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Biomedical subjects

G Gialdroni Grassi

Publications and source records attributed to G Gialdroni Grassi.

At least 19 recordsLinked to original sources
PubMed2001

Virulence of Mycobacterium tuberculosis affects interleukin-8, monocyte chemoattractant protein-1 and interleukin-10 production by human mononuclear phagocytes.

Microbial virulence and cytokine-mediated immune responses to Mycobacterium tuberculosis infection are important determinants of the pathogenesis of human tuberculosis. To determine the interrelationship between mycobacterial virulence and cytokine induction, human monocytes and monocyte-derived macrophages were infected with attenuated (H37Ra) and virulent (H37Rv and CH306) strains of M. tuberculosis and the amount of proinflammatory [interleukin (IL)-8 and monocyte chemoattractant protein (MCP)- 1] and inhibitory (IL- 10) cytokines was measured in the culture supernatants by enzyme-linked immunosorbent assay (ELISA). Infection with live bacilli induced de novo synthesis of IL-8, MCP-1 and IL-10, since cytokine release was abolished when cells were preincubated with the protein synthesis inhibitor cycloheximide. A differential production of antiinflammatory and inhibitory cytokines was observed. The amount of IL-8 and MCP-1 release was inversely related to strain virulence, the attenuated H37Ra strain being more prone than virulent strains to induce secretion of chemokines. In contrast, virulent strains induced greater amounts of the inhibitory cytokine IL-10. Efficient upregulation of IL-10 synthesis, but not of chemokines, required infection of cells with live bacilli, since heat killing of organisms or challenge with soluble mycobacterial products completely abrogated the effect. Moreover, cells infected with virulent strains produced IL-10 even at a very low bacillus-to-cell ratio and secreted IL-10 continuously during the 96 h that followed infection. The results suggest that the degree of virulence affects host cell responses to M. tuberculosis infection. Continued production of IL-10 may be one of the means by which M. tuberculosis downregulates acute local inflammatory reactions, favoring the development of tuberculosis.

Cells, Cultured↗
PubMed2000

Mycobacterial lipoarabinomannan affects human polymorphonuclear and mononuclear phagocyte functions differently.

BACKGROUND AND OBJECTIVE: The role of mycobacterial lipoarabinomannan (LAM) in regulating the granulomatous response and its effects on cells involved in early responses to tuberculosis have not been clearly defined. The aim of this study was to acquire further evidence about the mechanisms by which LAM takes part in the host response to mycobacterial infections. DESIGN AND METHODS: We compared the in vitro ability of mannosylated LAM (ManLAM) and LAM lacking the terminal mannosyl units (AraLAM) to induce distinct responses in human polymorphonuclear (PMNs) and mononuclear phagocytes [both monocytes and 48-hr monocyte-derived macrophages (MDMs)]. The responses examined were chemotaxis, transient changes in free cytosolic calcium, phagocytosis and metabolic activation. RESULTS: AraLAM and ManLAM affected mononuclear, but not polymorphonuclear, phagocyte functions. Both forms of LAM were chemotactic for monocytes and MDMs. The LAM-induced chemotactic response required new protein synthesis, did not induce a rise in cytosolic free calcium levels and was partially inhibited (about 50%) by genistein, but not by calphostin C or PD 98059. Lastly, at physiologic doses ManLAM significantly reduced phagocytosis of M. tuberculosis and zymosan particles by MDMs. INTERPRETATION AND CONCLUSIONS: Different phagocytic cells can exhibit variable responses to AraLAM and ManLAM. Moreover, LAMs affect cell functions through different mechanisms. Protein synthesis and activation of protein tyrosine kinases are important intermediates in the signal transduction pathway of the chemotactic response of mononuclear phagocytes to AraLAM and ManLAM; whereas ManLAM-induced inhibition of macrophage phagocytic ability could depend on the binding of macrophage mannose receptors and/or the insertion of this molecule into cellular plasma membrane. Together these data highlight the danger of making generalizations regarding the activity of LAMs on immune defenses.

Antigens, Bacterial↗
PubMed1997

Effect of different combinations of sparfloxacin, oxacillin, and fosfomycin against methicillin-resistant staphylococci.

The in vitro activity of combinations of sparfloxacin/oxacillin, sparfloxacin/fosfomycin, and oxacillin/fosfomycin was investigated against 16 methicillin-resistant Staphylococcus aureus (MRSA) isolates and 12 methicillin-resistant Staphylococcus epidermidis (MRSE) isolates moderately resistant to sparfloxacin. Synergic interactions were observed more frequently against MRSE than against MRSA strains. The most effective combination on both species was fosfomycin plus oxacillin, synergistic against ten of 16 MRSA and eight of 12 MRSE strains.

