Comparative bactericidal activity of ceftazidime against isolates of Pseudomonas aeruginosa as assessed in an in vitro pharmacodynamic model versus the traditional time-kill method.

Bactericidal activity, historically assessed by in vitro tests which employ fixed drug concentrations, may also be evaluated in in vitro pharmacodynamic models in which in vivo pharmacokinetics and bacterial growth conditions can be simulated. However, systematic comparisons between the two methods are lacking. We evaluated the bactericidal activities of ceftazidime, at two different concentration/MIC ratios (C/MICs), against 10 clinical isolates of Pseudomonas aeruginosa in a two-compartment model with continuous-infusion conditions and a 2-h half-life. These values were compared to those determined by traditional 24-h time-kill (TTK) methods at the same C/MICs. Bactericidal activities were compared by using area under the colony count-time curves. Antibiotic exposure (area under the drug concentration-time curve) was also evaluated. Although bactericidal activity appeared greater by the TTK method (P = 0.05), when it was normalized for drug exposure, these differences disappeared (P = 0.2). This disparity was likely due to differences in drug exposure in the TTK method and in the peripheral compartment of the model (site of bacteria) over the first 8 h of the experiment, during which the antibiotic accumulated to target concentrations. This suggests that the bactericidal effects with constant antibiotic concentrations are similar in the two methods; however, this may not hold true with fluctuating drug concentrations. Further, results from the pharmacodynamic model may theoretically be more relevant, as in vivo pharmacokinetics and bacterial growth conditions call be more faithfully simulated.     

Nasal continuous positive airway pressure in atelectasis

Nasal continuous positive airway pressure (CPAP) has been widely and safely used in the treatment of sleep disorders but has not been previously utilized for therapy of pulmonary atelectasis in adults. We observed three patients with significant atelectasis which was refractory to conventional chest physiotherapy. Bronchoscopy was not a viable therapeutic option in any patient. Therapy with continuous nasal CPAP was initiated at 10 to 15 cm H2O. The patients tolerated the therapy well and had prompt resolution of atelectasis. Nasal CPAP may be an effective modality for therapy of pulmonary atelectasis in spontaneously breathing patients, particularly when conventional therapies are not tolerated or are ineffectual.     

Clinical significance of in vitro replication-enhancing mutations of the hepatitis C virus (HCV) replicon in patients with chronic HCV infection

BACKGROUND: Mutations in nonstructural (NS) hepatitis C virus (HCV) proteins enhance replication in HCV-1a/b replicons. The prevalence of such mutations and their clinical significance in vivo are unknown. METHODS: Parts of HCV NS3 and NS4B-NS5B genes that included 31 in vitro replication-enhancing sites were sequenced for 26 patients with chronic HCV genotype 1 infection. RESULTS: Five patients showed specific mutations within NS3 at sites enhancing replication in the replicon. Those mutations were associated with a slower decrease in HCV RNA concentration during interferon (IFN)- alpha -based therapy (P = .007). Neither specific nor other mutations within NS3 and NS4B-NS5B were associated with baseline HCV RNA concentrations. Within NS5A, fewer mutations in the major HCV strain (P = .001) and increased quasi-species complexity (P = .02) and diversity (P = .02) correlated with increasing baseline HCV RNA concentrations. In silico analyses of NS3 protein structures suggested that the majority of observed mutations did not lead to major conformational changes. CONCLUSIONS: Specific mutations leading to enhanced replication in the replicon system were detected in 5 of 26 patients in vivo and were not associated with baseline HCV RNA concentrations but were associated with a slower decrease in HCV RNA concentration during IFN- alpha -based therapy. Quasi-species heterogeneity of NS5A correlated with baseline HCV RNA concentrations.     

