Immunomodulating effect of fosfomycin on gut-derived sepsis caused by Pseudomonas aeruginosa in mice

The Efficacy of Phage Therapy in a Murine Model of Pseudomonas aeruginosa Pneumonia and Sepsis

The emergence of multi-drug resistant Pseudomonas aeruginosa necessitates the search for treatment options other than antibiotic use. The use of bacteriophages is currently being considered as an alternative to antibiotics for the treatment of bacterial infections. A number of bacteriophages were introduced to treat pneumonia in past reports. However, there are still lack of knowledge regarding the dosages, application time, mechanism and safety of phage therapy against P. aeruginosa pneumonia. We used the bacteriophage KPP10 against P. aeruginosa strain D4-induced pneumonia mouse models and observed their outcomes in comparison to control models. We found that the nasal inhalation of highly concentrated KPP10 (MOI = 80) significantly improved survival rate in pneumonia models (P < 0.01). The number of viable bacteria in both lungs and in serum were significantly decreased (P < 0.01) in phage-treated mice in comparison to the control mice. Pathological examination showed that phage-treated group had significantly reduced bleeding, inflammatory cell infiltration, and mucus secretion in lung interstitium. We also measured inflammatory cytokine levels in the serum and lung homogenates of mice. In phage-treated models, serum TNFα, IL-1β, and IFN-γ levels were significantly lower (P < 0.05, P < 0.01, and P < 0.05, respectively) than those in the control models. In the lung homogenate, the mean IL-1β level in phage-treated models was significantly lower (P < 0.05) than that of the control group. We confirmed the presence of phage in blood and lungs, and evaluated the safety of bacteriophage use in living models since bacteriophage mediated bacterial lysis arise concern of endotoxic shock. The study results suggest that phage therapy can potentially be used in treating lung infections caused by Pseudomonas aeruginosa.

Efficacy of single and multiple oral doses of fosfomycin against Pseudomonas aeruginosa urinary tract infections in a dynamic in vitro bladder infection model

OBJECTIVES

We used a dynamic bladder infection in vitro model with synthetic human urine (SHU) to examine fosfomycin exposures to effectively kill, or prevent emergence of resistance, among Pseudomonas aeruginosa isolates.

METHODS

Dynamic urinary fosfomycin concentrations after 3 g oral fosfomycin were simulated, comparing single and multiple (daily for 7 days) doses. Pharmacodynamic response of 16 P. aeruginosa (MIC range 1 to >1024 mg/L) were examined. Baseline disc diffusion susceptibility, broth microdilution MIC and detection of heteroresistance were assessed. Pathogen kill and emergence of resistance over 72 h following a single dose, and over 216 h following daily dosing for 7 days, were investigated. The fAUC0-24/MIC associated with stasis and 1, 2 and 3 log10 kill were determined.

RESULTS

Pre-exposure high-level resistant (HLR) subpopulations were detected in 11/16 isolates after drug-free incubation in the bladder infection model. Five of 16 isolates had >2 log10 kill after single dose, reducing to 2/16 after seven doses. Post-exposure HLR amplification occurred in 8/16 isolates following a single dose and in 11/16 isolates after seven doses. Baseline MIC ≥8 mg/L with an HLR subpopulation predicted post-exposure emergence of resistance following the multiple doses. A PK/PD target of fAUC0-24/MIC >5000 was associated with 3 log10 kill at 72 h and 7 day-stasis.

CONCLUSIONS

Simulated treatment of P. aeruginosa urinary tract infections with oral fosfomycin was ineffective, despite exposure to high urinary concentrations and repeated daily doses for 7 days. Emergence of resistance was observed in the majority of isolates and worsened following prolonged therapy. Detection of a baseline resistant subpopulation predicted treatment failure.

