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PubMed1998

Synergistic antibacterial action of heat in combination with nisin and magainin II amide.

Lactobacillus plantarum has been exposed to mild heat at temperatures between 48 and 56 degrees C in combination with low concentrations of the lantobiotic nisin in different sequential set-ups. Exposure to heat and nisin caused synergistic reductions of Lact. Plantarum viability. Efficient antimicrobial action was dependent on the growth state of the culture as well as on levels and sequences of treatment applications. Listeria monocytogenes and Escherichia coli were treated at 55 degrees C in the presence of magainin II amide. Synergistic reductions in viable counts could be observed for L. monocytogenes and, after prolonged exposure, also for E. coli. the bacterial membrane could be identified by fluorometry and flow cytometry as an important target of applied treatment combinations.

Anti-Bacterial Agents↗

PubMed2006

Determination of survival, identity and stress resistance of probiotic bifidobacteria in bio-yoghurts.

AIMS: To determine the level of bifidobacteria in bio-yoghurts in the UK, identify the species, and compare the resistance of common Bifidobacterium spp. to acidity and oxidative stress. METHODS AND RESULTS: A storage trial of bio-yoghurts was carried out to determine the level and survival of bifidobacteria. The 16S rRNA gene targeted PCR was used to identify the species. Acid tolerance was determined by introducing the organisms to pH-adjusted skimmed milk and enumerating during storage at 4 degrees C. Oxidative stress resistance was determined using the H(2)O(2) disc diffusion assay technique. Nine of 10 bio-yoghurts contained bifidobacteria at levels >10(6) CFU g(-1) at the time of purchase. The viability of the organism decreased during storage and on expiry only five products retained viability >10(6) CFU g(-1) while two others were very close to the target population. Bifidobacterium animalis ssp. lactis showed superior survival abilities and stress tolerance compared with Bifidobacterium longum, Bifidobacterium breve, Bifidobacterium bifidum, Bifidobacterium adolescentis and Bifidobacterium longum biotype infantis. CONCLUSIONS: Bifidobacterium animalis ssp. lactis, the only Bifidobacterium spp. found in bio-yoghurts, had the greatest resistance to acidity and oxidative stress. SIGNIFICANCE AND IMPACT OF THE STUDY: The technological properties of B. animalis ssp. lactis make it suitable for inclusion in bio-yoghurts although its putative health benefits need further investigation.

Acids↗

PubMed1982

In vitro susceptibility of varicella-zoster virus to E-5-(2-bromovinyl)-2'-deoxyuridine and related compounds.

The in vitro susceptibility of eight strains of varicella-zoster virus (VZV) to E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) was examined in human embryonic fibroblasts by the following techniques: inhibition of focus formation by either cell-free VZV (4-day assay) or cell-associated VZV (2-day assay), inhibition of viral antigen formation (2-day assay), and inhibition of viral cytopathogenicity (15-day assay). The 50% inhibitory dose (ID50) of BVDU ranged from 0.001 microgram/ml (2-day assay) to 0.01 microgram/ml (15-day assay). BVDU appeared highly selective in its anti-VZV activity since even at concentrations as high as 100 micrograms/ml, BVDU did not markedly affect the viability of the host cells. The ID50 of BVDU for VZV was comparable to that of IVDU (E-5-(2-iodovinyl)-2'-deoxyuridine). Both drugs inhibited the replication of VZV at a much lower concentration than did other antiviral compounds such as iododeoxyuridine, ethyldeoxyuridine, arabinosylcytosine, arabinosyladenine, phosphonoacetic acid, iododeoxycytidine, and acycloguanosine. BVDU and IVDU were virtually inactive against a thymidine kinase-deficient VZV mutant, suggesting that phosphorylation by the viral enzyme is responsible, at least in part, for the selective anti-VZV activity of the compounds.

Antiviral Agents↗

PubMed1994

Ultrasonic enhancement of antibiotic action on gram-negative bacteria.

The effect of gentamicin upon planktonic cultures of Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and Staphylococcus aureus was measured with and without application of 67-kHz ultrasonic stimulation. The ultrasound was applied at levels that had no inhibitory or bactericidal activity against the bacteria. Measurements of the MIC and bactericidal activity of gentamicin against planktonic cultures of P. aeruginosa and E. coli demonstrated that simultaneous application of 67-kHz ultrasound enhanced the effectiveness of the antibiotic. A synergistic effect was observed and bacterial viability was reduced several orders of magnitude when gentamicin concentrations and ultrasonic levels which by themselves did not reduce viability were combined. As the age of the culture increased, the bacteria became more resistant to the effect of the antibiotic alone. Application of ultrasound appeared to reverse this resistance. The ultrasonic treatment-enhanced activity was evident with cultures of P. aeruginosa and E. coli but was not observed with cultures of gram-positive S. epidermidis and S. aureus. These results may have application in the treatment of bacterial biofilm infections on implant devices, which infections are usually more resistant to antibiotic therapy.

