Effects of antimalarial chemoprophylactic agents on the viability of the Ty21a typhoid vaccine strain.
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Chloroquine↗
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Results for “Microbial Viability”
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Influence of DNA on growth and viability of transformable group H streptococci.
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Chloramphenicol↗
Viability of Bacillus subtilis spores exposed to space environment in the M-191 experiment system aboard Apollo 16.
During the Apollo 16 space flight, in the experiment system M-191, (microbial response to space environment) spores of Bacillus subtilis 168 were exposed to space vacuum or solar UV irradiation with a peak wavelength of 254 nm or both. The effects of these space factors on the colony-forming ability of the spores were studied. It was found (i) that space vacuum alone did not affect the survival of pre-dried spores; (ii) that space vacuum in combination with solar UV irradiation with a peak wavelength of 254 nm had a synergistic effect, which may by attributed to a UV supersensitivity of the spores during vacuum exposure. These results agreed with findings of simulation experiments on earth. It was concluded that air dried spores may survive exposure to space vacuum if shielded against solar UV irradiation.
Bacillus subtilis↗
Removal of biofilm from endoscopes: evaluation of detergent efficiency.
BACKGROUND: Biofilm consisting of bacteria enclosed in a matrix of exopolysaccharide (EPS) forms on many medical devices such as catheters and implants. Nosocomial infection is, thus, a newly recognized scenario of biofilm development. Biofilm removal by physical methods such as ultrasound and mechanical cleaning is reasonably effective but difficult to supervise in practice. Chemical methods are often ineffective because of biofilm resistance to biocides. In this study, we compared the efficiency of different detergents used in endoscope reprocessing. METHODS: Escherichia coli biofilm was generated on Teflon and medical grade PVC tubing under low flow conditions. Sections of biofilm covered tubing were washed using test detergents and biofilm removal was assessed by counting remaining adherent bacteria after washing and by scanning electron microscopy to qualitatively assess the amount and nature of the remaining biofilm. RESULTS: Control tubing developed a multilayered biofilm consisting of >10(5) bacterial cells/cm(2). Only Matrix (Whiteley Medical, Sydney, Australia) produced >4 log reduction in viable bacterial numbers. Matrix and Epizyme Rapid (3M Australia, Pymble, Australia) were able to remove up to 75% and 60% of the biofilm, respectively. CONCLUSIONS: Many commonly used enzymatic cleaners fail to reduce the viable bacterial load or remove the bacterial EPS. Cleaners with high enzyme activity, Epizyme Rapid, removed more biofilm but failed to reduce bacterial numbers more than 2 logs. The only cleaner containing no enzymes, Matrix, significantly reduced bacterial viability and residual bacterial EPS.
Biofilms↗
Comparison of electronic and viability counting methods for determination of postantibiotic effect of oxacillin on Staphylococcus aureus.
The postantibiotic effect of oxacillin on Staphylococcus aureus ATCC 6538P was determined under different test conditions by reference (viability counting) and semiautomated (electronic counting) methods. Differences in durations of the postantibiotic effect obtained with the two counting methods were not statistically significant. The semiautomated method provided a more rapid and convenient alternative to viability counting.
Bacteriological Techniques↗
Measurement of the viability of Lawsonia intracellularis.
The objective of this study was to develop and test both a flow cytometry method (FCM) and a direct count method (DCM) that both use fluorescent stains to determine the viability of Lawsonia intracellularis (LI), an obligate intracellular bacterium and the cause of proliferative enteropathy (PE) in pigs and other animal species. Live LI were passaged in cell culture and harvested from infected McCoy cells. Dead LI were prepared by exposing live LI to 70% isopropyl alcohol for 30 min. Seven samples with dead:live ratios of 0:100 (live control), 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0 (dead control) were prepared for testing by both the FCM and the DCM. For the FCM, TO-PRO-3 iodine was applied to the samples, and viable LI were counted. For the DCM, the samples were stained with LIVE/DEAD BacLight, which contains SYTO 9 and propidium iodine, then filtered through 0.2-microm Nuclepore black polycarbonate filters, viewed, and counted with the use of an epifluorescence microscope. Data were evaluated by estimating 95% limits of agreement and the concordance correlation coefficient (CCC). The limits of agreement between the FCM and the DCM versus the standard ratio of added LI showed mean differences not equal to zero, suggesting that systematic bias was introduced. The CCC showed almost perfect agreement (r = 0.9898). With a specific fluorescent probe, the FCM is useful and as good as the DCM for determining LI viability.