Response of Lactobacillus plantarum WCFS1 to the Gram-Negative Pathogen-Associated Quorum Sensing Molecule N-3-Oxododecanoyl Homoserine Lactone

The bacterial quorum sensing phenomenon has been well studied since its discovery and has traditionally been considered to include signaling pathways recognized exclusively within either Gram-positive or Gram-negative bacteria. These groups of bacteria synthesize structurally distinct signaling molecules to mediate quorum sensing, where Gram-positive bacteria traditionally utilize small autoinducing peptides (AIPs) and Gram-negatives use small molecules such as acyl-homoserine lactones (AHLs). The structural differences between the types of signaling molecules have historically implied a lack of cross-talk among Gram-positive and Gram-negative quorum sensing systems. Recent investigations, however, have demonstrated the ability for AIPs and AHLs to be produced by non-canonical organisms, implying quorum sensing systems may be more universally recognized than previously hypothesized. With that in mind, our interests were piqued by the organisms Lactobacillus plantarum, a Gram-positive commensal probiotic known to participate in AIP-mediated quorum sensing, and Pseudomonas aeruginosa, a characterized Gram-negative pathogen whose virulence is in part controlled by AHL-mediated quorum sensing. Both health-related organisms are known to inhabit the human gut in various instances, both are characterized to elicit distinct effects on host immunity, and some studies hint at the putative ability of L. plantarum to degrade AHLs produced by P. aeruginosa. We therefore wanted to determine if L. plantarum cultures would respond to the addition of N-(3-oxododecanoyl)-L-homoserine lactone (3OC12) from P. aeruginosa by analyzing changes on both the transcriptome and proteome over time. Based on the observed upregulation of various two-component systems, response regulators, and native quorum sensing related genes, the resulting data provide evidence of an AHL recognition and response by L. plantarum.

Ex vivo penetration of fosfomycin into healthy and Lawsonia intracellularis-colonized swine intestinal mucosa

Fosfomycin (FOS) is an antibiotic used, mostly in Latin America, for the treatment of lung and enteric infections of pigs. Intracellular fluids of enterocytes can act as biophase for Lawsonia intracellularis, the causative agent of porcine proliferative enteropathy (PPE). The aim of this study was to determine whether the presence of L. intracellularis in the enterocytes modifies FOS penetration. Eight healthy pigs in growth-finishing stage were used to produce healthy (group A) and L. intracellularis-colonized (group B) intestinal explants. For both groups, treatment consisted of a 580 μg/ml concentration of calcium FOS, which was added to each explant (0.5-6 hr). For group B, the Enterisol Ileitis^® vaccine was used as source of the micro-organism. Previously to the assay, the time necessary for L. intracellularis to colonize the enterocytes was defined. Also, a PCR protocol was optimized to determine the presence of the pathogen in the explants. There were nonstatistical differences for the penetration of the antibiotic into healthy and L. intracellularis-colonized enterocytes. MIC₉₀ of FOS for L. intracellularis is unknown; nevertheless, MIC₉₀ of various antibiotics ranges between 0.125 and 128 μg/ml. FOS reaches inside the enterocyte concentrations which surpass the MICs₉₀ of other antibiotics that also act by the inhibition of cell wall synthesis; however, further studies should be carried out to determine fosfomycin MIC₉₀ for L. intracellularis to discern the usefulness of this antibiotic in the treatment of PPE.

