PubMed Health⌕ Search

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 991 records · Page 55Linked to original sources
PubMed1995

Influences on the antimicrobial activity of surface-adsorbed nisin.

The efficacy of the antimicrobial peptide nisin was examined after adsorption to silica surfaces. Three protocols were used to evaluate nisin's activity against adhered cells of Listeria monocytogenes: bioassay using Pediococcus pentosaceous FBB 61-2 as the sensitive indicator strain; visualization and enumeration of cells by microscopic image analysis; and viability of adhered cells as determined by lodonitrotetrazolium violet uptake and crystallization. The activity of adsorbed nisin was highly dependent upon conditions of adsorption. The highest antimicrobial activity of adsorbed nisin occurred with high concentrations of nisin (1.0 mg ml-1) and brief contact times (1 h) on surfaces of low hydrophobicity. Sequential adsorption of a second protein (beta-lactoglobulin or bovine serum albumin) onto surfaces consistently resulted in decreased nisin activity. These data provide direction for the development of applications to limit microbial attachment on food contact surfaces through the use of adsorbed antimicrobial peptides.

Adsorption↗
PubMed2006

Avian multiple inositol polyphosphate phosphatase is an active phytase that can be engineered to help ameliorate the planet's "phosphate crisis".

Contemporary phytase research is primarily concerned with ameliorating the problem of inadequate digestion of inositol hexakisphosphate (phytate; InsP6) in monogastric farm animal feed, so as to reduce the pollution that results from the high phosphate content of the manure. In the current study we pursue a new, safe and cost-effective solution. We demonstrate that the rate of hydrolysis of InsP6 by recombinant avian MINPP (0.7 micromol/mg protein/min) defines it as by far the most active phytase found to date in any animal cell (the corresponding activity of recombinant mammalian MINPP is only 0.006 micromol/mg protein/min). Although avian MINPP has less than 20% sequence identity with microbial phytases, we create a homology model of MINPP in which it is predicted that the structure of the phytase active site is well-conserved. This model is validated by site-directed mutagenesis and by use of a substrate analogue, scyllo-InsP6, which we demonstrate is only a weak MINPP substrate. In a model chicken cell line, we overexpressed a mutant form of MINPP that is secretion-competent. This version of the enzyme was actively secreted without affecting either cell viability or the cellular levels of any inositol phosphates. Our studies offer a genetic strategy for greatly improving dietary InsP6 digestion in poultry.

6-Phytase↗
PubMed1984

Investigations into the mechanism of action of the antibacterial agent norfloxacin.

Examination of the mechanism of action of norfloxacin upon susceptible strains of Escherichia coli K12 has shown that the drug exerts a potent bactericidal effect resulting from the inhibition of the A subunit of the essential enzyme DNA gyrase. It is also shown that the use of norfloxacin can reduce the total number of bacteria at the site of an infection as well as having significant effects upon the metabolism of treated cells in the interim period between the loss of viability and cell-lysis. These effects may provide a clue to a previously unsuspected mechanism of providing symptomatic relief which functions in parallel with the elimination of viable pathogenic bacteria.

Anti-Infective Agents, Urinary↗
PubMed1996

SYR2, a gene necessary for syringomycin growth inhibition of Saccharomyces cerevisiae.

The Pseudomonas syringae cyclic lipodepsipeptide syringomycin inhibits the growth of Saccharomyces cerevisiae. A novel yeast gene, SYR2, was found to complement two syringomycin-resistant S. cerevisiae mutants. SYR2 was cloned, sequenced, and shown to encode a 349 amino acid protein located in the endoplasmic reticulum. SYR2 was identical to SUR2, which is involved in survival during nutritional starvation. Gene disruption or overexpression of SYR2 did not affect cell viability or ergosterol levels, but did influence cellular phospholipid levels. The findings suggest that phospholipids are important for the growth inhibitory action of syringomycin.

Amino Acid Sequence↗
PubMed1992

Evaluation of a non-radioactive DNA probe for detecting Porphyromonas gingivalis in subgingival specimens.

