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PubMed1987

Enhanced Survival of the Cyanobacterium Oscillatoria terebriformis in Darkness under Anaerobic Conditions.

Oscillatoria terebriformis, a thermophilic cyanobacterium, maintained viability in darkness under anaerobic conditions by fermenting exogenous glucose or fructose to lactic acid. The time period of survival was greatly extended when the environmental redox potential was lowered by the addition of sodium thioglycolate or titanium(III) citrate. When exposed to aerobic conditions in darkness, many trichomes underwent lysis in 6 h, and death of all cells occurred in 2 to 3 days. The endogenous aerobic respiration rate was high, and the limited dark aerobic survival period appeared to be due to depletion of stored glycogen. Fructose or glucose did not support or increase aerobic respiration in darkness or lengthen aerobic survival time. Enhanced survival of O. terebriformis in darkness under anaerobic, reducing conditions correlates well with the natural nighttime position of this species within sulfide-rich microbial mats associated with hot springs of western North America.

Journal Article↗

PubMed2006

Effect of ginseng polysaccharide on the stability of lactic acid bacteria during freeze-drying process and storage.

Lactic acid bacteria (LAB) quickly attenuate or are killed during the freeze-drying process and storage. The effect of some natural polysaccharides, which are known as potent antitumor and immunomodulating substances, on the viability of the LAB, Lactobacillus acidophilus and Bifidobacterium breve, on freeze-drying and storage were investigated. Among the polysaccharides tested, red ginseng polysaccharide (RGP) and chitosan significantly inhibited the cell death of the LAB during freeze-drying, and fucoidan and RGP most potently protected the cell death of the LAB during storage. The stabilities of the LAB on the addition of RGP and fucoidan were comparable to that of skimmed milk. However, white ginseng polysaccharide (WGP) did not promote storage stability. When 5% skimmed milk/5% RGP treated LAB were freeze-dried and stored, their viabilities were found to be significantly higher those treated with 5% or 10% RGP. The stabilizing effect of 5% RGP/5% skimmed milk during LAB freeze-drying and storage stability was comparable to that of treatment with 10% skimmed milk. Based on these findings, we believe that RGP beneficially improves the stability of LAB during the freeze-dry process and storage.

Animals↗

PubMed1990

Effectiveness of ultrasonic files in the disruption of root canal bacteria.

The physical mechanisms of ultrasound, namely cavitation and acoustic streaming, generated by the Enac-Osada ultrasonic unit were investigated for effectiveness in disrupting Streptococcus mitis. In addition, the bactericidal effect of ultrasound in the presence of 2.5% sodium hypochlorite was examined. Bacterial suspensions were irradiated directly with ultrasound in simulated root canals, and the viability of bacteria was examined after growth on a blood agar medium under anaerobic conditions at 37 degrees C for 5 days. The results indicated that ultrasound per se failed to disrupt bacteria but resulted in increases in the viable counts; the former was considered to be because of the lack of cavitation and the latter because of the dispersal effects of acoustic streaming. The 2.5% sodium hypochlorite solution demonstrated powerful bactericidal activity.

Colony Count, Microbial↗

PubMed2005

Use of traditional African fermented beverages as delivery vehicles for Bifidobacterium lactis DSM 10140.

A microencapsulation delivery system for Bifidobacterium lactis, a possible probiotic suited for use by the rural population of South Africa, was evaluated using two existing traditional fermented foods, amasi and mahewu. Gellan/xanthan microcapsules containing viable B. lactis, were tested under simulated physiological conditions, and added to pasteurized beverages. The capsules protected the organism under simulated low pH conditions associated with the stomach and from the biocidal activity of pancreatic and bile acids. For mahewu, microencapsulation of B. lactis with storage aerobically at 4 degrees C and 22 degrees C enhanced survival over a 21-day period as compared to free cells. In amasi, differences in viability between immobilized and free cells were less noticeable. An analytically trained taste panel was unable to detect a significant difference in texture in any of the samples fortified with microcapsules. Although flavour differences were noted for mahewu containing either free or immobilized cells, after 14 days refrigerated storage, these were not disliked. No significant flavour difference was noted between amasi containing immobilized cells and untreated controls over the period tested.

Beverages↗

PubMed1991

Viable but nonculturable bacteria in drinking water.

