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PubMedDate not supplied

[Protection of Saccharomyces cerevisiae against oxidative and radiation-caused damage by alkyl hydroxybenzenes].

The effects of C7-alkylhydroxybenzene (C7-AHB) and p-hydroxyethylphenol (tyrosol), chemical analogs of microbial anabiosis autoregulators, on the viability of yeast cells under oxidative stress were investigated. The stress was caused by reactive oxygen species (ROS) produced under gamma irradiation of cell suspensions using doses of 10-150 krad at an intensity of 194 rad/s or by singlet oxygen generated in cells photosensibilized with chlorin e6 (10 micrograms/l). C7-AHB was found to exert a protective effect. The addition of 0.05-0.16 vol% of C7-AHB to cell suspensions 30 min before irradiation protected yeast cells from gamma radiation (50 krad). The protective effect of C7-AHB manifested itself both in the preservation of cell viability during irradiation and in the recovery of their capacity to proliferate after irradiation. In our studies on photodynamic cell inactivation, the fact that the phenolic antioxidant C7-AHB protects cells from intracellular singlet oxygen was revealed for the first time. The analysis of difference absorption spectra of oxidized derivatives of C7-AHB demonstrated that the protective mechanism of C7-AHB involves the scavenging of ROS resulting from oxidative stress. The fact that tyrosol failed to perform a photoprotective function suggests that the antioxidant properties of microbial C7-AHB are not related to their chaperon functions. The results obtained make an important addition to the spectrum of known antioxidant and antistress effects of phenolic compounds.

Antioxidants↗

PubMed1967

Resistivity of spores to ultraviolet and gamma radiation while exposed to ultrahigh vacuum or at atmospheric pressure.

Viability studies were conducted on microbial spores subjected to ultrahigh vacuum (UHV) in the 10(-9) to 10(-10) torr range. After 5 to 7 days in vacuum, they were exposed to ultraviolet (UV) or to gamma radiation either while still under vacuum or in the presence of dried air. Among the four test organisms subjected to UHV and ultraviolet radiation, Aspergillus niger was the most resistant; Bacillus megaterium, B. subtilis var. niger, and B. stearothermophilus were about equally less resistant. All four spores were more sensitive to ultraviolet radiation when UHV-dried than when desiccant-dried. Of the four test organisms subjected to UHV and gamma radiation, B. megaterium proved to be the most resistant; A. niger was the least resistant; and the remaining two organisms were of intermediate resistivity. All four organisms were less radiation resistant when UHV-dried than when irradiated in their normally hydrated state, and all showed an increased radiosensitivity after vacuum drying when oxygen was present. In addition, spores of B. subtilis var. niger and A. niger were less radiosensitive when UHV-dried and irradiated in vacuum than when "wet" and irradiated in air, whereas the reverse relationship was observed for the remaining two organisms. Based on the fact that microbial contaminants can be readily shielded from UV light by soils, metal particles, etc., and considering that the levels of ionizing radiations reported to be present in interstellar space are generally lower than those used in these experiments, the decrease in radioresistivity imparted by UHV drying is not of a sufficient magnitude to sterilize dependably portions of a spacecraft while on a mission.

Aspergillus↗

PubMed1979

Bacteria beneath composite restorations--a culturing and histobacteriological study.

The occurrence, viability and identification of the microbial flora under composite fillings using an anaerobic technique were studied. Class V cavities were prepared on clinically healthy buccal surfaces of 7 contralateral pairs of premolars in children 11--15 years of age. After preparation, rubber dam was applied and one cavity in each pair of teeth was washed with water blasted dry with air and filled with Adaptic. The other cavity was washed with a cavity cleaner (Tubulicid) and a cavity liner (Tubulitec) was applicated prior to filling with Adaptic. The teeth were extracted after 4--6 weeks. Under anerobic conditions the tooth crown was split. From one half samples were taken from the pulpal wall under the filling and cultured on blood agar and in broth medium. The other half was examined with histobacteriological technique. No growth occurred in cultures from lined cavities but in 6 of the 7 unlined cavities. Full agreement was observed between the findings from the culturing and histobacteriological examinations concerning presence or absence of microorganisms at the pulpal wall in all 14 teeth. The flora was mixed. Gram-positive bacteria, mainly Streptococcus and Actinomyces, dominated over gram-negative bacteria including Veillonella, Fusobacterium, Campylobacter and Selenomonas. The composition of the flora was more similar to that observed in dental plaque than that found in carious dentin or in saliva in other studies.

