Biomedical subjects

M Dal Sasso

Publications and source records attributed to M Dal Sasso.

At least 19 recordsLinked to original sources

PubMed2003

Gemifloxacin: effects of sub-inhibitory concentrations on various factors affecting bacterial virulence.

This study investigated the ability of sub-MICs of gemifloxacin to interfere with the bacterial virulence parameters of adhesiveness, haemagglutination, hydrophobicity and motility, as well as their interactions with host neutrophilic defences such as phagocytosis, killing and respiratory bursts. The adhesiveness of both Escherichia coli and Staphylococcus aureus was significantly reduced to a subinhibitory concentration of 1/32 MIC. Indirect fimbriation parameters, such as hydrophobicity and haemagglutination were significantly reduced at a concentration of 1/8 MIC, as was migration (swarming). Phagocytosis and the respiratory burst measured by means of chemiluminescence were not affected, but killing was significantly increased from 1/2 to 1/8 MIC. The interpolation of these pharmacodynamic findings with pharmacokinetic curves indicates that sub-MIC concentrations of gemifloxacin can prolong antimicrobial effects on virulence determinants up to 27 h after the antimicrobial concentration has fallen below the MIC value.

Bacterial Adhesion↗

PubMed2002

Effects of gatifloxacin on phagocytosis, intracellular killing and oxidant radical production by human polymorphonuclear neutrophils.

The ingestion and killing of bacteria by phagocytic cells is an important step in the sequence of interactions between invading microorganisms and host defense systems and may be affected by antibiotics. We investigated the effects of gatifloxacin on the phagocytosis, killing and oxidative bursts of human polymorphonuclear neutrophils (PMNs). The percentage phagocytosis and the phagocytosis index were unaffected by exposure of Escherichia coli strains to sub-MICs of gatifloxacin to a 1/64 dilution. However a significant increase in percentage intraphagocytic killing and the killing index occurred in one E. coli strain at 1/32 MIC and in two strains at 1/16 MIC. The incubation of PMNs with sub-MICs and supra-MICs of gatifloxacin (to 32 MIC) did not affect the oxidative bursts.

Anti-Infective Agents↗

PubMed2002

Daptomycin morphostructural damage in Bacillus cereus visualized by atomic force microscopy.

Daptomycin is a novel, rapidly bactericidal in vitro antibiotic that is under investigation for the treatment of serious Gram-positive infections. Although daptomycin appears to disrupt membrane function, the precise mechanism of action has not been fully elucidated. Atomic force microscopy (AFM) is an innovative technique that allows high-resolution visualization and digital image manipulation of cell surface structures in 3 dimensions without the use of photons and electrons. The aim of this study was to use AFM to investigate the morphostructural changes in Bacillus cereus that occur upon daptomycin administration. The effects of daptomycin at 4x and 8x the minimal inhibitory concentration were visualized during an 8-hour incubation period. Atomic force microscopy images showed aberrant bacterial surface formations, including flattening and shrinking of cells and leakage of cytoplasm through the membrane. In addition to structural changes, the destabilization of flagella was also observed. These results support previous data suggesting that daptomycin disrupts membrane function.

Anti-Bacterial Agents↗

PubMed2002

Interference of sub-inhibitory concentrations of gatifloxacin on various determinants of bacterial virulence.

The physico-chemical characteristics of the molecular array on the outermost surface of bacteria modulate various bacterial functions which, when expressed in the human environment, constitute important determinants of bacterial virulence. The present study investigated the ability of subinhibitory concentrations of gatifloxacin to interfere with various virulence determinants of Escherichia coli and with the adhesiveness of Staphylococcus aureus. The adhesiveness of S. aureus and E. coli to human epithelial cells was inhibited at gatifloxacin concentrations down to 1/32 and 1/64 the minimum inhibitory concentration (MIC). Sub-MICs of gatifloxacin down to 1/8-MIC significantly reduced hemagglutination and hydrophobicity, which are correlated with fimbriation and provide clues relating to the physico-chemical characteristics of the outer surface of bacteria. Swarming (motility) was reduced at concentrations down to 1/8 MIC. Phagocytosis was not affected but killing significantly increased from 1/8 to 1/2 MIC. The respiratory bursts of neutrophils investigated by a chemiluminescence procedure were not modified. The interpolation of these pharmacodynamic findings with pharmacokinetic curves indicates that the effect of sub-MIC concentrations of gatifloxacin can engender activity, prolonging antimicrobial effects on virulence determinants over 30 hours after the antimicrobial concentration has fallen below the MIC.

Anti-Infective Agents↗

PubMed2002

Inhibitory effects of zafirlukast on respiratory bursts of human neutrophils.