Klebsiella pneumoniae, Enterobacter aerogenes, Agrobacterium tumefaciens, Streptococcus faecalis, Micrococcus flavus, Bacillus subtilis, and Pseudomonas strains L2 and 719 were tested for the ability to grow and maintain viability in drinking water. Microcosms were employed in the study to monitor growth and survival by plate counts, acridine orange direct counts (AODC), and direct viable counts (DVC). Plate counts dropped below the detection limit within 7 days for all strains except those of Bacillus and Pseudomonas. In all cases, the AODC did not change. The DVC also did not change except that the DVC, on average, were ca. 10-fold lower than the AODC.

Bacteria↗

PubMed1990

Growth and metabolism of Pneumocystis carinii in axenic culture.

Recent analyses of rRNA have suggested a taxonomic relationship of Pneumocystis carinii with fungi. We investigated various liquid and solid media without feeder cells for the ability to support growth of P. carinii. Organisms were obtained from the lungs of immunosuppressed rats and separated from host cells by treatment with hypotonic solutions and a series of microfiltrations. The growth of P. carinii was quantitated by staining nuclei with Diff-Quik. Optimal replication was observed in media with neopeptone and N-acetylglucosamine at low pH. Increases of at least 8- to 10-fold occurred during the first 24 to 72 h. P. carinii replication was influenced by pH, temperature, inoculum size, and anti-P. carinii drugs. The viability of organisms was confirmed by incorporation of radiolabeled uracil, methionine, and N-acetylglucosamine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of trichloroacetic acid-precipitable compounds showed that [35S]methionine was incorporated into specific P. carinii proteins. Thus, P. carinii can metabolize and replicate in the absence of mammalian cells. This system should have applications for in vitro drug screening and other molecular and metabolic analyses.

Animals↗

PubMed1953

Effect of ketone bodies and other metabolites on the survival and multiplication of staphylococci and tubercle bacilli.

A study has been made of the fate of staphylococci and tubercle bacilli resuspended in aqueous media at slightly acid reactions. The tests were carried out at several acid reactions in balanced ionic media containing 0.5 per cent serum albumin. These experimental conditions were selected in order to approximate those which are probably encountered by pathogenic agents in inflammatory areas and in the intracellular environment of the leucocytes after phagocytosis. The viability of the microorganisms at a given pH was markedly influenced by the composition of the medium, being decreased by addition to the latter of lactic, acetic, propionic, and butyric acids, and increased by the addition of certain ketone bodies such as dihydroxyacetone and pyruvic, beta-hydroxybutyric, alpha-ketoglutaric, and oxalacetic acids. The presence of ketone bodies in the medium afforded to the microorganisms some protection against the bactericidal effect of lactic and acetic acids at acid reactions. The minimum and the optimum pH for growth were found to be dependent on the composition of the medium. Both were higher in the presence of lactic, acetic, propionic, and butyric acids than in the media without organic acids added. In contrast, the addition of ketone bodies to the medium allowed microbial multiplication even in acid media (approximately at pH 5.3 or even lower). The fact that lactic acid antagonizes, whereas ketone bodies favor, the survival and multiplication of staphylococci and tubercle bacilli at acid reactions, is discussed in relation to the high susceptibility to infection which is often associated with ketosis of various etiology.

Bacillus↗

PubMed2003

Susceptibility of oral bacteria to Melaleuca alternifolia (tea tree) oil in vitro.

The in vitro activity of Melaleuca alternifolia (tea tree) oil against 161 isolates of oral bacteria from 15 genera was determined. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) ranged from 0.003 to 2.0% (v/v). MIC90 values were 1.0% (v/v) for Actinomyces spp., Lactobacillus spp., Streptococcus mitis and Streptococcus sanguis, and 0.1% (v/v) for Prevotella spp. Isolates of Porphyromonas, Prevotella and Veillonella had the lowest MICs and MBCs, and isolates of Streptococcus, Fusobacterium and Lactobacillus had the highest. Time kill studies with Streptococcus mutans and Lactobacillus rhamnosus showed that treatment with > or = 0.5% tea tree oil caused decreases in viability of >3 log colony forming units/ml after only 30 s, and viable organisms were not detected after 5 min. These studies indicate that a range of oral bacteria are susceptible to tea tree oil, suggesting that tea tree oil may be of use in oral healthcare products and in the maintenance of oral hygiene.

Actinomyces↗

PubMed2005

An in vitro evaluation of the ability of ozone to kill a strain of Enterococcus faecalis.

