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Antimicrobial effect of ozonated water on bacteria invading dentinal tubules.

Ozone is known to act as a strong antimicrobial agent against bacteria, fungi, and viruses. In the present study, we examined the effect of ozonated water against Enterococcus faecalis and Streptcoccus mutans infections in vitro in bovine dentin. After irrigation with ozonated water, the viability of E. faecalis and S. mutans invading dentinal tubules significantly decreased. Notably, when the specimen was irrigated with sonication, ozonated water had nearly the same antimicrobial activity as 2.5% sodium hypochlorite (NaOCl). We also compared the cytotoxicity against L-929 mouse fibroblasts between ozonated water and NaOCl. The metabolic activity of fibroblasts was high when the cells were treated with ozonated water, whereas that of fibroblasts significantly decreased when the cells were treated with 2.5% NaOCl. These results suggest that ozonated water application may be useful for endodontic therapy.

Animals↗

Trypanosoma cruzi proline racemases are involved in parasite differentiation and infectivity.

Polyclonal lymphocyte activation is one of the major immunological disturbances observed after microbial infections and among the primary strategies used by the parasite Trypanosoma cruzi to avoid specific immune responses and ensure survival. T. cruzi is the insect-transmitted protozoan responsible for Chagas' disease, the third public health problem in Latin America. During infection of its mammalian host, the parasite secretes a proline racemase that contributes to parasite immune evasion by acting as a B-cell mitogen. This enzyme is the first described eukaryotic amino acid racemase and is encoded by two paralogous genes per parasite haploid genome, TcPRACA and TcPRACB that give rise, respectively, to secreted and intracellular protein isoforms. While TcPRACB encodes an intracellular enzyme, analysis of TcPRACA paralogue revealed putative signals allowing the generation of an additional, non-secreted isoform of proline racemase by an alternative trans-splicing mechanism. Here, we demonstrate that overexpression of TcPRAC leads to an increase in parasite differentiation into infective forms and in its subsequent penetration into host cells. Furthermore, a critical impairment of parasite viability was observed in functional knock-down parasites. These results strongly emphasize that TcPRAC is a potential target for drug design as well as for immunomodulation of parasite-induced B-cell polyclonal activation.

Amino Acid Isomerases↗

Extracellular proteases increase tolerance of Bacillus subtilis to nafcillin.

Mutants of Bacillus subtilis capable of secreting high amounts of protease were highly tolerant to the lethal and lytic effects of nafcillin. Protease-deficient mutants were more susceptible. However, when subtilisin was added to exogenously to a protease-deficient strain, the organism assumed the characteristics of nafcillin tolerance. Similarly, when phenylmethylsulfonyl fluoride, a serine protease inhibitor, was added to the tolerant strains, they became susceptible to nafcillin-induced lysis. The effects of nafcillin on B. subtilis were studied with both viability determinations and assay of cellular lysis. The minimum inhibitory concentrations of nafcillin tended to be higher for the protease hyperproducing strains, but these values could be reduced by the protease inhibitor. No loss of antibiotic activity was observed when nafcillin was incubated with either subtilisin or trypsin. Furthermore, protease and autolysin from B. subtilis were not modified by nafcillin. The results showed that extracellular proteases could render B. subtilis relatively tolerant to the killing and lytic effects of a cell wall antibiotic. The proteases were probably acting on the autolysins of the organism, thereby increasing tolerance to nafcillin.

Bacillus subtilis↗

The 19-kDa Mycobacterium tuberculosis protein induces macrophage apoptosis through Toll-like receptor-2.