Anti-Infective Agents↗
PubMed1997

Release of prostaglandin E2 and leukotriene B4 by alveolar macrophages from patients with sarcoidosis.

BACKGROUND: Mediators released by alveolar macrophages, as well as by T cells, play an important part in modulating local immune processes in sarcoidosis. Among alveolar macrophage secretory products, arachidonic acid metabolites are known to regulate inflammatory and immune reactions. It has been suggested that cyclo-oxygenase and lipoxygenase pathway metabolites of arachidonic acid modulate the evolution of the granulomatous inflammatory response in the lung differently. METHODS: Alveolar macrophages recovered from the bronchoalveolar lavage (BAL) fluid of 32 patients with sarcoidosis in different states of disease activity and 10 normal subjects were evaluated for their ability to release prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). Alveolar macrophages were cultured in the presence or absence of opsonised zymosan (500 micrograms/ml), and PGE2 and LTB4 levels in the culture supernatants were determined by enzyme immunoassay (EIA). RESULTS: Stimulated alveolar macrophages from patients with active sarcoidosis released higher LTB4 levels than those from normal subjects, but no differences in PGE2 release were observed between the two groups. The time course of LTB4 release by activated alveolar macrophages showed that normal cells produced similar levels of the hydroxyacid during the early and late times of culture while LTB4 release by activated cells from patients with sarcoidosis increased markedly after 60 minutes of culture, remaining elevated until 24 hours. Indomethacin (3 x 10(6) M) caused the expected inhibition of PGE2 formation without affecting LTB4 release. CONCLUSIONS: These results suggest that alveolar macrophages from the BAL fluid of patients with active sarcoidosis are primed to release LTB4, which may contribute to the locally heightened immune response.

Adult↗
PubMed1997

Inhibition of intracellular growth of Staphylococcus aureus by exposure of infected human monocytes to clarithromycin and azithromycin.

The direct effect of clarithromycin and azithromycin on human polymorphonuclear leukocyte (PMN) functions and their intracellular activity against Staphylococcus aureus, phagocytosed by human monocytes, were studied. The presence of both antibiotics, in the range of concentrations from 0.25 to 20 micrograms/ml, did not affect chemotaxis, opsonized-zymosan phagocytosis, respiratory burst measured by nitroblue tetrazolium reduction and phorbol myristate acetate-induced superoxide production, or the microbicidal activity of human PMNs against Candida albicans. Both macrolides were bactericidal against staphylococci in the monocyte system, while bacteriostatic activity was found in cell free system. At concentrations equal to the minimum inhibitory concentrations (MICs) (0.75 and 0.1 respectively for azithromycin and clarithromycin) more than 99% of intraphagocytic S. aureus were killed after 24 h incubation. Increasing the concentrations of each drug above the MICs (5 and 10 MICs) did not alter the killing rate of intracellular bacteria. Moreover, no differences between the intracellular bioactivity of these antibiotics were demonstrated, despite their different uptake kinetics.

Azithromycin↗
PubMed1997

Requirements for intracellular accumulation and release of clarithromycin and azithromycin by human phagocytes.

Determination of clarithromycin (CL) and azithromycin (AZ) uptake by human polymorphonuclear leukocytes (PMNs), monocytes and alveolar macrophages showed that AZ achieved higher levels than CL. The uptake kinetics of AZ were time-dependent over an 18 h period, while those of CL were similar to erythromycin (ER) kinetics, with a maximum level of incorporation being obtained after a 60 min incubation. The accumulation of both drugs was influenced by extracellular antibiotic-concentrations, PMN viability, extracellular calcium, physiological environmental temperature and pH. The uptake was not modified by inhibitors of cell metabolism or activators of cell membranes. After removal of extracellular antibiotic, the release of AZ from PMNs was very slow: nearly 50% of the drug remained cell-associated after 24 h incubation. The efflux of this derivative was significantly enhanced when drug-loaded PMNs were stimulated by phorbol-myristate acetate (PMA). The kinetics of CL release indicated that this macrolide behaved like ER. Nevertheless, about 10% of the initial cell-associated antibiotic showed a prolonged retention. On the whole, these data suggest that diffusion through cell membranes and trapping into acidic compartments of PMNs are important events in CL and AZ uptake.

Anti-Bacterial Agents↗
PubMed1996

Use of investigations in lower respiratory tract infection in the community: a European survey.

