bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Cell-Photosensitizer Binding and Cell Density on Microbial Photoinactivation
Authors: Demidova Tatiana N. , Hamblin Michael R. 
Published: May 2005

ABSTRACT

Photodynamic therapy involves the use of nontoxic dyes called photosensitizers and visible light to produce reactive oxygen species and cell killing. It is being studied as an alternative method of killing pathogens in localized infections due to the increasing problem of multiantibiotic resistance. Although much has been learned about the mechanisms of microbial killing, there is still uncertainty about whether dyes must bind to and penetrate various classes of microbe in order to produce effective killing after illumination. In this report, we compare the interactions of three antimicrobial photosensitizers: rose bengal (RB), toluidine blue O (TBO), and a poly-
l
-lysine chlorin(e6) conjugate (pL-ce6) with representative members of three classes of pathogens;
Escherichia coli
(gram-negative bacteria),
Staphylococcus aureus
(gram-positive bacteria),
Candida albicans
(yeast). We compared fluence-dependent cell survival after illumination with the appropriate wavelengths of light before and after extracellular dye had been washed out and used three 10-fold dilutions of cell concentration. pL-ce6 was overall the most powerful photosensitizer, was equally effective with and without washing, and showed a strong dependence on cell concentration. TBO was less effective in all cases after washing, and the dependence on cell concentration was less pronounced. RB was ineffective after washing (except for
S. aureus
) but still showed a dependence on cell concentration. The overall order of susceptibility was
S. aureus
>
E. coli
>
C. albicans
, but
C. albicans
cells were 10 to 50 times bigger than the bacteria. We conclude that the number and mass of the cells compete both for available dye binding and for extracellularly generated reactive oxygen species.
Human Salivary Mucin MUC7 12-Mer-land 12-Mer-dPeptides: Antifungal Activity in Saliva, Enhancement of Activity with Protease Inhibitor Cocktail or EDTA, and Cytotoxicity to Human Cells
Authors: Wei Guo-Xian , Bobek Libuse A. 
Published: May 2005

ABSTRACTMUC7 12-mer-lexhibits potent in vitro antifungal activity in low-ionic-strength buffers. In this study, we investigated the anticandidal activity and stability of MUC7 12-mer-land its all-d-amino-acid isomer, along with Hsn5 12-mer (P113) and magainin-II, in human clarified and unclarified saliva in the absence or presence of protease inhibitor cocktail (PIC, which includes EDTA) or EDTA alone. In the absence of PIC or EDTA in saliva, only MUC7 peptides showed significant candidacidal activity. At a 100 μM concentration in clarified saliva and unclarified saliva, MUC7 12-mer-ddemonstrated 94 versus 64% killing, respectively; MUC7 12-mer-lshowed 57 versus 32% killing; Hsn5 12-mer showed 16 versus 0% killing; and magainin-II showed no killing. Addition of PIC or EDTA to either saliva caused the enhancement of antifungal activities of all peptides, although to different degrees. Taken together, the results suggest that EDTA (a metal-dependent protease inhibitor and/or divalent cation chelator) enhanced the antifungal activity of all four peptides mainly by chelation of divalent cations present in saliva (known to inhibit peptide antifungal activity), and PIC enhanced the activity of the threelpeptides above that achievable by EDTA alone through inhibition of all classes of proteases. Peptide stability in saliva monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed no degradation of MUC7 12-mer-dand 23, 60, and 75% degradation of MUC7 12-mer-l, Hsn5 12-mer, and magainin-II, respectively. Cytotoxicity assays determined that, at 100 μM peptide concentrations, MUC7 12-mer-dand 12-mer-lcaused 3.5 and 4.3% hemolysis in phosphate-buffered saline and no toxicity to the HOK-16B cell line (derived from normal human oral keratinocytes). In summary, MUC7 12-mer peptides appear to be excellent candidates for investigation of antifungal activity in in vivo models of oral candidiasis.
Microdialysis Study of Imipenem Distribution in Skeletal Muscle and Lung Extracellular Fluids of Noninfected Rats
Authors: Marchand Sandrine , Dahyot Claire , Lamarche Isabelle , Mimoz Olivier , Couet William 
Published: May 2005