Fosfomycin: Uses and potentialities in veterinary medicine

Fosfomycin (FOS) is a natural bactericidal broad-spectrum antibiotic which acts on proliferating bacteria by inhibiting cell wall and early murein/peptidoglycan synthesis. Bactericidal activity is evident against Gram positive and Gram negative bacteria and can also act synergistically with other antibiotics. Bacterial resistance to FOS may be natural or acquired. Other properties of this drug include inhibition of bacterial adhesion to epithelial cells, exopolysaccharide biofilm penetration, immunomodulatory effect, phagocytosis promotion and protection against the nephrotoxicity caused by other drugs. FOS has chemical characteristics not typically observed in organic phosphoric compounds and its molecular weight is almost the lowest of all the antimicrobials. It tends to form salts easily due to its acidic nature (disodium salt, for intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration; calcium and trometamol salt: for oral (PO) administration). FOS has a very low protein binding (<0.5%) which, along with its low molecular weight and water solubility, contributes to its good diffusion into fluids (cerebrospinal fluid, aqueous and vitreous humor, interstitial fluid) and tissues (placenta, bone, muscle, liver, kidney and skin/fat). In all species, important differences in the bioavailability have been found after administration in relation to the various derivatives of FOS salts. Pharmacokinetic profiles have been described in humans, chickens, rabbits, cows, dogs, horses and weaning piglets. The low toxicity and potential efficacy of FOS are the main factors that contribute to its use in humans and animals. Thus, it has been used to treat a broad variety of bacterial infections in humans, such as localized peritonitis, brain abscesses, severe soft tissue infections, cystitis and other conditions. In veterinary medicine, FOS is used to treat infectious diseases of broiler chickens and pigs. In broilers, it is administered for the treatment of E. coli and Salmonella spp. infections. In piglets, the drug is prescribed to treat a wide variety of bacterial infections. FOS penetration is demonstrated in phagocytic, respiratory (HEP-2) and intestinal (IPEC-J2) cells. Although not widely used in animals, the drug has shown good results in human medicine. The potentialities of FOS suggest that this drug is a promising candidate for the treatment of infections in veterinary medicine. For these reasons, the aim of this work is to provide animal health practitioners with information on a drug that is not extensively recognized.

The revival of fosfomycin

Fosfomycin, originally named phosphonomycin, was discovered in Spain in 1969. There are three forms of fosfomycin: fosfomycin tromethamine (a soluble salt) and fosfomycin calcium for oral use, and fosfomycin disodium for intravenous use. Fosfomycin is a bactericidal antibiotic that interferes with cell wall synthesis in both Gram-positive and Gram-negative bacteria by inhibiting the initial step involving phosphoenolpyruvate synthetase. It has a broad spectrum of activity against a wide range of Gram-positive and Gram-negative bacteria. It is highly active against Gram-positive pathogens such as Staphylococcus aureus and Enterococcus, and against Gram-negative bacteria such as Pseudomonas aeruginosa and Klebsiella pneumoniae. Its unique mechanism of action may provide a synergistic effect to other classes of antibiotics including beta-lactams, aminoglycosides, and fluoroquinolones. Oral fosfomycin is mainly used in the treatment of urinary tract infections, particularly those caused by Escherichia coli and Enterococcus faecalis. Intravenous fosfomycin has been administered in combination with other antibiotics for the treatment of nosocomial infections due to multidrug-resistant (MDR) Gram-positive and Gram-negative bacteria. Fosfomycin has good distribution into tissues, achieving clinically relevant concentrations in serum, kidneys, bladder wall, prostate, lungs, inflamed tissues, bone, cerebrospinal fluid, abscess fluid, and heart valves. Fosfomycin is well tolerated, with a low incidence of adverse events. Further randomized controlled trials are needed in order to evaluate the efficacy of intravenous fosfomycin for the management of nosocomial infections due to MDR pathogens.

Translocation of Pseudomonas aeruginosa from the intestinal tract is mediated by the binding of ExoS to an Na,K-ATPase regulator, FXYD3

The intestinal tract is considered the most important reservoir of Pseudomonas aeruginosa in intensive care units (ICUs). Gut colonization by P. aeruginosa underlies the development of invasive infections such as gut-derived sepsis. Intestinal colonization by P. aeruginosa is associated with higher ICU mortality rates. The translocation of endogenous P. aeruginosa from the colonized intestinal tract is an important pathogenic phenomenon. Here we identify bacterial and host proteins associated with bacterial penetration through the intestinal epithelial barrier. We first show by comparative genomic hybridization analysis that the exoS gene, encoding the type III effector protein, ExoS, was specifically detected in a clinical isolate that showed higher virulence in silkworms following midgut injection. We further show using a silkworm oral infection model that exoS is required both for virulence and for bacterial translocation from the midgut to the hemolymph. Using a bacterial two-hybrid screen, we show that the mammalian factor FXYD3, which colocalizes with and regulates the function of Na,K-ATPase, directly binds ExoS. A pulldown assay revealed that ExoS binds to the transmembrane domain of FXYD3, which also interacts with Na,K-ATPase. Na,K-ATPase controls the structure and barrier function of tight junctions in epithelial cells. Collectively, our results suggest that ExoS facilitates P. aeruginosa penetration through the intestinal epithelial barrier by binding to FXYD3 and thereby impairing the defense function of tight junctions against bacterial penetration.