A questionnaire survey was performed on the use of investigations and their impact on treatment of adult lower respiratory tract infection in the community. Data on the management of 2,056 such infections were obtained simultaneously from general practitioners in France, Germany, Italy, Spain and the UK. Diagnostic tests were only performed in 29% of cases. Chest radiographs were performed most frequently (22%), followed by peripheral blood white cell count (15%) and microbiological examination of sputum (7%), with major differences being found in the frequency of these tests both by clinical diagnosis and country. A change in initial antibiotic therapy was made in 12% of cases, with use of investigation being significantly linked to such changes. Second- and third-line antibiotics were significantly different to first-line therapy, with macrolides the most frequently prescribed second-line and quinolones the most frequently prescribed third-line antibiotics.

Adult↗
PubMed1995

The place of tobramycin in lower respiratory tract infections (LRTI).

The Author provides a review of clinical experience with tobramycin as therapy for lower respiratory tract infections, in comparison to other aminoglycosides, including the pharmacokinetics and toxicity, dwelling on oto- and nephrotoxicity. The article includes a discussion of various dosing regimens of the aminoglycosides, focussing on efficacy and toxicity arising from once-daily administration. The Author then provides a more detailed description of tobramycin's pharmacokinetics, indications for its use, and the possibilities of once-daily dosing, concluding that toxicity is favorably influenced by a single daily administration as well as efficacy, and that patient compliance and reduced hospital costs are other advantages of this regimen.

Administration, Oral↗
PubMed1995

In vitro effect of bombesin-related peptides on the procoagulant activity of alveolar macrophages.

Bombesin-related peptides (BRP) are present in the lung during foetal life and are mitogenic for normal bronchial epithelial cells, pulmonary fibroblasts, and small-cell lung carcinoma cell lines. Increased levels of BRP have been described in the adult lung of cigarette smokers and in smoking related lung diseases. BRP have also been involved in the network of neuroimmune interactions, having been shown to modulate the phagocytic function of monocytes and alveolar macrophages. BRP have recently been shown to modulate the release of procoagulant activity (PCA) by human monocytes and alveolar macrophages after a 24 h culture. The aim of this study was to evaluate the effect of bombesin on cell-associated PCA of alveolar macrophages (AMs) obtained from asymptomatic subjects. In basal conditions, AMs were found to possess a low procoagulant activity, that was not affected by their preincubation (4 h at 37 degrees C) with phorbol myristate acetate (1 microgram-mL-1). On the contrary, endotoxin (lipopolysaccharide (LPS)) induced a significant increase of procoagulant activity of macrophages when used at a concentration of 1 microgram.mL-1, in the same experimental conditions; whilst a lower (1 ng.mL-1) concentration of LPS nonsignificantly enhanced cell-associated PCA. Treatment of AMs with synthetic bombesin (BN) alone (10(-6) to 10(-10) M) did not enhance cell-associated PCA, whilst a significant effect was seen when BN was added to the lower concentration of LPS (BN 10(-6) M+LPS 1 ng.mL-1: 12.6 U.10(-6) cells; LPS alone 1 ng.mL-1: 7.8 U.10(-6) cells).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation Factors↗
PubMed1995

Guidelines for the management of community-acquired pneumonia in adults. Italian Society of Pneumology. Italian Society of Respiratory Medicine. Italian Society of Chemotherapy.

In general practice Community-acquired Pneumonia (CAP) is most often treated on an empyrical basis. Therefore, it is of the utmost importance to know the epidemiology of respiratory pathogens in order to give some guidelines for the empirical management of CAP. At present in cases of mild and moderate severity, ampicillin or amoxycillin, preferably in association with sulbactam and clavulanic acid respectively, and macrolides are the antibiotics of first choice. The latter can be an alternative to beta-lactams when Legionella, Mycoplasma and Chlamydia are the suspected etiologic agents or when patients are allergic to penicillins. They can also be used in combination with beta-lactams when etiological diagnosis is extremely uncertain. The course and severity of the disease, a chest radiograph, the results of microbiological and other laboratory examinations will determine the choice of further antibiotic treatment and other therapeutic measures, if necessary.

Adult↗
PubMed1993

Bioactivity of flurithromycin and other macrolides against intracellular susceptible staphylococci.

