Pinning and depinning of the polarization of exciton-polariton condensates at room temperature.

A room temperature polariton condensate realized in a microcavity with embedded GaN quantum wells emits linearly polarized light at threshold with the plane of polarization pinned to one of the crystallographic axes. With increasing pumping power, a depinning of the polarization is observed resulting in a progressive decrease of the polarization degree of the emitted light. This depinning is understood in terms of polariton-polariton repulsion competing with the static disorder potential effect. The polarization behavior differs from that of conventional lasers where the polarization degree usually increases as a function of pumping power.

Piperacillin-tazobactam monotherapy in high-risk febrile and neutropenic cancer patients.

Combination therapy with a beta-lactam plus an aminoglycoside has been the standard approach for treating febrile neutropenia for many years. More recently, beta-lactam monotherapy has also been shown to be a reliable and safe approach. In the present study, 763 eligible patients with fever and neutropenia received piperacillin-tazobactam monotherapy. On day 3, according to the study protocol, 165 patients with persistent fever who fulfilled the study entry criteria were randomised to receive vancomycin or a placebo. The success rate was 51% in the intention-to-treat analysis and 62% in the per-protocol analysis. The overall mortality rate was 8% (58/763), with only 18 (2.4%) deaths attributed to the initial or subsequent infection. Randomisation had no influence on the study endpoints. The adverse event rate was evaluated only in the patient population not included in the randomised part of the study. Among these patients, adverse events probably or definitely related to piperacillin-tazobactam therapy were uncommon, confirming the favourable safety profile of piperacillin-tazobactam. It was concluded that piperacillin-tazobactam could be considered as monotherapy for patients with high-risk febrile neutropenia.

Cefepime versus imipenem-cilastatin for treatment of nosocomial pneumonia in intensive care unit patients: a multicenter, evaluator-blind, prospective, randomized study.

In a randomized, evaluator-blind, multicenter trial, we compared cefepime (2 g three times a day) with imipenem-cilastatin (500 mg four times a day) for the treatment of nosocomial pneumonia in 281 intensive care unit patients from 13 centers in six European countries. Of 209 patients eligible for per-protocol analysis of efficacy, favorable clinical responses were achieved in 76 of 108 (70%) patients treated with cefepime and 75 of 101 (74%) patients treated with imipenem-cilastatin. The 95% confidence interval (CI) for the difference between these response rates (-16 to 8%) failed to exclude the predefined lower limit for noninferiority of -15%. In addition, therapy of pneumonia caused by an organism producing an extended-spectrum beta-lactamase (ESBL) failed in 4 of 13 patients in the cefepime group but in none of 10 patients in the imipenem group. However, the clinical efficacies of both treatments appeared to be similar in a secondary intent-to-treat analysis (95% CI for difference, -9 to 14%) and a multivariate analysis (95% CI for odds ratio, 0.47 to 1.75). Furthermore, the all-cause 30-day mortality rates were 28 of 108 (26%) patients in the cefepime group and 19 of 101 (19%) patients in the imipenem group (P = 0.25). Rates of documented or presumed microbiological eradication of the causative organism were similar with cefepime (61%) and imipenem-cilastatin (54%) (95% CI, -23 to 8%). Primary or secondary resistance of Pseudomonas aeruginosa was detected in 19% of the patients treated with cefepime and 44% of the patients treated with imipenem-cilastatin (P = 0.05). Adverse events were reported in 71 of 138 (51%) and 62 of 141 (44%) patients eligible for safety analysis in the cefepime and imipenem groups, respectively (P = 0.23). Although the primary end point for this study does not exclude the possibility that cefepime was inferior to imipenem, some secondary analyses showed that the two regimens had comparable clinical and microbiological efficacies. Cefepime appeared to be less active against organisms producing an ESBL, but primary and secondary resistance to imipenem was more common for P. aeruginosa. Selection of a single agent for therapy of nosocomial pneumonia should be guided by local resistance patterns.

Vancomycin versus placebo for treating persistent fever in patients with neutropenic cancer receiving piperacillin-tazobactam monotherapy.