This study compared the ability of a nonradioactive digoxigenin-labeled DNA probe and anaerobic culture to identify subgingival Porphyromonas gingivalis. Total cellular DNA from P. gingivalis ATCC 33277T was labeled using the Genius kit from Boehringer Mannheim Biochemicals. Anaerobic culture was performed using VMGA III transport medium and enriched brucella blood agar. The DNA probe could detect as little as 1000 P. gingivalis cells added to supragingival plaque. Also, the probe could detect P. gingivalis when it was present in proportions too low to be visualized on overgrown bacterial plates. The probe showed no visible reaction with strains of various oral species or with thousands of non-P. gingivalis colonies from plaque samples. VMGA III could maintain the viability of P. gingivalis for up to 6 days, as evidenced by DNA probing of colony blot of subgingival cultures. A total cellular DNA probe for detecting P. gingivalis seems to offer a simple and reliable method of detecting the organism in subgingival specimens.

Colony Count, Microbial↗
PubMed1996

Survival of Salmonella enteritidis Pt4 and Salm. typhimurium Swindon in aerosols.

Small particle aerosols of plate-grown Salmonella enteritidis and Salm. typhimurium were generated and maintained within a rotating drum at 75% relative humidity and 24 degrees C for 2 h. Plate-grown organisms were found to be more aerosol-stable than broth-grown organisms. Differences were observed between the two species; plate-grown Salm. typhimurium retained 100% viability after 2 h compared to approximately 70% for plate-grown Salm. enteritidis. A large proportion of cells of both serotypes remained viable in aerosols after 2 h, confirming the potential for airborne transmission for these organisms, e.g. within henhouses and during food processing.

Aerosols↗
PubMed2000

Flow cytometric monitoring of antibiotic-induced injury in Escherichia coli using cell-impermeant fluorescent probes.

Three fluorescent nucleic acid binding dyes-propidium iodide, TO-PRO-1, and SYTOX green-were evaluated, and their abilities to distinguish between bacterial cells with and without an intact cytoplasmic membrane were compared. Each dye was readily able to discriminate between healthy and permeabilized cells of Escherichia coli, although SYTOX green showed a greater enhancement in fluorescence intensity on staining-compromised, as opposed to healthy, cells in log-phase growth, than either PI or TO-PRO-1. Flow cytometric analysis of E. coli stained with these dyes after exposing them to several antimicrobial agents showed that all three dyes were able to detect antimicrobial action. Notably, however, the intensity of the cell-associated fluorescence was related to the mechanism of action of the antimicrobial agent. Large changes in fluorescence intensity were observed for all the dyes subsequent to beta-lactam antibiotic action, but smaller changes (or no change) were seen subsequent to exposure to antimicrobials acting directly or indirectly on nucleic acid synthesis. Furthermore, cell-associated fluorescence did not relate to loss of viability as determined by plate counts. Despite offering much insight into antimicrobial mechanisms of action, these fundamental problems become relevant to the development of rapid antimicrobial susceptibility tests if colony formation is used as the standard.

Anti-Bacterial Agents↗
PubMed1979

Effect of glycerol on viability and other properties of starved Mycobacterium fortuitum.

Cells of Mycobacterium fortuitum kept in 0.85% saline solution containing 0.1% Tween 80 (without glycerol) survive for a long time. In glycerol-enriched medium, they continue to lose their viability at a high rate; after 71 days of exposure the percentage of survival as indicated by colony formation and respiratory and dehydrogenase activities is lower than 1%. Surviving cells starved in medium without glycerol revealed unchanged sensitivity to streptomycin, p-aminosalicylic acid, and isoniazid.

Antitubercular Agents↗
PubMed2004

Killing of periodontopathogenic bacteria by photodynamic therapy.