Adolescent↗

PubMed1995

[The role of food in cholera transmission].

The spreading of cholera, from Peru to other Latinoamerican countries in 1991, raised questions regarding food safety, food transportation and handling. Control, prevention and risks implied in food import-export were also matters of concern. We deemed it interesting to determine the viability of Vibrio cholerae in wide consumption food locally. Selected food had different intrinsic characteristics such as: acidity (pH), water activity (aw), chemical composition, indigenous flora and other biologic and physic parameters. Twenty food products were contaminated with V. cholerae O1, Ogawa, toxigenic and not toxigenic strains: yoghurt, cream cheese, apricot marmelade, hip rose marmelade, mayonnaise, italian pasta for "empanadas", "dulce de leche", meat sausage, meat and spinach ravioli, margarine, milk dessert (made with cocoa, milk confiture, starch and additives), lettuce, tuna fish, ricotta and sterilized milk. Table I shows the viability of V. cholerae in tested foods, its pH and the reasons why the experiments were ended: 75% of the products studied could tolerate the development of the microorganism for a period ranging from one day (pasta for "empanadas") to ninety days (sterilized milk). Foods with acredity higher than pH 5.5 did not favor the growth of Vibrio. When pH was neutral or slightly acid, viability persisted independently from aw, microbial antagonisms and other physic, chemical or biologic parameters. Nevertheless, other factors such as: surface adherence, amino acids, magnesium and environmental influences not yet well determined, could eventually modify the persistence of V. cholerae in food. According to this study, most food products could tolerate growth and persistence of the infectant agent, up for three months in some cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Cholera↗

PubMedDate not supplied

[Electron-radioautographic study of the action of "levosin" ointment and the ointment base (polyethylene oxide) on Staphylococcus aureus].

Morphological properties and intensity of RNA synthesis in the Staphylococcus aureus cells exposed to levosin ointment or it base alone (a mixture of polyethylene glycols) were studied with electron microscopy. It was found that the exposure to the substances led to various destructions in the microbial cells, marked inhibition of their viability evident from lower levels of RNA synthesis by the bacteria and a decrease in the count of the bacterial cells. There were certain differences in the effect of the substances on the morphological properties of the bacteria, while the level of their viability inhibition was the same.

Anti-Bacterial Agents↗

PubMed2002

Effect of electrical charges and fields on injury and viability of airborne bacteria.

In this study, the effects of the electric charges and fields on the viability of airborne microorganisms were investigated. The electric charges of different magnitude and polarity were imparted on airborne microbial cells by a means of induction charging. The airborne microorganisms carrying different electric charge levels were then extracted by an electric mobility analyzer and collected using a microbial sampler. It was found that the viability of Pseudomonas fluorescens bacteria, used as a model for sensitive bacteria, carrying a net charge from 4100 negative to 30 positive elementary charges ranged between 40% and 60%; the viability of the cells carrying >2700 positive charges was below 1.5%. In contrast, the viability of the stress-resistant spores of Bacillus subtilis var. niger (used as simulant of anthrax-causing Bacillus anthracis spores when testing bioaerosol sensors in various studies), was not affected by the amount of electric charges on the spores. Because bacterial cells depend on their membrane potential for basic metabolic activities, drastic changes occurring in the membrane potential during aerosolization and the local electric fields induced by the imposed charges appeared to affect the sensitive cells' viability. These findings facilitate applications of electric charging for environmental control purposes involving sterilization of bacterial cells by imposing high electric charges on them. The findings from this study can also be used in the development of new bioaerosol sampling methods based on electrostatic principles.

Bacillus subtilis↗

PubMed2001

Short term exposure to airborne microbial agents during farm work: exposure-response relations with eye and respiratory symptoms.