Macrophages infected with Mycobacterium tuberculosis undergo increased rates of apoptosis. Important objectives are to define the microbial factors that cause apoptosis, the mechanisms involved and the impact on infection. The 19-kDa M. tuberculosis glycolipoprotein (p19) is both cell wall-associated and secreted and is a candidate virulence factor. We investigated the potential of recombinant, His-tagged p19 lacking the secretion/acylation signal to induce macrophage apoptosis. The TUNEL assay and annexin V binding to membrane phosphatidylserine were used to measure apoptosis. The results show that p19 does act to induce apoptosis in differentiated THP-1 cells and monocyte-derived macrophages and that this effect is both dose- and time-dependent. Furthermore, this effect of p19 is Toll-like receptor (TLR)-2-mediated because preincubation of either THP-1 cells or TLR-2-expressing CHO cells with anti-TLR-2 mAb inhibited apoptosis induced by p19. Apoptosis of macrophages in response to p19 was found to be caspase-8 dependent and caspase-9 independent consistent with a transmembrane pathway signaling cell death through TLR-2. The viability of M. tuberculosis in cells undergoing apoptosis induced by p19 was significantly reduced suggesting the possibility that this may favor containment of infection. Although native p19 is a mycobacterial glycolipoprotein, based upon the use of recombinant p19 where the acylation signal had been removed, we conclude that it is the polypeptide component of p19 that is responsible for signaling through TLR-2 and that the lipid moiety is not required.

Animals↗

Response of developing branched bacteria to adverse environments. I. Membrane-transfer techniques for assessment and SEM visualization of drug activity against Nocardia asteroides.

Membrane-transfer technique (MTT) is proposed as a method for assessing antimicrobial activity against branched bacteria at different phases of development. After preliminary cultivation up to the desired stage, colonies developing on membranes are transferred onto media containing various concentrations of drugs to be tested. Different exposure times and drug combinations are possible. Following exposure to the toxicant, membranes can be examined macroscopically, by light or electron microscopy and/or transferred to drug-free media to evaluate viability and possible recovery. Some results on the effects of benzylpenicillin, fusidic acid, gentamicin and sulfadiazine on the morphology of Nocardia asteroides, as detected by scanning electron microscopy, are presented. The progression of alterations, due to increasing exposures to various concentrations of gentamicin, has also been followed. Minimal inhibitory concentration values for the same antibiotic vary according to the growth phase; in particular in the early developmental stages they appear directly related. Advantages of MTT over classical "antigermination" tests in assessing susceptibility to different toxicants and its possible application to the study of environmental effects on morphogenesis of branched bacteria are discussed.

Anti-Bacterial Agents↗

Oxidation of microbial iron-sulfur centers by the myeloperoxidase-H2O2-halide antimicrobial system.

Myeloperoxidase, H2O2, and a halide (chloride, bromide, or iodide) form a potent microbicidal system that contributes to the antimicrobial activity of neutrophils. The mechanism of toxicity is not completely understood. Powerful oxidants are formed that presumably attack the microbe at a variety of sites. Among the consequences of this attack is the release of a large proportion of 59Fe of prelabeled organisms. We report here that the myeloperoxidase-H2O2-halide system oxidizes the iron-sulfur centers of model compounds (spinach ferredoxin) and intact microorganisms (Escherichia coli) with the loss of labile sulfide. The oxidation of the iron-sulfur centers of ferredoxin was measured by the fall in absorbance at 420 nm (bleaching) and by the loss of 5,5'-dithiobis-(2-nitrobenzoic acid) reducing activity. The latter compound is a sulfhydryl reagent that is reduced by ferredoxin labile sulfide during denaturation. The oxidation of E. coli iron-sulfur centers by the peroxidase system was determined by the loss of labile sulfide content, as measured by the release of H2S by acid and its reaction with zinc acetate to form ZnS. The halides were effective as components of the peroxidase system in the order I greater than Br greater than Cl. The oxidation of E. coli iron-sulfur centers by the peroxidase system was rapid and preceded the loss of viability. Gentamicin, at a concentration which produced a loss of viability comparable to that of the peroxidase system, did not cause a loss of labile sulfide from E. coli, suggesting that labile sulfide loss is not a nonspecific reflection of the loss of viability, but a direct consequence of the action of the myeloperoxidase system. The oxidation of iron-sulfur centers in microorganisms by the myeloperoxidase-H2O2-halide system may contribute to the death of the organism.

Animals↗

Every ribosomal suppressor mutation in Aspergillus nidulans has a unique and highly pleiotropic phenotype.

