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Synthesis of biologically active quinolone natural products extracted from the actinomycete Pseudonocardia sp. CL38489Salvaggio, Flavia January 2014 (has links)
No description available.
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Cell uptake properties of Polyhexamethylene Biguanide (PHMB) and applications in intracellular deliveryChindera, Kantaraja January 2014 (has links)
No description available.
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Rapid screening for antimicrobial genes in novel nocardiophagesShibayama, Youtaro 08 December 2008 (has links)
There has been an increase in number of human infections by mycobacteria and
opportunistic pathogens of the closely related nocardioform bacteria. Frequent multiple
drug resistance in these organisms makes it desirable to identify novel targets for
antimicrobial agents. Bacteriophages offer one way to do this as analysis of their DNA
reveals great diversity in their genetic makeup, suggesting variety in the way they
interfere with host cells. Four novel nocardiophages were therefore isolated from soil
and characterized. Libraries of their nucleic acid were constructed and screened for
clones inhibitory to a nocardioform of the genus Rhodococcus. Nine clones were
characterized, and minimum necessary DNA for inhibitory activity sequenced. Of 18
ORFs predicted on these DNAs, 13 could not be assigned a function. Genes similar to
ones in databases apparently interfered with DNA metabolism, protein synthesis, or
integrity of plasma membrane. This genetic approach may be an efficient and effective
way to discover novel targets for antibiotics.
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Chemical constituents from the rhizome of coptis chinensis and their antibacterial activitiesMeng, Fan Cheng January 2018 (has links)
University of Macau / Institute of Chinese Medical Sciences
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Antibacterial activity of Myrciaria dubia (Camu camu) against Streptococcus mutans and Streptococcus sanguinisCamere Colarossi, Rosella, Ulloa Urizar, Gabriela, Medina Flores, Dyanne, Caballero García, Stefany, Mayta Tovalino, Frank, Del Valle Mendoza, Juana Mercedes 09 1900 (has links)
Objective: To evaluate the antibacterial and cytotoxic effect of Myrciaria dubia (Camu camu) (M. dubia) methanol extract, against Streptococcus mutans (ATCC 25175) (S. mutans) and Streptococcus sanguinis (ATCC 10556) (S. sanguinis). Methods: Two methanol extracts of M. dubia were prepared in vitro, from the seeds and pulp. Ten independent tests were prepared for each type of extract, using 0.12% chlorhexidine solution as positive control. Agar diffusion test was used by preparing wells with the experimental solutions cultivated in anaerobic conditions for 48 h at 37 °C. Meanwhile, the minimum inhibitory concentration and the cytotoxic effect over MDCK cell line was found. Results: A higher antibacterial effect was observed with the methanol seed extract with an inhibitory halo of (21.36 ± 6.35) mm and (19.21 ± 5.18) mm against S. mutans and S. sanguinis, respectively. The methanol extract of the pulp had an effect of (16.20 ± 2.08) mm and (19.34 ± 2.90) mm, respectively. The minimum inhibitory concentration of the pulp extract was 62.5 µg/mL for both strains, whereas for the seed antibacterial activity was observed even at low concentrations. The CC50 of the seeds extract was at a higher concentration than 800 µg/mL and 524.37 µg/mL for the pulp extract. / This study was supported by Universidad Peruana de Ciencias Aplicadas (UPC) Lima-Peru with Grant No. MANUSCRIPT ACCEPTED ACCEPTED MANUSCRIPT UPC-501-2015
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Investigating the fluoroquinolone-topoisomerase interaction by use of novel fluoroquinolone and quinazoline analogsMarks, Kevin Randall 01 May 2011 (has links)
Fluoroquinolones are broad-spectrum antibacterial agents based on the structure of nalidixic acid. For nearly five decades it has been known that fluoroquinolones inhibit bacterial growth by blocking the enzymatic action of type II topoisomerases such as DNA gyrase and topoisomerase IV. Only recently has it been discovered that some fluoroquinolones are capable of a mechanism that results in fragmented DNA and leads to rapid bacterial cell death. This mechanism is not well understood. Presented here are studies towards understanding the structure activity relationship (SAR) of fluoroquinolones, specifically to determine what leads to the novel mechanism termed "rapid lethality." This work is based on the hypothesis that structurally unique fluoroquinolones interact with the DNA-topoisomerase complex in a unique manner that ultimately leads to rapid cell death.
The first approach to understand SAR for killing was to evaluate the effect of a ring fusion between N-1 and C-8 of the fluoroquinolone core. Known lethal fluoroquinolones are substituted by N-1 cyclopropyl and C-8 methoxy, but some clinically important fluoroquinolones contain a 2-methylmopholino moiety between these two positions. Novel fluoroquinolones were synthesized and clinically available agents were obtained to create a panel of drug molecules with one of six C-7 substituents and either the morpholine ring system or N-1 cyclopropyl and C-8 methoxy. Bacteriostatic and bactericidal activities of these compounds were determined. Bactericidal studies were conducted both in the presence and absence of chloramphenicol, a protein synthesis inhibitor used to simulate non-growing bacteria. Lethality in the presence of chloramphenicol is also important when considering co-administration of fluoroquinolones with other antibiotic classes.
In a second study, fluoroquinolones were synthesized with a C-2 thioalkyl substitution. Substitutions at the C-2 position are severely lacking in clinical fluoroquinolones, with only prulifloxacin, a newly developed antibiotic, being substituted by an N-1 to C-2 thiazetidine ring structure. Analogs of ciprofloxacin and moxifloxacin were synthesized such that the N-1, C-2, and C-8 positions were substituted with cyclopropyl, thioethyl/thioisopropyl, and methoxy groups, respectively. The compounds were then evaluated for antibiotic activity against three different bacterial strains to evaluate the contribution of the C-2 thioalkyl substituent to antibacterial activity.