The intracellular activity of flurithromycin, erythromycin, roxithromycin and miocamycin against susceptible clinical isolates of Staphylococcus aureus, phagocytosed by human monocytes, was investigated. Intracellular bioactivity was studied in a 24-hour assay, using experimental conditions which allowed the intracellular growth of bacteria. A colony counting method was used to differentiate between intracellular bacteriostatic and bactericidal activity of antibiotics. Moreover, the effect of macrolides against extracellular staphylococci was assessed. All agents showed higher intracellular than extracellular activity against staphylococci. At low concentration (0.1 mg/l) they had intracellular bacteriostatic activity. At concentrations higher than the minimal inhibitory ones (1 and 5 mg/l), miocamycin only still produced a bacteriostatic effect while flurithromycin, erythromycin and roxithromycin also showed intracellular bactericidal activity.

Anti-Bacterial Agents↗
PubMed1992

Cefodizime host-defence enhancement: considerations of dose-response relationships in healthy volunteers.

Studies with cefodizime in animals have shown that this new aminothiazolyl cephalosporin, possessing a broad antibacterial spectrum, positively influences a number of immunological parameters. In most investigations in which different dosage regimens were compared, a bell-shaped dose-response relationship was determined, i.e. activity after higher doses returned to near-baseline levels. This finding is typical of most immunomodulating agents. On this basis, the results obtained in healthy subjects were reviewed. Studies for investigating the biological response modifying (BRM) properties of cefodizime have been conducted in this population with either 2 g once daily i.v. or--in the majority--with 2 x 2 g/day i.v. After seven days of treatment with 1 x 2 g daily, no relevant changes could be demonstrated in healthy subjects, whereas there was an increase in monocyte and granulocyte chemotaxis in a parallel group of patients with multiple myeloma. In contrast, treatment with 2 x 2 g daily induced higher lymphocyte responsiveness and significantly increased nonspecific phagocytosis of both neutrophils and monocytes. The experience in healthy volunteers clearly demonstrates that the latter dose, usually the highest required for antibiotic treatment with cefodizime, is still located on the upward slope of the dose-response curve of positive BRM effects.

Animals↗
PubMed1992

Immunological and clinical effect of long-term oral treatment with RU 41740 in patients with chronic bronchitis: double-blind trial long-term versus standard dose regimen.

The immunological and clinical effects of two oral treatment schedules of RU 41740 (standard for 3 months vs. long-term for 6 months) were assessed in 40 patients with chronic bronchitis by a controlled, double-blind, randomized trial. Both treatments significantly improved phagocytosis index of both neutrophils and monocytes, and the phagocytosis frequency and the candidacidal activity of neutrophils, showing the maximum stimulation at the end of the third course of treatment. Both treatment schedules reduced the number and the duration of infectious exacerbations of chronic bronchitis with respect to those observed in the corresponding period of the previous year. However, no significant difference between standard and long-term treatment with RU 41740 was found with respect to the immunological and clinical effect and tolerability.

Administration, Oral↗
PubMed1992

Uptake of flurithromycin by human polymorphonuclear phagocytes: partial characterization of the entry mechanism.

The ability of flurithromycin and erythromycin to enter human polymorphonuclear phagocytes were studied and compared by a velocity centrifugation gradient technique. Both macrolides were markedly concentrated by human cells and attained cellular to extracellular concentration ratios (C/E) > or = 10. The incorporation was rapid and essentially complete after 60 min incubation. When PMNs were pretreated with formaldehyde, or incubated at low temperatures (4-25 degrees C) or at low pH, the transport ratios of both molecules were reduced. Sodium fluoride and 2,4-dinitrophenol, which decreased erythromycin uptake, did not affect flurithromycin penetration. Perturbation of cell membrane by phorbol myristate acetate, but not by formyl methionyl leucyl peptide, affected C/E ratios of both antibiotics. The addition of amino acids or nucleosides did not influence their transfer into PMNs.

Adult↗
PubMed1990

Fosfomycin trometamol: historical background and clinical development.

A brief historical review of the clinical development of fosfomycin is given. Fosfomycin has attracted great interest because of its broad spectrum of activity and excellent tolerability. However, some problems have arsen because of the rapid emergence of resistant strains, and the poor bioavailability by oral route. Fosfomycin trometamol (a salt of fosfomycin with tromethamine) overcomes this difficulty: in fact when given by oral route it reaches very high and persistent urinary concentrations (up to 48 h). This behaviour allows a long-lasting bactericidal activity in urine to be obtained and the emergence of resistant variants to be prevented. These characteristics allowed proposing the drug for the "single dose therapy" of lower uncomplicated urinary tract infections. The clinical trials confirmed that this assumption was correct, demonstrating the excellent therapeutic activity of the drug in this indication.

Administration, Oral↗