Differences In Antibacterial Activity Research Articles

Preliminary comparative analysis of antibacterial effects of activated and non-activated of expired platelet concentrate by disc diffusion method

Platelets release more than 30 cytokines to provide primary hemostatic function. In addition, platelets are also known to release antimicrobial peptides upon activation by thrombin. In this study, comparative analysis of antibacterial activity of activated and non-activated expired platelet concentrate was determined against Gram-positive and Gram-negative bacteria by Kirby-Bauer disk diffusion method. Thrombin was used to prepare activated platelet concentrate. Gram-positive bacteria tested in this study were S.aureus and S.pyogenes and Gram-negative bacteria were E.coli and K.oxytoca. All the bacteria used in this study were sensitive strains from clinical isolates. Activated and non-activated platelet showed no zone of inhibition against S.pyogenes and E.coli. Activated platelet showed antibacterial activity against S.aureus and K.oxytoca with the zone of inhibition of 8.3 ± 0.6 mm and 7.7 ± 0.2 mm, respectively. Zone of inhibition observed in non-activated platelet against S.aureus and K.oxytoca were 7.8 ± 0.4 mm and 7.5 ± 0.3 mm, respectively. These findings showed that no significant differences in antibacterial activity produced by activated and non-activated platelet. However, zone of inhibition observed in activated and non-activated platelet indicate the presence of antibacterial property in expired platelet.

Effect of polymorphism in egg white lysozyme on muramidase and antibacterial activities as well as hatchability in the Japanese quail (Coturnix japonica)

Lysozyme is one of the best characterized antimicrobial proteins in egg white. Three phenotypes of egg white lysozyme in Japanese quail, Coturnix japonica, (namely fast; slow; and the combination, FS) were observed by acid polyacrylamide gel electrophoresis. The fast phenotype showed faster mobility on Acid-PAGE than the slow phenotype. Comparison of the coding sequences for lysozyme derived from the slow and fast phenotypes revealed a nonsynonymous SNP at nucleotide position 115 from the translation initiation site, which alters AA sequence of lysozyme. This nonsynonymous SNP converted glutamine (Q) in the slow phenotype to lysine (K) in the fast phenotype at AA residue 21 of mature lysozyme (Q21K). Here, we investigated the effect of these phenotypes on muramidase activity, antibacterial activity, and hatchability. Muramidase activity toward isolated cell walls of Micrococcus lysodeikticus was in the order: fast allozyme > slow allozyme > chicken (Gallus gallus), but no significant difference was found among the 3 (P > 0.05). Antibacterial activity against live Staphylococcus aureus cells was significantly greater for the fast allozyme than the slow allozyme from 20 h after incubation (P < 0.05). For the antibacterial effects against live Escherichia coli cells, the activity of fast was significantly higher than that of slow at 16 h after incubation (P < 0.05). Hatchability was estimated for reciprocal crosses of Japanese quail with the FF (fast) and SS (slow) genotypes. Hatchability was 92.5% in FF male × SS female crosses and 87.2% in SS male × FF female crosses. A Cochran-Mantel-Haenszel test revealed a significant difference between the crosses (P < 0.05) and indicated that the female-derived slow phenotype led to improved rates of hatching. Our results suggest that the nonsynonymous SNP in Japanese quail lysozyme influences the electrophoretic migration, muramidase activity, and antibacterial activity of the protein, in addition to the hatchability of the eggs. These results demonstrate, for the first time, a significant difference in antibacterial activity and hatchability between 2 lysozyme phenotypes in Japanese quail.