Biofilms↗

PubMed1971

Tobramycin (nebramycin factor 6): in vitro activity against Pseudomonas aeruginosa.

Tobramycin (factor 6 of the nebramycin complex) is a new aminoglycoside antibiotic isolated from Streptomyces tenebrarius which is active against S. aureus, Enterobacteriaceae, and Pseudomonas aeruginosa. Susceptibility to tobramycin of 96 strains of P. aeruginosa, including 45 recent isolates from blood, was studied by using agar and broth dilution methods. The minimum inhibitory concentration (MIC) for 83 of 96 strains was 3.12 mug/ml or lower in Mueller Hinton agar; MIC values were two to eight times lower in Mueller Hinton broth tests. Agar dilution MIC values were generally lower than those obtained in parallel tests with gentamicin. Killing curves obtained from serial sampling of broth cultures showed a 100- to 10,000-fold decline in viability of log-phase organisms within 30 min of exposure to the drug. Two-dimensional agar dilution tests with carbenicillin and tobramycin with 79 strains showed additive or synergistic effects; no antagonism was documented. Seventy-eight of 79 strains were inhibited by a combination of 50 mug of carbenicillin per ml and 1.56 mug of tobramycin per ml, blood levels which seem attainable in man. Tobramycin appears to be a potent, rapidly bactericidal antibiotic against P. aeruginosa and merits clinical evaluation.

Agar↗

PubMed2026

Genome mining and metabolomics unveil new napyradiomycin antibiotics from Streptomyces sp. 0H2M.

Napyradiomycins are a family of meroterpenoid natural products known for their promising antibiotic activities. In this study, four new napyradiomycins derivatives were identified, SF2415B4 (1), SF2415B5 (2), SF2415B6 (3), and SF2415B7 (4) from Streptomyces sp. 0H2M, alongside a known molecule, A80915A (5) through the synergy between genome mining and metabolomics analysis. Their structures were elucidated through a combination of spectroscopic and spectrometric analyses, including HRMS-ESI, NMR, and DP4+. Genome sequencing identified a putative biosynthetic gene cluster, and subsequent analyses revealed a distinct biosynthetic pathway with an unprecedented tailoring mechanism mediated by novel hydroxylases and halogenases. Biological assays demonstrated significant activity against Bacillus subtilis, Bacillus cereus and methicillin-resistant Staphylococcus aureus due to perturbation of cell membrane integrity, and minimum inhibitory concentration (MIC) values ranged from 0.24 to 30.7 μM. Additionally, in vitro cytotoxicity experiments indicated that compounds 2-5 very mildly inhibited the viability of human non-small cell lung cancer (NSCLC) cell line A549 in a concentration-dependent manner, with IC50 values of 16.7, 39.1, 65.0, and 32.8 μM, respectively. Moreover, they were shown to induce apoptosis and autophagy in A549 cells, evidenced by increased levels of cleaved PARP, decreased expression of anti-apoptotic proteins (Bcl-2, Bcl-xL, and Survivin), and accumulation of LC3-II. These findings offer new insights into the natural product chemistry in Streptomyces and the pharmacology of napyradiomycin class antibiotics.

Streptomyces↗

PubMed1998

Nonculturable Enterococcus faecalis cells are metabolically active and capable of resuming active growth.

Entry into the viable but nonculturable (VNC) state is a survival mechanism that bacteria can adopt when they find themselves in an adverse environment. When in this state, bacteria are still viable but are unable to form colonies on growth medium. The possibility of Gram-positive species entering the VNC state when environmental conditions are adverse and remaining viable and capable of resuming active growth is demonstrated for the first time in this study by using exponential-phase cultures of Enterococcus faecalis inoculated in filtered, sterilized water from Lake Garada (Italy). Over the 60-day study, the number of total cells stained with a fluorescent or counted with a Coulter Counter remained constant, while the number of cells capable of forming colonies on Tryptic Soy Agar (TSA) declined rapidly from 10(6) CFU/ml on day 0 to 10(3) CFU/ml on day 4. On day 14 no colonies could be observed when 50 ml of inoculated lake water were plated. E. faecalis cells conserved their viability while in the VNC state, as can be demonstrated by active uptake of amino acids, which are also incorporated into proteins, and by continuous detection of E. faecalis specific DNA by PCR throughout the experiment. The possibility of revival of the E. faecalis cells in the VNC state when returned to conditions supporting its cell growth has also been demonstrated. The data obtained in this study lend further support to recent criticisms of the traditional methods used to evaluate water quality based on plate counts, assessing fecal contamination indicators such as Escherichia coli and fecal streptococci.