In a third study, quinazoline-2,4-diones, a new antibiotic class structurally and mechanistically similar to fluoroquinolones, were modified at the C-4 position in an effort to understand the binding interaction between these compounds and the target enzyme. Importantly, the quinazoline-2,4-diones typically retain activity against bacterial cells known to be resistant to fluoroquinolones and are less likely to select for resistant mutants. In this study, the C-4 carbonyl was replaced with either a thiocarbonyl or a hydroxylimine and the new compounds, bearing C-7 substituents common to potent antibiotic fluoroquinolones and quinazolines, were evaluated for activity against bacterial cells.
Despite the findings of recently published X-ray crystallography, it was determined that one of the greatest determinants in antibiotic activity of fluoroquinolones is the C-7 substituent. Additionally, there is increasing evidence that the C-2 carbonyl of quinazoline-2,4-diones affords the increase in activity against resistant mutants by creating a unique binding interaction. Collectively, the conclusions reached here add to our understanding of the structure activity relationship of the fluoroquinolone antibiotic class for rapidly killing bacterial cells and overcoming resistant mutants.
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Antibacterial Activity of beta-bungarotoxin B chainLin, Wen-Yi 05 July 2012 (has links)
Our previous studies showed that recombinant £]-bungarotoxin B chain exhibited membrane-damaging activity. Given that membrane-damaging activity is crucial for bactericidal effect of antibacterial peptide, the causal relationship between membrane-damaging activity and antibacterial action of B chain was performed in this study. £]-bungarotoxin B chain exhibited a growth inhibition on Escherichia coli (Gram-negative bacteria), but marginally displayed bactericidal effect on Staphylococcus aureus (Gram-positive bacteria). Destabilization of lipopolysaccharide (LPS) layer and inhibition of lipoteichoic acid (LTA) biosynthesis on cell wall increased bactericidal effect of B chain on E. coli and S. aureus. B chain induced leakage and fusion of bacterial membrane-mimicking liposomes. Compared with LPS, LTA notably suppressed membrane-damaging activity and fusogenicity of B chain. B chain showed similar binding affinity with LPS and LTA. Circular dichroism measurement revealed that LPS- and LTA-binding differently induced conformational change of B chain. Taken together, our data indicate that antibacterial action of B chain is related to its ability to induce membrane permeability and fusogenicity, and suggest that LTA- and LPS- induced conformational change of B chain affect membrane-damaging activity, fusogenicity and antibacterial activity of B chain.
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Antimicrobial activities of saponin-rich guar meal extractHassan, Sherif Mohamed 15 May 2009 (has links)
Three saponin-rich extracts (20, 60, 100% methanol), four 100% methanol subfractions
and seven independently acquired fractions (A-G) from guar meal, Cyamopsis
tetragonoloba L. (syn. C. psoraloides), were evaluated for antimicrobial and hemolytic
activities. These activities were compared against quillaja bark (Quillaja saponaria),
yucca (Yucca schidigera), and soybean (Glycine max) saponins in 96-well plates using
eight concentrations (0.01 to 1.0 and 0.1 to 12.5 mg extract/mL). Initial guar meal
butanol extract was 4.8 ± 0.6% of the weight of original material dry matter (DM).
Butanol extract was purified by preparative reverse-phase C-18 chromatography. Two
fractions eluted with 20, and one each with 60, and 100% methanol with average yields
of 1.72 ± 0.47, 0.88 ± 0.16, 0.91 ± 0.16 and 1.55 ± 0.15% of DM, respectively. Further
purification of the 100% methanol fraction using normal-phase silica gel preparatory
high pressure liquid chromatography eluted 4 peaks at 16, 39, 44 and 46 min. Only the
100% methanol fraction, its 16 min peak, F and G fractions, and quillaja saponin,
exhibited both hemolytic and antibacterial activities against Staphylococcus aureus,
Salmonella Typhimurium and E. coli, but 20 and 60% methanol fractions stimulated
Lactobacillus spp. growth. Guar meal (0 or 5%) was added to diets fed to chicks from 1 to 21 days of age. Chicks fed both diets were unchallenged or challenged with 5 x 103
Eimeria tenella sporulated oocysts at 10 days. Guar meal diets reduced oocysts shed per
gram of feces, body weight, and feed efficiency. Adding 2.5% guar meal, 1% guar gum,
or 0.125% saponin-rich guar meal extract to diets fed to chicks to 21 days of age showed
that guar meal increased the cfu concentrations of digesta more than controls following a
challenge with 107 cfu of Clostridium perfringens at 14 days. Body weights of chicks fed
guar meal and saponin-rich extract were significantly lower than control body weights at
21 days of age, whereas the weekly feed to gain ratio of chicks fed saponin-rich extract
was higher than controls. Guar meal reduced severity of Eimeria tenella infection and
guar saponin-rich extract exhibited antimicrobial activity against several common
poultry pathogens.
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The synthesis and practical applications of novel N-halamine biocidesBarnes, Paul Kevin, Worley, Shelby D. January 2006 (has links)
Dissertation (Ph.D.)--Auburn University,2006. / Abstract. Vita. Includes bibliographic references (p.138-140).
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Antibacterial effects of nanoparticles on cariogenic organisms林志華, Lam, Chi-wah. January 2005 (has links)
published_or_final_version / Dentistry / Master / Master of Dental Surgery
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