AIM: To evaluate the potential of ozone as an antibacterial agent using Enterococcus faecalis as the test species. METHODOLOGY: Ozone was produced by a custom-made bench top generator and its solubility in water determined by ultraviolet (258 nm) spectrophotometric analysis of solutions through which ozone was sparged for various time-periods. The antibacterial efficacy of ozone was tested against both broth and biofilm cultures. Ozone was sparged for 30, 60, 120 and 240 s, through overnight broth cultures of a strain of E. faecalis (E78.2) and compared with those that were centrifuged, washed and resuspended in water. Enterococcus faecalis (E78.2) biofilms were grown on cellulose nitrate membrane filters for 48 h and suspended in water through which ozone gas was sparged with stirring for 60, 120 and 240 s in a standard fashion. In a separate test, biofilms were also exposed to gaseous ozone. Sodium hypochlorite (NaOCl) was used as a positive control. All experiments were repeated four times. RESULTS: There were significant (P < 0.05) reductions of bacteria in the unwashed (2 log(10) reductions) and washed (5 log(10) reductions) broth cultures following 240 s applications. Biofilms incubated for 240 s with ozonated water showed no significant reduction in cell viability attributable to ozone alone, whereas with NaOCl no viable cells were detected over the same time. Gaseous ozone applied for 300 s had no effect on these biofilms. CONCLUSIONS: Ozone had an antibacterial effect on planktonic E. faecalis cells and those suspended in fluid, but little effect when embedded in biofilms. Its antibacterial efficacy was not comparable with that of NaOCl under the test conditions used.

Anti-Bacterial Agents↗

PubMed1992

Disparate efficacy of tobramycin on Ca(2+)-, Mg(2+)-, and HEPES-treated Pseudomonas aeruginosa biofilms.

Mucoid exopolysaccharide (MEP) obtained from Pseudomonas aeruginosa 579 was suspended in 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) pH 7.2 containing 0.1-10.0 mM of CaCl2.2H2O or MgCl2.4H2O. MEP treated with HEPES or < 5.0 mM of the Ca2+ or Mg2+ salts remained soluble and bound tobramycin in an equilibrium dialysis bioassay. MEP treated with 5.0 or 10.0 mM of the Ca2+ or Mg2+ salts did not bind tobramycin. Five and 10 mM Ca(2+)-treated MEP precipitated but Mg(2+)-treated MEP did not. Pseudomonas aeruginosa 579 biofilms formed using a defined growth medium having < 1 mM Ca2+ or Mg2+ were treated for 1 h with 10 mM HEPES +/- 5.0 mM CaCl2.2H2O or MgCl2.4H2O, prior to an 8-h exposure to HEPES, or the defined growth medium, +/- 125 micrograms/mL of tobramycin. The tobramycin kill kinetics for the HEPES-, Mg(2+)-, and Ca(2+)-treated biofilms were similar and gradual from T = 0-6 h. The viability of the HEPES- and Mg(2+)-treated populations declined sharply (from 6 to 8 h). Bacteria dispersed from the MEP in control biofilms at 0 and 8 h did not grow in the presence of 7.81 micrograms/mL of tobramycin. Thus, binding of tobramycin of P. aeruginosa 579 MEP may not be as influential to the impediment of tobramycin diffusion as is the steric hindrance imposed by the Ca2+ condensation of the polymer.

Binding Sites↗

PubMed1999

Attachment of Escherichia coli O157:H7 to lettuce leaf surface and bacterial viability in response to chlorine treatment as demonstrated by using confocal scanning laser microscopy.

Confocal scanning laser microscopy was used to observe the location of Escherichia coli O157:H7 on and within lettuce leaves. Sections of leaves (ca. 0.5 by 0.5 cm) were inoculated by submersion in a suspension of E. coli O157:H7 (ca. 10(7) to 10(8) CFU/ml) overnight at 7 degrees C. Fluorescein isothiocyanate-labeled antibody was used to visualize the attached bacteria. E. coli O157:H7 was found attached to the surface, trichomes, stomata, and cut edges. Three-dimensional volume reconstruction of interior portions of leaves showed that E. coli O157:H7 was entrapped 20 to 100 microm below the surface in stomata and cut edges. Agar plate culturing and microscopic observation indicated that E. coli O157:H7 preferentially attached to cut edges, as opposed to the intact leaf surface. Dual staining with fluorescein isothiocyanate-labeled antibody and propidium iodide was used to determine viability of cells on artificially contaminated lettuce leaves after treatment with 20 mg/liter chlorine solution for 5 min. Many live cells were found in stomata and on cut edges following chlorine treatment. E. coli O157:H7 did not preferentially adhere to biofilm produced by Pseudomonas fluorescens on the leaf surface. In contrast to E. coli O157:H7, Pseudomonas adhered to and grew mainly on the intact leaf surface rather than on the cut edges.