Colony Count, Microbial↗

PubMed1992

PBS2, a yeast gene encoding a putative protein kinase, interacts with the RAS2 pathway and affects osmotic sensitivity of Saccharomyces cerevisiae.

The yeast gene PBS2 encodes a presumed protein kinase. The gene is essential for manifestation of resistance to the antibiotic polymyxin B. Deletion of PBS2 enables a ras2-530 null mutant to grow on nonfermentable carbon sources; overexpression of PBS2+ enhances viability of a RAS2Val19 mutant. Overexpression of PBS2+ also diminishes cellular response to mating pheromone MF alpha. These results suggest that the PBS2 and RAS2 genes affect a common pathway that may communicate with the pheromone response pathway. In addition, disruption of PBS2 renders cells sensitive to high osmolarity: exposure to 0.9 M-NaCl causes growth arrest, appearance of bizarre morphological forms, and eventual death. A mutation suppressing pbs2 deletion has been found. That mutation restores full polymyxin B resistance but only partially corrects the osmotic sensitivity defect. These observations indicate that PBS2 is involved in diverse physiological pathways in yeast.

Carbon↗

PubMed1997

Mechanism of suppression of piperacillin resistance in enterobacteria by tazobactam.

Resistance to piperacillin in several isolates of Citrobacter freundii and Enterobacter cloacae was investigated and confirmed to occur at a frequency of 10(-7) to 10(-6). Development of resistance to piperacillin was significantly suppressed by tazobactam but not by clavulanic acid. To elucidate the mechanism by which resistance suppression occurs, the effect of piperacillin plus tazobactam on the induction of AmpC beta-lactamase was analyzed by monitoring the beta-galactosidase activity of an inducible ampC-lacZ gene fusion in Escherichia coli. The combination exerted no inhibitory effect on AmpC beta-lactamase induction. Tazobactam also had no effect on the accumulation of a key intermediate in the AmpC beta-lactamase induction pathway, 1,6-anhydromurotripeptide, in an ampD mutant strain of E. coli. However, the addition of tazobactam to liquid cultures of E. cloacae 40001 in the presence of piperacillin at four times the MIC caused a delay in the recovery of the culture to piperacillin-induced stress. At 16 times the MIC, a complete suppression of regrowth occurred. Analysis of culture viability on piperacillin plates showed that the culture recovery was due to growth by moderately resistant mutants preexisting in the cell population, which at 16 times the MIC became susceptible to the combination. Evidence from the kinetics of inhibition of the E. cloacae 40001 AmpC beta-lactamase by clavulanic acid, sulbactam, and tazobactam and from the effects of these drugs on the frequency of resistance to piperacillin suggests that the suppressive effect of tazobactam on the appearance of resistance is primarily mediated by the beta-lactamase inhibitory activity.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Thermal analysis of the plant encapsulation-dehydration cryopreservation protocol using silica gel as the desiccant.

The encapsulation-dehydration cryopreservation protocol is critically dependent upon the evaporative desiccation step, which must optimise survival with the retention of glass stability on sample cooling and rewarming. Desiccation is usually achieved evaporatively by drying in a sterile airflow. However, chemical desiccation using silica gel has advantages for laboratories that do not have environmental control and/or which are exposed to high relative humidities and risks of microbial contamination. This study characterised thermal profiles of silica gel-desiccated encapsulated shoot-tips of two Ribes species using Differential Scanning Calorimetry. For both species silica gel-desiccation at 16 degrees C for 5 h decreased bead water content from ca. 75 to 28% fresh weight (3.8 to 0.4 g x g(-1) dry weight); further desiccation (for 6 and 7 h) reduced the bead water content to 21% (0.3 g x g(-1) dry weight). These changes in water status altered the thermal properties of beads for both species. After 7 h desiccation over silica gel stable glass transitions were observed on both cooling and rewarming of beads containing meristems. Tg mid-point temperatures ranged from -78 to -51 degrees C (cooling) and from -88 to -54 degrees C (warming) [at cooling and warming rates of 10 and 5 degrees C min(-1), respectively] after 5 to 7 h silica gel-desiccation. Post-cryopreservation viability of both species was ca. 63%. Thermal analysis studies revealed that an encapsulation/dehydration protocol using silica gel as a desiccant should comprise a minimum 5 h drying (at 16 degrees C). This reduces bead moisture content to a critical point (ca. 0.4 g x g(-1) dry weight) at which stable glasses are formed on cooling and rewarming. It is concluded that silica gel has advantages for use as a desiccant for alginate-encapsulated plant meristems by promoting stable vitrification and is useful in laboratories and/or geographical locations where environmental conditions are not under stringent control.

