Formation Of Inhibition Zones Research Articles

Antimicrobial effect of photodynamic therapy using a highly pure chlorin e6

The aim of the present study is to evaluate the antimicrobial effect of photodynamic therapy (PDT) using a highly pure chlorin e(6) (Ce(6)), against various pathogenic bacteria. To examine the antimicrobial effect of Ce(6)-mediated PDT against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Salmonella enterica serovar Typhimurium, inhibition zone formation, CFU quantification, and bacterial viability were evaluated. Inhibition zone analysis showed that Ce(6)-mediated PDT is very effective to inhibit the growth of S. aureus and P. aeruginosa, but has only minor effect to E. coli and S. Typhimurium, which was dependent on the energy density of laser and dose of Ce(6). Ce(6)-mediated PDT also nearly inhibited the colony formation of S. aureus and P. aeruginosa, and partially inhibited that of E. coli and S. Typhimurium. In addition, the number of viable bacteria decreased greatly after PDT application with LS-chlorin e6 of 10 microM and laser and energy density of 20 J/cm(2). These results show that Ce(6)-mediated PDT can be an effective alternative for antimicrobial treatment.

Isolation, characterization and biological evaluation of bioactive metabolites from Nocardia levis MK-VL_113

An Actinomycete isolate found to be prominent in the laterite soils of Acharya Nagarjuna University (ANU) Campus, Guntur was identified as Nocardia levis MK-VL_113 by 16S rRNA analysis. Cultural, morphological and physiological characteristics of the strain were recorded. Screening of secondary metabolites obtained from 4-day old culture broth of the strain led to the isolation of two fractions active against a wide variety of Gram-positive, Gram-negative bacteria and fungi. The structure of the first active fraction was elucidated using FT-IR, EI-MS, (1)H NMR and (13)C NMR spectra and identified as 1-phenylbut-3-ene-2-ol which is first time reported as a natural product. The compound exhibited good antimicrobial potential against the opportunistic and pathogenic bacteria and fungi. The antifungal activity of the strain and its metabolite were further confirmed with in vitro and in vivo studies. Evidence for the antagonism of the strain against Fusarium oxysporum, causing wilt disease in sorghum was demonstrated by the formation of inhibition zone in in vitro plate assay and reduction in the incidence of wilt of sorghum plants by using a green house trial. Analysis of the rhizosphere soil extracts by high performance liquid chromatography also demonstrated the production of the compound by the strain under in vivo conditions. As compared to the commercial fungicide mancozeb, the bioactive compound, 1-phenylbut-3-ene-2-ol was highly effective in controlling wilt of sorghum. Besides, the partially purified second fraction (PPF) subjected to gas chromatography-mass spectrometry revealed the presence of phenylethyl alcohol, dibutyl phthalate and 1,2-benzenedicarboxylic acid, 3-nitro.

Mineral distribution and CLSM analysis of secondary caries inhibition by fluoride/MDPB-containing adhesive system after cariogenic challenges

Objective To evaluate the inhibition zone formation (IZ) and mineral distribution along the interface of adhesive systems either containing fluoride and antibacterial primer or not, after chemical and biological artificial caries challenges. Methods Forty-eight third molars were used. Artificial caries was developed with S. mutans in a 4 mm × 4 mm area of occlusal dentin surface. Carious dentin was removed and cavities were restored with Adper Scotchbond Multi-Purpose (SBM) and Clearfil Protect Bond (CPB) ( n = 24). Samples were submitted to secondary caries development by chemical (C) (acidic gel) or biological (B) ( S. mutans culture) methods for 5 days. Four groups were tested ( n = 12): (1) SC (SBM + C); (2) SB (SBM + B); (3) CC (CPB + C); (4) CB (CPB + B). The IZ and outer lesion (OL) formations were analyzed by confocal laser scanning microscopy (CLSM). The distribution of calcium (Ca) and phosphorus (P) content along the interface was analyzed by micro X-ray fluorescence spectrometer by energy-dispersive (μEDX). Results The frequency of IZ formation and mean values of IZ thickness differed among the groups. The CC group presented the lowest OL depth. μEDX analysis showed that CPB had the highest mineral loss by the biological method, but the lowest mineral loss by the chemical method. SC and SB groups showed intermediate values of mineral loss. Conclusion The mineral loss along the dentin/restoration interface was affected by the artificial caries method, and hybrid layer formation by adhesive systems used. The adhesive system containing fluoride and antibacterial primer did not prevent secondary caries formation.