The effects of zafirlukast, a cysteinyl-leukotriene receptor antagonist, on the generation of the reactive oxygen species (ROS) released during respiratory bursts of human polymorphonuclear neutrophils (PMNs) is still unknown. The aim of this study was to investigate the ability of zafirlukast to interfere with the respiratory burst of PMNs. Respiratory burst responses of PMNs were investigated by luminol-amplified chemiluminescence (LACL) using particulate (Candida albicans and zymosan) and soluble stimulants [N-formyl-methionylleucyl-phenylalanine (fMLP) and phorbol 12 myristate 13 acetate (PMA)]. When incubated with PMNs for 10 min at concentrations ranging from 5 x 10(-9) M to 5 x 10(-6) M, zafirlukast did not significantly affect the respiratory bursts of PMNs induced by either the particulate or soluble stimuli. However, after incubation for 60 min, it did reduce the respiratory bursts of PMNs in a concentration-related fashion when the PMNs were stimulated with fMLP, and at a concentration of 5 x 10(-6) M when the stimulus was PMA. No significant effects were seen when the PMNs were challenged with particulate stimuli. Zafirlukast is able to interfere with the activation of the PMNs respiratory burst induced by soluble stimulants. The different behavior determined by different times of contact and different stimuli opens the way to interpretations concerning the antioxidant effect of zafirlukast.

Candida albicans↗

PubMed2002

The SH-metabolite I of erdosteine, a mucolytic drug, enhances the inhibitory effect of salbutamol on the respiratory burst of neutrophils.

Reactive oxygen species (ROS) are a common denominator of airway inflammation associated with chronic obstructive pulmonary disease (COPD) and asthma, as well as with less frequent lung diseases such as idiopathic pulmonary fibrosis (IPF), acute respiratory distress syndrome (ARDS) and cystic fibrosis (CF). The most frequently administered drugs used to treat these diseases are bronchodilators, antioxidant/antiphlogistic agents and mucoactive drugs. The metabolization of the mucoactive drug erdosteine produces an active metabolite (Met I) with a reducing SH group. In addition to its mucolytic action, Met I also has useful antioxidant activity. The various activities of beta 2-agonists include their ability to reduce the respiratory burst of neutrophils and the subsequent release of ROS. beta 2-Agonists and mucoactive drugs may be administered to the same patients during the treatment of lung diseases. The aim of this study was to investigate the ability of Met I to potentiate the activity of salbutamol in inhibiting the in vitro respiratory burst of neutrophils by means of chemiluminescence. The combination of Met I 5 and 10 micrograms/ml with salbutamol 10(-5), 10(-6) and 10(-7) M led to a significant reduction in respiratory bursts when the neutrophils were stimulated with the soluble stimulant N-formyl-methionylleucyl-phenylalanine (fMLP). The combinations of the two drugs that reduced the respiratory bursts when a particulate stimulus (Candida albicans) was used were those containing 10(-5) M of salbutamol. The reasons for this different behavior remain unclear and raise questions about the specific roles, sites and mechanisms of action of the different types of stimulation undergone by the respiratory airways.

Albuterol↗

PubMed2000

Assessment of the antioxidant activity of the SH metabolite I of erdosteine on human neutrophil oxidative bursts.

Acute and chronic lung diseases both lead to an extensive recruitment of neutrophils in the lungs. These cells play a major defensive role but, when activated, they are also an important source of reactive oxygen species, which generate a cytotoxic oxidant stress that triggers a self-sustaining phlogogenic loop. Erdosteine (CAS 84611-23-4) is a mucoactive drug whose metabolization leads to active metabolites with an SH group, and molecules bearing an SH group are also considered to have antioxidant activity. Luminol amplified chemiluminescence was used to investigate the oxidative bursts of human neutrophils and it was found that concentrations of 2.5, 5, 10 and 20 micrograms/ml of metabolite I of erdosteine significantly inhibit oxidative bursts in a concentration-related manner that overlaps the inhibition induced by the control drug N-acetylcysteine. Chemiluminescence was also studied in cell-free systems to see whether the drug also has direct scavenger activity, which was observed from 2.5 to 20 micrograms/ml of metabolite I using the xanthine/xanthine oxidase assay and at concentrations of 0.039 to > or = 2.5 micrograms/ml using the highly-sensitive hypochlorous acid/H2O2 assay. The findings indicate that the metabolite I of erdosteine has antioxidant activity which, together with the drug's mucomodifying activity, may lead to a useful antiphlogistic effect.

Acetylglucosamine↗

PubMed1999

Effects of erdosteine and its metabolites on bacterial adhesiveness.