Antibacterial activity of povidone–iodine against an artificial biofilm of Porphyromonas gingivalis and Fusobacterium nucleatum

ObjectiveTo investigate the antibacterial activity of povidone–iodine (PVP–I) on an artificial dual species biofilm of periodontal pathogens. DesignPorphyromonas gingivalis or Fusobacterium nucleatum grown in broth culture was inoculated on polycarbonate membrane (PCM) tissue culture inserts. After incubation for 72h, PVP–I solutions were applied to the biofilm for the time period ranging from 0.5 to 5min. After addition of a deactivator, each PCM was removed and the biofilm on the PCM was serially diluted and plated on blood agar plates and cultured anaerobically for 7 days. Then viable bacteria were enumerated. ResultsIn the dual species biofilm model, F. nucleatum showed an approximately 200-fold increase in viable counts when compared with mono-microbial biofilm. In dual species biofilm, PVP–I with concentration equal to or greater than 2% was required to significantly reduce P. gingivalis and F. nucleatum. When the contact time of PVP–I was increased to 1min or greater, no difference in antibacterial activity of PVP–I was observed in any concentration. ConclusionThese results suggest that 30s application of 2% PVP–I would be effective in suppressing both P. gingivalis and F. nucleatum in dual-species biofilm, and this provides clinical implication for the control of subgingival biofilm.

Tuning of antibacterial activity of a cyclopropyl fluoroquinolone by variation of the substituent at position C-8

If substituted at position C-8 by a methoxy group, fluoroquinolones possess antibacterial efficacy considerably improved over that of C-H analogues. The new veterinary fluoroquinolone pradofloxacin bears a cyano group at C-8 and it was attempted to define the ranges of activity unfolding upon variation of this moiety. Pradofloxacin and six analogues were subjected to MIC and mutant prevention concentration (MPC) analysis; we determined comparative activities against one wild-type and two isogenic first-step fluoroquinolone-resistant variants each of Escherichia coli and Staphylococcus aureus. Ciprofloxacin, enrofloxacin and its 8-CN analogue, the R,R-pyrrolidinopiperidine enantiomer of pradofloxacin as well as the 8-OH congener of pradofloxacin served as references. MICs were of limited utility in resolving differences in antibacterial activity. Regarding MPCs, E. coli was inhibited most effectively by ciprofloxacin. However, pradofloxacin and analogues bearing Cl or F closely matched that activity. MPCs of O-alkyl and the R,R-pyrrolidinopiperidine-substituted compounds indicated lower activities, while the 8-OH metabolite, essentially, had lost activity. Replacement of 8-H by CN, resulting in up to 7-fold reduced MPCs, was a prerequisite for high activity against the wild-type strains and first-step fluoroquinolone-resistant variants. Narrowed mutant selection windows, observed for both variants of E. coli and wild-type S. aureus, indicated an improved potential of pradofloxacin for restricting the selection of clones with reduced susceptibility. Substitution of hydrogen at position C-8 of an analogue of pradofloxacin by CN provided for MPCs lower than those of 8-O-CH(3) and almost similar to C-8-halogenated compounds, while alkoxy substituents caused reduced activity and hydroxylation resulted in inactivation. Efficacy was co-dependent on the amine moiety located at C-7.

Comparative study of titania nanoparticles and nanotubes as antibacterial agents

Anatase titania nanoparticles with a high surface area (about 587.7 m 2/g) were synthesized by sol–gel method using isobutyl alcohol as solvent, and then anatase titania nanotubes with needlelike shape, which had diameters of about 5 nm and wall thickness of about 1 nm, could be obtained by microwave process using the above titania nanoparticles as precursors. Both titania nanoparticles and nanotubes were characterized through X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, photoluminescence spectroscopy and nitrogen adsorption–desorption isotherm technique. The antibacterial activities of both titania nanoparticles and nanotubes against Escherichia coli ( E. coli) were developed by quantification and qualitative ways, e.g. microcalorimetric method and disk diffusion method. At the same time, their antibacterial activities against E. coli were also investigated in dark and under UV irradiation. As a result, both the titania nanoparticles and nanotubes had good antibacterial activities against E. coli due to their low inhibitory concentration and large diameter of antibacterial circle. In addition, the titania nanoparticles displayed higher antibacterial activities than those of the titania nanotubes under UV irradiation, though they presented similar antibacterial activities in dark. The differences in antibacterial activities between titania nanoparticles and nanotubes might be attributed to the changes of their microstructure in our works.