Cell Survival↗

PubMed2005

Detection of galangin-induced cytoplasmic membrane damage in Staphylococcus aureus by measuring potassium loss.

Galangin is one of the active antimicrobial principles of propolis or 'bee glue' and Helichrysum aureonitens, a perennial herb used by South African indigenes to treat infection. The effect of this compound and antibacterial agents with known mechanisms of action upon the cytoplasmic membrane integrity of Staphylococcus aureus was investigated by comparing potassium loss profiles from bacterial cell suspensions. Using an agar dilution assay, the minimum inhibitory concentrations (MICs) of the flavonol galangin, the bacteriostatic antibiotic novobiocin and the bactericidal antibiotic penicillin G against Staphylococcus aureus NCTC 6571 were determined as being 50 microg/mL, 62.5 ng/mL and 31.3 ng/mL, respectively. When 5x10(7)cfu/mL Staphylococcus aureus were suspended in 'potassium-free' media containing 50 microg/mL galangin, a 60-fold decrease in viability was observed after 12 h. Populations of 1x10(9) cfu/mL Staphylococcus aureus incubated for 12 h in 50 microg/mL galangin lost 21% more potassium than untreated control populations. Novobiocin had no effect on potassium loss, but populations incubated in 31.3 ng/mL penicillin G exhibited a 6% increase in potassium loss. This data clearly demonstrates that galangin causes a significant increase in potassium loss from Staphylococcus aureus cells, which may be attributed to either direct damage to the cytoplasmic membrane or indirect damage effected through autolysis/weakening of the cell wall and consequent osmotic lysis.

Anti-Bacterial Agents↗

PubMed2005

Survival of probiotic lactobacilli in acidic environments is enhanced in the presence of metabolizable sugars.

Lactobacillus rhamnosus GG is an industrially significant probiotic strain with proven health benefits. In this study, the effect of glucose on L. rhamnosus GG survival was analyzed in simulated gastric juice at pH 2.0. It was found that the presence of 19.4 mM glucose resulted in up to 6-log10-enhanced survival following 90 min of exposure. Further work with dilute HCl confirmed that glucose was the sole component responsible. Comparative analysis with other Lactobacillus strains revealed that enhanced survival was apparent in all strains, but at different pH values. The presence of glucose at concentrations from 1 to 19.4 mM enhanced L. rhamnosus GG survival from 6.4 to 8 log10 CFU ml(-1) in simulated gastric juice. The mechanisms behind the protective effect of glucose were investigated. Addition of N',N'-dicyclohexylcarbodiimide to simulated gastric juice caused survival to collapse, which was indicative of a prominent role in inhibition of F0F1-ATPase. Further work with neomycin-resistant mutants that exhibited 38% to 48% of the F0F1-ATPase activity of the parent confirmed this, as the survival in the presence of glucose of these mutants decreased 3 x 10(6)-fold compared with the survival of the wild type (which had a viability of 8.02 log10 CFU ml(-1)). L. rhamnosus GG survival in acidic conditions occurred only in the presence of sugars that it could metabolize efficiently. To confirm the involvement of glycolysis in the glucose effect, iodoacetic acid was used to inhibit glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity. The reduction in GAPDH activity caused survival to decrease by 8.30 log10 CFU ml(-1) in the presence of glucose. The data indicate that glucose provides ATP to F0F1-ATPase via glycolysis, enabling proton exclusion and thereby enhancing survival during gastric transit.

Adenosine Triphosphate↗

PubMed2000

Thatch biodegradation and antifungal activities of two lignocellulolytic Streptomyces strains in laboratory cultures and in golf green turfgrass.