Erdosteine (CAS 84611-23-4) is administered as a mucolytic drug in patients with pulmonary disorders who suffer from a thickening of bronchial mucus with altered physico-chemical characteristics. Erdosteine itself does not have a free thiol group but its metabolization produces active metabolites with a -SH group that is capable of breaking disulfide bonds of mucins and improving the mucociliary clearance of the airways, and thus reproducing the effects of the class of muco-active drugs having a thiol group. It has also been reported that muco-active drugs with this group reduce bacterial adhesiveness to human mucosal cells. The aim of this study was to investigate whether erdosteine and its SH-metabolites are capable of interfering with bacterial adhesiveness. Metabolite I significantly reduces both S. aureus and E. coli adhesiveness to human mucosal epithelial cells at concentrations of 2.5, 5 and 10 micrograms/ml. The same concentrations of erdosteine, metabolite II, metabolite III and N-acetylcysteine (as a control drug) were devoid of such activity, whereas the results of hemagglutination and hydrophobicity assays showed that the behaviour of metabolite I overlapped that of bacterial adhesiveness, thus indicating that interference takes place at a fimbrial level. This is confirmed by the fact that the incubation of human buccal cells with drugs does not reduce the adhesiveness of untreated bacteria. The presence of this additional activity in a muco-active drug is useful because bacteria not only adhere to epithelial cells but also to tracheobronchial secretions.

Animals↗

PubMed1999

Pharmacodynamic effects of subinhibitory concentrations of rufloxacin on bacterial virulence factors.

It has been reported that subinhibitory concentrations (sub-MICs) of some fluoroquinolones are still capable of affecting the topological characteristics of DNA (inhibition DNA-gyrase) and that this leads to a reduction in some of the factors responsible for bacterial virulence (by means of the disruption of protein synthesis and alterations in phenotype expression), even though the microorganisms themselves are not killed. The present study investigated the ability of sub-MICs of rufloxacin, an orally absorbed monofluorinated quinolone with a long half-life (28 to 30 h), to interfere with the bacterial virulence parameters of adhesiveness, hemagglutination, hydrophobicity, motility, and filamentation, as well as their interactions with host neutrophilic defenses such as phagocytosis, killing, and oxidative bursts. It was observed that Escherichia coli adhesiveness was significantly reduced at rufloxacin concentrations of 1/32 MIC, hemagglutination and hydrophobicity were significantly reduced at concentrations of, respectively, 1/4 MIC and 1/8 MIC, and motility was significantly reduced at concentrations of 1/16 MIC; filamentation was still present at concentrations of 1/4 MIC. Phagocytosis was not affected, but killing significantly increased from 1/2 MIC to 1/8 MIC; oxidative bursts measured by means of chemiluminescence were not affected. The fact that sub-MICs are still effective in interfering with the parameters of bacterial virulence is useful information that needs to be correlated with pharmacokinetic data in order to extend our knowledge of the most effective concentrations that can be used to optimize treatment schedules, for example, single administrations, particularly in noncomplicated lower urinary tract infections.

Anti-Infective Agents↗

PubMed1998

Age-associated differences in neutrophil oxidative burst (chemiluminescence).

Phagocytic defensive functions consist of a sequence of events, including migration, phagocytosis, secretion, and the release of reactive oxygen species (ROS). The last of these (also called "oxidative burst") has not received due attention in the elderly, even though it can be considered the most important event in the process of killing an invading microorganism. The aim of the present study was to investigate the oxidative burst activity of polymorphonuclear neutrophil leukocytes (PMNs) in relation to age, using a technique that specifically identifies ROS production: luminol-amplified chemiluminescence (LACL). Besides the use of LACL, a particular feature of the study was the use of five rather than just one or two different stimulants: two particulate (Candida albicans and zymosan) and three soluble ones [N-formyl-methionyl-leucyl-phenylalanine (fMLP), phorbol 12 myristate 13 acetate (PMA), and polyanetholesulfonate (liquoid)]. This approach allowed us to observe a dichotomy between the effects of Candida and zymosan (particulates), which were not significantly different in the elderly subjects compared to the young controls, and those of fMLP, PMA, and liquoid (solubles), which showed a significant reduction in LACL in the elderly group. Considering the different results obtained with the various stimulants adopted that are all believed to have NADPH oxidase as a common final target of oxidative burst, it may be postulated that aging can influence the different transductional pathways in different ways.

Adult↗

PubMed1998

Influence of age on oxidative bursts (chemiluminescence) of polymorphonuclear neutrophil leukocytes.