ABSTRACT

The aim of this study was to investigate the imipenem distribution in muscle and lung interstitial fluids by microdialysis in rats and to compare the free concentrations in tissue with the free concentrations in blood. Microdialysis probes were inserted into the jugular vein, hind leg muscle, and lung. Imipenem recoveries in these three media were determined in each rat by retrodialysis by drug period before drug administration. Imipenem was infused intravenously at a dose of 120 mg · kg
−1
over 30 min, and microdialysis samples were collected for 150 min. The whole study was conducted with nonhydrated rats (
n
= 4) and hydrated rats (
n
= 6) while the animals were under isoflurane anesthesia. The decay of free concentrations in blood, muscle, and lung with time were monoexponential; and the concentration profiles in these three media were virtually superimposed in both groups. Accordingly, the ratios of the area under the curve (AUC) for tissue (muscle or lung) to the AUC for blood were always virtually equal to 1. Compared to values previously determined with awake rats, clearance was reduced by 2 and 1.5 in nonhydrated and hydrated rats, respectively, but the volume of distribution was unchanged. By combining microdialysis in blood and tissues, it was possible to demonstrate that free imipenem concentrations were virtually identical in blood, muscle, and lung.
Penetration of Linezolid into Soft Tissues of Healthy Volunteers after Single and Multiple Doses
Authors: Dehghanyar Pejman , Bürger Cornelia , Zeitlinger Markus , Islinger Florian , Kovar Florian , Müller Markus , Kloft Charlotte , Joukhadar Christian 
Published: May 2005

ABSTRACT

The present study tested the ability of linezolid to penetrate soft tissues in healthy volunteers. Ten healthy volunteers were subjected to linezolid drug intake at a dose of 600 mg twice a day for 3 to 5 days. The first dose was administered intravenously. All following doses were self-administered orally. The tissue penetration of linezolid was assessed by use of in vivo microdialysis. In the single-dose experiments the ratios of the area under the concentration-time curve from 0 to 8 h (AUC
0-8
) for tissue to the AUC
0-8
for free plasma were 1.4 ± 0.3 (mean ± standard deviation) and 1.3 ± 0.4 for subcutaneous adipose and muscle tissue, respectively. After multiple doses, the corresponding mean ratios were 0.9 ± 0.2 and 1.0 ± 0.5, respectively. The ratios of the AUC from 0 to 24 h (AUC
0-24
) for free linezolid in tissues to the MIC were between 50 and 100 for target pathogens with MICs between 2 and 4 mg/liter. In conclusion, the present study showed that linezolid penetrates rapidly into the interstitial space fluid of subcutaneous adipose and skeletal muscle tissues in healthy volunteers. On the basis of pharmacokinetic-pharmacodynamic calculations, we suggest that linezolid concentrations in soft tissues can be considered sufficient to inhibit the growth of many clinically relevant bacteria.
Cellular Uptake and Efflux of Azithromycin, Erythromycin, Clarithromycin, Telithromycin, and Cethromycin
Authors: Bosnar Martina , Kelnerić Željko , Munić Vesna , Eraković Vesna , Parnham Michael J. 
Published: May 2005

