Bactericidal Action (bactericidal + action)

Distribution by Scientific Domains

Selected Abstracts

Induction of complement sensitivity in Escherichia coli by citric acid and low pH

C. Ocaa-Morgner
Aims:,The lytic functions of the complement system play an important role in the control of Gram-negative infections. Complement-resistant Escherichia coli LP1395 (O18) grown under normal conditions can survive the bactericidal action of complement present in human serum. Towards elucidating the mechanisms of complement resistance, the resistance of E. coli LP1395 grown under conditions of low pH and in the presence of citric acid was tested. Methods and Results:,E. coli LP1395 becomes sensitive to complement after growth in the presence of citric acid at pH 5. Complement resistance could be restored when the cells were transferred to pH 7 media. However, this recovery was greatly impaired when the cells were transferred to pH 7 media with chloramphenicol. This implies that protein synthesis may be involved in complement resistance. The cells exposed to citric acid at pH 5 showed no indication of a generalized outer membrane (OM) permeability when compared with those grown under normal conditions in terms of sensitivity to lysozyme, uptake of lipophilic dye, or sensitivity to a number of antibiotics. Conclusions:,Complement-resistant LP1395 may acquire a sensitivity to complement due not to a generalized disruption of the OM barrier, but possibly to the alteration of the activity of one or more normal complement resistance factors. Significance and Impact of the Study:,The elucidation of the echanisms of complement resistance of Gram-negative pathogens would bring important information about bacterial infections. Complement resistance factors could also be potential targets in antimicrobial therapies. [source]

Membrane permeability and antimicrobial kinetics of cecropin P1 against Escherichia coli,

Steven Arcidiacono
Abstract The interaction of cecropin P1 (CP1) with Escherichiacoli was investigated to gain insight into the time-dependent antimicrobial action. Biophysical characterizations of CP1 with whole bacterial cells were performed using both fluorescent and colorimetric assays to investigate the role of membrane permeability and lipopolysaccharide (LPS) binding in lytic behavior. The kinetics of CP1 growth inhibition assays indicated a minimal inhibitory concentration (MIC) of 3 M. Bactericidal kinetics at the MIC indicated rapid killing of E.coli (<30 min). Membrane permeability studies illustrated permeation as a time-dependent event. Maximum permeability at the MIC occurred within 30 min, which correlates to the bactericidal action. Further investigation showed that the immediate permeabilizing action of CP1 is concentration-dependent, which correlates to the concentration-dependent nature of the inhibition assays. At the MIC and above, the immediate permeability was significant enough that the cells could not recover and exhibit growth. Below the MIC, immediate permeability was evident, but the level was insufficient to inhibit growth. Dansyl polymyxin B displacement studies showed LPS binding is essentially the same at all concentrations investigated. However, it does appear that only the immediate interaction is important, because binding continued to increase over time beyond cell viability. Our studies correlated CP1 bactericidal kinetics to membrane permeability suggesting CP1 concentration-dependent killing is driven by the extent of the immediate permeabilizing action of the peptide. Copyright 2009 European Peptide Society and John Wiley & Sons, Ltd. [source]

Effects of dimerization of the cell-penetrating peptide Tat analog on antimicrobial activity and mechanism of bactericidal action

Wan Long Zhu
Abstract The cell-penetrating peptide Tat (48,60) (GRKKRRQRRRPPQ) derived from HIV-1 Tat protein showed potent antibacterial activity (MIC: 2,8 M). To investigate the effect of dimerization of Tat (48,60) analog, [Tat(W): GRKKRRQRRRPWQ-NH2], on antimicrobial activity and mechanism of bactericidal action, its dimeric peptides, di-Tat(W)-C and di-Tat(W)-K, were synthesized by a disulfide bond linkage and lysine linkage of monomeric Tat(W), respectively. From the viewpoint of a weight basis and the monomer concentration, these dimeric peptides displayed almost similar antimicrobial activity against six bacterial strains tested but acted more rapidly against Staphylococcus aureus on kinetics of bactericidal activity, compared with monomeric Tat(W). Unlike monomeric Tat(W), these dimeric peptides significantly depolarized the cytoplasmic membrane of intact S. aureus cells at MIC and induced dye leakage from bacterial-membrane-mimicking egg yolk L -,-phosphatidylethanolamine/egg yolk L -,-phosphatidyl- DL -glycerol (7:3, w/w) vesicles. Furthermore, these dimeric peptides were less effective to translocate across lipid bilayers than monomeric Tat(W). These results indicated that the dimerization of Tat analog induces a partial change in the mode of its bactericidal action from intracellular target mechanism to membrane-targeting mechanism. Collectively, our designed dimeric Tat peptides with high antimicrobial activity and rapid bactericidal activity appear to be excellent candidates for future development as novel antimicrobial agents. Copyright 2009 European Peptide Society and John Wiley & Sons, Ltd. [source]