This prospective, double-blind trial assessed whether the addition of a glycopeptide would be able to reduce the time to defervescence in neutropenic patients with cancer who had persistent fever 48-60 h after the initiation of empirical piperacillin-tazobactam monotherapy. Of 763 eligible patients, 165 with persistent fever were randomized to receive piperacillin-tazobactam therapy plus either vancomycin therapy or placebo. Defervescence was observed in 82 (95%) of 86 patients in the vancomycin group and in 73 (92%) of 79 patients in the placebo group (P=.52). The distributions of the time to defervescence were not statistically significant between the 2 groups (estimated hazard ratio, 1.03; 95% confidence interval, 0.75-1.43; P=.75). The number of additional episodes of gram-positive bacteremia and the percentage of patients for whom amphotericin B was empirically added to their therapy regimen were also similar in both groups. This study failed to demonstrate that the empirical addition of vancomycin therapy to the treatment regimen is of benefit to persistently febrile neutropenic patients with cancer.

Teichoic acids are not required for Streptococcus pneumoniae and Staphylococcus aureus cell walls to trigger the release of tumor necrosis factor by peripheral blood monocytes.

In gram-negative bacteria, the outer membrane lipopolysaccharide is the main component triggering cytokine release from peripheral blood mononuclear cells (PBMCs). In gram-positive bacteria, purified walls also induce cytokine release, but stimulation requires 100 times more material. Gram-positive walls are complex megamolecules reassembling distinct structures. Only some of them might be inflammatory, whereas others are not. Teichoic acids (TA) are an important portion (> or =50%) of gram-positive walls. TA directly interact with C3b of complement and the cellular receptor for platelet-activating factor. However, their contribution to wall-induced cytokine-release by PBMCs has not been studied in much detail. In contrast, their membrane-bound lipoteichoic acids (LTA) counterparts were shown to trigger inflammation and synergize with peptidoglycan (PGN) for releasing nitric oxide (NO). This raised the question as to whether TA are also inflammatory. We determined the release of tumor necrosis factor (TNF) by PBMCs exposed to a variety of TA-rich and TA-free wall fragments from Streptococcus pneumoniae and Staphylococcus aureus. TA-rich walls from both organisms induced measurable TNF release at concentrations of 1 microg/ml. Removal of wall-attached TA did not alter this activity. Moreover, purified pneumococcal and staphylococcal TA did not trigger TNF release at concentrations as high as > or =100 microg/ml. In contrast, purified LTA triggered TNF release at 1 microg/ml. PGN-stem peptide oligomers lacking TA or amino-sugars were highly active and triggered TNF release at concentrations as low as 0.01 microg/ml (P. A. Majcherczyk, H. Langen, et al., J. Biol. Chem. 274:12537-12543,1999). Thus, although TA is an important part of gram-positive walls, it did not participate to the TNF-releasing activity of PGN.

Clinafloxacin monotherapy (CI-960) versus ceftazidime plus amikacin for empirical treatment of febrile neutropenic cancer patients.

OBJECTIVE: To assess the efficacy and safety of clinafloxacin as a single agent for the empirical treatment of febrile episodes and bacterial infections in neutropenic cancer patients. METHODS: An open label, active-controlled, randomized, parallel treatment, multicenter study was conducted where clinafloxacin monotherapy was compared to the combination of ceftazidime plus amikacin (plus optional vancomycin or teicoplanin). Four hundred and nineteen patients were randomized to receive either intravenous clinafloxacin 200 mg every 12 h or intravenous ceftazidime (2 g) iv every 8 h plus intravenous amikacin (15 mg/kg) per day in divided doses. All randomized patients were to receive a minimum of 48 h of primary study drug treatment, after which the primary treatment could be modified. Clinical and microbiological responses were evaluated at 7-21 days post-treatment after study treatment and long term (maximum 28 days), in intent-to-treat and modified intent-to-treat populations. RESULTS: Clinafloxacin and ceftazidime-amikacin were statistically equivalent for the 72-h defervescence rate, overall defervescence rate, time to defervescence, clinical success rate, by-pathogen microbiological eradication rate, and survival rate. Clinical cure was achieved in 84% (59/70) of patients who received clinafloxacin monotherapy. There were no significant differences between treatments in rates of adverse events or treatment discontinuation rates due to adverse events. CONCLUSIONS: Clinafloxacin appears to be an appropriate agent for empirical treatment in febrile neutropenic cancer patients.