The use of lignocellulolytic Streptomyces spp. as biological agents, to enhance thatch degradation in turf and to slow its rate of accumulation while controlling fungal growth in the thatch layer, was studied. In flask scale studies, two lignocellulolytic Streptomyces violaceusniger (= hygroscopicus) strains (YCED9 and WYE53) decomposed thatch (> 30% dry weight) over a 12-week incubation period. Biodegradation was accompanied by production of extracellular cellulases, xylanases, and peroxidases. The accumulation of the polymeric, water-soluble lignin degradation intermediate acid, precipitable polymeric lignin (APPL), was also observed. Residual thatch from 12-week-old cultures had an increased lignin-to-carbohydrate ratio, an indication that although lignin was metabolized, carbohydrates were preferential carbon sources for these actinomycetes. A spore-containing soluble dry powder formulation was used as an inoculum in an in situ field experiment. This formulation was maintained in storage at 4 degrees C for over two years without viability loss. Results from the golf green experiment showed that although treated thatch layers in established greens were not appreciably reduced over the course of one summer, the Streptomyces were active and maintained their populations within the thatch, while fungal growth was suppressed as compared to controls. The results show that treatment of turfgrass with these Streptomyces may be useful for the long-term control of fungal populations within the thatch. Longer field studies are required to assess the long-term potential for also controlling thatch build-up and fungal pathogens.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2005

Role of superoxide in the germination of Bacillus anthracis endospores.

The spore forming Gram-positive bacterium Bacillus anthracis, the causative agent of anthrax, has achieved notoriety due to its use as a bioterror agent. In the environment, B. anthracis exists as a dormant endospore. Germination of endospores during their internalization within the myeloid phagocyte, and the ability of those endospores to survive exposure to antibacterial killing mechanisms such as superoxide (O(2)*-, is a key initial event in the infective process. We report herein that endospores exposed to fluxes of O(2)*- typically found in stimulated phagocytes had no effect on viability. Further endospores of the Sterne strain of B. anthracis were found to scavenge O(2)*-, which may enhance the ability of the bacterium to survive within the hostile environment of the phagolysosome. Most intriguing was the observation that endospore germination was stimulated by a flux of O(2)*- as low as 1 microM/min. Data presented herein suggest that B. anthracis may co-opt O(2)*- which is produced by stimulated myeloid phagocytes and is an essential element of host immunity, as a necessary step in productive infection of the host.

Bacillus anthracis↗

PubMed2001

Effects of dipeptide bestatin on Porphyromonas gingivalis and epithelial cells.

BACKGROUND: Dipeptide bestatin has been previously reported to selectively inhibit the growth of Porphyromonas gingivalis. The aims of this study were to investigate the mechanism of action of bestatin and to evaluate its effect on epithelial cells. METHODS: The inhibitory effect of bestatin on P. gingivalis was tested in vitro (culture medium) and in vivo (guinea pig model). Radiolabeled compounds were used to investigate the effect of bestatin on the uptake of amino acids and peptides. The cytotoxic effect of bestatin was evaluated using a keratinocyte cell line. RESULTS: The growth inhibition of P. gingivalis by bestatin was concentration-dependent. Even at high concentrations, compounds possessing a chemical structure or an aminopeptidase inhibitor activity related to bestatin had no effect on growth of P. gingivalis. When injected in the presence of P. gingivalis, bestatin was able to prevent the development of a necrotic abscess in a guinea pig model. Data were obtained suggesting that bestatin does not act on proteinases of P. gingivalis. Rather, bestatin was found to inhibit the intracellular uptake of radioactivity from 14C-labeled amino acids or heat-denatured type I collagen. This was not observed with a spontaneous mutant of P. gingivalis, whose growth was not affected by bestatin. In the second part of the study, bestatin was found to have no effect on epithelial cell viability in culture at concentrations effective on P. gingivalis. In addition, bestatin did not show effects on epithelial cell migration or production of gelatinases. CONCLUSIONS: This study suggests that bestatin selectively inhibits growth of P. gingivalis by affecting the intracellular uptake of amino acids and peptides, which serve as energy and nitrogen sources for this bacterial species. Bestatin has no cytotoxicity and may represent a therapeutic molecule for local treatment of P. gingivalis-associated periodontitis.

Abscess↗

PubMed2000

Interaction of polyphemusin I and structural analogs with bacterial membranes, lipopolysaccharide, and lipid monolayers.