Susceptibility of clinical Staphylococcus aureus isolates to innate defense antimicrobial peptides

Antimicrobial peptides (AMPs) are effector molecules of innate immunity. To determine whether AMP susceptibility of S. aureus varies according to different types of infection, 102 isolates from patients with S. aureus bacteremia or recurrent skin and soft tissue infection, and colonizing isolates were investigated. Using microbroth dilution assays we found a narrow range of MICs of human β-defensin-3, cathelicidin LL-37 and bovine indolicidin without significant differences between the groups. Colony-forming unit (CFU) assays revealed minor differences in bactericidal activity with slightly but not significantly higher CFU reduction in colonizing isolates. These data do not support a role for differential AMP susceptibility in vitro as a major determinant of S. aureus invasive infection.

Two Major Medicinal Honeys Have Different Mechanisms of Bactericidal Activity

Honey is increasingly valued for its antibacterial activity, but knowledge regarding the mechanism of action is still incomplete. We assessed the bactericidal activity and mechanism of action of Revamil® source (RS) honey and manuka honey, the sources of two major medical-grade honeys. RS honey killed Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa within 2 hours, whereas manuka honey had such rapid activity only against B. subtilis. After 24 hours of incubation, both honeys killed all tested bacteria, including methicillin-resistant Staphylococcus aureus, but manuka honey retained activity up to higher dilutions than RS honey. Bee defensin-1 and H2O2 were the major factors involved in rapid bactericidal activity of RS honey. These factors were absent in manuka honey, but this honey contained 44-fold higher concentrations of methylglyoxal than RS honey. Methylglyoxal was a major bactericidal factor in manuka honey, but after neutralization of this compound manuka honey retained bactericidal activity due to several unknown factors. RS and manuka honey have highly distinct compositions of bactericidal factors, resulting in large differences in bactericidal activity.

Antibacterial activity of aqueous and ethanol crude extracts of the root barks of Alstonia boonei and preliminary phytochemical test of Morinda lucida

The antibiotic activity of aqueous and ethanol extracts of the root bark of two plants Alstonia boonei De wild and Morinda lucida locally used for treating different diseases especially fever were studied against seven bacteria. Crude extracts obtained from A. boonei were not potent against any of the bacterial tested. Bacillus subtilis was the most sensitive organism to the ethanol root bark extracts of M.Iucida while Pseudomonas aeruginosa was the least sensitive. Difference in antibacterial activity of these plants show that different bioactive components are present in each species. Preliminary phytochemical test of M. Iucida plant parts showed presence of saponins, anthraquinone, cardenolides, alkaloids but absence of tannins. Key words: Antibacterial activity, preliminary phytochemistry, Morinda lucida, Alstonia boonei.

Photocatalytic Antibacterial Effect of TiO2 Film of TiAg on Streptococcus mutans

To test through various oxidation procedures the differences in antibacterial activities against Streptococcus mutans (S mutans) of Titanium (Ti) and Titanium silver (TiAg) metals coated with TiO(2). This study examined the photocatalytic antibacterial effects on S mutans of Ti and TiAg ubstrates coated with two crystalline forms of TiO(2) by thermal and anodic oxidation. A bacterial suspension of S mutans was pipetted onto TiO(2)-coated metal specimens and uncoated specimens with ultraviolet A (UVA) illumination for 20 to 100 minutes. The same specimen without UVA was used as the control. The level of colony-forming units of S mutans after UVA illumination was compared with that of the control. The level of colony-forming units of S mutans was significantly lower on TiO(2)-coated Ti and TiAg metal specimens after UVA illumination than on uncoated Ti and TiAg specimens. The level of colony-forming units of S mutans was significantly lower on the metals coated by anodic oxidation than on those coated by thermal oxidation. The TiO(2) coating on TiAg had a significantly higher and more rapid antibacterial effect than did the TiO(2) coating on Ti. The antibacterial effect of a TiO(2) film formed by anodic oxidation was superior to that formed by thermal oxidation. The addition of Ag to the Ti specimen indicated a synergistic effect on the photocatalytic antibacterial property against S mutans.