BAL9141, a novel extended-spectrum cephalosporin active against methicillin-resistant Staphylococcus aureus in treatment of experimental endocarditis.

The therapeutic efficacy of BAL9141 (formerly Ro 63-9141), a novel cephalosporin with broad in vitro activity that also has activity against methicillin-resistant Staphylococcus aureus (MRSA), was investigated in rats with experimental endocarditis. The test organisms were homogeneously methicillin-resistant S. aureus strain COL transformed with the penicillinase-encoding plasmid pI524 (COL Bla+) and homogeneously methicillin-resistant, penicillinase-producing isolate P8-Hom, selected by serial exposure of parent strain P8 to methicillin. The MICs of BAL9141 for these organisms (2 mg/liter) were low, and BAL9141was bactericidal in time-kill curve studies after 24 h of exposure to either two, four, or eight times the MIC. Rats with experimental endocarditis were treated in a three-arm study with a continuous infusion of BAL5788 (formerly Ro 65-5788), a carbamate prodrug of BAL9141, or with amoxicillin-clavulanate or vancomycin. The rats were administered BAL9141 to obtain steady-state target levels of 20, 10, and 5 mg of per liter or were administered either 1.2 g of amoxicillin-clavulanate (ratio 5:1) every 6 h or 1 g of vancomycin every 12 h at changing flow rates to simulate the pharmacokinetics produced in humans by intermittent intravenous treatment. Treatment was started 12 h after bacterial challenge and lasted for 3 days. BAL9141 was successful in the treatment of experimental endocarditis due to either MRSA isolate COL Bla+ or MRSA isolate P8-Hom at the three targeted steady-state concentrations and sterilized >90% of cardiac vegetations (P < 0.005 versus controls; P < 0.05 versus amoxicillin-clavulanate and vancomycin treatment groups). These promising in vivo results with BAL9141 correlated with the high affinity of the drug for PBP 2a and its stability to penicillinase hydrolysis observed in vitro.

Macrophage migration inhibitory factor (MIF) modulates innate immune responses induced by endotoxin and Gram-negative bacteria.

Discovered in the early 1960s as a T-cell cytokine, MIF has emerged to be an important mediator of the innate immune system. MIF was identified recently to be released by a vast array of cells, including monocytes/macrophages, T-cells, B-cells, endocrine cells and epithelial cells in response to infection and stress. Bacteria, microbial toxins and cytokines have been shown to be powerful inducers of MIF secretion by macrophages. MIF stimulates the expression of pro-inflammatory mediators by immune cells and functions to counterbalance the anti-inflammatory and immunosuppressive effects of glucocorticoids. Like TNF and IL-1, MIF plays an important role in host responses to infection. Recombinant MIF was found to exacerbate lethal endotoxemia or bacterial sepsis when co-injected with LPS or Escherichia coli in mice. Conversely, MIF knockout mice or mice treated with anti-MIF antibodies were protected from shock induced by LPS, staphylococcal exotoxins or bacterial peritonitis, even when anti-MIF therapy was started after the onset of infection. Given the central role played by MIF in innate immune responses against microbial pathogens and in the regulation of inflammatory responses, pharmacological modulation of MIF production or neutralization of MIF activity could have broad clinical applications and may offer new treatment options for the management of patients with severe sepsis or septic shock.

Interplay between galanin and leptin in the hypothalamic control of feeding via corticotropin-releasing hormone and neuropeptide Y.

