Role of fosfomycin tromethamine in modulating non-specific defence mechanisms in chronic uremic patients towards ESBL-producing Escherichia coli.

Antimicrobial agents and polymorphonuclear cells (PMNs) have the potential to interact in such a way that improve the therapy for infectious diseases. In immunocompromised patients highly susceptible to microbial infections with high morbidity and mortality, several metabolic and functional alterations in PMNs, mostly related to microbicidal activity, are observed. Therefore, the antibiotic of choice should have a good antimicrobial effect without impairing host defences. The aim of this study is to evaluate in vitro effects of sub-inhibiting fosfomycin tromethamine (FT) concentrations on the primary functions of PMNs from healthy subjects and immunocompromised patients (haemodialysed and renal transplant recipients), against an ESBL-producing Escherichia coli, the most common aetiological agent in urinary tract infections (UTIs). FT is considered a first line drug in the eradication of UTIs due to its appropriate antimicrobial spectrum, oral bioavailability and minimal risk of microbial resistance. Our results provide evidence that FT is able to induce enhancement of the depressed phagocytic response of PMNs from patients on chronic haemodialysis and from renal transplant recipients, restoring their primary functions in vitro against ESBL-producing E. coli. All these data permit the conclusion that uremic-infected patients might additionally benefit from the immunomodulating properties of FT.

N-acetylcysteine synergizes with oseltamivir in protecting mice from lethal influenza infection.

Many studies have shown that oxidative stress is important in the pathogenesis of pulmonary damage during influenza virus infections. Antioxidant molecules are therefore potentially useful against viral infection. Our previous studies show that N-acetylcysteine (NAC) has a protective effect in a model of lethal influenza infection in mice. NAC administration significantly decreased the mortality in infected mice. Further studies have demonstrated that NAC enhanced survival in combination with the antiviral agent ribavirin. In the present study, we report the effect of combined treatment with NAC and Oseltamivir, clinically used in the treatment and prevention of influenza virus infection, in a murine model of lethal influenza infection. NAC was given as a single daily dose of 1000 mg/kg starting from 4 h before infection and until day 4 after infection; Oseltamivir was given twice daily at dose of 1 mg/kg/die for 5 days, starting from 4 h before infection. End-point evaluation was 21-days survival. NAC alone was slightly effective (20%), since a suboptimal treatment was used. Survival increased to 60% with Oseltamivir and to 100% with Oseltamivir and NAC used in combination. Since NAC alone does not show any antiviral action, the present findings suggest that antioxidant therapy increase survival by an improvement in host defense mechanisms, and/or by a direct antioxidant effect against oxidative stress associated with viral infection. Our studies demonstrate the effectiveness of combining agents acting through different mechanisms, such as antiviral drugs oseltamivir and the antioxidant NAC, indicating a possible advantage of combining the two treatments.

In vivo effect of an immunostimulating bacterial lysate on human B lymphocytes.

The aim of the present study is to investigate in humans the mechanism by which the oral vaccine Polyvalent Mechanical Bacterial Lysate (PMBL) can rapidly mobilize specific immune response and evaluate the efficacy of its immunostimulating activity in preventing recurrent infections of the upper respiratory tract (URTIs) in a group of patients with a medical history of URTI recurrence. Patients received, by sublingual route, PBML, an immunostimulating lysate obtained by mechanical lysis of the most common bacteria responsible for upper respiratory tract infections. The treatment was administered for 10 consecutive days/month for 3 consecutive months. After the end of the treatment period the patients were followed up for an additional 3 months. The frequency of IgM memory B cells and the expression of the activation marker CD25 in peripheral blood lymphocytes were measured using the flow cytometric method before the start and at days 30 and 90 of the treatment cycle. To correlate clinical results to immunological parameters, the patients were monitored at different time-points during the treatment and at the end of follow-up period. The results showed that PMBL exerts a therapeutic and preventing effect in acute and recurrent infections of the upper respiratory tract and that this effect correlated with the activation and enhancement of both IgM memory B lymphocytes (CD24+/CD27+ cells) and IL2 receptor-expressing lymphocytes (CD25+ cells) involved either in humoral or cellular immunity.

In vitro effects of an immunostimulating bacterial lysate on human lymphocyte function.