Daptomycin in experimental murine pneumococcal meningitis

BackgroundDaptomycin, a lipopeptide antibiotic, could be an alternative to vancomycin for treatment of pneumococcal meningitis. We determined the activity of daptomycin versus vancomycin, with dexamethasone as an adjuvant, in a murine model of pneumococcal meningitis.MethodsNinety-six 25–30 gram mice were inoculated intracisternally with serotype 3 Streptococcus pneumoniae modified by the integration of a luminescent lux operon. All mice were treated with either dexamethasone 1 mg/kg intraperitoneally every 6 hours alone or in combination with either vancomycin or daptomycin, also administered intraperitoneally. Serum antimicrobial concentrations were selected to approximate those achieved in humans. Following treatment, bioluminescence and cerebrospinal fluid (CSF) bacterial concentrations were determined. Caspase-3 staining was used to assess apoptosis on brain histopathology.ResultsSixteen hours post intracisternal inoculation, bacterial titers in CSF were 6.8 log10 cfu/ml. Amongst the animals given no antibiotic, vancomycin 50 mg/kg at 16 and 20 hours or daptomycin 25 mg/kg at 16 hours, CSF titers were 7.6, 3.4, and 3.9 log10 cfu/ml, respectively, at 24 hours post infection (p-value, < 0.001 for both vancomycin or daptomycin versus no antibiotic); there was no significant difference in bactericidal activity between the vancomycin and daptomycin groups (p-value, 0.18). CSF bioluminescence correlated with bacterial titer (Pearson regression coefficient, 0.75). The amount of apoptosis of brain parenchymal cells was equivalent among treatment groups.ConclusionDaptomycin or vancomycin, when given in combination with dexamethasone, is active in the treatment of experimental pneumococcal meningitis.

On the Enhanced Antibacterial Activity of Antibiotics Mixed with Gold Nanoparticles.

The bacterial action of gentamicin and that of a mixture of gentamicin and 15-nm colloidal-gold particles onEscherichia coliK12 was examined by the agar-well-diffusion method, enumeration of colony-forming units, and turbidimetry. Addition of gentamicin to colloidal gold changed the gold color and extinction spectrum. Within the experimental errors, there were no significant differences in antibacterial activity between pure gentamicin and its mixture with gold nanoparticles (NPs). Atomic absorption spectroscopy showed that upon application of the gentamicin-particle mixture, there were no gold NPs in the zone of bacterial-growth suppression in agar. Yet, free NPs diffused into the agar. These facts are in conflict with the earlier findings indicating an enhancement of the bacterial activity of similar gentamicin–gold nanoparticle mixtures. The possible causes for these discrepancies are discussed, and the suggestion is made that a necessary condition for enhancement of antibacterial activity is the preparation of stable conjugates of NPs coated with the antibiotic molecules.

Studyon biological effect of a kind of hetero-bimetallic Schiff-base on Escherichia coli

The biological activity of a kind of hetero-bimetallic Schiff-base complex was studied using Escherichia coli (E. coli) cell as the target. By microcalorimetry, the difference of anti-bacterial activity between the binuclear Schiff-base and the ligand was determined and analyzed. To analyze the inhibition of the bacterial growth internally, the E. coli cells grown in the presence of hetero-bimetallic Schiff-base complex were observed by scanning electron microscopy. The images in high resolution revealed the damage of outer cell membrane caused the inhibitory effect on E. coli. Inductively coupled plasma-mass spectrometry results proved the absorption of the complex by cells, which confirmed the interaction between the Schiff-base and biological macromolecule.