BACKGROUND: The aim of this study was to evaluate a new approach for killing periodontopathogenic bacteria using photodynamic therapy (PDT). METHODS: In this study, we investigated the photosensitizers chlorin e6, BLC 1010, and BLC 1014 by three different methods for their effect in PDT on the viability of periodontopathogenic bacterial species. The methods included examination of inhibition zones on agar plates, determination of colony-forming units (CFU), and the use of a bacterial viability kit. RESULTS: Using the CFU method, we were able to demonstrate that the anaerobic bacteria Porphyromonas gingivalis, Fusobacterium nucleatum, and Capnocytophaga gingivalis can be photoinactivated completely by illumination with an intensity of 5.3 J/cm2 in the presence of 10 microM chlorin e6 and 10 microM BLC 1010. With the photosensitizers chlorin e6 and BLC 1010, we were able to induce zones of inhibition on agar plates. BLC 1014 failed to produce a zone of inhibition. The results of the bacterial viability test also showed that the photosensitizer BLC 1014 provides the lowest photodynamic effect in comparison to the others. CONCLUSION: The data collected to date suggest that photodynamic therapy with chlorin e6 and BLC 1010 is advantageous for suppressing periodontopathogenic bacteria.

Aggregatibacter actinomycetemcomitans↗
PubMed2005

Bacterial strains from moldy buildings are highly potent inducers of inflammatory and cytotoxic effects.

UNLABELLED: We aimed to identify inflammatory and cytotoxic potential of individual indoor air bacterial and fungal strains, as well as extracts of indoor air filter samples containing bacteria and fungi. Mouse RAW264.7 macrophages were exposed in vitro to four bacterial strains; Streptomyces californicus, Mycobacterium terrae, Bacillus cereus and Pseudomonas fluorescens, and three fungal strains; Penicillium spinulosum, Aspergillus versicolor and Stachybotrys chartarum. Furthermore, RAW264.7 macrophages were exposed to indoor air filter sample extracts representing 'low' (n = 21) and 'high' (n = 20) exposure to viable fungi or bacteria. Production of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) as well as cell viability were measured after 24 h exposure. The results show that the bacterial strains induce more profound production of NO, TNF-alpha and IL-6 than the studied fungal strains. They also decrease the viability of mouse macrophages. Similarly, the indoor air filter samples with high concentration of bacteria induced a statistically significant increase in TNF-alpha and IL-6 production as well as a decrease in cell viability. Altogether, these results suggest that indoor air bacterial strains are potent inducers of inflammatory responses and thus possibly related to adverse health effects of the inhabitants. PRACTICAL IMPLICATIONS: There is abundant documentation of the association between building dampness and mold and adverse health effects on occupants, but the causal agents of the effects are still unclear. In order to reveal these causal links, experimental studies with in vitro and in vivo methods are needed. The present findings shed new light on studies of the microbial constituents of indoor air in moldy buildings responsible for adverse health effects. These results imply that bacteria should also be monitored in cases of suspected microbial contamination of indoor air.

Air Microbiology↗
PubMed2002

The relationship of temperature to desiccation and starvation tolerance of the Mycobacterium avium complex.

Mycobacterium avium grew in media at 14-37 degrees C, and persisted at 4 degrees C and 42 degrees C. The bacteria lost approximately 90% viability after 3 months in reverse-osmosis deionized water at 4-37 degrees C. Cooler temperatures lowered the death rate. Death rates also decreased after a 5- to 10-day starvation adaptation period. Alterations of the steady-state levels of different mycolic acid classes, presumably to facilitate thermoadaptation, were found. Following desiccation, M. avium lost viability at a constant rate (half-life of 2.3 days). This implies that bacilli contaminating dry medical surfaces would persist for short periods of time. The remarkable stress survival exhibited by M. avium further suggests persistence in a range of environmental and clinical settings.

Bacterial Proteins↗
PubMed1990

Pharmacogenetics of cyclic guanylate, antioxidants, and antioxidant enzymes in Saccharomyces.

Supplements of antioxidants, superoxide dismutase (SOD), catalase, cyclic guanylate (cGMP), and theophylline, or omission of iron and copper from the medium are therapeutic for the inferior growth and viability of yeast mutants doubly deficient in mitochondrial and exocellular SOD isozymes under oxidative stresses. Cyclic adenylate tends to be ineffective or counterproductive. Oxy-stress resistant revertants are cross-resistant to other oxy-stresses and acquire one, the other, or both isozymes. The principal conclusions are: i) a genetic defect in cGMP metabolism probably compromises regulation of the enzymes' synthesis; ii) the enzymes are only essential for growth and viability under oxidative stresses; iii) oxidative toxicity is mediated by both exo- and endocellular oxy-radicals, particularly hydroxyl radicals; and iv) the pharmacogenetic features and the mutants' phenotypes are quite similar to those of negative antioxidant enzyme regulatory mutants of the related ascomycete Neurospora.