Effect of grilling process on antibiotic residues in edible tissues of poultry by FPT method

Regarding to vast application of the antibiotic drugs in animals quality control of food stuff, from point view of not containing antibiotic residues, is necessary. Existing of antibiotic residues in food stuff, especially meat, and their transference to the body of consumer, is the cause of effects like bacterial resistance, allergic reactions, toxicity, carcinogenic effects and disturbing of natural micro flora of intestine. This paper presents the net change by grilling on residues of antibiotics in edible tissues of poultry. Four-plate test is one of the microbiologic methods for detecting antibiotic residues in food stuff, which is at the base of inhibition zone formation around the sample in four culture media with different pH and test bacteria. For this purpose, 40 carcasses were collected on each of eight visits from Tabriz poultry slaughtering houses. Four locations were sampled aseptically from each carcass: breast muscle; skin; liver and gizzard. After doing different phases of four-plate test on raw samples , from total 40 muscle samples, 25 cases (62/5%); from total 40 liver samples, 40 cases (100%); from total 40 skin samples, 21 cases (52/5%) and from total 40 gizzard samples, 15 cases (37/5%) are diagnosed to be polluted to antibiotic residues. Then positive samples incubated in 200 °C. incubation time regarding to usual cooking time were as follows: muscle 40 min; skin 15min; liver 25 min; gizzard 60 min then we perused samples by FPT method again for present of antibiotic residue and non of the positive raw samples have any residue of antibiotics after grilling (P< 0.05). Therefore enough cooking temperature & time can have a great effect on antibiotics residues in food.

Rostrupiella danica gen. et sp. nov., a Lulworthia-like marine lignicolous species from Denmark and the USA

Abstract A Lulworthia-like species with affinities to Lulworthia opaca (=Halophiobolus opacus) and L. longirostris (=H. longirostris) was discovered on driftwood collected along the Danish coast and from the northwestern coast of the USA. Examination of the type material of L. opaca and L. longirostris leads to the conclusion that the two species are different at the generic level. Lulworthia longirostris shares several characters in common with the Lulworthia-like species collected in Denmark. A detailed study of the Lulworthia-like species has provided evidence for the erection of a new genus Rostrupiella to accommodate it. The new taxon is characterised by large ascomata that are deeply seated within the wood, with long necks extending through the wood to the surface, a bell-like structure protruding into the centrum, large, melanised bladder cells present in the wood cells and formation of inhibition zones in the host tissue. Partial nuclear LSU ribosomal RNA gene of Rostrupiella was sequenced to determine its phylogenetic relationship with other genera in the Lulworthiales.

Gentamicin Release from Photopolymerized PEG Diacrylate and pHEMA Hydrogel Discs and Their In Vitro Antimicrobial Activities

Hydrogels based on poly(ethylene glycol)-diacrylate (PEG-DA) and 2-hydroxyethyl methacrylate (HEMA) were polymerized with cross-linking agent ethylene glycol diacrylate (EGDMA) under mild photoinitiating conditions. PEG-DA and HEMA concentrations of disks with 1 ± 0.3 mm thickness were 30% and 50% w/w and 40% and 60% w/w, respectively. Gentamicin sulphate was incorporated into the hydrogel during photopolymerization and its release kinetics were tested by spectrophotometric method at 255 nm wavelength in phosphate buffer (pH 7.4) and citrate buffer (pH 2.2). The drug release in citrate buffer was faster compared with to phosphate buffer. The release of drug from 40% HEMA containing hydrogel showed Fickian diffusion mechanisms in phosphate buffer (pH 7.4). Antimicrobial efficiency of the samples was tested by agar diffusion method in two different bacterial cultures (Pseudomonas aeruginosa [ATCC 10145], Staphylococcus aureus [ATCC 25923]). Inhibition zone diameter (mm) surrounding each sample was measured after 24 hr incubation of drug loaded disks onto agar plates at 37°C. Inhibition zone formation also confirms that gentamicin sulphate preserves its antimicrobial activity after subjected to photopolymerization conditions.