18 suppressors of alcR125 have been selected in Aspergillus nidulans. They have been located in genes as follows: 12 in suaA, 1 in suaB and 5 in suaC. Suppressors have been examined to see whether their phenotype is diagnostic for their genotype. Several new traits are described: conidial viability, cycloheximide resistance, fertility, suppression of niaD500, niaD501 and fwA1. These tests, added to those already in use, provide a battery of tests suitable for assigning suppressor mutations to physiological type (tRNA or ribosomal), and in one case to a specific gene since only suaA mutations suppressed fwA1. A very broad range of phenotypes was associated with suppressors such that every mutation had a unique phenotype. This indicates that the ribosomal suppressor mutations are in genes which code directly for ribosomal proteins, rather than genes which code for modifying enzymes.

Aspergillus nidulans↗

A chemically modified tetracycline (CMT-3) is a new antifungal agent.

Several chemically modified tetracycline analogs (CMTs), which were chemically modified to eliminate their antibacterial efficacy, were unexpectedly found to have antifungal properties. Of 10 CMTs screened in vitro, all exhibited antifungal activities, although their efficacies varied. Among these compounds, CMT-315, -3, and -308 were found to be the most potent as antifungal agents. The MICs of CMT-3 against 47 strains of fungi in vitro were determined by using amphotericin B (AMB) and doxycycline as positive and negative controls, respectively. The MICs of CMT-3 were generally found to be between 0.25 and 8.00 microg/ml, a range that approximates the blood levels of this drug when administrated orally to humans. Of all the yeast species tested to date, Candida albicans showed the greatest sensitivity to CMT-3. The filamentous species most susceptible to CMT-3 were found to be Epidermophyton floccosum, Microsporum gypseum, Pseudallescheria boydii, a Penicillium sp., Scedosporium apiospermum, a Tricothecium sp., and Trichophyton rubrum. Growth inhibition of C. albicans by CMT-3, determined by a turbidity assay, indicated a 50% inhibitory concentration of 1 microg/ml. Thirty-nine strains, including 20 yeasts and 19 molds, were used to measure viability (the ability to grow after treatment with a drug) inhibition by CMT-3 and AMB. CMT-3 exhibited fungicidal activity against most of these fungi, especially the filamentous fungi. Eighty-four percent (16 of 19) of the filamentous fungi tested showed more than 90% inhibition of viability by CMT-3. In contrast, AMB showed fungicidal activity against all yeasts tested. However, most of the filamentous fungi (16 of 19) showed less than 50% inhibition of viability by AMB, indicating that AMB is fungistatic against most of these filamentous fungi. To begin to identify the sites in fungal cells affected by CMT-3, C. albicans and a Penicillium sp. were incubated with the compound at 35 degrees C, and then the fluorescence of CMT-3 was observed by confocal laser scanning electron microscopy. CMT-3 appeared to have widespread intracellular distribution throughout C. albicans and the Penicillium sp. The mechanisms of the antifungal activity of CMT-3 are now being explored.

Amphotericin B↗

Effects of quaternary-ammonium-based formulations on bacterial community dynamics and antimicrobial susceptibility.

Quaternary ammonium compounds (QACs) are widely used as adjuncts to hygiene in domestic cleaning products. Current concern that the increased use of such biocides in consumer products might contribute to the emergence of antibiotic resistance has led us to examine the effects of a QAC-containing domestic cleaning fluid on the population dynamics and antimicrobial susceptibility of domestic sink drain biofilm communities. QAC susceptibilities of numerically dominant, culturable drain bacteria (15 genera, 17 species) were determined in vitro before and after repeated QAC exposure (14 passages). A fully characterized drain microcosm was then exposed to short-term (12 days) and long-term (3 months) dosing with a QAC-containing domestic detergent (QD). QAC exposure of isolated cultures caused both increases (three species) and circa twofold decreases (six species) in QAC susceptibility. The susceptibility of Ralstonia sp. was considerably decreased following 14 consecutive QAC passages. Control drain microcosm biofilms maintained dynamic stability, as evidenced by culture and denaturing gradient gel electrophoresis (DGGE) analysis. Bacterial population densities were largely unaffected during short-term exposure to use levels of QD, although 50% QD caused circa 10-fold viability reductions. DGGE analysis supported these observations; identified the major microcosm genera as Pseudomonas, Pseudoalteromonas, Erwinia, and Enterobacter, and showed that aeromonads increased in abundance under 10 to 50% QD. Long-term exposure of the microcosms to QD did not significantly alter the pattern of antimicrobial susceptibility. These data demonstrate the recalcitrance of domestic drain biofilms toward QAC and that although repeated QAC exposure of drain isolates in pure culture results in susceptibility change in some test bacteria, such changes do not necessarily occur within complex communities.