Fosfomycin suppresses RS-virus-induced Streptococcus pneumoniae and Haemophilus influenzae adhesion to respiratory epithelial cells via the platelet-activating factor receptor

Human respiratory syncytial virus (RSV) sometimes causes acute and severe lower respiratory tract illness in infants and young children. The platelet-activating factor (PAF) receptor, which is a receptor for Streptococcus pneumoniae and Haemophilus influenzae, is upregulated by RSV infection in the pulmonary epithelial cell line A549. Fosfomycin, an antimicrobial agent, significantly suppressed PAF receptor induction by RSV infection at the mRNA and cell surface expression levels. Fosfomycin also suppressed RSV-induced adhesion of fluorescence-labeled S. pneumoniae and H. influenzae cells, as determined by flow cytometry and fluorescence microscopy. The RSV-induced bacterial adhesion was suggested to be host-PAF-receptor and bacterial-phosphocholine mediated. Fosfomycin, which has been shown to exhibit antimicrobial and immunomodulatory activities, was found here to suppress adhesion by disease-causing bacteria. Thus, fosfomycin might prevent secondary bacterial infection during RSV infection.

Clinical significance of the pharmacokinetic and pharmacodynamic characteristics of fosfomycin for the treatment of patients with systemic infections

The advancing antimicrobial drug resistance in common bacterial pathogens, along with the relative shortage of new antibacterial agents, call for the re-evaluation of available therapeutic options. Fosfomycin is an established treatment option for uncomplicated urinary tract infections. Here we review and evaluate the main pharmacokinetic and pharmacodynamic parameters of intravenously administered fosfomycin with regard to its use for systemic infections. Fosfomycin is a relatively small, hydrophilic agent with almost negligible serum protein binding. It is excreted unchanged in urine, achieving high concentrations for a prolonged period. Fosfomycin has good distribution into tissues, achieving clinically relevant concentrations in sites such as serum, soft tissue, lungs, bone, cerebrospinal fluid and heart valves. Fosfomycin has shown antimicrobial activity against biofilms, particularly in combination with fluoroquinolones. It also exerts immunomodulatory effects, mainly on lymphocyte and neutrophil function. Potentially useful properties of fosfomycin regarding its use in combination regimens include reduction in the expression of certain penicillin-binding proteins and attenuation of nephrotoxicity caused by several antimicrobial agents. In conclusion, the pharmacokinetic and pharmacodynamic properties of fosfomycin do not preclude its use for various types of systemic infections and suggest further research on relevant clinical applications of this agent.

Pharmacokinetics of disodium-fosfomycin in mongrel dogs

Pharmacokinetic variables of fosfomycin were determined after administration of buffered disodium-fosfomycin intravenously (IV), intramuscularly (IM), subcutaneously (SC) and orally (PO), in mongrel dogs, at 40 and 80 mg/kgday for three days. Renal integrity was also assessed by measuring key serum variables. Day 1, day 2 and day 3 plasma concentration vs. time profiles were undistinguishable, but there appears to be a lineal increase in serum concentrations vs. time with the dose. A non-accumulative kinetic behavior was observed after three days with both doses and most pharmacokinetic variables remain unaltered. Considering a MIC range from 1 mirog/mL to 16 microg/mL of fosfomycin in serum for sensitive bacteria, and a negligible plasma protein binding of fosfomycin (<0.5%), useful plasma concentrations can only be achieved after the SC injection of 80 mg/kg every 12h, having a C(max)=18.96+/-0.3 microg/mL; a T(1/2beta)=2.09+/-0.06 microg/mL and a bioavailability of 84-85%. No alterations were observed in serum variables of kidney-related biochemical values.

Oral administration of Bifidobacterium longum prevents gut-derived Pseudomonas aeruginosa sepsis in mice

AIMS

The aim of the study was to evaluate the efficacy of probiotics on gut-derived sepsis caused by Pseudomonas aeruginosa in immunocompromised mice.