The release of reactive oxygen species (ROS) during neutrophil oxidative bursts is the last of a sequence of different steps leading to the neutralization of pathogen microorganisms. Using luminol-amplified chemiluminescence (LACL), the oxidative burst activity of neutrophils in elderly people (> or = 75 years) was compared with that in younger controls (39 years on average) after activation with both particulate (Candida albicans) and soluble (formyl-methionyl-leucyl-phenylalanine; fMLP) stimulants. After Candida stimulation, a reduction in LACL was observed in the elderly subjects in comparison with the controls, but the difference did not reach statistical significance. After fMLP stimulation, the reduction in LACL was significant, thus suggesting that the Candida pathway of chemiluminescence production seems to be less affected than the fMLP pathway. This finding raises questions concerning the complex differences in the pathways of cell killing and ROS generation, and their efficacy in the elderly. Various possible explanations are discussed, all of which need further investigation.

Adult↗

PubMed1997

Cefodizime: effects of sub-inhibitory concentrations on adhesiveness and bacterial morphology of Staphylococcus aureus and Escherichia coli: comparison with cefotaxime and ceftriaxone.

Exposure of Staphylococcus aureus and Escherichia coli strains to different subMICs of cefodizime, cefotaxime and ceftriaxone significantly reduced the bacterial attachment to human buccal cells, but the resultant patterns of inhibition were different for S. aureus and E. coli and for the behaviour of the three cephalosporins. Morphological anomalies such as clusters of enlarged S. aureus cells and filamentation with spheroplast-like structures and bulge formations in E. coli were also present. Analogies between the different patterns of inhibition of adhesiveness and the corresponding degree of morphological changes were observed. Cefodizime behaved differently from cefotaxime and ceftriaxone and this could be attributed to the presence in the cefodizime molecule of an additional substituent, a 3-methyl-5-carboxymethyl-1,3-thiazole-2-thio group in the 3' position, not present in cefotaxime or ceftriaxone.

Bacterial Adhesion↗

PubMed1997

Effects of nedocromil sodium on the oxidative burst of polymorphonuclear leukocytes: comparison with salbutamol.

The effects of nedocromil sodium and of salbutamol on the generation of oxygen-derived free radicals in human polymorphonuclear leukocytes (PMNs) were compared in vitro by the luminol-amplified-chemiluminescence (LACL) assay induced by both particulate (Candida albicans) and soluble formyl-methionyl-leucyl-phenylalanine (fMLP) stimulants. Inhibitory dose-effect linear regressions were observed from 10(-3) to 10(-8) M for nedocromil and salbutamol after a 3' period of incubation with either C. albicans or fMLP. There was a linear regression with nedocromil sodium after 30' incubation, but desensitization was observed with salbutamol after this longer period of incubation. The generation of oxygen-derived free radicals was significantly greater for asthmatic patients than for normal subjects; therefore antiasthmatic drugs with this inhibitory activity could be an extra pharmacological benefit in the treatment of asthmatic patients.

Albuterol↗

PubMed1996

Penetration of brodimoprim into human neutrophils and intracellular activity.

The entry of an antibiotic into phagocytes is a prerequisite for its intracellular bioactivity against susceptible facultative or obligatory intracellular microorganisms. Brodimoprim is a dimethoxybenzylpyrimidine that has recently entered into clinical use, and its uptake into and elimination from human polymorphonuclear neutrophils (PMNs), together with its effects on normal phagocytic and antimicrobial mechanisms, have been investigated. Brodimoprim uptake by PMNs was determined by a velocity-gradient centrifugation technique under various experimental conditions and was expressed as the ratio of the intracellular to the extracellular drug concentration (C/E) in comparison with the C/E of trimethoprim, which was used as a control drug. After incubation with 7.5 micrograms of brodimoprim per ml, PMNs accumulated brodimoprim (C/E, 74.43 +/- 12.35 at 30 min) more avidly than trimethoprim (C/E, 20.97 +/- 6.61 at 30 min). The cellular uptake of brodimoprim was not affected by temperature, 2,4-dinitrophenol, or potassium fluoride and was increased with an increase in the pH of the medium. It was reduced in formaldehyde-killed PMNs. The efflux of brodimoprim was very rapid (46% after 5 min). The liposolubility of brodimoprim was about three times that of trimethoprim, as was the uptake. Therefore, a possible passive transmembrane diffusion mechanism might be proposed. Brodimoprim did not decrease either phagocytosis or phagocyte-mediated bactericidal activity, nor did it affect oxidative burst activity, as investigated by luminol-amplified chemiluminescence. On the basis of the pharmacokinetic data for brodimoprim, the concentration of 7.5 micrograms/ml was chosen as the highest concentration attainable in serum by oral therapy, and at this concentration of brodimoprim, the amount of drug that penetrated into PMNs was able to maintain its antimicrobial activity without interfering with the functions of the PMNs.