Animals↗
Elevated microbial tolerance to metals and antibiotics in metal-contaminated industrial environments.
To test the hypothesis that industrial metal contaminants select for microorganisms tolerant to unrelated agents, such as antibiotics, we analyzed metal and antibiotic tolerance patterns in microbial communities in the intake and discharge of ash settling basins (ASBs) of three coal-fired power plants. High-throughput flow-cytometric analyses using cell viability probes were employed to determine tolerances of entire bacterioplankton communities, avoiding bias toward culturable versus nonculturable bacteria. We found that bacterioplankton collected in ASB discharges were significantly more tolerant to metal and antibiotic exposures than bacterioplankton collected in ASB intakes. Optical properties of microorganisms collected in ASB discharges indicated no defensive physiological adaptations such as formation of resting stages or excessive production of exopolymers. Thus, it is likely that the elevated frequency of metal and antibiotic tolerances in bacterioplankton in ASB discharges were caused by shifts in microbial community composition, resulting from the selective pressure imposed by elevated metal concentrations or organic toxicants present in ASBs.
Anti-Bacterial Agents↗
Airborne bacteria and viruses.
Coughing, sneezing, talking, bed-making, turning pages of books, etc. all generate microbial aerosols which are carried and dispersed by air movements. Inhalation of these particles may cause allergic responses but whether or not infectious disease ensues depends in part on the viability and infectivity of the inhaled microbes and their landing sites. Desiccation is experienced by all airborne microbes; gram-negative bacteria and lipid-containing viruses demonstrate phase changes in their outer phospholipid bilayer membranes owing to concomitant changes in water content and/or temperature. These changes most likely lead to cross-linking reactions of associated protein moieties principally at mid to high relative humidity (RH). For lipid-free viruses these reactions of their surface protein moieties occur most rapidly at low RH. Radiation, oxygen, ozone and its reaction products and various pollutants also decrease viability and infectivity through chemical, physical and biological modification to phospholipid, protein and nucleic acid moieties. The extent of damage and the degree of repair together with the efficacy of host defence mechanisms largely controls whether the causative microbes take hold and spread disease via the airborne route. At least indoors, where desiccation is the predominant stress, the general reversibility of membrane-phase changes by vapour-phase rehydration when coupled with efficacious microbial enzymatic repair mechanisms under genetic control, virtually ensures the spread of disease by the aerobiological pathway.
Aerosols↗
Influence of living and autoclaved yeasts of Saccharomyces boulardii on in vitro ruminal microbial metabolism.
Experimental data on the effects of Saccharomyces boulardii on rumen microbial metabolism are scarce. The aim of this study was to examine whether S. boulardii had an effect on parameters of rumen microbial metabolism at different dosages and whether the yeast would be suitable as a probiotic agent for ruminants. To test whether the potential positive effects of S. boulardii could be attributed to the yeast's viability or to its content of nutrients, living and autoclaved yeasts were tested simultaneously. For this purpose, incubation trials were carried out using the long-term rumen simulation technique. Living and autoclaved yeasts were added to fermentation vessels at a concentration of 0.5 or 1.5 g/d. The addition of living and autoclaved yeasts stimulated microbial metabolism, with no major differences between the treatments. It was concluded that ruminal microbes digested the supplied yeast of S. boulardii as an additional substrate and that S. boulardii, at least in ruminants, is utilized as a prebiotic rather than as a probiotic agent.
Ammonia↗
[The effect of treatment with sodium periodate on bacterial cell viability and transmission of multiple drug resistance by E. coli K-12].
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Drug Resistance, Microbial↗
Activated sludge deflocculation under temperature upshifts from 30 to 45 degrees C.