Anti-Bacterial Agents↗

Viability of a five-strain mixture of Listeria monocytogenes in vacuum-sealed packages of frankfurters, commercially prepared with and without 2.0 or 3.0% added potassium lactate, during extended storage at 4 and 100 degrees C.

The viability of Listeria monocytogenes was monitored on frankfurters containing added potassium lactate that were obtained directly from a commercial manufacturer. Eight links (ca. 56 g each) were transferred aseptically from the original vacuum-sealed bulk packages into nylon-polyethylene bags. Each bag then received a 4-ml portion of a five-strain mixture of the pathogen. Frankfurters containing 2.0 or 3.0% potassium lactate were evaluated using 20 CFU per package, and frankfurters containing 3.0% potassium lactate were evaluated using 500 CFU per package. The packages were vacuum-sealed and stored at 4 or 10 degrees C for up to 90 or 60 days, respectively. During storage at 4 degrees C, pathogen numbers remained at about 1.6 log10 CFU per package over 90 days in packages containing frankfurters with 2.0% potassium lactate that were inoculated with about 20 CFU. In packages containing frankfurters with 3.0% potassium lactate that were inoculated with about 20 CFU and stored at 4 degrees C, pathogen numbers remained at about 1.4 log10 CFU per package over 90 days. In packages containing frankfurters with 3.0% potassium lactate that were inoculated with about 500 CFU and stored at 4 degrees C, pathogen numbers remained at about 2.4 log10 CFU per package over 90 days. However, in the absence of any added potassium lactate, pathogen numbers increased to 4.6 and 5.0 log10 CFU per package after 90 days of storage at 4 degrees C for starting levels of 20 and 500 CFU per package, respectively. During storage at 10 degrees C, pathogen numbers remained at about 1.4 log10 CFU per package over 60 days in packages containing frankfurters with 2.0% potassium lactate that were inoculated with about 20 CFU. In packages containing frankfurters with 3.0% potassium lactate that were inoculated with about 20 CFU and stored at 10 degrees C, pathogen numbers remained at about 1.1 log10 CFU per package over 60 days of storage. In the absence of any added potassium lactate, pathogen numbers increased to 6.5 log10 CFU per package after 28 days and then declined to 5.0 log10 CFU per package after 60 days of storage at 10 degrees C. In packages containing frankfurters with 3.0% potassium lactate that were inoculated with about 500 CFU per package, pathogen numbers remained at about 2.4 log10 CFU per package over 60 days of storage at 10 degrees C, whereas in the absence of any added potassium lactate, pathogen numbers increased to about 6.6 log10 CFU per package within 40 days and then declined to about 5.5 log10 CFU per package after 60 days of storage. The viability of L. monocytogenes in frankfurter packages stored at 4 and 10 degrees C was influenced by the pH and the presence or levels of lactate but not by the presence or levels of indigenous lactic acid bacteria or by the proximate composition of the product. These data establish that the addition of 2.0% (P < 0.0004) or 3.0% (P < 0.0001) potassium lactate as an ingredient in frankfurters can appreciably enhance safety by inhibiting or delaying the growth of L. monocytogenes during storage at refrigeration and abuse temperatures.

Animals↗

[Mutants of cyanobacterium Synechocystis sp. PCC6803 with insertion of the sodB gene encoding Fe-superoxide dismutase].

The sodB gene encoding the only superoxide dismutase (Fe-SOD) in cells of the cyanobacterium Synechocystis sp. PCC6803 was inactivated with gentamycin resistance aacC1 marker insertions located in the direct or inverted order toward the sodB gene. The corresponding delta sodB12 and delta sodB22 mutants are characterized by the complete absence of superoxide dismutase activity and the loss of viability upon standard photoautotrophic cultivation. Mutant cells can grow under conditions of a decreased illumination intensity and upon addition of NaHCO3 with catalase or bovine serum albumin in the growth medium. The delta sodB22 mutant is auxotrophic for leucine due to the polar effect of insertion into the sodB gene on the downstream leuB gene controlling leucine biosynthesis. These data suggest that Fe-SOD is very important for providing tolerance of Synechocystis cells to oxidative stress and that sodB and leuB genes are organized into a single operon.