Anti-Infective Agents↗

PubMed1996

Digital subtraction angiography for arteriovenous malformations in stereotactic radiosurgery.

Images coming from digital subtraction angiography (DSA) are affected by a perspective distortion due to the use of image intensifiers. As a result, DSA cannot be used for the accurate definition of stereotactic coordinates. A correction method has been developed to enable the use of DSA for the radiosurgery of arteriovnous malformations. A software program and a special phantom tool were employed. The phantom is made by a computer-controlled drilling machine which makes holes in a Plexiglas plate. It has 865 calibration steel spheres with coordinates determined with a precision of 0.01 mm. A calibration image is acquired by a personal computer, and the software calculates the transformation algorithm to superimpose the image on the known positions of the phantom. This algorithm is saved and then recalled to transform the diagnostic images.

Angiography, Digital Subtraction↗

PubMed1995

Alterations in surface morphology of Candida albicans produced by rilopirox: a scanning electron microscopy study.

The topological changes produced in Candida albicans cells by incubation in vitro with rilopirox have been investigated by scanning electron microscopy. Rilopirox is a new hydroxypyridone compound with fungicidal activity and the effects of 1x MIC (2.9 micrograms/ml) and 4 x MIC (11.6 micrograms/ml) after 1, 12, 24 hours of incubation were evaluated. The morphological alterations produced by rilopirox are round shapes, collapsed cells, surface folds, clusters, holes and thorn-like extrusion. The effects of rilopirox are already evident at 1 x MIC and after 1 h but their frequency and severity are correlated with the time of incubation and the MIC.

Antifungal Agents↗

PubMed1995

Neltenexine: morphological investigation of protection against elastase-induced emphysema in rats.

The instillation of elastase into airways is a widely adopted experimental method to quickly produce emphysematous lesions that mimic human disease anatomically and physiologically. Experiments were undertaken to determine whether of not neltenexine, a new drug active on surfactant production, would diminish the severity of this disease. Anaesthetized rats were instilled tracheally with porcine pancreatic elastase (46 U/mg) dissolved in saline, in a single instillation of 0.33 mg/100 microliters. Neltenexine was administered in one experiment at the dose of 25 mg/kg i.p. daily for 30 days. In a second test, neltenexine was given at the same dose six days before the elastase instillation and then by the same schedule as in the first experiment; this was done in search of a possible preventive action. At the end of the treatment, lungs were removed and fixed, and slices were dehydrated, critically point dried, coated with gold and observed by scanning electron microscopy (SEM). Rats that were both pretreated and treated with neltenexine showed a significant reduction in the alveolar deformation induced by elastase. There were no differences between pretreated and treated animals. These experimental findings suggest that neltenexine might prove to be useful for preventing pulmonary emphysema. Biochemical studies in man are needed to confirm the clinical application of neltenexine.

Ambroxol↗

PubMed1995

Inhibition of Candida albicans adhesiveness to human buccal and vaginal cells by sub-inhibitory concentrations of rilopirox.

Candida albicans is an opportunistic dimorphic pathogenic yeast which is present on the human mucosal epithelial cell surface. Its adhesion is considered to be an important first step in colonization and in the subsequent symptomatic or asymptomatic infection of buccal or vaginal mucosa. Because the ability to adhere is an important element of the pathogenicity of Candida we investigated in this study the compared effects of sub-inhibitory concentrations (sub-MICs) of rilopirox (CAS 104153-37-9) with those of ciclopirox olamine (CAS 41621-49-2) in inhibiting Candida adhesion to human buccal (BEC) and vaginal cells (VEC). Rilopirox is a new hydroxypyridone antimycotic agent with strong activity, especially against Candida albicans. There was a significant reduction in the mean number of Candida adhering to both buccal and vaginal cells with up to 1/8 MIC rilopirox for buccal and 1/16 MIC for vaginal cells, while for ciclopirox olamine reduction was significant up to 1/16 MIC for buccal and 1/8 MIC for vaginal cells. There were no significant differences in the dose-effect curves for BEC and VEC with either rilopirox and ciclopirox olamine, but on a molar basis, rilopirox was more active than ciclopirox olamine. The present in-vitro results support the developmental concept of an oropharyngeal and vaginal preparation of rilopirox. It can be expected that even sub-inhibitory concentrations of rilopirox exert an important additional effect in the treatment of oral and vaginal candidosis by impairing the pathogenic adhesion process of the fungus.

Antifungal Agents↗