MLBL is an oral immunostimulating vaccine consisting of bacterial standardized lysates obtained by mechanical lysis of different strains of Gram-positive and Gram-negative bacteria that can cause acute and chronic infections of the respiratory tract. Previous studies suggested a stimulating effect of MLBL both on humoral and cellular immune responses. In the present study, the in vitro effects of MLBL on human lymphocyte effector functions and its mechanisms of action were evaluated. The results show that the most remarkable effects of MLBL on the immune system are: i) activation of the IL-2 receptor (IL-2Ralpha) on different lymphocyte subsets (B, CD4+ T and CD8+ T cells) involved both in humoral and cellular immune responses; ii) induction of cytokine synthesis (IL-2, IL-10, IL-12, IFNgamma) in the immune competent cells that induce and regulate immune responses; iii) generation of CD4+ and CD8+ effector T cells. Overall, these results suggest that the therapeutic effect of MLBL on acute and recurrent infections of the respiratory tract is related to its ability to activate the responses of different subsets of immune competent cells both for humoral and cellular immunity. Moreover, these effects can be induced either by direct immune cell activation or through the generation and activation of immune effector cells.

Synergistic combination of N-acetylcysteine and ribavirin to protect from lethal influenza viral infection in a mouse model.

Oxidative stress is implicated in the pathogenesis of pulmonary damage during viral infections. In a previous study we observed a significant improvement of survival of influenza-infected mice with NAC, 1g/kg divided in two daily administrations, for 8 days including a pretreatment on day 1 before infection. In order to test NAC in a more realistic model, we studied the effect of combined treatment with NAC and the antiviral drug, ribavirin. Since in the present work we wanted to test a possible synergistic effect by combination of NAC and ribavirin, we used a different NAC's treatment regimen (1 g/kg, once a day for 4 days) that, alone, did not significantly protect mice from death. Mice (12 per group) infected intranasally with a lethal dose of influenza A virus APR/8. NAC was given as a single daily dose of 1000 mg/kg starting from 4 h after infection and until day 4 after infection, in association with ribavirin (100 mg/kg, i.p.). End-point evaluation was 14-day survival. With this schedule survival in infected mice was 17%, it was not significantly changed by NAC (25%). Survival increased to 58% with ribavirin and to 92% (n=12) with a combined treatment with ribavirin and NAC. This suggest that antioxidant therapy can increase survival by either improving the defenses against virus or by protecting from the pathogenesis of lung inflammation.

In-vitro susceptibility of quinolone-resistant clinical isolates of Escherichia coli to fosfomycin trometamol.

Escherichia coli (E. coli) is the most commonly isolated microorganism in uncomplicated lower urinary tract infections (UTI). Due to the increased isolation of E. coli strains resistant to quinolones, it is important to have available alternative drugs to this class of antibiotics as therapy for UTIs caused by this pathogen. Among the large number of currently available antimicrobial agents, fosfomycin trometamol is a useful alternative due to its peculiar microbiological and pharmacokinetic properties. Therefore, we tested the in vitro susceptibility of 79 quinolone-resistant clinical urinary isolates of E. coli to fosfomycin trometamol in comparison with amoxicillin, chloramphenicol, cotrimoxazole, netilmicin, nitrofurantoin and tetracycline. Fosfomycin trometamol showed high activity with a MIC90 of 4 mg/l. While no strains were resistant to fosfomycin trometamol, 83.5%, 63.3%, 58.2%, and 48.1% of the isolates were resistant to tetracycline, amoxicillin, chloramphenicol and cotrimoxazole, respectively. Nitrofurantoin and netilmicin resistance was present only in 12.7% and 6.3% of the strains, respectively. In conclusion, fosfomycin trometamol has retained its activity against quinolone-resistant strains of E. coli and cross-resistance with other classes of antimicrobial agents is not presently a problem. The strains tested did present high levels of resistance to other classes of antibiotics.

Synthesis and anti-HIV evaluation of new 2',3'-dideoxy-3'-thiacytidine prodrugs.