Antimicrobial analysis of different root canal filling pastes used in pediatric dentistry by two experimental methods

The objective of this study was to compare, by two experimental methods, the antimicrobial efficacy of different root canal filling pastes used in pediatric dentistry. The tested materials were: Guedes-Pinto paste (GPP), zinc oxide-eugenol paste (OZEP), calcium hydroxide paste (CHP), chloramphenicol + tetracycline + zinc oxide and eugenol paste (CTZP) and Vitapex. Fiven microbial strains (S. aureus, E. faecalis, P. aeruginosa, B. subtilis and C. albicans) obtained from the American Type Culture Collection were inoculated in Brain Heart Infusion (BHI) and incubated at 37 degrees C for 24 h. For the direct exposure test (DET), 72 paper points were contaminated with the standard microbial suspensions and exposed to the root canal filling pastes for 1, 24, 48 and 72 h. The points were immersed in Letheen Broth (LB), followed by incubation at 37 degrees C for 48 h. An inoculum of 0.1 mL obtained from LB was then transferred to 7 mL of BHI, under identical incubations conditions and the microbial growth was evaluated. The pastes showed activity between 1 and 24 h, depending on the material. For the agar diffusion test (ADT), 30 Petri plates with 20 mL of BHI agar were inoculated with 0.1 mL of the microbial suspension, using sterile swabs that were spread on the medium. Three cavities were made in each agar plate (total = 90) and completely filled with one of the filling root canal pastes. The plates were pre-incubated for 1 h at room temperature and then incubated at 37 degrees C for 24 to 48 h. The inhibition zone around each well was recorded in mm. The complete antimicrobial effect in the direct exposure test was observed after 24 h on all microbial indicators. All root canal filling materials induced the formation of inhibition zones, except for Vitapex (range, 6.0-39.0 mm).

Detection and characterization of Leucocin OZ, a new anti-listerial bacteriocin produced by Leuconostoc carnosum with a broad spectrum of activity

Leucocin OZ is a novel, anti-listerial, and plasmid-encoded small bacteriocin produced by Leuconostoc carnosum OZ, a lactic acid bacterium isolated from vacuum-packaged sucuk. The bacterium was found to be associated with the spoilage of this product. Leucocin OZ is sensitive to proteolytic enzymes, resistant to heat up to 121 °C for 15 min, and active over a wide range of pH (2–12). Leucocin OZ activity against L. plantarum cells was bactericidal in nature since exposure of cell suspensions of L. plantarum to leucocin produced cell viability loss, as determined from the reduction in cfu after treatment. SDS gel stained with Coomassie Brilliant Blue showed several polypeptide bands. Among these bands, the band responsible for antimicrobial activity shown against a wide range of Gram-positive bacteria many of which are associated with food spoilage and food borne diseases including Listeria monocytogenes was shown tentatively linked to 3.5 kDa protein, as understood from the formation of inhibition zone on a lawn of Lactobacillus plantarum NCDO955 corresponding to this band. Proteins in other bands exhibited no antimicrobial activity. Since Leuconostoc carnosum OZ-D2 is associated with spoilage, it cannot be used for in situ bacteriocin production. However, the antimicrobial peptide it produces can be alternatively used as biopreservative in foods to control the growth of spoilage bacteria and food borne pathogens such as L. monocytogenes.

Influence of Soft Rot Bacteria on Growth of Listeria monocytogenes on Potato Tuber Slices

Growth of Listeria monocytogenes on potato tuber slices and its interaction with four representative species of soft rot bacteria (Pseudomonas fluorescens, P. viridiflava, Erwinia carotovora subsp. carotovora, and Xanthomonas campestris) were investigated. When potato tuber slices were inoculated with one of two L. monocytogenes strains (Scott A and ATCC 15313), an increase in numbers of 3 to 4 logs per gram of tissue was observed with samples that were stored at 20°C for 6 days. However, an increase of about 2 logs was observed with samples that were stored at 8°C for 12 days. When potato slices were simultaneously inoculated with L. monocytogenes and one of the four soft rot bacteria, the growth of L. monocytogenes was inhibited in the presence of P. fluorescens or P. viridiflava but was not significantly affected in the presence of E. carotovora or X. campestris. The antagonism of the two pseudomonads to L. monocytogenes was also observed in potato tuber extract and in culture media. Formation of inhibition zones was observed only in iron-deficient media but not in the medium supplemented with FeCl3. In addition, production of fluorescent siderophore (pyoverdin) by these two pseudomonads was demonstrated. L. monocytogenes was unable to colonize macerated plant tissue induced by soft-rotting bacteria 2 days before inoculation of the pathogen. These results indicate that growth of L. monocytogenes on potato tuber slices is differentially affected by soft rot bacteria and that antagonism of fluorescent pseudomonads to L. monocytogenes is possibly caused by the production of iron-chelating siderophore by these pseudomonads.