ABSTRACT
Macrolide antibiotics have an outstanding ability to concentrate within host cells, particularly phagocytes. In the study described in this paper five different macrolide antibiotics were compared regarding the uptake and release kinetics in human peripheral blood polymorphonuclear neutrophils (PMNs) and three different cell lines, two phagocytic cell lines (RAW 264.7 and THP-1) and an epithelial cell line (MDCK). Based on the results obtained, the substances tested could be clustered into different groups. Azithromycin constituted the first group, characterized by rapid and nonsaturable uptake into phagocytic cells and a high degree of retention in the preloaded cells. The second group included erythromycin and clarithromycin. These two substances do not exhibit cell specificity; consequently, they are taken up to a similar extent and are released by all cell types studied. Ketolides constituted the last group. Their uptake was saturable in cells of monocytic lineage as well as in nondifferentiated cells of myeloid lineage, and they were rapidly released from all the cell lines studied. However, in PMNs, ketolide uptake was not saturable; and unlike telithromycin, cethromycin rapidly egressed from the loaded cells.
Antimycobacterial Agents Differ with Respect to Their Bacteriostatic versus Bactericidal Activities in Relation to Time of Exposure, Mycobacterial Growth Phase, and Their Use in Combination
Authors: Bakker-Woudenberg Irma A. J. M. , van Vianen Wim , van Soolingen Dick , Verbrugh Henri A. , van Agtmael Michiel A. 
Published: May 2005

ABSTRACT

A number of antimycobacterial agents were evaluated with respect to their bacteriostatic activity (growth inhibition) versus the bactericidal activity against a clinical isolate of
Mycobacterium avium
(
Mycobacterium avium
complex [MAC] strain 101) in relation to the time of exposure and the growth phase of the mycobacteria. In terms of growth inhibition the MAC in the active phase of growth was susceptible to clarithromycin, ethambutol, rifampin, amikacin, and the quinolones moxifloxacin, ciprofloxacin, and sparfloxacin. In terms of bactericidal activity in relation to the time of exposure these agents differed substantially with respect to the killing rate. An initial high killing capacity at low concentration was observed for amikacin, which in this respect was superior to the other agents. The bactericidal activity of clarithromycin and ethambutol was only seen at relatively high concentrations and increased with time. Killing by rifampin was concentration dependent as well as time dependent. The bactericidal activity of moxifloxacin was marginally dependent on the concentration or the time of exposure. The activity of clarithromycin in combination with ethambutol was not significantly enhanced compared to single-agent exposure. Only an additive effect was observed. The addition of rifampin or moxifloxacin as a third agent only marginally effected increased killing of MAC. However, by addition of amikacin the activity of the clarithromycin-ethambutol combination was significantly improved. The combination of amikacin and amoxicillin-clavulanic acid exhibited synergistic antimycobacterial activity. Towards MAC at low growth rates, only the quinolones exhibited a bactericidal effect.
Proline Conformation-Dependent Antimicrobial Activity of a Proline-Rich Histone H1 N-Terminal Peptide Fragment Isolated from the Skin Mucus of Atlantic Salmon
Authors: Lüders Torben , Birkemo Gunn Alice , Nissen-Meyer Jon , Andersen Øivind , Nes Ingolf F. 
Published: May 2005

ABSTRACT

A 30-residue N-terminally acetylated peptide derived from the N-terminal part of histone H1 was identified as the dominant antimicrobial peptide in skin mucus from Atlantic salmon (
Salmo salar
). The peptide (termed salmon antimicrobial peptide [SAMP H1]) was purified to homogeneity by a combination of reversed-phase and cation-exchange chromatographies. By Edman degradation of the deacetylated peptide and by sequencing of the PCR-amplified DNA that encodes the peptide, the complete amino acid sequence was determined to be AEVAPAPAAAAPAKAPKKKAAAKPKKAGPS. The theoretical molecular weight of N-terminally acetylated SAMP H1 was calculated to be 2,836, which is the same as that determined by matrix-assisted laser desorption ionization mass spectrometry. The peptide was active against both gram-negative and -positive bacteria. The N-terminal acetyl group was not necessary for activity since deacetylation did not reduce the activity. A synthetic peptide whose sequence was identical to that of the isolated fragment was initially inactive but could be activated by binding it to a cation-exchange column. Treatment of the synthetic peptide when it was bound to the exchange column with peptidylproline
cis
-
trans
-isomerase increased the amount of active peptide, indicating that isomerization of the proline peptide bond(s) was necessary for activation of the synthetic peptide. Comparison of the active and inactive forms by circular dichroism and chromatographic analyses suggests that the active form, both the natural and the synthetic forms, is more structured, condensed, and rigid than the inactive form, which has a more nonstructured conformation. This work shows for the first time the importance of proline isomers in the activity of an antimicrobial peptide.
Effects of a High-Fat Meal on the Relative Oral Bioavailability of Piperaquine
Authors: Sim Ing-Kye , Davis Timothy M. E. , Ilett Kenneth F. 
Published: May 2005