Twelve independent batch experiments (<9h) with fresh municipal activated sludge were conducted to assess the occurrence and the mechanisms of deflocculation under a temperature shift from 30 to 45 degrees C. In each experiment, a transient reactor (2 L) was subjected to the temperature shift and a control reactor was operated at a constant temperature of 30 degrees C. The occurrence of deflocculation was demonstrated by the increase in turbidity and in the concentrations of biopolymers in the sludge supernatant from the transient reactor. The maximum levels of proteins in the supernatants ranged from 53 to 81 mg/L, for DNA from 34 to 36 mg/L, for humic compounds from 20 to 40 mg/L, and for carbohydrates from 21 to 31 mg/L. All the biopolymer concentrations in the control reactor remained below 5-10 mg/L. The release of biopolymers was accompanied by an increase in sludge supernatant conductivity (16-32% increase, up to 1.20 mS/cm), soluble chemical oxygen demand (from 129 to 440 mg/L), total suspended solids (>25 mg/L up to 128 mg/L), and a decrease in the mixed liquor volatile suspended solids (up to 11%). The temperature shift was also found to inhibit microbial metabolism by reducing the sludge biomass substrate removal capacity, as measured by oxygen-uptake rates. The temperature shift had a marginal effect causing sludge lysis (as an increase in beta-galactosidase activity) and had no significant impact on sludge viability (live/dead ratio of bacterial cells). It was concluded that sludge deflocculation under a temperature shift from 30 to 45 degrees C involves the solubilisation of extracellular polymeric substances from the flocs and likely also floc fragmentation. In addition, sludge deflocculation and the inhibition of microbial metabolism explain the poor treatment performance observed in previous continuous reactors under similar temperature shifts.
Bacteria, Anaerobic↗
The development of an in vitro screening strategy for topically applied products.
The objective of this study was the pharmaco-toxicological understanding of the constituents of an authenticated herbal mixture. The mixture was prepared by maceration in ethanol and subsequent dilution to produce a topically applied lotion, for which the intended target conditions are psoriasis and eczema. A three-tiered in vitro screening strategy was adopted for evaluating this product, comprising cytotoxicity assays; mutagenicity screening and therapeutic evaluation. Viability assays performed with dilutions of both the herbal concentrate and final product on organotypic cell lines indicated that neither preparation acted as an irritant. Genotoxicity screening using six strains of Salmonella typhimurium showed no mutagenic potential, and furthermore significant anti-microbial activity was evident. Therapeutic evaluation involved assessing the antioxidant potential of the extract, which can be correlated to an anti-inflammatory effect. Nitroblue-tetrazolium (NBT) assay results indicate that the extract can reduce superoxide anion generation by 45%. The extract also increased cell viability on exposure to hydrogen peroxide by 28%, illustrating its dismutation potential. A 3-D skin culture system, EpiDerm, released 3000 microg/ml upon exposure to the extract, implying that the components enhance arachidonic acid metabolism. Overall, it may be concluded that the herbal extract is sufficiently non-toxic for dermal application and possesses anti-inflammatory activity.
Animals↗
Lactose digestion from yogurt: influence of a meal and additional lactose.
Lactose in yogurt is better digested than lactose in other dairy foods by lactase-deficient individuals, in part because of intraintestinal activity of yogurt microbial beta-galactosidase (beta-gal). The survival and activity of yogurt beta-gal depend on gastrointestinal transit, pH, and viability of the yogurt culture. To evaluate the ability of yogurt beta-gal to digest lactose when yogurt is consumed with food or with additional lactose, 22 healthy lactose-maldigesting individuals were fed 10 test meals. Results of breath-hydrogen expiration, incidence of symptoms, and enzyme and lactose content of gastric aspirates indicate that the consumption of a meal with yogurt does not inhibit, and may slightly improve, lactose digestion from yogurt. However, yogurt beta-gal appears unable to assist in the digestion of additional lactose beyond that normally present in yogurt.
Adult↗
Immunotoxicity of explosives-contaminated soil before and after bioremediation.
Soils from the Yorktown Naval Base contaminated with trinitrotoluene (TNT) and other explosives were used to prepare eluates before and after bioremediation using microbial growth amendments in the presence (P1 eluates) or absence (P2 eluates) of exogenous white rot fungus. Effectiveness of bioremediation was examined by several immunotoxicity assays-viability/growth of lymphocytes, cytokine production, and expression of the interleukin-2 (IL-2) receptor-using human peripheral blood mononuclear cells exposed to the eluates. Although TNT concentrations decreased in both P1 and P2 eluates relative to untreated baseline soil (BL) eluates, a recovery in lymphocyte growth/viability and IL-2 secretion was seen with P2 but not P1 eluates relative to BL eluates. IL-2 receptor levels were higher in cells exposed to BL and P2 eluates than when exposed to P1 eluates. Interferon-gamma, tumor necrosis factor-beta, and IL-10 levels were highest in BL and P2 eluates and lowest in P1 eluates. Taken together, these results suggest that treatment of the soil with microbial growth amendments in the absence but not the presence of exogenous white rot fungi lead to partial bioremediation as assessed by lymphocyte functions.
Biodegradation, Environmental↗
A rapid colorimetric assay of killer toxin activity in yeast.