A series of anti-HIV prodrugs possessing various polyaminated side arms have been developed. The incorporation of a N-Boc protected monoamine or diamine side arm into the backbone of the 2',3'-dideoxy-3'-thiacytidine 1 (BCH-189) provided an increase in antiviral potency, which could be several orders magnitude greater than the parent drug (1) depending on the cell culture systems used (MT-4 or MDMs). Twenty six 2',3'-dideoxy-3'-thiacytidine prodrugs which differ from each other by the length, the nature of the 5'-O function and the 5'-O or/and N-4 position on the nucleoside moiety were synthesized. Among this new series of prodrugs, several congeners (12c and 12a) were found to inhibit HIV-1 replication in cell culture with 50% effective concentrations EC50 of 10 and 50 nM respectively, in MT-4 cells. Compound 12c was found more active on infected MDMs cells with 50% effective concentration of 0.01 nM. The synthesis and the antiviral properties of these compounds are discussed.

Protective effect of n-acetylcysteine in a model of influenza infection in mice.

Reactive oxygen intermediates (ROI) and cytokines, particularly tumor necrosis factor (TNF) have been implicated in the pathogenesis of influenza. Using a murine model of influenza, we have studied the levels of TNF, interleukin 6 (IL-6) and of superoxide-generating xanthine oxidase (XO). Mice infected intranasally with influenza virus APR/8 had high levels of XO, TNF and IL-6 in the broncoalveolar lavage, as early as 3 d after infection. XO was elevated also in serum and lung tissue. Administration of the antioxidant N-acetylcysteine (NAC,1 g/kg per day, orally) significantly decreased the mortality in infected mice, indicating a role for RO1 in the lethality associated with influenza infection.

Activity of aerosol thiamphenicol glycinate acetylcysteinate in a mouse model of S. pyogenes pneumonia.

Thiamphenicol glycinate acetylcysteinate (TGA, CAS 20192-91-0) is a water soluble ester of thiamphenicol (TAP) that allows a rapid utilization by the systemic route but also a direct local action when used as aerosol. To assess the efficacy of aerosolized TGA in the treatment of experimental pneumonia in mice, we compared its in vivo activity with that of thiamphenicol glycinate hydrochloride (TG), erythromycin (ERT) and amoxicillin (AMX), the last two compounds being more active in vitro than TAP. TGA, administered by aerosol route, showed better efficacy than the aerosolized TG, particularly as far as survival rate is concerned, and was significantly more potent than ERT and similar to AMX either administered by oral route. No significantly different therapeutic efficacy was observed when TGA was parenterally administered. The rapid release, at the site of infection, of TAP and N-acetylcysteine and the favourable pharmacokinetic properties of TGA accounted in large part for its high therapeutic efficacy against Streptococcus pyogenes pneumonia.

In vitro antibacterial activity of thiamphenicol glycinate acetylcysteinate against respiratory pathogens.

After 30 years of therapeutic use, thiamphenicol glycinate acetylcysteinate (CAS 20192-91-0) is still widely employed in the treatment of upper and lower respiratory tract infections. This is due to its particular characteristic to exert at pulmonary level, either the antibacterial activity of thiamphenicol (CAS 15318-45-3) and the mucolytic activity of N-acetylcysteine (CAS 616-91-1). The aim of this study was to evaluate the present pattern of susceptibility of several clinical isolates to thiamphenicol and the interference of N-acetylcysteine on this parameter. The studies have been performed in vitro. Equimolar concentrations of N-acetylcysteine and even higher concentrations did not interfere with the antibacterial activity of thiamphenicol against Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae. The spectrum of activity of thiamphenicol was similar to that observed in the past and was superior to that of erythromycin and amoxicillin. The activity of thiamphenicol was greater than that of erythromycin against H. influenzae and streptococci and equivalent versus Branhamella catarrhalis. In comparison with amoxicillin the activity of thiamphenicol was higher against H. influenzae and B. catarrhalis and slightly lower against streptococci. The results demonstrate that thiamphenicol maintains its therapeutic value confirming the importance of thiamphenicol glycinate acetylcysteinate in the treatment of respiratory tract infections.

Antiviral activity of nerve growth factor in vitro.

The antiviral activity of 'nerve growth factor' (NGF) on non-oncogenic DNA, on RNA viruses and on Moloney sarcoma retrovirus was evaluated in vitro. NGF was active against herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and Moloney sarcoma virus (MSV) at non toxic concentrations. The effects of different treatment regimens on HSV-1 infections indicate that the inhibitory action of NGF occurs at the early stages of viral replication. No activity was noted against coxsackie virus B1 (Cox B1), respiratory syncytial virus (RSV), Semliki forest virus (SFV), encephalomyocarditis (Columbia SK) and adenovirus of infectious canine hepatitis (ICH) at the highest concentrations tested.