ABSTRACT

Piperaquine (PQ) is an antimalarial drug whose high lipid solubility suggests that its absorption can be increased by a high-fat meal. We examined the pharmacokinetics of PQ phosphate (500 mg given orally) in the fasting state and after a high-fat meal in eight healthy Caucasian volunteers (randomized crossover). Plasma PQ concentration-time profiles were analyzed by using noncompartmental pharmacokinetic analysis. In the fed state, the geometric mean
C
max
increased by 213%, from 21.0 to 65.8 μg/liter (
P
< 0.001). The time of
C
max
was not significantly different between the fasting and fed states. The geometric mean area under the concentration-time curve from zero onward (AUC
0-∞
) increased by 98%, from 3,724 to 7,362 μg h/liter (
P
= 0.006). The oral bioavailability of PQ relative to the fasting state was 121% greater after the high-fat meal (95% confidence interval, 26 to 216% increase;
P
= 0.020). The side effects, postural blood pressure changes, electrocardiographic corrected QT interval, serum glucose, and other biochemical and hematological indices were similar in the fasting and fed states over 28 days of follow-up.
Effects of Acyl versus Aminoacyl Conjugation on the Properties of Antimicrobial Peptides
Authors: Radzishevsky Inna S. , Rotem Shahar , Zaknoon Fadia , Gaidukov Leonid , Dagan Arie , Mor Amram 
Published: May 2005

ABSTRACT

To investigate the importance of increased hydrophobicity at the amino end of antimicrobial peptides, a dermaseptin derivative was used as a template for a systematic acylation study. Through a gradual increase of the acyl moiety chain length, hydrophobicity was monitored and further modulated by acyl conversion to aminoacyl. The chain lengths of the acyl derivatives correlated with a gradual increase in the peptide's global hydrophobicity and stabilization of its helical structure. The effect on cytolytic properties, however, fluctuated for different cells. Whereas acylation gradually enhanced hemolysis of human red blood cells and antiprotozoan activity against
Leishmania major
, bacteria displayed a more complex behavior. The gram-positive organism
Staphylococcus aureus
was most sensitive to intermediate acyl chains, while longer acyls gradually led to a total loss of activity. All acyl derivatives were detrimental to activity against
Escherichia coli
, namely, but not solely, because of peptide aggregation. Although aminoacyl derivatives behaved essentially similarly to the nonaminated acyls, they displayed reduced hydrophobicity, and consequently, the long-chain acyls enhanced activity against all microorganisms (e.g., by up to 12-fold for the aminolauryl derivative) but were significantly less hemolytic than their acyl counterparts. Acylation also enhanced bactericidal kinetics and peptide resistance to plasma proteases. The similarities and differences upon acylation of MSI-78 and LL37 are presented and discussed. Overall, the data suggest an approach that can be used to enhance the potencies of acylated short antimicrobial peptides by preventing hydrophobic interactions that lead to self-assembly in solution and, thus, to inefficacy against cell wall-containing target cells.
Pharmacokinetics and Pharmacodynamics of Imipenem during Continuous Renal Replacement Therapy in Critically Ill Patients
Authors: Fish Douglas N. , Teitelbaum Isaac , Abraham Edward 
Published: May 2005

