaxime reduced intracellular bacterial viability to a lesser extent than either azithromycin or erythromycin. The presence of neutrophils did not significantly affect the activity of azithromycin in this system. Azithromycin may be a useful agent for the treatment of bacterial diarrhea, and clinical trials should be considered.

Azithromycin↗

PubMed2006

Enhanced survival of GroESL-overproducing Lactobacillus paracasei NFBC 338 under stressful conditions induced by drying.

GroESL-overproducing Lactobacillus paracasei NFBC 338 was dried, and its viability was compared with that of controls. Spray- and freeze-dried cultures overproducing GroESL exhibited approximately 10-fold and 2-fold better survival, respectively, demonstrating the importance of GroESL in stress tolerance, which can be exploited to enhance the technological performance of sensitive probiotic cultures.

Bacterial Proteins↗

PubMed1989

Killing of Cryptococcus neoformans by rat alveolar macrophages.

The addition of [51Cr]-labeled yeast cells of Cryptococcus neoformans to monolayers of Lewis rat alveolar macrophages (AM phi) provided a sensitive and reproducible in vitro assay of phagocytosis. AM phi and yeast cells were incubated in 10% (v:v) normal rat serum for 1 h, non-AM phi associated yeast cells were removed and the AM phi-associated radioactivity (phagocytosis) determined. Replicate wells were replenished with fresh medium and reincubated. At different times, yeast-AM phi monolayers were treated with a non-cryptococcocidal mixture of DNAse and sodium deoxycholate to release the yeast cells from the AM phi. The fate of the yeast cells was critically evaluated by [51Cr]-release and viable plate counts. Killing was detected by plate counts within an hour following phagocytosis and did not increase significantly during the next 5 h. Strains of C. neoformans with small, medium, or large capsules varied in their susceptibility to killing from 10% to 95% but susceptibility to killing was not directly related to capsule size and the extent of phagocytosis. Release of 51Cr did not correlate with viability as determined by culture. The 51Cr was associated with two pools in the yeast cells; one, representing 15-20% of the radiolabel, was easily released and was probably bound to low molecular weight compounds in the cytoplasm. The majority of label was tightly bound to the particulate alkali-soluble cell wall fraction.

Animals↗