METHODS AND RESULTS

After oral inoculation of P. aeruginosa, mice were treated with cyclophosphamide to induce leucopenia and translocation of the intestinal P. aeruginosa into blood, thereby producing gut-derived sepsis. In this model, administration of 1 x 10(9) CFU of Bifidobacterium longum strain BB536 for 10 days significantly (P < 0.01) increased the survival rate compared with groups of mice administered either with Bifidobacterium breve strain ATCC 15700 or excipients contained in the probiotic bacterial powder. Administration of B. longum significantly decreased viable counts of P. aeruginosa in the liver and blood compared with other groups. Culture of intestinal contents revealed a significantly lower viable count of P. aeruginosa in the jejunum of B. longum-treated mice compared with other groups of mice. Furthermore, in vitro data demonstrated that B. longum possessed apparently higher adherent activity to Caco-2 cell monolayers and significantly suppressed the adherence of P. aeruginosa to the monolayers of cells compared with other groups.

CONCLUSION

Oral administration of B. longum protects mice against gut-derived sepsis caused by P. aeruginosa, and the effect may be due to interference of P. aeruginosa adherence to intestinal epithelial cells. SIGNIFICANCE AND IMPACT OF THIS STUDY: This study demonstrated that oral administration of B. longum BB536 is effective to protect against opportunistic infection with drug-resistant bacteria such as P. aeruginosa. The results suggest that probiotics may play an important role even in the immunocompromised patients.

Intravenous and intramuscular pharmacokinetics of a single-daily dose of disodium-fosfomycin in cattle, administered for 3 days

Pharmacokinetic parameters of fosfomycin in cattle were determined after administration of buffered disodium fosfomycin either intravenously (i.v.) or intramuscularly (i.m.) at a dose of 20 mg/kg/day for 3 days. Calculated concentrations at time zero and maximum serum concentrations were 34.42 and 10.18 mug/mL, respectively. The variables determined, the elimination half-life of the drug remained unchanged during the 3 days ( = 1.33 +/- 0.3 h for the i.v. route and = 2.17 +/- 0.4 h for the i.m. route). Apparent volumes of distribution suggest moderated distribution out of the central compartment (V(darea) = 673 mL +/- 27 mL/kg and V(dss) = 483 +/- 11 mL/kg). Bioavailability after i.m. administration was 74.52%. Considering fosfomycin as a time-dependent antibacterial drug, plasma concentration vs. time profiles obtained in this study, suggest that clinically effective plasma concentrations of fosfomycin could be obtained for up to 8 h following i.v. administration and approximately 10 h after i.m. injection of 20 mg/kg, for susceptible bacteria. In addition to residue studies in milk and edible tissues, a series of clinical assessments, using fosfomycin at 20 mg/kg b.i.d. or t.i.d. are warranted before this antibacterial drug should be considered for use in cattle.

Immunomodulatory effects of fosfomycin in experimental human endotoxemia

To evaluate the effect of fosfomycin on proinflammatory cytokines, a bolus of 2 ng of bacterial lipopolysaccharide/kg of body weight was injected intravenously into healthy volunteers. After 2 h, subjects received 8 g of fosfomycin or placebo in a randomized crossover study design. The resulting concentrations of tumor necrosis factor alpha, interleukin-1beta (IL-1beta), and IL-6 expressed as protein and mRNA levels were almost identical with and without fosfomycin.

Efficacy of bacteriophage therapy against gut-derived sepsis caused by Pseudomonas aeruginosa in mice

We evaluated the efficacy of bacteriophage (phage) therapy by using a murine model of gut-derived sepsis caused by Pseudomonas aeruginosa that closely resembles the clinical pathophysiology of septicemia in humans. Oral administration of a newly isolated lytic phage strain (KPP10) significantly protected mice against mortality (survival rates, 66.7% for the phage-treated group versus 0% for the saline-treated control group; P<0.01). Mice treated with phage also had lower numbers of viable P. aeruginosa cells in their blood, liver, and spleen. The levels of inflammatory cytokines (tumor necrosis factor alpha TNF-alpha, interleukin-1beta [IL-1beta], and IL-6) in blood and liver were significantly lower in phage-treated mice than in phage-untreated mice. The number of viable P. aeruginosa cells in fecal matter in the gastrointestinal tract was significantly lower in phage-treated mice than in the saline-treated control mice. We also studied the efficacy of phage treatment for intraperitoneal infection caused by P. aeruginosa and found that phage treatment significantly improved the survival of mice, but only under limited experimental conditions. In conclusion, our findings suggest that oral administration of phage may be effective against gut-derived sepsis caused by P. aeruginosa.