Pioglitazone elicits long-term improvements in insulin sensitivity in patients with type 2 diabetes: comparisons with gliclazide-based regimens

Aims/hypothesis Recent studies have demonstrated that pioglitazone (PIO) has beneficial effects on insulin sensitivity compared with placebo in patients with type 2 diabetes. The effects of PIO and gliclazide (GLIC)-based therapy on insulin sensitivity have not previously been directly compared. This analysis aimed to compare the effects of 52 weeks of treatment with PIO (30–45 mg/day) and GLIC (80–320 mg/day), both titrated to maximum tolerable doses, as monotherapy or in combination with metformin (MET), on insulin sensitivity and lipid parameters known to be related to insulin sensitivity in patients with type 2 diabetes.Methods We performed an analysis of 1,880 patients with inadequately controlled type 2 diabetes (HbA₁c 7.5–11.0%) who were participants in two parallel-group, double-blind, double-dummy, randomised, multicentre, clinical trials. Measures of insulin sensitivity and lipids were assessed.Results The PIO- and GLIC-based regimens produced similar levels of glycaemic control (HbA₁c). In both trials, insulin sensitivity as assessed using the homeostasis model assessment was improved in patients receiving PIO, but decreased in those receiving GLIC (mean change, baseline to endpoint: PIO 15.5, GLIC –15.6; p<0.001 and PIO+MET 18.9, GLIC+MET –5.3; p<0.001). Improvements in the atherogenic index of plasma (mean change: PIO –0.17, GLIC –0.08; p<0.001 and PIO+MET –0.17, GLIC+MET –0.02; p<0.001), triglycerides (mean change, mmol/l: PIO+MET –0.62, GLIC+MET –0.22; p<0.001) and NEFA (mean change, mmol/l: PIO+MET –0.12, GLIC+MET–0.05; p<0.001) were greater in PIO-treated patients than in patients receiving GLIC.Conclusions/interpretation The PIO-based regimens resulted in improved insulin sensitivity and more favourable insulin sensitivity-related lipid profiles compared with the GLIC-based regimens. These benefits may be important in the management of cardiovascular risk in patients with type 2 diabetes.     

Proton MR Spectroscopy of Neurometabolites in Hepatic Encephalopathy During L-Ornithine-L-Aspartate Treatment–Results of a Pilot Study

Hepatic encephalopathy (HE) is associated with typical changes in neurometabolites most likely being caused by an elevated systemic ammonia level. Blood ammonia is a valid overall biomarker of HE and thus is regularly determined in clinical trials. The neurometabolites affected in HE can be assessed in vivo by proton magnetic spectroscopy. The aim of this study was to show the effect of the ammonia lowering drug L-ornithine-L-aspartate (OA) on the cerebral glutamate+glutamine/creatine (Glu+GLN/Cr) ratio. In an open clinical trial (pilot study), 15 patients with stable HE were treated with an infusion of 40 g OA over 8 h (5 g/h). Immediately before and 6–8 (mean 6.8) h after start of the infusion, spectroscopy of the parietal white matter was performed and arterial blood ammonia quantified. Glu+GLN/Cr-ratios correlated significantly with ammonia data (Spearman's correlation coefficient rs = 0.72, p < 0.001). Likewise, the OA induced changes (versus baseline before infusion) in blood ammonia level and in Glu+GLN/Cr-ratios correlated significantly rs = 0.54, p = 0.0375). Magnetic resonance (MR) spectroscopy assesses the neurometabolite variation present in HE. OA induced changes in cerebral Glu+GLN/Cr-ratio were significantly correlated with the drug effects on arterial blood ammonia. These pilot data indicate that MR spectroscopy detects a specific biomarker of HE that may reflect the extent of the cerebral alterations associated with the disease.     