Bactericidal activity of orally available agents against methicillin-resistant Staphylococcus aureus

The recent proliferation of community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA) has led to a marked increase in the need for outpatient treatment of MRSA infections. Many oral agents active against MRSA have been available for years, and a paucity of literature compares them, leaving physicians with little guidance for choosing among them. The purpose of the present study was to compare the bactericidal effects of orally available antibiotics against MRSA and to determine whether there were differences in antimicrobial killing activity against CA-MRSA and hospital-acquired (HA) MRSA isolates. A total of 12 unique patient MRSA isolates were studied. Six strains were CA, carrying the staphylococcal chromosomal cassette (SCCmec) type IVa, while six were HA and carried SCCmec type II. Time-kill methods were used to study the bactericidal activity of the orally available antimicrobials linezolid, rifampicin, trimethoprim/sulfamethoxazole, clindamycin, minocycline, and moxifloxacin alone and in combination in vitro. Trimethoprim/sulfamethoxazole was rapidly bactericidal resulting in >2 log(10) cfu/mL decrease at 8 h and >3 log(10) cfu/mL decrease at 24 h in vitro. No antibiotic combination exhibited better killing than trimethoprim/sulfamethoxazole alone. Adding rifampicin to trimethoprim/sulfamethoxazole showed a trend towards antagonism in vitro. There were no differences in the bactericidal activity of any antimicrobial or antimicrobial combination against MRSA isolates carrying SCCmec type IVa versus those carrying SCCmec type II. Trimethoprim/sulfamethoxazole is rapidly bactericidal against MRSA in vitro when compared with most other orally available antimicrobials. No differences in bactericidal activity were detected when activities against CA-MRSA and HA-MRSA were compared.

Association of a bovine CXCR2 gene polymorphism with neutrophil survival and killing ability

Recent research in our lab has demonstrated a significant association between the incidence of subclinical mastitis and specific polymorphisms of the CXCR2 gene in Holstein dairy cows. This gene encodes a receptor for interleukin-8 (IL-8), a key regulator of neutrophil migration, killing and survival. Because of the importance of this gene in neutrophil function, we hypothesized that differences in neutrophil killing and survival may exist among the CXCR2 genotypes and potentially contribute to the observed variation in intramammary infections. To test this hypothesis, neutrophils were isolated from cows representing each CXCR2 +777 genotype (GG, GC or CC) and tested for suppression of apoptosis, reactive oxygen species (ROS) generation, glutathione levels, and bactericidal activity. A significant increase in survival was observed in neutrophils from cows with a CC genotype when compared to those with a GG genotype in response to IL-8, but not dexamethasone. In contrast, a significant reduction in neutrophil ROS generation in response to phorbol-13-myristate-12 acetate (PMA) was observed in cows with a CC genotype when compared to those with a GG genotype. However, no differences in bactericidal activity or glutathione levels were observed among genotypes. The functional activity of neutrophils from cows heterozygous for this polymorphism was intermediate between those with homozygous genotypes for those assays where differences were observed among homozygous genotypes. In summary, our results suggest that neutrophils from Holstein cows with different CXCR2 genotypes vary in their ability to suppress apoptosis and produce ROS. These differences have the potential to influence overall neutrophil function and may partially explain the variation observed with respect to mastitis in vivo. These results provide a foundation for future research aimed at better understanding the basic differences between dairy cows genetically more or less susceptible to mastitis and has the potential to provide novel preventive and therapeutic measures against inflammatory diseases such as mastitis.