Bacterial Adhesion↗

PubMed2006

[Susceptibility of Streptococcus mutans biofilm to antimicrobial agents].

OBJECTIVE: To investigate the susceptibility of Streptococcus mutans (S. mutans) biofilms to antimicrobial agent by confocal laser scanning microscopy (CLSM). METHODS: S. mutans biofilms formed in vitro on glass slice were acted on with penicillin of different concentrations for 3 h. Then these biofilms were stained by fluorescence and were observed by CLSM. The bacterial density and viability of biofilms were recorded. RESULTS: When S. mutans biofilms were exposed to penicillin of 2 500 mg/L for 3 h, it was not completely killed. The higher the concentration of penicillin was, the weaker the biofilms against penicillin. CONCLUSIONS: Compared with planktonic S. mutans, S. mutans biofilms produced stronger resistance to penicillin. It suggests that we should find new strategies to control the infection caused by biofilm in clinic.

Anti-Infective Agents↗

PubMed2005

The potential for acquiring cryptosporidiosis or giardiosis from consumption of mung bean sprouts in Norway: a preliminary step-wise risk assessment.

The current work evolved from a microbial survey of fruits and vegetables conducted in Norway between 1999 and 2001. This survey found that mung bean sprouts were more likely to be contaminated with Cryptosporidium and Giardia than the other produce included in the survey. To support this observation and to demonstrate to public health officials that this might be a risk warranting further attention, a simple risk assessment was initiated. Assuming that 60,000 people in Norway consume a single serving of bean sprouts per week, and contamination levels are similar to those found in the survey, it was calculated that there could be in the order of 20 cases of Giardia or Cryptosporidium infection per 100,000 population attributable to consumption of mung bean sprouts. A number of assumptions were made for the calculations, including parasite factors (e.g. viability, genotype), product factors (e.g. extent of product contamination) and host factors (e.g. composition and extent of consumer group). These assumptions and areas of uncertainty, where further data would improve the risk assessment, are highlighted throughout. Not only does the risk assessment identify new areas of research, but it also demonstrates how risk assessment can be used as a tool to try to influence public health surveillance.

Animals↗

PubMed2003

A role for balance of interferon-gamma and interleukin-4 production in protective immunity against Neospora caninum infection.

A suitable balance in the production of Th1/Th2-type cytokines has a crucial role in the control of microbial infections. We investigated cytokine production patterns and effects during Neospora caninum infection, based on two mouse models and an in vitro system. In the acute infection of N. caninum, BALB/c-background IFN-gamma-deficient mice that were sensitive to the N. caninum infection showed high levels of IL-10 production, whereas significant levels of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production were observed in resistant wild type mice. BALB/c mice vaccinated with recombinant vaccinia virus expressing N. caninum surface protein NcSRS2 resisted parasite spread throughout the body, low levels of IFN-gamma production and high levels of IL-4 production were observed compared to unvaccinated animals. The treatment of N. caninum-infected cells with IFN-gamma or IL-10 decreased the host-cell viability in an in vitro system using mouse macrophage J774A.1 cells. On the other hand, IL-4, but not IL-10 administration, increased the viability of N. caninum-infected and IFN-gamma-treated cells. In the light of the balance of Th1/Th2-type cytokine production, an IFN-gamma/IL-4 balance may have a crucial role for the control of cellular responses against the parasite invasion.

Animals↗

PubMed1993

Dormancy in Stationary-Phase Cultures of Micrococcus luteus: Flow Cytometric Analysis of Starvation and Resuscitation.