The pale yellow redox indicator 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) is reduced to a dark blue end-product, MTT-Formazan, by the mitochondrial dehydrogenases of living cells. MTT reduction can be measured spectrophotometrically at a wavelength of 570 nm and a method is described to assay the cidal activity of Williopsis mrakii killer toxin against sensitive cells of Candida glabrata. The MTT assay is rapid, quantitative and compares favourably with traditional plating techniques for the assessment of sensitive viability.
Candida↗
Cell structure degradation in Escherichia coli and Thermococcus sp. strain Tc-1-95 associated with thermal death resulting from brief heat treatment.
The thermal death mechanism of microorganisms when heated at lethally high temperatures is still not fully understood. In this study, we examined the relationship between thermal death and degradation of the cell structure in the mesophilic bacterium Escherichia coli strain W3110 and the hyperthermophilic archaeon Thermococcus sp. strain Tc-1-95. By heating the microorganisms at lethally high temperatures only briefly (1.5 s duration) in a flow-type apparatus, we studied the microbial cells at very early and critical stages of the thermal death process. For E. coli, it was found that the loss of viability was not associated with thermal damage to the cell envelope. Deformation of the nucleoid was observed. These results suggest that the thermal death of E. coli is attributed to thermal denaturation or degradation of cytoplasmic molecules. On the other hand, the thermal death of Thermococcus sp. strain Tc-1-95 was strongly associated with rupture of the cell envelope. Furthermore, massive deformation of the S-layer with lethal thermal stress was observed. These results demonstrate that the thermal deaths of the two microorganisms investigated proceed via very different mechanisms. The contrast can be attributed to the difference in their cell envelope structures.
Cell Membrane↗
Intracellular infection by Leishmania donovani inhibits macrophage apoptosis.
The phagocytic macrophage plays a critical role in host immune responses to microbial infection, and represents a major source of inflammatory and growth cytokines. Intramacrophage infection by the protozoan parasite Leishmania donovani results in increased viability of the host cell in the absence of exogenous growth factor. We demonstrate that infection of bone marrow-derived macrophages (BMMs) by L. donovani promastigotes or treatment of BMMs with lipophosphoglycan LPG, the major surface molecule of the promastigote, inhibits apoptosis in the macrophage induced by the removal of macrophage (M)-CSF. This effect was also achieved by supernatants collected from L. donovani-infected macrophages, implicating the elaboration of a soluble factor by infected cells as the mediator of this inhibition. To identify candidate factors, reverse transcription PCR was employed to characterize the mRNA cytokine profile of infected macrophages. L. donovani infection of BMMs was found to induce gene expression for granulocyte-macrophage CSF, TNF-alpha, TGF-beta, and IL-6, but not M-CSF or IL-1 beta. Of the cytokines induced by L. donovani, rTNF-alpha and recombinant granulocyte-macrophage CSF were shown to inhibit apoptosis of BMMs induced by the removal of M-CSF. The amount of these cytokines in L. donovani-infected cell supernatants was quantified by ELISA. The mechanism by which L. donovani may inhibit apoptosis is discussed.
Animals↗
Lasting biological effects of early environmental influences. V. Viability, growth, and longevity.
The effects of neonatal influences on the growth and longevity of mice were studied by using animals derived from a highly inbred germfree colony that had been reassociated with a microbial flora free of known pathogens. The size of the animals at weaning time could be conditioned predictably by manipulating the diet of their mothers during gestation and lactation or by shortening or lengthening the period of lactation. A deficient diet during gestation or during lactation decreased the metabolic efficiency of the adult animal, even if it was fed an optimum diet after weaning. The effect was greatest when malnutrition occurred during both pregnancy and lactation. In contrast, an optimum diet during gestation and lactation rendered the animal less susceptible to the depressing effects of nutritional deficiency during adult life. A marked and lasting growth depression could be reproducibly achieved by contaminating newborn mice orally with an unidentified enterovirus. But neonatal infection with enterobacteria or mycobacteria even though severe, did not significantly alter the growth rate. Regardless of its initial cause, the depression of the growth rate during the preweaning period persisted throughout the whole life span of the animals, even when they were placed under optimum sanitary and nutritional conditions after weaning. Agencies (nutritional or infectious) which brought about a depression of whole body weight also affected the absolute and relative sizes of the various organs, especially of the brain. By manipulating neonatal influences, it was possible to produce at will in a given colony of highly inbred mice a family of strikingly different growth curves. This could be done without causing the death of any animal or affecting longevity.
Animals↗