Pharmacokinetics and pharmacokinetic/pharmacodynamic integration of orbifloxacin in Korean Hanwoo cattle

The pharmacokinetics and pharmacodynamics of orbifloxacin were studied in six clinically healthy Hanwoo cows after intravenous (i.v.) and intramuscular (i.m.) administration at a dose of 3 mg/kg. Orbifloxacin concentrations were determined by high performance liquid chromatography with fluorescence detection. Steady-state volume of distribution and clearance of orbifloxacin after i.v. administration were 0.92 L/kg and 0.24 L/hkg, respectively. Following i.m. administration, a slow and complete absorption with absolute bioavailability of 101.4%, and a maximum concentration (Cmax) of 1.17 ,g/mL at 1.04 h were observed. The in vitro serum protein binding was 14.76%. The in vitro antibacterial activity of orbifloxacin against a pathogenic strain of Mannheimia haemolytica (M. haemolytica), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was determined. The ex vivo activity of orbifloxacin against M. haemolytica strain was also determined, and these data were integrated with the ex vivo bacterial counts to establish AUC24h/MIC values producing bacteriostatic action, bactericidal action and elimination of bacteria. Mean values were 32.7, 51.6 and 102.6 h, respectively. From these data, we predict that orbifloxacin, when administered i.m. at a dosage of 2.5,5 mg/kg once a day, would be effective against bovine pathogens, such as M. haemolytica. Additional studies may be needed to confirm its efficacy in a clinical setting, and to evaluate the penetration of the drug in diseased tissues. [source]

Enhanced bactericidal action and masking of allergen structure of soy protein by attachment of chitosan through Maillard-type protein-polysaccharide conjugation

Masakatsu Usui
Abstract The soy protein-chitosan conjugate was formed by the Maillard reaction in dry state (relative humidity 65%) at 60C for 2 weeks to improve the functional properties. The antimicrobial activity of the Maillard-type soy protein-chitosan conjugates enhanced 2,3 times that of soy protein-chitosan mixture. The soy protein-chitosan conjugate showed excellent emulsifying property with the progress of Maillard-type conjugation. The allergenicity of soy protein was greatly decreased by the attachment of chitosan through Maillard reaction. The immonoblotting analysis with patient's sera revealed that soy protein-chitosan conjugate was more effective to mask the allergen structure of soy protein causing from 34 kDa-protein (Gly m Bd 30K) than soy protein-galactomannan conjugate. The Western blotting showed that allergen (34 kDa-protein) was completely masked by soy protein-chitosan conjugation, while it was not completely masked by soy protein-galactomannan conjugation. [source]

Sensitivity of genera Porphyromonas and Prevotella to the bactericidal action of C-terminal domain of human CAP18 and its analogues

E. Isogai
This paper reports the effect of the synthesized 27-amino acid sequence in the C-terminal domain of human CAP18 (hCAP18), a human cationic antibacterial protein or cathelicidin, on certain strains belonging to the genera Porophyromonas and Prevotella. The domain binds lipopolysaccharides (LPS) from Porophyromonas gingivalis and Porophyromonas circumdentaria as well as enterobacterial LPS. Two analogues of hCAP18, designated LL/CAP18 and FF/CAP18, were also tested to determine whether additional activity was obtained. The analogue peptides replaced with hydrophobic and cationic amino acid residues showed more potent bactericidal and LPS-binding activities than the original one. [source]

Sensitivity of Actinobacillus actinomycetemcomitans and Capnocytophaga spp. to the bactericidal action of LL-37: a cathelicidin found in human leukocytes and epithelium