Cultures of the copiotrophic bacterium Micrococcus luteus were stored in spent growth medium for an extended period of time following batch culture. After an initial decrease, the total cell counts remained constant at approximately 60 to 70% of the counts at the beginning of storage. The level of viability, as judged by plate counts, decreased to less than 0.05%, while respiration and the ability to accumulate the lipophilic cation rhodamine 123 decreased to undetectable levels. However, using penicillin pretreatment (to remove viable cells) and flow cytometry and by monitoring both the total and viable counts, we found that at least 50% of the cells in populations of 75-day-old cultures were not dead but were dormant. Resuscitation in liquid medium was accompanied by the appearance of a population of larger cells, which could accumulate rhodamine 123 and reduce the dye 5-cyano-2,3-ditolyl tetrazolium chloride to a fluorescent formazan, while a similar fraction of the population was converted to colony-forming, viable cells. We surmise that dormancy may be far more common than death in starving microbial cultures.

Journal Article↗

PubMed1995

Pharmacodynamic effects of meropenem on gram-negative bacteria.

The in vitro initial killing and post-antibiotic effect (PAE) of meropenem on five gram-negative reference strains were evaluated by bioluminescence assay of bacterial adenosine triphosphate (ATP) and viable count. Morphology studies were performed in parallel. Meropenem showed concentration-dependent long (2-5 h) PAEs on Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens when assayed by bioluminescence and induced spheroplasts at almost all concentrations. The bioluminescence PAEs reached a maximum response at 4 x MIC. These PAEs of meropenem on Escherichia coli, Klebsiella pneumoniae and Serratia marcescens were longer than corresponding PAEs of imipenem shown in previous studies. The higher affinity of meropenem than imipenem for PBP 3 might explain the longer PAEs obtained with meropenem. However, there was only a very short PAE, no PAE or even a negative PAE when viable count was used as the initial value for the PAE calculation. A strong initial decrease in viability but a less pronounced change in intracellular ATP was registered. Since this initial change in cell numbers is the initial value for the PAE calculation, the length of PAE was highly method dependent. In summary, a strong initial killing and no PAE were shown using viable count as the initial value for the PAE calculation, but a weak initial killing and long PAEs were shown when bioluminescence was used throughout the experiments.

Gram-Negative Bacteria↗

PubMed1985

Pure gelatin microcarriers: synthesis and use in cell attachment and growth of fibroblast and endothelial cells.

A new type of microcarrier was described using bead emulsion-polymerization techniques. An aqueous solution of gelatin and glutaraldehyde was dispersed in a hydrophobic phase of mineral oil, using Triton X-114 as an emulsifier, and polymerization was initiated. The resultant spherical beads, composed entirely of gelatin, showed excellent mechanical stability to ethanol drying, sterilization, and long-term use in microcarrier spinner cultures. The solid gelatin microcarriers supported the growth of L-929 fibroblast, swine aorta endothelial, human umbilical endothelial, and HeLa-S3 cultures with no adverse effects on cell morphology or growth. The beads were transparent in growth medium and attached cells were clearly visualized without staining. The beads were also compatible with techniques for scanning electron microscopy. Collagenase could be used to entirely digest the gelatin beads, leaving the cells free from microcarriers and suspended in solution while retaining 98% cell viability. The results further showed that after collagenase treatment the cells would populate fresh gelatin microcarriers and grow to confluence. Cell attachment kinetics revealed that the endothelial cells attached to the gelatin beads at the same rate as to tissue culture plates, whereas the fibroblast cells attached to the beads more slowly. However, once the fibroblast cells were attached to the gelatin microcarriers they spread and grew normally.

Animals↗

PubMed1999

Nisin A depletes intracellular ATP and acts in bactericidal manner against Mycobacterium smegmatis.

Nisin is a bacteriocin produced by many strains of Lactococcus lactis. This study examined the effect of nisin on Mycobacterium smegmatis, a non-pathogenic species of Mycobacterium. Nisin had a minimum inhibitory concentration of 8.0 micrograms ml-1 and a minimum inhibitory dose of 7.5 micrograms ml-1 against Myco. smegmatis. Treatment with 25.0 micrograms ml-1 nisin caused partial inhibition of Myco smegmatis; the survivors were nisin-sensitive when tested in a separate experiment. Mycobacterium smegmatis cells exposed to 50.0 micrograms ml-1 of nisin, lost their viability. the effect of nisin on the growth of Myco. smegmatis was both time- and concentration-dependent. Nisin (10.0 micrograms ml-1) caused 97.7 +/- 2.0% reduction in internal ATP and leakage of intracellular ATP out of Myco. smegmatis cells after several hours of treatment. These data suggest that nisin inhibits Myco. smegmatis by the same mechanism by which it inhibits other bacteria and warrants further investigation as a possible antitubercular agent.

Adenosine Triphosphate↗