Anti-Bacterial Agents↗

Successful islet isolation from preserved rat pancreas following pancreatic ductal collagenase at the time of harvesting.

In an attempt to develop an improved method for preserving the pancreas prior to islet isolation, the effects of warm and cold ischemia were examined on rat pancreases, from which reproducible high yields of islets can be obtained when fresh. Both warm and cold preservation rapidly decreased islet yield. Use of Hanks' or modified Sacks' solution also led to marked decrease in islet yield. After 6 hrs of preservation, the islet yield was 1/5-1/10 of those of fresh pancreases (374 +/- 74, n = 14), and no islets were obtained after 24 hrs of preservation regardless of the preservation solution. Monitoring of ductal pressure during forced injection of Hanks' solution in 6 hrs-preserved pancreas with HBSS showed a significantly earlier and lower peak of pressure than those of fresh pancreases. On the other hand, simple hypothermic preservation after pancreatic ductal distention with collagenase Hanks' solution at the time of harvesting resulted in a significantly higher islet yield up to 6 hours (171 +/- 58, n = 14, P less than 0.01), as compared with conventional methods. The viability of the islets isolated by this method was confirmed by the ability to restore normoglycemia of STZ-induced diabetic B6 mice on transplantation of 400 islets in the renal subcapsular space. These findings indicated that loss of the integrity of the ductal system against forced collagenase injection during cold preservation led to poor distention and digestion of the pancreas, ductal collagenase injection at the time of pancreas harvesting followed by simple preservation is recommended to obtain viable islets from the preserved pancreas.

Animals↗

Fractionation of functional lymphocytes sensitized to basic encephalitogen on derivatized collagen and gelatin gels.

The lymph node cells of basic encephalitogen (BE)-sensitized guinea pigs were fractionated on derivatized collagen and gelatin gels. The population of cells specifically reactive to this antigen can be isolated from derivatized gelatin gels and retain their viability and functionality as assayed in vitro. The specific binding of BE-sensitized cells to BE-derivatized gels comprised between 1 and 2% of the cells applied per plate. The ratio of sensitized cells bound to non-sensitized cells bound ranged between 4 and 6. The viability and functionality of adherent cells detached from collagen gels after enzymatic degradation were impaired. In contrast, the responses obtained with the adherent cell population released from the gelatin gels, by melting at 37 degrees C, were equal or greater than those of the original unfractionated lymph node cell cultures. Furthermore, it was possible to obtain a nonadherent cell population which was virtually completely depleted of the capacity to respond to the sensitizing antigen.

Animals↗

In vitro assessment of the upper gastrointestinal tolerance of potential probiotic dairy propionibacteria.

This study aimed to assess the transit tolerance of potential probiotic dairy propionibacteria strains in human upper gastrointestinal tract in vitro, and to evaluate the effect of food addition on viability of these strains in simulated pH 2.0 gastric juices. The transit tolerance of 13 dairy propionibacteria strains was determined at 37 degrees C by exposing washed cell suspensions to simulated gastric juices at pH values at 2.0, 3.0, and 4.0, and simulated small intestinal juices (pH 8.0) with or without 0.3% bile salts. The viability of dairy propionibacteria in pH 2.0 simulated gastric juice with So-Good original soymilk or Up & Go liquid breakfast was also determined. The simulated gastric transit tolerance of dairy propionibacteria was strain-dependent and pH-dependent. All tested strains were tolerant to simulated small intestinal transit. The addition of So-Good original soymilk or Up & Go liquid breakfast greatly enhanced the survival of dairy propionibacteria strains in pH 2.0 simulated gastric juices. Dairy propionibacteria strains demonstrate high tolerance to simulated human upper gastrointestinal tract conditions and offer a relatively overlooked, yet alternative source for novel probiotics besides Lactobacillus and Bifidobacterium.

Colony Count, Microbial↗

Survival and growth of acid-adapted and unadapted Shigella flexneri in a traditional fermented Ghanaian weaning food as affected by fortification with cowpea.