Secondary Fungal Metabolites and Their Biological Activities, V. Investigations Concerning the Induction of the Biosynthesis of Toxic Secondary Metabolites in Basidiomycetes

In cultures of the basidiomycetes Heterobasidion annosum, Gloeophyllum abietinum or Armillaria ostoyae, the biosynthesis of some of their toxic secondary metabolites is enhanced up to 400-fold when they grow in the presence of an antagonist. This stimulation is induced before any cell contact occurs. The "inducing signals" are not macromolecules, polypeptides or constituents of the cell membranes, but the same toxins which are synthesized already in monocultures in very low concentrations. After excretion and diffusion into the media, the fungi thus recognize the proximity of the antagonist in dualcultures. As a consequence, the enormous stimulation of toxin synthesis takes place. The increasing toxin concentrations in the fungal dual cultures finally cause the formation of mycel-free growth inhibition zones between the fungi, or sometimes one of the contrahents is killed. This stimulation of toxin synthesis is achieved by an enhanced de novo synthesis of enzymes of the corresponding secondary pathways.

Production of antibiotics by plant pathogenic Pseudomonads.

Plant pathogenic pseudomonads such as Pseudomonas glumae, Ps. gladioli pv. gladioli, Ps. cepacia and Ps. avenae formed growth inhibition zone around their colonies on the lawn of other plant pathogenic bacteria, Agrobaclerium tumefaciens, Corynebacterium michiganense pv. michiganense, Erwinia carotovora subsp. carotovora, Ps. solanacearum, Ps. syringae pv. syringae, Xanthomonas campestris pv. citri and X. campestris pv. oryzae, used as indicators. The activity spectra shown on the indicator bacteria were much varied depending upon the species and isolates of pseudomonads, suggesting that various antibiotic substances participated in the formation of inhibition zones.

Isolation and cryopreservation of O-methylthreonine-resistant Rosa cell lines altered in the feedback sensitivity of l-threonine deaminase

O-Methylthreonine (OMT) inhibits the growth of plated Rosa cells (ID50≃6·10(-6)M). Isoleucine is able to reverse efficiently and specifically this OMT toxicity. From OMT-resistant colonies occurring at a frequency of 1.58·10(-7) variants per cell plated at 10(-4)M OMT, the variant strains OMT(R)-1 and OMT(R)-2 were isolated, cloned via protoplasts and characterized. Both variants were ten times more resistant to OMT than the wildtype and were cross-resistant to another isoleucine analog, DL-4-thiaisoleucine. The resistant variants retained their resistance after storage for three years in liquid nitrogen. Both resistant strains were stable for several months when subcultured in the absence of OMT although it was shown in a reconstitution experiment that wildtype cells overgrow OMT(R)-2 variant cells if co-cultivated for many passages in drug-free medium. One case of instability was observed upon long-term subculturing in drug-free medium: the strain OMT(R)-1D(*) partially lost phenotypic properties. Resistance to OMT was followed qualitatively by a new method based on inhibition-zone formation in cell suspensions plated in agar medium. The OMT-resistant variants showed a reduction in sensitivity of the enzyme L-threonine deaminase to feedback inhibition by isoleucine, a decreased stability of L-threonine deaminase when stored at-18°C or incubated at +55°C and a two- to threefold increase of the free isoleucine pool within the cells. The genetical events and the biochemical mechanisms which might lead to the observed stable and biochemically defined character are discussed with particular reference to the high ploidy level of the Rosa cell line.

Antibiogram of single, double and triple chain Aroyl hydrazine against some gram positive and gram negative bacteria

The antibacterial sensitivity of some single, double and triple chain aroylhydrazine against gram positive and gram negative bacteria were performed by disc diffusion method. Most of the compounds showed appreciable antibacterial activity against different gram positive and gram negative bacteria. The single chain hydrazines are more active then double chain and triple chain hydrazine. Among the single chain aroylhydrazines studied only 4-n-hexyloxy benzoyl hydrazine is the most active. The significant activity of 4-n-hexyloxybenzoyl hydrazine and heptyloxybenzoyl hydrazine against gram positive and gram negative bacteria may be (formation of inhibition zone 8 to 22 mm with most of the test bacteria) due to their liophilicity of the bacterial cell membrane. Anti-microbial activity decreases as the number of carbon of single chain hydrazine increases (C6 &gt; C7 &gt; C8 &gt; C9 &gt; C10 single chain hydrazine). Double chain hydrazines (3, 5 or 3, 4) are more active than triple chain hydrazines (3, 5 &gt; 3, 4 &gt; 3, 4, 5 hydrazine). The antibacterial activities of hydrazines are being decreased as their increasing number of side chain.Keyword: Antibacterial sensitivity; Aroyl hydrazine.DOI: http://dx.doi.org/10.3329/ijns.v1i1.8610 International Journal of Natural Sciences (2011), 1(1):17-21