Over long periods, feeding and metabolism are tightly regulated at the central level. The total amount of nutrients ingested is thought to result from a delicate balance between orexigenic and anorexigenic factors expressed and secreted by specialized hypothalamic neuronal populations. We have developed a system of perifused hypothalamic neurons to characterize the relationships existing between the orexigenic peptide galanin and two other physiological modulators of feeding: neuropeptide Y (NPY) and corticotropin-releasing hormone (CRH). We demonstrated that galanin stimulates CRH and NPY secretion from hypothalamic neurons in a dose-dependent manner. Exposure to leptin for 24 h before galanin stimulation decreased NPY secretion by 30%, leaving the responsiveness of CRH neurons intact. These results suggest that CRH and NPY neurons participate to the intrahypothalamic signaling pathway of galanin, an observation that can explain the lower potency of galanin to stimulate food intake in vivo compared with NPY. The differential effects exerted by leptin on CRH and NPY suggest that there exists a subset of NPY neurons that are exquisitely sensitive to marked variations in leptin levels, and that the CRH neurons are less responsive to increases in leptin concentrations.

Efficacies of moxifloxacin, ciprofloxacin, and vancomycin against experimental endocarditis due to methicillin-resistant Staphylococcus aureus expressing various degrees of ciprofloxacin resistance.

The new 8-methoxyquinolone moxifloxacin was tested against two ciprofloxacin-susceptible Staphylococcus aureus strains (strains P8 and COL) and two ciprofloxacin-resistant derivatives of strain P8 carrying a single grlA mutation (strain P8-4) and double grlA and gyrA mutations (strain P8-128). All strains were resistant to methicillin. The MICs of ciprofloxacin and moxifloxacin were 0.5 and 0.125 mg/liter, respectively, for P8; 0.25 and 0.125 mg/liter, respectively, for COL; 8 and 0.25 mg/liter, respectively, for P8-4; and >or=128 and 2 mg/liter, respectively, for P8-128. In vitro, the rate of spontaneous resistance of P8 and COL was 10(-7) on agar plates containing ciprofloxacin at two times the MIC, whereas it was

Critical role of lipopolysaccharide-binding protein and CD14 in immune responses against gram-negative bacteria.

LPS-binding protein (LBP) and CD14 potentiate cell activation by LPS, contributing to lethal endotoxemia. We analyzed the contribution of LBP/CD14 in models of bacterial infection. Mice pretreated with mAbs neutralizing CD14 or LBP showed a delay in TNF-alpha production and died of overwhelming infection within 24 h, after a challenge with 250 CFU of virulent Klebsiella pneumoniae. Blockade of TNF-alpha also increased lethality, whereas pretreatment with TNF-alpha protected mice, even in the presence of LBP and CD14 blockade. Anti-LBP or anti-CD14 mAbs did not improve or decrease lethality with a higher inoculum (10(5) K. pneumoniae) and did not affect outcome following injections of low or high inocula of Escherichia coli O111. These results point to the essential role of LBP/CD14 in innate immunity against virulent bacteria.

Macrophage migration inhibitory factor and innate immune responses to bacterial infections.

OBJECTIVES: To review the role of macrophage migration inhibitory factor (MIF) in host responses to infection and to explore the potential of MIF as a novel target for therapeutic intervention in patients with severe sepsis and septic shock. DATA SOURCES: Published articles on the role of MIF in innate immune responses against microbial pathogens. DATA SUMMARY: MIF has emerged recently as an important effector molecule of the innate immune system. MIF is expressed constitutively by monocytes/macrophages, T cells, B cells, endocrine cells, and epithelial cells. Microbial toxins and cytokines are powerful inducers of MIF release by immune cells. MIF expression is up-regulated during the course of inflammatory and infectious diseases and was found to play an important role in the pathogenesis of sepsis and septic shock. CONCLUSION: Given the role of MIF in innate immune responses against microbial pathogens and in the regulation of inflammatory responses, modulation of MIF production or neutralization of its activity may offer new therapeutic options for the management of patients with sepsis.

Association between antifungal prophylaxis and rate of documented bacteremia in febrile neutropenic cancer patients.