ABSTRACT

The pharmacokinetics of imipenem were studied in adult intensive care unit (ICU) patients during continuous venovenous hemofiltration (CVVH;
n
= 6 patients) or hemodiafiltration (CVVHDF;
n
= 6 patients). Patients (mean ± standard deviation age, 50.9 ± 15.9 years; weight, 98.5 ± 15.9 kg) received imipenem at 0.5 g every 8 to 12 h (total daily doses of 1 to 1.5 g/day) by intravenous infusion over 30 min. Pre- and postmembrane blood (plasma) and corresponding ultrafiltrate or dialysate samples were collected 1, 2, 4, and 8 or 12 h (depending on dosing interval) after completion of the drug infusion. Drug concentrations were measured using validated high-performance liquid chromatography methods. Mean systemic clearance (CL

S

) and elimination half-life (
t
1/2
) of imipenem were 145 ± 18 ml/min and 2.7 ± 1.3 h during CVVH versus 178 ± 18 ml/min and 2.6 ± 1.6 h during CVVHDF, respectively. Imipenem clearance was substantially increased during both CVVH and CVVHDF, with membrane clearance representing 25% and 32% of CL

S

, respectively. The results of this study indicate that CVVH and CVVHDF contribute to imipenem clearance to a greater degree than previously reported. Imipenem doses of 1.0 g/day appear to achieve concentrations adequate to treat most common gram-negative pathogens (MIC up to 2 μg/ml) during CVVH or CVVHDF, but doses of 2.0 g/day or more may be required to adequately treat and prevent resistance in pathogens with higher MICs (MIC = 4 to 8 μg/ml). Higher doses should only be used after consideration of potential central nervous system toxicities or other risks of therapy in these severely ill patients.
Influence of Efflux Transporters on the Accumulation and Efflux of Four Quinolones (Ciprofloxacin, Levofloxacin, Garenoxacin, and Moxifloxacin) in J774 Macrophages
Authors: Michot Jean-Michel , Seral Cristina , Van Bambeke Françoise , Mingeot-Leclercq Marie-Paule , Tulkens Paul M. 
Published: May 2005

ABSTRACTCiprofloxacin is subject to efflux from J774 macrophages through a multidrug resistance-related protein-like transporter (J. M. Michot, F. Van Bambeke, M. P. Mingeot-Leclercq, and P. M. Tulkens, Antimicrob. Agents Chemother.48:2673-2682, 2004). Here, we compare ciprofloxacin to levofloxacin, garenoxacin, and moxifloxacin for transport. At 4 mg/liter, an apparent steady state in accumulation was reached after 30 to 60 min for all quinolones but to quite different levels (approximately 3, 5, 10, and 16 fold). Accumulation of ciprofloxacin was increased (to about 16 to 20 fold) by ATP depletion, increase in extracellular concentration, and the addition of probenecid, gemfibrozil, or MK571 (but not verapamil or GF120918). These treatments did not affect the accumulation of moxifloxacin. Levofloxacin and garenoxacin showed an intermediate behavior. Efflux of ciprofloxacin was slowed down by probenecid (half-life, 7.2 versus 1.6 min). Moxifloxacin efflux was faster and unaffected by probenecid (half-lifes, 0.27 versus 0.33 min). Efflux of levofloxacin and garenoxacin was modestly decreased by probenecid (1.5 and 2.1 fold). Accumulation of14C-labeled ciprofloxacin was increased by unlabeled ciprofloxacin and moxifloxacin, but moxifloxacin was two times less potent. Accumulation of moxifloxacin at 4°C was almost identical to that at 37°C, whereas that of ciprofloxacin was minimal (levofloxacin and garenoxacin showed intermediate behaviors). Cells subjected to thermal shock (56°C; 10 min) accumulated all quinolones at a similar level (16 to 23 fold). We conclude that moxifloxacin is apparently not subject to efflux from J774 macrophages, even though it can interact with the ciprofloxacin transporter. Levofloxacin and garenoxacin are partially effluxed. Data suggest that efflux plays an important role in the differential accumulation of quinolones by J774 macrophages.
Comparable Efficacies of the Antimicrobial Peptide Human Lactoferrin 1-11 and Gentamicin in a Chronic Methicillin-Resistant
Staphylococcus aureus
Osteomyelitis Model
Authors: Faber Christopher , Stallmann Hein P. , Lyaruu D. M. , Joosten Uwe , von Eiff Christof , van Nieuw Amerongen Arie , Wuisman Paul I. J. M. 
Published: May 2005