OBJECTIVES: Exposure to high levels of non-infectious microbial agents is recognised as a cause of respiratory disease in working populations, but except for endotoxins, little is known about exposure-response relations. As these effects do not depend on viability, exposure to non-viable microbial agents is important. Various methods not based on microbial cultures were explored to study the complex microbial exposure of farmers and associations with acute symptoms during work. METHODS: Airborne exposure was measured when farmers carried out specific tasks. Fungal spores, bacteria, endotoxins, beta(1-->3)-glucans, fungal antigens specific for Penicillium and Aspergillus species, and mites were measured by methods not based on microbial cultures. Also silica, inorganic and organic dust, ammonia, hydrogen sulphide, and nitrogen dioxide were measured. Respiratory, and nose and eye symptoms experienced during measurements were recorded by a short questionnaire. Both univariate and multivariate statistical analyses were applied to assess the relations between exposure and acute symptoms. RESULTS: 106 Farmers and their spouses participated in this study. Prevalences of work related symptoms were: wheezing 3%; chest tightness 7%; cough 14%; eye symptoms 18%; and nose symptoms 22%. Prevalence ratios for nose and eye symptoms were 4-8 after exposure to 20-500x10(3) fungal spores/m(3) and higher, and a prevalence ratio for cough was 4 after exposure to 500-17,000x10(3) fungal spores/m(3). Nose symptoms were also associated with exposure to silica with prevalence ratios of 4-6 after exposure to 0.015-0.075 mg /m(3) and higher. CONCLUSIONS: Farmers had a high occurrence of symptoms of the nose and eyes as well as cough during work. These symptoms were associated in a dose dependent manner with exposure to fungal spores. Nose symptoms were also associated with exposure to silica.

Aged↗

PubMed1986

Culture of squamous head and neck cancer on 3T3 fibroblasts following isokinetic velocity sedimentation.

Growth in culture of squamous head and neck cancer is hampered by microbial contamination, low plating efficiency, and cellular heterogeneity within tumors. Furthermore, clumps of cells must be removed if plating efficiency is to be accurately determined. Isokinetic velocity sedimentation was applied to 44 primary tumor specimens in an effort to minimize these problems. Seven fractions were evaluated for cell number, clump number, cell viability, clonogenic growth, plating efficiency, and microbial overgrowth. Unseparated specimens were simultaneously cultured. Microbial growth was significantly associated with the highest gradient fraction. Clumps were significantly associated with the lowest gradient fraction. Colony formation was significantly associated with middle gradient isokinetic velocity sedimentation, although seven specimens grew only when fractionated, suggesting the possibility of inhibitor cells within the tumor specimen.

Carcinoma, Squamous Cell↗

PubMedDate not supplied

Use of lipophilic anions for estimation of biomass and cell viability.

A method is described to estimate the microbial biomass of a sample, to enumerate the cells, and to distinguish the portion of metabolically active cells in the population by measuring the binding of phenyldicarbaundecaborane (PCB(-)) to the cells. This method can also be used for the analysis of a complex population of microorganisms if the cells composing the sample are sensitive to different biocidal agents. In addition, the analysis of PCB(-) binding is useful for the enumeration of the phage-infected cells and phage particles.

Bacteriophages↗

PubMed2005

Immobilization of octadecyl ammonium chloride on the surface of titanium and its effect on microbial colonization in vitro.

The aim of our study was twofold: to immobilize an organosilicon quaternary ammonium salt (3-(trimethoxysilyl)-propyldimethyl-octadecyl ammonium chloride, Si-QAC) on the surface of pure titanium and to investigate the antimicrobial activity of Si-QAC-immobilized titanium against microbial adherence and biofilm formation. The results of ToF-SIMS analysis of Si-QAC-titanium suggested the possibility of immobilizing Si-QAC on titanium surface through Ti-O-Si coupling, and that Si-QAC treatment significantly reduced both the adherence and colonization of Candida albicans and Streptococcus mutans isolates. The antimicrobial activity was achieved through at least two mechanisms: the first was attributed to the octadecyl alkyl chain which inhibited initial adherence, and the second was attributed to the quaternary ammonium salt which killed initial adherent cells as well as retarded or inhibited subsequent microbial growth. Further, thermocycling did not significantly reduce the antimicrobial activity of Si-QAC-titanium, and no significant cytotoxicity of Si-QAC-titanium was observed in either cell viability test or proinflammatory cytokine production test using human gingival fibroblasts. These results, taken together, favorably suggested that Si-QAC treatment would be a helpful means to inhibit dental plaque or denture plaque formation.

Analysis of Variance↗

PubMed2000

Lactoferrin is responsible for the fungistatic effect of human milk.