Activity of FCE 20696, a new synthetic immunomodulator, in models of viral and bacterial pathology.

The dibenzopyran derivative FCE 20696 is an immunomodulator which protects mice infected with several viral agents and with Mycobacterium tuberculosis. The compound is able to decrease the severity of the lung lesions caused by influenza virus infection. Doses ranging from 12.5 to 100 mg/kg are effective even after a single administration. Activity is demonstrated by intraperitoneal, subcutaneous and oral administration of the drug. In systemic infection with herpes simplex virus type 1, the 100 mg/kg dosage, administered subcutaneously, is able to increase both the percentage and the mean survival time of mice. To have effect by oral administration it is necessary to give the compound twice in the day. Moreover, some activity has also been observed in mice infected by M. tuberculosis, when the compound is administered orally at doses of 1-2.5 mg/kg twice weekly for 5 weeks, during the course of the disease.

Comparative in vitro susceptibility studies of FCE 22250 and rifampicin on Legionella and Chlamydia trachomatis strains.

The in vitro activities of rifampicin and the new rifamycin FCE 22250 were evaluated against the intracellular pathogens Legionella and Chlamydia trachomatis. The data reported in this study give evidence that FCE 22250 shows excellent in vitro results, even better than those obtained with rifampicin, leading to the possibility of clinical applications of this new drug on Legionnaire's disease and chlamydial infections.

Laboratory evaluation of a new long-acting 3-azinomethylrifamycin FCE 22250.

FCE 22250 (3-(N-piperidinomethylazino)methylrifamycin SV) is a member of the new class of 3-azinomethylrifamycins characterized by a long persistance in animals, a good oral absorption and a broad antibacterial spectrum including mycobacteria. In the experimental mice infection sustained by Mycobacterium tuberculosis H37Rv, FCE 22250 shows an efficacy 14 times higher than rifampicin and is still therapeutic when administered once every three weeks.

Novel rifamycins. III. Synthesis and antibacterial activity of 3-amidino- and of 4-aminoimidazolo[4,5-c]rifamycin derivatives.

A number of semisynthetic rifamycin derivatives modified at position 3 and/or 4, belonging to general structures 2 and 4 (see Scheme 1), have been obtained. The synthesis and the biological activities of the new compounds are described. Compounds 4p and 4q display very good antimycobacterial activity in mice.

LM 427, a new spiropiperidylrifamycin: in vitro and in vivo studies.

The spiropiperidylrifamycin LM 427 (4-deoxo-3,4-[2-spiro-N-isobutyl-4-piperidyl]-(1H)-imidazo-(2,5-dihydro) rifamycin S) displays a broad spectrum of potent antibacterial activity in vitro. In vivo it is particularly effective in the therapy of experimental tubercular infections of mice. Three schedules of treatment were employed and the best results were obtained when intermittent administrations were used (ED50 of LM 427; 7 times lower than rifampicin). LM 427 is well distributed in tissues of mice and rats, with lung concentrations 10 to 20 times higher than plasma levels.

Biological activity of a new class of rifamycins. Spiro-piperidyl-rifamycins.

The biological properties of spiro-piperidyl-rifamycins, a new class of rifamycin antibiotics, are described. In these derivatives the positions 3 and 4 have been incorporated into an imidazolyl ring bearing a spiro-piperidyl group N substituted with linear and branched aliphatic chains. The in vitro antibacterial activity against Staphylococcus aureus and Mycobacterium tuberculosis increases with the number of the carbon atoms in the linera side chain, whereas the inhibitory effect on Escherichia coli is lowered. The antibacterial activity is only marginally affected by branching of the side chain. In vivo (experimental infections of mice) the optimal therapeutic activity against M. tuberculosis is shown by compounds bearing 3 approximately 5 carbon atoms as a linear or branched side chain; in comparison with rifampicin, the potency of these derivatives is 2 approximately 3 times higher. The finding is in a good agreement with the exceptional tissue tropism, which seems to be a favourable property of this group of derivatives.