Virulence of Pseudomonas aeruginosa in a murine model of gastrointestinal colonization and dissemination in neutropenia

Pseudomonas aeruginosa bacteremia in cancer patients develops from initial gastrointestinal (GI) colonization with translocation into the bloodstream in the setting of chemotherapy-induced neutropenia and GI mucosal damage. We established a reproducible mouse model of P. aeruginosa GI colonization and systemic spread during neutropenia. Mice received 2 mg of streptomycin/ml of drinking water and 1,500 U of penicillin G/ml for 4 days and then ingested 10(7) CFU of P. aeruginosa per ml of drinking water for 5 days. After GI colonization levels were determined, cyclophosphamide (Cy) was then injected intraperitoneally (i.p.) three times every other day or an antineutrophil monoclonal antibody, RB6-8C5, was injected i.p. once. Dissemination was defined by the presence of P. aeruginosa in spleens of moribund or dead mice. In this mouse model, P. aeruginosa colonizes the GI tract and then disseminates systemically once Cy or RB6-8C5 is administered. The duration and intensity of neutropenia, related to Cy dose, was found to be a means to compare the virulence of different P. aeruginosa strains, as exhibited by comparisons of strains lacking or producing the virulence-enhancing ExoU cytotoxin. The lipopolysaccharide outer core polysaccharide and O side chains were critical in establishing GI colonization, and P. aeruginosa mutants lacking the aroA gene (necessary for synthesizing aromatic amino acids) were able to establish GI colonization but unable to disseminate. Both the colonization and dissemination phases of P. aeruginosa pathogenesis can be studied in this model, which should prove useful for evaluating pathogenesis, therapies, and associated means to control P. aeruginosa nosocomial infections.

Modulatory effect of fosfomycin on acute inflammation in the rat air pouch model

We examined the effect of fosfomycin (FOM) on the inflammatory response induced by carrageenan in the rat. Air pouches were induced subcutaneously on the backs of rats and injected with carrageenan. The rats were treated with either vehicle or FOM at a dose of 100 mg/kg 1 h before carrageenan challenge. After carrageenan challenge (48 h), the air pouches were removed and analyzed. The volume, protein amounts and cell counts in the exudate obtained from FOM-treated animals were significantly reduced compared with that from vehicle-treated animals. The contents of PGE(2) and TNF-alpha, and mRNA for cyclooxygenase-2 were also markedly suppressed in FOM-treated rats. Histological examination showed suppression of the inflammatory response in the pouch tissues from FOM-treated rats.

Time- and dose-dependent effect of fosfomycin on suppression of infection-induced endotoxin shock in mice

Therapeutic effects of fosfomycin (FOF) and imipenem (IPM) were investigated in a novel model for endotoxin shock that was caused by intraperitoneal (i.p.) infection with 10(8) colony forming units of attenuated Salmonella typhimurium. Acute lethal shock was observed in BALB/c and ddY but not in lipopolysaccharide (LPS)-nonresponder BALB/lps(d) mice. Effects of FOF, but not its enantiomer, and IPM were dose- and time-dependent, since therapeutic efficacy was demonstrated in mice injected i.p. or orally at doses of more than 20 mg/kg 15 min before or 1 h after infection. Treatment with FOF 1 h postinfection (p.i.) resulted in significant decreases in bacterial numbers in spleen and liver, suggesting that the antimicrobial activity of FOF seems to closely correlate to suppression of infection-induced lethal shock. Regarding coagulation systems, FOF inhibited increase in the prothrombin time but upregulated fibrinogen concentration. Plasma levels of LPS released from bacilli were significantly higher in FOF- than IPM-treated mice and infection controls, but both antibiotics showed similar efficacy in protection.