Interferon-gamma inhibits replication of subgenomic and genomic hepatitis C virus RNAs

Persistent infection with hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. All treatments known so far rely on the antiviral activity of interferon alfa (IFN-alpha) that is given alone or in combination with ribavirin. Unfortunately, only a fraction of the patients clear the virus during therapy and for those who do not respond there is currently no alternative treatment. Selectable subgenomic HCV RNAs (replicons) have been recently used to investigate the effect of IFN-alpha on HCV replication. However, it has not yet been analyzed whether other cytokines also play a role in the innate immune response against HCV. Here we show that IFN-gamma inhibits protein synthesis and RNA replication of subgenomic and genomic HCV replicons. We further show that the inhibitory action of IFN-gamma does not rely on the production of nitric oxide or the depletion of tryptophan. In conclusion, our results suggest that cytotoxic T cells and natural killer cells may contribute to HCV clearance not only by cell killing but also by producing IFN-gamma, thereby enhancing the intracellular inhibition of viral replication.     

Treatment of genotype 2 and 3 chronic hepatitis C virus-infected patients

AIM: Before pegylated interferon alpha (IFN) was introduced for the therapy of chronic hepatitis C virus (HCV)-induced hepatitis, conventional thrice weekly IFN therapy was supplemented by ribavirin. Also, at that time, higher and more frequent doses of IFN were expected to be more effective than the standard regimen of 3 MU thrice weekly. As ribavirin significantly increases side effects and negatively influences the quality of life particularly in young patients, we started a prospective non-randomized study with a daily IFN-2a monotherapy as an initial treatment for chronic hepatitis C. METHODS: Forty-six consecutive chronic HCV-infected patients received 3 MU IFN-2a per day as an initial treatment. Patients with genotype 2 or 3 (n = 12) were treated for 24 wk, and patients with genotypes other than 2 or 3 (n = 34) for 48 wk. Treatment outcome was followed up for 48 wk after the end of treatment (EOT). Virological response was defined as the absence of detectable serum HCV-RNA. Patients without virological response at 12 wk after the start of treatment received low-dose ribavirin (10 mg(kg·d)) additionally. RESULTS: During treatment, three genotype 3 patients were excluded from the study due to incompliance. The remaining patients (n = 9) infected with genotype 2 or 3 showed an initial virological response rate of 100%. Six patients (66.7%) were still found to be virus-free at the end of follow-up period. In these patients, initial virological response was evident already after 2 wk of treatment. In contrast, initial virological response occurred first after 4 wk of treatment in the three patients who relapsed (33.3%). In comparison, patients infected with genotypes other than 2 or 3 (n = 34) showed an initial virological response rate of only 23.5% (n = 8), and even in combination with ribavirin a sustained virological response (SVR) rate of only 11.8% (n = 4) could be achieved. CONCLUSION: In chronic HCV-infected patients with genotype 2 or 3, a SVR can be expected after 24 wk of daily dose IFN-2a treatment without ribavirin, if initial virological response develops early. This finding is worth to be confirmed in a prospective randomized study with pegylated IFN.     

Functional deficiencies of granulocyte-macrophage colony stimulating factor and interleukin-3 contribute to insulitis and destruction of beta cells

The pathogenesis of type 1 diabetes (T1D) involves the immune-mediated destruction of insulin-producing beta cells in the pancreatic islets of Langerhans. Genetic analysis of families with a high incidence of T1D and nonobese diabetic (NOD) mice, a prototypical model of the disorder, uncovered multiple susceptibility loci, although most of the underlying immune defects remain to be delineated. Here we report that aged mice doubly deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) manifest insulitis, destruction of insulin-producing beta cells, and compromised glucose homeostasis. Macrophages from mutant mice produce increased levels of p40 after LPS stimulation, whereas concurrent ablation of interferon-gamma (IFN-gamma) ameliorates the disease. The administration of antibodies that block cytotoxic T lymphocyte associated antigen-4 (CTLA-4) to young mutant mice precipitates the onset of insulitis and hyperglycemia. These results, together with previous reports of impaired hematopoietic responses to GM-CSF and IL-3 in patients with T1D and in NOD mice, indicate that functional deficiencies of these cytokines contribute to diabetes.