Shigellae are among the major causes of diarrheal diseases in infants and young children in developing countries. We conducted a study to determine the effect of fermentation of corn and corn/cowpea doughs used to prepare a traditional weaning porridge on the survival and growth characteristics of acid-adapted and unadapted Shigella flexneri. Porridges were prepared from doughs fermented for 0, 24, and 48 h at 30 degrees C. Four-strain mixtures of acid-adapted and unadapted S. flexneri cells were separately inoculated (10(4)-10(5) and 10(6)-10(7) cfu/ml) into porridges made from unfermented (pH 5.74-6.05) and fermented (pH 4.07-4.38) doughs. Viability of acid-adapted cells was retained at higher levels in porridge made from fermented dough, compared to unfermented dough, regardless of composition of the porridge or incubation temperature. Cells inoculated into the porridges containing fermented dough were not detected (<1 cfu/ml) within 4 h at 48 degrees C. Results indicate that prior exposure of cells to acid stress renders them more resistant to subsequent acidic conditions. The addition of cowpea flour to corn dough followed by fermentation had little effect on the survival of S. flexneri in porridges made from the dough.

Adaptation, Physiological↗

Improved detection of bacteria by flow cytometry using a combination of antibody and viability markers.

A proprietary fluorogenic marker for cell viability (Chemchrome) was investigated for the detection of bacteria using flow cytometry. This marker was used in combination with fluorescently labelled monoclonal antibodies (against Salmonella typhimurium). Owing to the former's broad band emission spectrum, it was necessary to use the novel dye RED613 for the antibodies. This combined protocol, being sensitive only to the live Salm. typhimurium cells, reduced errors due to intrinsic fluorescence and non-specific binding. Detection of the order of 100 cells ml-1 was achieved in 30 min. This level was achieved even in the presence of large numbers of non-target or dead organisms.

Antibodies, Monoclonal↗

Antigiardial activity of the bile salt-like antibiotic sodium fusidate.

Possible antigiardial activity of the bile salt-like antibiotic, sodium fusidate has been investigated during 24 h liquid culture of Giardia lamblia trophozoites and in 4 h microassays for parasite motility inhibition and viability. Sodium fusidate inhibited Giardia growth (ED50 0.2 mM; MIC 0.3 mM) but was considerably less potent than metronidazole (ED50 0.002 mM; MIC 0.05 mM). Sodium fusidate and metronidazole were active inhibitors of parasite motility (ED50 0.9 and 0.3 mM respectively) but were largely without effect in the 4 h viability assay. Sodium fusidate was active at concentrations well below its critical micellar concentration (2.7 mM) suggesting that its effect was not merely related to its membranolytic detergent properties. Its taurine and glycine conjugates were markedly less potent and paradoxically stimulated growth at low concentration. The studies suggest that sodium fusidate does have antigiardial activity and in view of its relative freedom from teratogenic and other toxic effects may be useful in pregnancy when other antigiardial agents are contra-indicated or as an adjunct in combination therapy when other single agents have failed to eradicate infection.

Animals↗

Microbicidal efficacy of ozonated water against Candida albicans adhering to acrylic denture plates.

BACKGROUND/AIMS: Ozone is known to act as a strong antimicrobial agent against bacteria, fungi, and viruses. We examined the effect of ozonated water on Candida albicans on acrylic denture plate. METHODS: The heat-cured acrylic resins were cultured with C. albicans. After treatment of flowing ozonated water, the number of attached C. albicans was counted. In some experiments, the test samples were treated with ozonated water in combination with ultrasonication. RESULTS: After exposure to flowing ozonated water (2 or 4 mg/l) for 1 min, viable C. albicans cells were nearly nonexistent. The combination of ozonated water and ultrasonication had a strong effect on the viability of C. albicans adhering to the acrylic resin plates. There were no significant differences in antimicrobial activity against C. albicans between plates immersed in ozonated water with ultrasonication and those treated with commercially available denture cleaners. In addition, electron microscopic analysis revealed that small amounts of C. albicans remained on the plate after exposure to flowing ozonated water or immersion in ozonated water with ultrasonication. CONCLUSION: Our results suggest that application of ozonated water may be useful in reducing the number of C. albicans on denture plates.

Acrylic Resins↗