Published data have suggested a correlation between antifungal prophylaxis and bacteremia in febrile neutropenia. This correlation was investigated among 3002 febrile neutropenic patients enrolled in 4 trials during 1986-1994. Globally, 1322 patients (44%) did not receive antifungal prophylaxis; 835 (28%) received poorly absorbable antifungal agents and 845 (28%) received absorbable antifungal agents. The rates of bacteremia for these groups were 20%, 26%, and 27%, respectively (P=.0001). In a multivariate model without including antifungal prophylaxis, factors associated with bacteremia were: age, duration of hospitalization, duration of neutropenia before enrollment, underlying disease, presence of an intravenous catheter, shock, antibacterial prophylaxis, temperature, and granulocyte count at onset of fever. When antifungal prophylaxis was included, the adjustment quality of the model improved slightly (P=.05), with an odds ratio of 1.19 (95% confidence interval [CI], 0.92-1.55) for patients receiving nonabsorbable and 1.42 (95% CI, 1.07-1.88) for those who were receiving absorbable antifungal agents. Antifungal prophylaxis with absorbable agents might have an impact on the rate of documented bacteremia in febrile neutropenia. This effect should be confirmed prospectively.

Study of Staphylococcus aureus pathogenic genes by transfer and expression in the less virulent organism Streptococcus gordonii.

Because Staphylococcus aureus strains contain multiple virulence factors, studying their pathogenic role by single-gene inactivation generated equivocal results. To circumvent this problem, we have expressed specific S. aureus genes in the less virulent organism Streptococcus gordonii and tested the recombinants for a gain of function both in vitro and in vivo. Clumping factor A (ClfA) and coagulase were investigated. Both gene products were expressed functionally and with similar kinetics during growth by streptococci and staphylococci. ClfA-positive S. gordonii was more adherent to platelet-fibrin clots mimicking cardiac vegetations in vitro and more infective in rats with experimental endocarditis (P < 0.05). Moreover, deleting clfA from clfA-positive streptococcal transformants restored both the low in vitro adherence and the low in vivo infectivity of the parent. Coagulase-positive transformants, on the other hand, were neither more adherent nor more infective than the parent. Furthermore, coagulase did not increase the pathogenicity of clfA-positive streptococci when both clfA and coa genes were simultaneously expressed in an artificial minioperon in streptococci. These results definitively attribute a role for ClfA, but not coagulase, in S. aureus endovascular infections. This gain-of-function strategy might help solve the role of individual factors in the complex the S. aureus-host relationship.

Sensitive bioassay for determination of fluconazole concentrations in plasma using a Candida albicans mutant hypersusceptible to azoles.

The antifungal agent fluconazole (FLC) is widely used in clinical practice. Monitoring FLC levels is useful in complicated clinical settings and in experimental infection models. A bioassay using Candida pseudotropicalis, a simple and cost-effective method, is validated only for FLC levels ranging from 5 to 40 mg/liter. An extension of the analytical range is needed to cover most yeast MICs. A new bioassay in RPMI agar containing methylene blue was developed using C. albicans DSY1024, a mutant rendered hypersusceptible to FLC constructed by the deletion of the multidrug efflux transporter genes CDR1, CDR2, CaMDR1, and FLU1. Reproducible standard curves were obtained with FLC concentrations in plasma ranging from 1 to 100 mg/liter (quadratic regression coefficient > 0.997). The absolute sensitivity was 0.026 microg of FLC. The method was internally validated according to current guidelines for analytical method validation. Both accuracy and precision lied in the required +/-15% range. FLC levels measured by bioassay and by high-performance liquid chromatography (HPLC) performed with 62 plasma samples from humans and rats showed a strong correlation (coefficients, 0.979 and 0.995, respectively; percent deviations of bioassay from HPLC values, 0.44% +/- 15.31% and 2.66% +/- 7.54%, respectively). In summary, this newly developed bioassay is sensitive, simple, rapid, and inexpensive. It allows nonspecialized laboratories to determine FLC levels in plasma to within the clinically relevant concentration range and represents a useful tool for experimental treatment models.

CD14 expression on monocytes and TNF alpha production in patients with septic shock, cardiogenic shock or bacterial pneumonia.