미량원소 강화 식품소재의 항균효과

식중독 미생물에 의한 식중독 예방은 물론 부족하기 쉬운 필수 미량원소의 섭취량을 증가시키기 위하여 아연 및 게르마늄 등의 필수 미량원소를 강화시킨 식품소재의 항균효과 및 그 이용가능성을 검토하였다. 식중독 6 균주에 대하여 gelatin, dextrin, 불가사리 및 어류에서 추출한 collagen 등의 식품소재에 각종 미량원소를 강화하여 항균활성을 측정한 결과, 식품소재의 종류에 따른 항균활성의 차이는 거의 없었다. 사용된 미량금속 중 아연과 게르마늄만이 식중독 세균에 대하여 항균활성을 나타내었으며, 특히, 아연 강화식품소재는 P. fluorescens와 S. aureus에 대한 항균활성이 가장 큰 것으로 나타났고, E. coli, V. parahaemolyticus, B. cereus, B. subtilis에 대하여는 비슷한 활성을 나타내었다. 아연을 강화한 식품소재는 산성영역에서 안정하였으며, 게르마늄 강화 식품소재는 산성영역보다 알칼리 영역에서 보다 안정하였다. 또한, 미량원소 강화 식품소재는 열에 매우 안정하므로 가열식품인 통조림 제품이나 레토르트 식품에도 사용 가능할 것으로 사료된다. 식품의 코팅제로 사용되고 있는 gelatin과 아연을 혼합한 용액에 시판 어묵을 침지하여 코팅한 것을 저온 및 상온에 저장하면서 생균수 변화를 살펴본 결과, 저장온도 10℃에서 대조구는 초기부패(10^(7-8) CFU/g)까지 7일정도 걸리는데 반하여 시료 용액에 침지한 어묵은 15일정도로 저장기간을 8일정도 더 연장시킬 수 있을 것으로 판단되었다. 25℃와 35℃의 경우도 1% zinc acetate와 3% gelatin의 혼합 용액으로 코팅된 어묵의 경우 대조구에 비하여 균 증식이 억제되었다. 따라서 아연 강화 식품소재 코팅에 의하여 식품 오염 세균의 증식을 억제시켜 어묵 제품의 유통기간을 연장시키는 것은 물론 필수 미량원소인 아연의 섭취량을 증가시킬 수 있을 것으로 판단된다.

The effect of honey and surfactant type on the antibacterial properties of the leaf essential oil of Ocimum gratissimum Linn. against common wound-infecting organisms

Summary Honey is reported to have wound healing properties. This study aimed at investigating its effect as well as those of surfactants on the antibacterial activity of the essential oil of Ocimum gratissimum L. (ocimum oil). The antibacterial activity of dispersions of ocimum oil (2%) in methanol, honey, a macrogol blend, nonionic and ionic emulsifiers were assessed by cup–plate method using type bacteria and wound isolates. Honey enhanced the antibacterial activity of ocimum oil to a greater extent than the macrogol blend. The activity of ocimum oil emulsion in cetrimide (cationic) was lower than obtained for cetrimide solution. Emulsion of the oil in sodium lauryl sulphate (anionic) exhibited a slightly higher activity than the solution of the surfactant alone. Although Tween® 20 (nonionic) and aqueous methanol had no activity, the emulsion of the oil in Tween® 20 showed lesser activity than the oil solution in methanol. Honey’s inherent antibacterial activity, surfactant charge interaction and the effect of emulsification were adduced to the observed differences in antibacterial activity of the ocimum oil formulations. Our findings indicated honey as a suitable base for ocimum oil especially in the treatment of infected wounds. Caution is, however, desirable in the use of surfactants with ocimum oil.

Interactions between Mytilus haemocytes and different strains of Escherichia coli and Vibrio cholerae O1 El Tor: role of kinase-mediated signalling