Human milk has recognized anti-microbial effects and it has been repeatedly shown that breast-fed infants have fewer and less severe infections than formula-fed infants. While most studies have focused on anti-bacterial and anti-viral activities few have focused on the anti-fungal effect of human milk. Dermal and other infections caused by fungi are common in very low birth weight (VLBW) infants. Using a liquid culturing method and Candida albicans and Rhodotorula rubra as representative fungi, we studied the anti-fungal effect of human milk and certain human milk proteins. In vitro, human milk showed potent inhibitory effect on fungal growth. Most, if not all of this effect was caused by lactoferrin via its iron-binding capacity; increasing the iron content of the incubation medium abolished the inhibitory effect. In contrast, other human milk proteins with known or suggested anti-microbial effects rather increased fungal growth. Viability test and electron microscopy revealed that the growth inhibitory effect of human milk, i.e. mediated by lactoferrin, is fungistatic rather than fungicidal.

Antifungal Agents↗

PubMed2004

Short-duration low-direct-current electrical field treatment is a practical tool for considerably reducing counts of gram-negative bacteria entrapped in gel beads.

Application of a direct-current electrical field for very short times can serve as a practical nonthermal procedure to reduce or modify the microbial distribution in gel beads. The viability of Escherichia coli and Serratia marcescens entrapped in alginate and agarose beads decreases as the field intensity and duration of electrical field increase.

Alginates↗

PubMed2005

Application of a direct fluorescence-based live/dead staining combined with fluorescence in situ hybridization for assessment of survival rate of Bacteroides spp. in drinking water.

To evaluate the viability and survival ability of fecal Bacteroides spp. in environmental waters, a fluorescence-based live/dead staining method using ViaGram Red+ Bacterial gram stain and viability kit was combined with fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probe (referred as LDS-FISH). The proposed LDS-FISH was a direct and reliable method to detect fecal Bacteroides cells and their viability at single-cell level in complex microbial communities. The pure culture of Bacteroides fragilis and whole human feces were dispersed in aerobic drinking water and incubated at different water temperatures (4 degrees C, 13 degrees C, 18 degrees C, and 24 degrees C), and then the viability of B. fragilis and fecal Bacteroides spp. were determined by applying the LDS-FISH. The results revealed that temperature and the presence of oxygen have significant effects on the survival ability. Increasing the temperature resulted in a rapid decrease in the viability of both pure cultured B. fragilis cells and fecal Bacteroides spp. The live pure cultured B. fragilis cells could be found at the level of detection in drinking water for 48 h of incubation at 24 degrees C, whereas live fecal Bacteroides spp. could be detected for only 4 h of incubation at 24 degrees C. The proposed LDS-FISH method should provide useful quantitative information on the presence and viability of Bacteroides spp., a potential alternative fecal indicator, in environmental waters.

Apoptosis↗

PubMed2003

Trans-shell infection by pathogenic micro-organisms reduces the shelf life of non-incubated bird's eggs: a constraint on the onset of incubation?

Many birds initiate incubation before clutch completion, which results in asynchronous hatching. The ensuing within-brood size disparity often places later-hatched nestlings at a developmental disadvantage, but the functional significance of the timing of the onset of incubation is poorly understood. Early incubation may serve to maintain the viability of early-laid eggs, which declines over time owing to the putative effects of ambient temperature. An unexplored risk to egg viability is trans-shell infection by micro-organisms. We experimentally investigated the rate and magnitude of microbial trans-shell infection of the egg, and the relative effects of ambient temperature and micro-organisms on hatching success. We show that infection of egg contents is prevalent and occurs within the time required to lay a clutch. The probability of infection depends on the climatic conditions, the exposure period and the phylogenetic composition of the eggshell microbiota. We also demonstrate that microbial infection and ambient temperature act independently to reduce egg viability considerably. Our results suggest that these two factors could affect the onset of avian incubation in a wide range of environments.

Analysis of Variance↗

PubMed1998

Microbial inhibitory properties and stability of topotecan hydrochloride injection.

The viability of five microorganisms in topotecan 1 mg/mL (as the hydrochloride salt) in sterile water and the stability of the drug were studied. Duplicate portions of topotecan 1 mg/mL were inoculated with Escherichia coli. The process was repeated for Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus niger. Samples were removed from each solution initially and after 6, 16, and 24 hours and 3, 7, 14, 21, and 28 days of incubation at 20-25 degrees C. To test stability, vials of reconstituted topotecan hydrochloride injection were stored at each of three temperatures--5, 25, and 30 degrees C--and other vials were used for time zero analysis. For each temperature, vials were removed at 1, 7, and 14 days and the remaining vials at 28 days for analysis by high-performance liquid chromatography and for visual and pH assessment. P. aeruginosa, S. aureus, and E. coli lost viability at 16 hours, 24 hours, and 28 days, respectively. C. albicans and A. niger did not lose viability, but their numbers did not grow. No differences in color or clarity were observed, and pH was constant. In all solutions, the topotecan concentration was > 98% of the initial concentration. Topotecan 1 mg/mL in sterile water stored at 20-25 degrees C for up t 28 days did not support growth of the five microorganisms studied; in solutions stored at 5, 25, or 30 degrees C for up to 28 days, topotecan 1 mg/mL remained stable.