ABSTRACT

The therapeutic efficacy of an antimicrobial peptide, human lactoferrin 1-11 (hLF1-11), was investigated in a model of chronic methicillin-resistant
Staphylococcus aureus
(MRSA) (gentamicin susceptible) osteomyelitis in rabbits. We incorporated 50 mg hLF1-11/g or 50 mg gentamicin/g cement powder into a calcium phosphate bone cement (Ca-P) and injected it into the debrided tibial cavity, creating a local drug delivery system. The efficacy of hLF1-11 and gentamicin was compared to that of a sham-treated control (plain bone cement) (
n
= 6) and no treatment (infected only) (
n
= 5). The results were evaluated by microbiology, radiology, and histology. MRSA was recovered from all tibias in both control groups (
n
= 11). On the other hand, hLF1-11 and gentamicin significantly reduced the bacterial load. Furthermore, no growth of bacteria was detected in five out of eight and six out of eight specimens of the hLF1-11- and gentamicin-treated groups, respectively. These results were confirmed by a significant reduction of the histological disease severity score by hLF1-11 and gentamicin compared to both control groups. The hLF1-11-treated group also had a significantly lower radiological score compared to the gentamicin-treated group. This study demonstrates the efficacy of hLF1-11 incorporated into Ca-P bone cement as a possible therapeutic strategy for the treatment of osteomyelitis, showing efficacy comparable to that of gentamicin. Therefore, the results of this study warrant further preclinical investigations into the possibilities of using hLF1-11 for the treatment of osteomyelitis.
Antifungal Protein PAF Severely Affects the Integrity of the Plasma Membrane ofAspergillus nidulansand Induces an Apoptosis-Like Phenotype
Authors: Leiter Éva , Szappanos Henrietta , Oberparleiter Christoph , Kaiserer Lydia , Csernoch László , Pusztahelyi Tünde , Emri Tamás , Pócsi István , Salvenmoser Willibald , Marx Florentine 
Published: May 2005

ABSTRACTThe small, basic, and cysteine-rich antifungal protein PAF is abundantly secreted into the supernatant by the β-lactam producerPenicillium chrysogenum. PAF inhibits the growth of various important plant and zoopathogenic filamentous fungi. Previous studies revealed the active internalization of the antifungal protein and the induction of multifactorial detrimental effects, which finally resulted in morphological changes and growth inhibition in target fungi. In the present study, we offer detailed insights into the mechanism of action of PAF and give evidence for the induction of a programmed cell death-like phenotype. We proved the hyperpolarization of the plasma membrane in PAF-treatedAspergillus nidulanshyphae by using the aminonaphtylethenylpyridinium dye di-8-ANEPPS. The exposure of phosphatidylserine on the surface ofA. nidulansprotoplasts by Annexin V staining and the detection of DNA strand breaks by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) gave evidence for a PAF-induced apoptotic-like mechanism inA. nidulans. The localization of reactive oxygen species (ROS) by dichlorodihydrofluorescein diacetate and the abnormal cellular ultrastructure analyzed by transmission electron microscopy suggested that ROS-elicited membrane damage and the disintegration of mitochondria played a major role in the cytotoxicity of PAF. Finally, the reduced PAF sensitivity ofA. nidulansstrain FGSC1053, which carries a dominant-interfering mutation infadA, supported our assumption that G-protein signaling was involved in PAF-mediated toxicity.