Marine bivalves accumulate large amounts of bacteria from the environment (mainly Vibrionaceae and coliforms). Although persistence of different bacteria in bivalve tissues largely depends on their sensitivity to the bactericidal activity of circulating haemocytes and haemolymph soluble factors, the mechanisms involved in bacteria-host cell interactions in these invertebrates are largely unknown. In the mussel Mytilus, differences in interactions between haemocytes and different Escherichia coli and Vibrio cholerae strains [E. coli MG155, a wild-type strain carrying type 1 fimbriae, and its unfimbriated derivative, AAEC072 Deltafim; V. cholerae O1 El Tor biotype strain N16961, carrying the mannose-sensitive haemagglutinin (MSHA), and its MSHA mutant] lead to differences in bactericidal activity in the presence of serum. Here we show that different bacteria induced distinct patterns of phosphorylation of mitogen-activated protein kinases (MAPKs), in particular of the stress-activated MAPKs involved in the immune response. Differences in phosphorylation of PKC-like proteins were also observed. The results support the hypothesis that, like in mammalian host cells, different bacteria can modulate the signalling pathways of mussel haemocytes. The lower anti-bacterial activity towards the mutant E. coli strain and wild-type V. cholerae compared with wild E. coli may result from a reduced capacity of activating MAPKs. Moreover, the mutant V. cholerae strain that was the most resistant to the haemocyte bactericidal activity induced downregulation of cell signalling and showed the strongest effect on lysosomal membrane stability, evaluated as a marker of bivalve cell stress. These data suggest that certain bacteria could evade the bactericidal activity of mussel haemocytes through disruption of the host signalling pathways.

Pharmacodynamics of amoxicillin/clavulanic acid against Haemophilus influenzae in an in vitro kinetic model: a comparison of different dosage regimens including a pharmacokinetically enhanced formulation

Objective To study the pharmacodynamics of amoxicillin/clavulanic acid against different strains of Haemophilus influenzae in an in vitro kinetic model. The concentrations used corresponded to human serum levels obtained after 875 mg amoxicillin/clavulanic acid given b.i.d, 500/125 mg amoxicillin/clavulanic acid given t.i.d. and those obtained with a pharmacokinetically enhanced formulation containing 1125/125 mg amoxicillin/clavulanic acid (immediate release) and 875 mg amoxicillin (sustained release) given b.i.d.Methods Bacteria at an initial inoculum of 106 colony-forming units (CFU)/mL were exposed to amoxicillin/clavulanic acid with an initial concentration of approximately 15/3 mg/L, 8/3 mg/L simulating the peak levels in humans achieved after a dose of 875/125 mg and 500/125 mg with a half-life of 1 h. In addition, experiments with a 2000/125 mg pharmacokinetically enhanced formulation of amoxicillin/clavulanic acid given b.i.d were performed. A repeated dose was given at 12 h after the initial dose of 875/125 mg and the pharmacokinetically enhanced formulation or at 8 and 16 h after the dose of 500/125 mg. The experiments were performed in an in vitro kinetic model, which consists of a spinner flask with a filter membrane fitted in between the upper part and the bottom part in order to prevent bacterial dilution. The medium is removed from the culture flask, through the filter, at a constant rate with a pump. Repeated samples were taken at intervals of 1–2 h up to 24 h during the experiments for viable counting. One of the strains of H. influenzae was also exposed to a constant concentration corresponding to the peak serum levels obtained after a dose of 500/125 mg.Results The concentrations of amoxicillin in the in vitro kinetic model were as expected. At the end of the experiment (24 h), there was a tendency for a greater bactericidal effect with 500/125 mg t.i.d, as compared to 875/125 b.i.d., with differences in CFUs between the two dosing regimens of 2.6 log10 CFU for H. influenzae LH 2803 and 1.8 log10 CFU for the other clinical strains. However, these differences did not reach statistical significance (P = 0.075 and 0.10, respectively). A statistically significant higher bactericidal effect was seen in the experiments with the pharmacokinetically enhanced formulation in comparison with the b.i.d. regimen both at 8, 16 and 24 h and at 8 and 16 h with the t.i.d. regimen. With the new formulation, no regrowth was seen at 24 h, similar to the results obtained with a constant concentration.Conclusions Neither of the standard dosing regimens of amoxicillin (875/125 mg b.i.d. or 500/125 mg) used in our study, in which the time that the free (non-protein-bound) concentration the MIC (T > MIC) exceeding was less than 50%, was sufficient to achieve a complete bactericidal effect during the first 24 h of treatment. However, a statistically significant difference in bactericidal activity was seen at 8, 16 and 24 h vs. the b.i.d. regimen and at 8 and 16 h vs. the t.i.d. regimen with the pharmacokinetically enhanced formulation. This formulation gave a longer T > MIC (73–79%) of amoxicillin even though the concentration of clavulanic acid was only detectable for 45% of the dosing interval, and complete killing of all strains was obtained after 24 h.