OBJECTIVES: In patients with septic shock, circulating monocytes become refractory to stimulation with microbial products. Whether this hyporesponsive state is induced by infection or is related to shock is unknown. To address this question, we measured TNF alpha production by monocytes or by whole blood obtained from healthy volunteers (controls), from patients with septic shock, from patients with severe infection (bacterial pneumonia) without shock, and from patients with cardiogenic shock without infection. MEASUREMENTS: The numbers of circulating monocytes, of CD14+ monocytes, and the expression of monocyte CD14 and the LPS receptor, were assessed by flow cytometry. Monocytes or whole blood were stimulated with lipopolysaccharide endotoxin (LPS), heat-killed Escherichia coli or Staphylococcus aureus, and TNF alpha production was measured by bioassay. RESULTS: The number of circulating monocytes, of CD14+ monocytes, and the monocyte CD14 expression were significantly lower in patients with septic shock than in controls, in patients with bacterial pneumonia or in those with cardiogenic shock (p < 0.001). Monocytes or whole blood of patients with septic shock exhibited a profound deficiency of TNF alpha production in response to all stimuli (p < 0.05 compared to controls). Whole blood of patients with cardiogenic shock also exhibited this defect (p < 0.05 compared to controls), although to a lesser extent, despite normal monocyte counts and normal CD14 expression. CONCLUSIONS: Unlike patients with bacterial pneumonia, patients with septic or cardiogenic shock display profoundly defective TNF alpha production in response to a broad range of infectious stimuli. Thus, down-regulation of cytokine production appears to occur in patients with systemic, but not localised, albeit severe, infections and also in patients with non-infectious circulatory failure. Whilst depletion of monocytes and reduced monocyte CD14 expression are likely to be critical components of the hyporesponsiveness observed in patients with septic shock, other as yet unidentified factors are at work in this group and in patients with cardiogenic shock.

MIF regulates innate immune responses through modulation of Toll-like receptor 4.

Macrophages are pivotal effector cells of the innate immune system, which is vital for recognizing and eliminating invasive microbial pathogens. When microbial products bind to pathogen-recognition receptors, macrophages become activated and release a broad array of cytokines that orchestrate the host innate and adaptive immune responses. Initially identified as a T-cell cytokine, macrophage migration inhibitory factor (MIF) is also a macrophage cytokine and an important mediator of inflammation and sepsis. Here we report that MIF is an essential regulator of macrophage responses to endotoxin (lipopolysaccharide) and Gram-negative bacteria. Compared with wild-type cells, MIF-deficient macrophages are hyporesponsive to lipopolysaccharide and Gram-negative bacteria, as shown by a profound reduction in the activity of NF-kappaB and the production of tumour-necrosis factor-alpha. This reduction is due to a downregulation of Toll-like receptor 4 (TLR4), the signal-transducing molecule of the lipopolysaccharide receptor complex, and is associated with decreased activity of transcription factor PU.1, which is required for optimal expression of the Tlr4 gene in myeloid cells. These findings identify an important role for MIF in innate immunity and provide a molecular basis for the resistance of MIF-deficient mice to endotoxic shock.

Role of plasma, lipopolysaccharide-binding protein, and CD14 in response of mouse peritoneal exudate macrophages to endotoxin.

Plasma lipopolysaccharide (LPS)-binding protein (LBP) and membrane CD14 function to enhance the responses of monocytes to low concentrations of endotoxin. Surprisingly, recent reports have suggested that LBP or CD14 may be dispensable for macrophage responses to low concentrations of LPS or may even exert an inhibitory effect in the case of LBP. We therefore investigated whether LBP and CD14 participated in the response of mouse peritoneal exudate macrophages (PEM) to LPS stimulation. In the presence of a low amount of plasma (<1%) or of recombinant mouse or human LBP, PEM were found to respond to low concentrations of LPS (<5 to 10 ng/ml) in an LBP- and CD14-dependent manner. However, tumor necrosis factor production (not interleukin-6 production) by LPS-stimulated PEM was reduced when cells were stimulated in the presence of higher concentrations of plasma or serum (5 or 10%). Yet, the inhibitory effect of plasma or serum was not mediated by LBP. Taken together with previous results obtained with LBP and CD14 knockout mice in models of experimental endotoxemia, the present data confirm a critical part for LBP and CD14 in innate immune responses of both blood monocytes and tissue macrophages to endotoxins.