Antineoplastic Agents↗

PubMed1992

On-line biomass monitoring by capacitance measurement.

An in-situ, steam-sterilizable capacitance probe was used to follow the biomass concentration on-line, in bioreactors from 20 to 2000 l total volume. Microbial cultures of Saccharomyces cerevisiae, Pichia pastoris and Streptomyces virginiae were grown in batch and fed-batch culture in both defined and complex media in order to demonstrate the wide dynamic operating range of the instrument. A linear correlation was found between the on-line capacitance measurement and the off-line measurements (optical density, OD620; packed mycelial volume, PMV; biomass concentration X, and colony forming units, CFU ml-1) for biomass concentrations (dry cell weight) up to 30 g l-1 (St. virginiae), 106 g l-1 (S. cerevisiae) and 89 g l-1 (P. pastoris). The on-line capacitance measurement was slightly influenced by variations in agitation speed and strong extraneous radio frequencies. A specific capacitance constant (Cs) was defined for all microbial cells which was dependent on cell viability and cell size. The Cs was easy to calculate using the on-line capacitance measurement and an off-line estimation of biomass concentration. The Biomass Monitor proved suitable for precise on-line monitoring of both homogeneous (uni-cellular) and heterogeneous (mycelial) cultures in bioreactors.

Biotechnology↗

PubMed2005

Control of oral biofilm formation by an antimicrobial decapeptide.

Oral biofilms are mixed-species microbial communities, and their uncontrolled outgrowth can express as oral diseases. Antimicrobial peptides represent alternative classes of antimicrobials that exhibit selectivity for prokaryotes. We wanted to test the effect of a synthetic decapeptide antimicrobial, KSL, on the development of oral biofilms formed by isolated human salivary bacteria. We used differential interference contrast microscopy, coupled with a dual-flow cell system, to determine the effect of KSL on oral biofilm development. We used reductions of viable counts and confocal microscopy to assess the bactericidal activity of KSL on mature oral biofilms. KSL effectively blocked biofilm development. A significant effect on the viability of mature biofilms was observed when KSL was used in the presence of a surface-active agent, or after biofilms were mechanically disrupted. This study shows that KSL may be a useful adjunct for conventional oral hygiene to prevent plaque-mediated dental diseases.

Anti-Bacterial Agents↗

PubMed2001

Antibacterial effect of antibiotic solution on cellular viability in canine veins.

Pretreatment of tissue by using antibiotics is a critical step to prevent microbial contamination before venous transplantation. In this study, the optimal time and temperature of antibiotic solution treatment for maintaining cellular viability with antibacterial effect were investigated. The antibiotic-nutrient solutions were composed of cefoxitin, lincomycin, vancomycin, and polymyxin B in RPMI-1640 medium. After various antibiotic solution treatment times (4, 8, and 12 h) and temperatures (4, 25, and 37 degrees C), the viabilities of cells dissociated from veins (jugular vein, femoral vein, superior vena cava, and inferior vena cava) were determined. Double staining by Griffonia simplicifolia agglutins-fluorescein isothiocyanate (GS1-FITC) and propidium iodide was used. To measure the antibacterial effect of the antibiotic solution, canine veins were artificially infected by 3 kinds of bacteria (Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae) and were treated by antibiotic solutions as viability test conditions. After the treatment with the antibiotic solution, the tissue was minced, and the homogenized tissue fraction was cultured on standard method agar. The colony that seemed to be resistant to the antibiotic solution was counted. At 37 and 25 degrees C, the viability of whole cells decreased significantly Asymptotic Significance 2-tailed (Asymp.Sig 2-tailed) < 0.05 after 4 h of antibiotic solution treatment, whereas at 4 degrees C it began to reduce significantly after 8 h of treatment. By antibiotic solution treatment at all 3 temperatures for 4 h, no significant difference in viability of the endothelial cells and whole cells was observed. To maintain the donor vein's cellular viability until transplantation, antibiotic solution treatment for 4 h at 4 degrees C is assumed to be appropriate.

Animals↗