Homodimeric θ-Defensins from Rhesus macaqueLeukocytes: ISOLATION, SYNTHESIS, ANTIMICROBIAL ACTIVITIES, AND BACTERIAL BINDING PROPERTIES OF THE CYCLIC PEPTIDES

Rhesus theta-defensin 1 (RTD-1) is a unique tridisulfide, cyclic antimicrobial peptide formed by the ligation of two 9-residue sequences derived from heterodimeric splicing of similar 76-amino acid, alpha-defensin-related precursors, termed RTD1a and RTD1b (Tang, Y. Q., Yuan, J., Osapay, G., Osapay, K., Tran, D., Miller, C. J., Ouellette, A. J., and Selsted, M. E. (1999) Science 286, 498-502). The structures of RTD-2 and RTD-3 were predicted to exist if homodimeric splicing of the RTD1a and RTD1b occurs in vivo. Western blotting disclosed the presence of putative theta-defensins, distinct from RTD-1, in leukocyte extracts. Two new theta-defensins, RTD-2 and RTD-3, were purified by reverse-phase high performance liquid chromatography and characterized by amino acid analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and comparison to the synthetic standards. RTD-2 and RTD-3 are the predicted homodimeric splicing products of RTD1b and RTD1a, respectively. The cellular abundances of RTD-1, -2, and -3 were 29:1:2, indicating that there is a preference for the heterodimeric ligation that generates RTD-1. RTD-1, -2, and -3 had similar antimicrobial activities against Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans, whereas the activity of RTD-2 against Escherichia coli was 2-3-fold less than those of RTD-1 and RTD-3. Equal amounts of each theta-defensin bound to E. coli cells, indicating that the differences in antibacterial activities are the result of post-binding processes.

Antibacterial Activity of Poly-acrylonitrile Fibers that Contain Different Basic Groups as their Copolymer Components.

To evaluate antibacterial activities, 4 types of acrylic fibers, each with a different basic group as its copolymer component (ie.2-methyl-5-vinylpyridine (PyF), 2-(dimethylamino)etylmetacrylate(TAF)/TAF-n, and N-2-hydroxy3-methacryloxypropyl-N, N, N- trimethylammonium chloride (QAF) were prepared. TAF-n was prepared from TAF and various alkyl chrorides (alkyl groups: buthyl, octhyl, dodecy, hexadecyl, and octadecyl). Basicity of these fibers was investigated with respect to surface dyeability and the ζ-potential. Antibacterial activities were assessed against 3 speciesof gram-positive, and 3 species of gram-negative bacteria The dyeabilities of PyF and TAF decreased remarkably at high pHs of 7.2 or 8.0. The dyeability of TAF-n was stable at pHs of 3.5 and 7.2, but was also unstable at 8.0. Interestingly, the dyeability of QAF was unaffected. &zeta-potential decreased from positive to negative with increasing PH in all samples. This data demonstrates that basicity influenced the antibacterial activity derived from, and the stability of, the basic groups. The order of basicity strength determined to be QAF>TAF-n>TAF>PyF. Differences in antibacterial activity of the fibers are discussed with respect to their basicity. PyF did not display antibacterial activity, and TAF showed only slight activity. TAF-n antibacterial activity was enhanced proportionately with an increase in the carbon number of alkyl chain above 8, whereby TAF-16 and TAF-18 exhibited the best antibacterial activity in TAF-n. QAF had the highest activity of the tested fibers. In these experiments, antibacterial activity was not gram-specific, but the data suggests that it is species-specific.