Three structural variants (PV5, PV7, and PV8) of the horseshoe crab cationic antimicrobial peptide polyphemusin I were designed with improved amphipathic profiles. Circular dichroism spectroscopy analysis indicated that in phosphate buffer polyphemusin I, PV7, and PV8 displayed the spectrum of a type II beta-turn-rich structure, but, like polyphemusin I, all three variants adopted a typical beta-sheet structure in an anionic lipid environment. Both polyphemusin I and variants were potent broad spectrum antimicrobials that were clearly bactericidal at their minimal inhibitory concentrations. The variants were moderately less active in vitro but more effective in animal models. Moreover, these variants exhibited delayed bacterial killing, whereas polyphemusin I killed Escherichia coli UB1005 within 5 min at 2.5 microg/mL. All the peptides showed similar abilities to bind to bacterial lipopolysaccharide (LPS) and permeabilize bacterial outer membranes. Consistent with this was the observation that all peptides significantly inhibited cytokine production by LPS-stimulated macrophages and penetrated polyanionic LPS monolayers to similar extents. None of the peptides had affinity for neutral lipids as evident from both tryptophan fluorescence spectroscopy and Langmuir monolayer analysis. As compared to polyphemusin I, all variants showed reduced ability to interact with anionic lipids, and the hemolytic activity of the variants was decreased by 2-4-fold. In contrast, polyphemusin I efficiently depolarized the cytoplasmic membrane of E. coli, as assessed using a membrane potential sensitive fluorescent dye 3,3-dipropylthiacarbocyanine (diSC(3)5) assay, but the variants showed a substantially delayed and decreased depolarizing ability. The coincident assessment of cell viability indicated that depolarization of the bacterial cytoplasmic membrane potential by polyphemusin I occurred prior to lethal damage to cells. Our data suggest that increase of amphipathicity of beta-sheet polyphemusin I generally resulted in variants with decreased activity for membranes. Interestingly, all variants showed an improved ability to protect mice both against infection by Pseudomonas aeruginosa and from endotoxaemia.

Animals↗

PubMed2003

Efficiency of procedures for induction and cultivation of Pseudomonas syringae pv. pisi L-form.

The L-form of Pseudomonas syringae pv. phaseolicola has been proved to induce resistance to bean halo blight. Various procedures were tested to induce the L-form of Pseudomonas syringae pv. pisi for its potential use as biocontrol agent of pea bacterial blight. Cell-wall deficient cells were induced in a liquid medium with penicillin following a protocol described for P. s. pv. phaseolicola. Cell growth on solid induction medium developed as typical granular and vacuolated structures, and characteristic colonies were observed in the first transfer. However, there was poor growth in subsequent transfers and some reversion to the parental type. To improve the induction procedure, the following new procedures were applied: (1) viability of cells was monitored during induction. The optimum induction time in liquid medium with penicillin was lower for pv. pisi than for pv. phaseolicola. Viability of L-forms in solid induction medium with penicillin was low and decreased in time. (2) the inducer ticarcillin was combined with clavulanic acid, which prevented the reversion to the parental type and (3) a range of concentrations of penicillin and ticarcillin/clavulanic acid was applied by the spiral gradient endpoint method for calculation of minimum inhibitory concentrations (MIC). Based on the results from these tests an induction method for P. s. pv. pisi L-form is proposed and the relevance of L-form is discussed for practice.

Anti-Bacterial Agents↗

PubMed1996

In-vitro and in-vivo antibacterial activity of plaunotol, a cytoprotective antiulcer agent, against Helicobacter pylori.

Recently, some antiulcer agents have been reported to have antibacterial activity against Helicobacter pylori, which is highly associated with gastritis and peptic ulcers. In-vitro and in-vivo activity of plaunotol, a cytoprotective antiulcer agent, against H. pylori was investigated. Antibacterial activity of plaunotol against a standard strain (NCTC 11637) and 14 clinical isolates was compared with those of other cytoprotective antiulcer agents: benexate, sofalcone, teprenone, cetraxate, and gefarnate, by an agar dilution method. The MIC50 and MIC90 of plaunotol against 15 strains were 6.25 and 12.5 mg/L, respectively, making it the most potent of the cytoprotective antiulcer agents. The bactericidal effect of plaunotol was investigated using an in-vitro killing assay. Plaunotol at concentrations of more than 6 mg/L induced a rapid reduction of culture turbidity, with an extensive loss of viability, within 30 min. Observation by scanning electron microscopy revealed that plaunotol caused autolysis and treated cells were deformed. In-vivo activity of plaunotol against H. pylori was examined in a nude mouse gastritis model. Plaunotol significantly decreased the number of H. pylori in the stomach of nude mice. In addition, the antiulcer agent enhanced the antibacterial activity of amoxycillin or clarithromycin in the infection model.

Amoxicillin↗