Antioxidants↗
PubMed2000

Polymyxin permeabilization as a tool to investigate cytotoxicity of therapeutic aromatic alkylators in DNA repair-deficient Escherichia coli strains.

Chlorambucil (CLB; N,N-bis(2-chloroethyl)-p-aminophenylbutyric acid) and its biologically active beta-oxidation product phenylacetic acid mustard (PAM; N,N-bis(2-chloroethyl)-p-aminophenylacetic acid) are bifunctional aromatic alkylators. CLB is in wide clinical use as an anticancer drug and also as an immunosuppressant. The chemical structures indicate that CLB and PAM are mutagenic, teratogenic and carcinogenic, but the mode of action has remained obscure. We have investigated the biological effects of CLB and PAM with DNA repair-deficient Escherichia coli strains. In contrast to MNNG (N-methyl-N'-nitro-N-nitrosoguanine), CLB and PAM were not toxic to E. coli, but permeabilization of the outer membrane of the cells through use of polymyxin B nonapeptide (PMBN) rendered them susceptible to these compounds. The importance of DNA repair, shown by reversal of damage and attenuation of the toxicity of CLB and PAM, was indicated by the susceptibility of cells lacking O(6)-methylguanine-DNA methyltransferase I and II (ada ogt). Similarly, the protective role of base excision repair (BER) was substantiated by demonstration of an even more increased susceptibility to CLB and PAM of cells lacking 3-methyladenine-DNA glycosylase I and II (alkA1 tag-1). Cells deficient in mismatch repair (mutS) appeared to be slightly more sensitive than normal cells to CLB and PAM, although no such sensitivity to MNNG was observed. This implicates the role of mismatches in CLB- and PAM-related cytotoxicity. It is generally believed that bifunctional alkylating agents, like CLB and PAM, exert their cytotoxic action via DNA cross-linking. Our results with O(6)-methyltransferase- and 3-methyladenine-DNA glycosylase-deficient cells indicate that removal of the adducts prior to the formation of cross-links is an important mechanism maintaining cell viability. We conclude that PMBN permeabilization provides a valuable tool to investigate genetically engineered E. coli cells, whose outer membrane is not naturally permeable to mutagens or other interesting compounds.

Alkylating Agents↗
PubMed2003

Liposomal entrapment of cefoxitin to improve cellular viability and function in human saphenous veins.

Liposomal cefoxitin was prepared and applied to the pretreatment of human saphenous vein (HSV) for implantation. The possible use of liposomal cefoxitin to improve cellular viability and function and to maintain its potential sterilization effect was investigated. Entrapment efficiency and size distribution of liposomal cefoxitin were 75.7% and 652 +/- 75.7 nm, respectively. The weight ratio between cefoxitin and liposome was calculated at 1 : 40.6. When cefoxitin was entrapped with liposome, the released amount of cefoxitin was not affected by temperature conditions (37 degrees C, 25 degrees C, and 4 degrees C). The amount of free cefoxitin present in HSV reached 59% at 0.5 h and gradually decreased with time, while liposomal cefoxitin showed a maximum amount (63%) at 1.5 h, indicating that liposomal cefoxitin seemed to control the initial amount of cefoxitin present in HSV. Liposomal cefoxitin showed better viabilities of whole cells and endothelial cells dissociated from HSV than free cefoxitin and remarkably superior function of endothelial cells, as determined by Griffonia simplicifolia agglutinins-fluorescein isothiocyanate/propidium iodide double-staining methods combined with flow cytometry and endothelial nitric oxide synthase assay, respectively. In terms of sterilization effect, there was no significant difference between liposomal cefoxitin and free cefoxitin. These results suggest that liposomal entrapment of cefoxitin could improve cellular viability and functions and maintain the original sterilization effect.

Anti-Bacterial Agents↗
PubMed1999

Growth inhibition of Staphylococcus aureus by H2O2-producing Lactobacillus paracasei subsp. paracasei isolated from the human vagina.