D. Tanaka
The bactericidal activity of synthetic LL-37, a cathelicidin, was assessed against Actinobacillus actinomycetemcomitans (three strains) and Capnocytophaga spp. (three strains). All strains were sensitive to LL-37, and exhibited 99% effective dose of 7.5-to-11.6 ,g/ml. An amidated form of LL-37, pentamide-37, killed with about the same efficacy as LL-37. Partial inhibition of killing was noted at physiologic concentrations of NaCl, and complete inhibition was observed at 400 mM NaCl. At approximately the 99% effective dose , i.e., 10 ,g/ml , LL-37 also lost activity against A. actinomycetemcomitans in the presence of native or heat-inactivated 10,15% normal human AB serum. Pentamide-37 was less sensitive to serum inhibition than LL-37. In conclusion, certain oral, gram-negative bacteria are sensitive to the bactericidal activity of LL-37 at low concentrations of serum and salt, a condition likely to be found within the membrane-delimited phagolysosome. Modified forms of LL-37, such as pentamide-37, may be more suitable for future therapeutic application in the presence of serum. [source]

Antibacterial activity of polygodial

Isao Kubo
Abstract Polygodial was found to possess moderate antibacterial activity against gram-positive bacteria including Bacillus subtilis, Staphylococcus aureus and gram-negative bacteria including Escherichia coli and Salmonella choleraesuis with minimum bactericidal concentrations (MBC) of 100 and 100 g/mL (0.34 mm) and 100 and 50 g/mL, respectively. The time kill curve study showed that polygodial was bactericidal against B. subtilis and S. choleraesuis. However, there was a difference in its bactericidal action against endospore-forming B. subtilis and food-borne S. choleraesuis. Copyright 2005 John Wiley & Sons, Ltd. [source]

One-Step, Painting-Like Coating Procedures To Make Surfaces Highly and Permanently Bactericidal

Daewon Park
Previously we found that covalent attachment of long-chained, moderately hydrophobic polycations to surfaces of solid objects renders the latter permanently bactericidal. Herein we replaced such surface-specific, multistep immobilization techniques with a single-step, general procedure akin to common painting. Glass or polyethylene slides were briefly dipped into organic solutions of certain optimally hydrophobic N -alkyl-PEI (where PEI stands for branched 750-kDa polyethylenimine) polycations, followed by solvent evaporation. The resultant polycation-coated slides were able to kill on contact all of the encountered bacterial cells, whether the Gram-positive human pathogen Staphylococcus aureus or its Gram-negative brethren Escherichia coli. This biocidal effect was found not to be caused by N -alkyl-PEI molecules leached from the surface. Further examination of the mechanism of this bactericidal action suggested that the surface-deposited N -alkyl-PEI kills bacteria by rupturing their cellular membranes. This conclusion was further supported by studies in which the molecular weight of PEI and the hydrophobicity of the alkyl moiety were varied. [source]

Key considerations in the treatment of complicated staphylococcal infections

R. N. Jones
Abstract Substantial increases in antimicrobial resistance among Gram-positive pathogens, particularly Staphylococcus aureus, are compromising traditional therapies for serious bacterial infections. There has been an alarming increase in the rates of methicillin-resistant S. aureus (MRSA) over the past two decades, and the more recent emergence of heterogenous vancomycin-intermediate (hVISA), vancomycin-intermediate (VISA) and vancomycin-resistant S. aureus (VRSA) strains limits the use of vancomycin, the current standard of care for MRSA infections. Tolerance to vancomycin, which represents a lack of bactericidal activity of vancomycin, is another troublesome property of some S. aureus strains that can adversely affect the outcome of antimicrobial therapy. Increasing MICs of vancomycin for staphylococci, poor tissue penetration by the drug and a slow rate of bactericidal action of the drug have also raised concerns about its efficacy in the contemporary treatment of MRSA infections. There is an increasingly apparent need for new agents for the treatment of staphylococcal infections, ideally with potent bactericidal activity against MRSA, hVISA, VISA and VRSA and with superior susceptibility profiles as compared with glycopeptides. [source]

The Bactericidal Effects of Electrolyzed Oxidizing Water on Bacterial Strains Involved in Hospital Infections

Nina V. Vorobjeva
Abstract:, The study is designed to investigate bactericidal actions of electrolyzed oxidizing water on hospital infec-tions. Ten of the most common opportunistic pathogens are used for this study. Cultures are inoculated in 4.5 mL of electrolyzed oxidizing (EO) water or 4.5 mL of sterile deionized water (control), and incubated for 0, 0.5, and 5 min at room temperature. At the exposure time of 30 s the EO water completely inactivates all of the bacterial strains, with the exception of vegetative cells and spores of bacilli which need 5 min to be killed. The results indicate that electrolyzed oxidizing water may be a useful disinfectant for hospital infections, but its clinical application has still to be evaluated. [source]