H2O2 production by certain Lactobacillus strains is one of the mechanisms that helps to regulate the vaginal ecosystem. This paper describes the kinetics of H2O2 production by two different strains of Lactobacillus paracasei subsp. paracasei under different culture conditions and the effect of this metabolite on the growth of Staphylococcus aureus. L. paracasei F2 produced 2.72 mmol 1-1 H2O2 while L. paracasei F28 produced 1.84 mmol l(-1), both in agitated cultures. Although L. paracasei F2 produced a higher H2O2 concentration than L. paracasei F28, H2O2 production per number of live bacterial cells was 10-fold higher for F28. The latter also showed a faster decrease in viability during the stationary phase. There were no detectable levels of H2O2 in cultures without agitation. H2O2-producing lactobacilli inhibited growth of S. aureus in a plaque assay and in mixed cultures, depending on the initial inoculum of the pathogen.

Catalase↗
PubMed1998

Invasion and persistence of Streptococcus dysgalactiae within bovine mammary epithelial cells.

Little is known about bacterial and host factors that contribute to the establishment and persistence of intramammary infection by Streptococcus dysgalactiae. Streptococcus dysgalactiae adheres to epithelial cells from the bovine mammary gland and to extracellular matrix proteins in vitro and invades mammary epithelial cell cultures, all of which can be potentially important pathogenic mechanisms. In this study, mechanisms involved in the invasion of Strep. dysgalactiae into epithelial cells from the bovine mammary gland were characterized. Studies were conducted to determine whether Strep. dysgalactiae invaded mammary epithelial cell cultures in a dose-dependent manner and whether mammary epithelial cells that harbored different numbers of Strep. dysgalactiae for varying times were damaged. Bacterial invasion increased as inoculum size increased; however, the number of intracellular bacteria was not proportional to the inoculum size, increased; however, the number of intracellular bacteria was not proportional to the inoculum size, indicating that a finite number of organisms is capable of invading epithelial cells. No net increase in intracellular organisms was detected at any bacterial density evaluated; however, Strep. dysgalactiae remained viable throughout the evaluation. In addition, Strep. dysgalactiae did not appear to cause cell injury at any bacterial density or time point evaluated. These data suggest that Strep. dysgalactiae can survive within mammary epithelial cells for an extended time without losing viability or damaging the eukaryotic cell. This feature may be associated with the development of persistent infection and protection of organisms from antimicrobial drugs and host defense mechanisms and may provide a route for bacterial colonization of subepithelial tissues.

Animals↗
PubMed2004

The biogenic amine tyramine modulates the adherence of Escherichia coli O157:H7 to intestinal mucosa.

The environmental factors that influence the ability of Escherichia coli O157:H7 to attach to the intestinal mucosa are incompletely understood. In the present study, the ability of one of the most common biogenic amines present in food, tyramine, to influence the ability of E. coli O157:H7 to adhere to murine cecal mucosa was examined. Ex vivo full-thickness sheets of murine cecum were mounted in Ussing chambers, which preserved the enteric nervous system innervation of the luminal epithelia and thereby allowed us to achieve a closer approximation of bacterial adherence than would be encountered in vivo. After exposure of the luminal aspect of the cecum to tyramine, E. coli O157:H7 was added for 90 min. The cecal tissue was then removed and washed, and adhered E. coli O157:H7 was enumerated using a selective medium. Tyramine significantly increased E. coli O157:H7 adherence to cecal mucosa when compared to that of controls. The 50% effective concentration of tyramine was 92.6 microM. Specific adrenergic antagonists were then employed to examine whether the effect of tyramine was mediated through alpha- or beta-adrenergic receptors on the intestinal tissue. Pretreatment of tissues with either the alpha-adrenergic receptor antagonist phentolamine or the beta-adrenergic receptor antagonist propranolol prevented the action of tyramine. Measurement of active transepithelial ion transport and ionic permeability in the cecal sheets before and after the addition of tyramine and E. coli O157:H7 did not show any impairment of tissue viability or transepithelial conductance. Further, tyramine did not influence either the growth of E. coli O157:H7 or the expression of the intimin attachment factor. The present findings suggest that biogenic amines, such as tyramine, present within the food matrix influence host susceptibility to E. coli O157:H7 infection.

Animals↗