Fosfomycin inhibits neutrophil function via a protein kinase C-dependent signaling pathway

We investigated effects of fosfomycin (FOM) on neutrophil function, specifically the oxidative burst and adhesion molecule expression (CD11b/CD18, or MAC-1) using flow cytometry assay. Preincubation of polymorphonuclear leukocytes (PMNL) with FOM from 1 to 100 microg/ml prior to stimulation by phorbol 12-myristate 13-acetate (PMA, 2 ng/ml) significantly suppressed the oxidative burst in a concentration-dependent manner. However, FOM did not affect the oxidative burst of PMNL stimulated by a chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (FMLP). Stimulation with PMA (2 ng/ml) caused a rapid up-regulation of CD11b surface expression on PMNL, followed by time-dependent loss of this receptor. FOM also suppressed loss of CD11b in PMNL stimulated by PMA. FOM then inhibits the PMA-induced oxidative burst and CD11b epitope loss in PMNL. The suppressive effect appears to be mediated by the protein kinase C-dependent signaling pathway.

Modulation of release of proinflammatory bacterial compounds by antibacterials: potential impact on course of inflammation and outcome in sepsis and meningitis

Several bacterial components (endotoxin, teichoic and lipoteichoic acids, peptidoglycan, DNA, and others) can induce or enhance inflammation and may be directly toxic for eukaryotic cells. Bactericidal antibiotics which inhibit bacterial protein synthesis release smaller quantities of proinflammatory/toxic bacterial compounds than B-lactams and other cell wall-active drugs. Among the B-lactams, compounds binding to penicillin-binding protein 2 (PBP-2) release smaller amounts of bacterial substances than antibacterials inhibiting PBP-3. Generally, high antibiotic concentrations (more than 10 times the MIC) induce the release of fewer bacterial proinflammatory/toxic compounds than concentrations close to the MIC. In several in vitro and in vivo systems, bacteria treated with protein synthesis inhibitors or B-lactams inhibiting PBP-2 induce less inflammation than bacteria treated with PBP-3-active B-lactams. In mouse models of Escherichia coli peritonitis sepsis and of Streptococcus pneumoniae meningitis, lower release of proinflammatory bacterial compounds was associated with reduced mortality. In conclusion, sufficient evidence for the validity of the concept of modulating the release of proinflammatory bacterial compounds by antibacterials has been accumulated in vitro and in animal experiments to justify clinical trials in sepsis and meningitis. A properly conducted study addressing the potential benefit of bacterial protein synthesis inhibitors versus B-lactam antibiotics will require both strict selection and inclusion of a large number of patients. The benefit of this approach should be greatest in patients with a high bacterial load.

Fosfomycin nebulizer therapy to chronic sinusitis

OBJECTIVE

effects of Fosfomycin (FOM) nebulizer therapy were studied in patients with chronic sinusitis.

METHODS

about 28 patients with chronic sinusitis were administered 2 ml of FOM sodium (3% w/v) by nebulizer three times per week for 4 weeks. Levels of IL-1 beta, IL-6, IL-8, and TNF-alpha in nasal lavage were also measured before and at the end of treatment.

RESULTS

the overall efficacy of this treatment on the basis of both subjective and objective symptoms, was 'excellent' for 28.6%, 'good' for 10.7%, 'fair' for 39.4%, and yield 'no change' for 21.4% of the patients. Both IL-1 beta and IL-6 concentrations were significantly decreased after treatment. Although the IL-8 level did not significantly decrease, it seems to be related to the overall efficacy. TNF-alpha was not detected in all of the samples.

CONCLUSION

FOM nebulization therapy is highly effective in treatment for chronic sinusitis, and efficacy may be due to an immunomodulatory mechanism, as well as its bactericidal effect.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Effect of antiflagellar human monoclonal antibody on gut-derived Pseudomonas aeruginosa sepsis in mice

We evaluated the effect of antiflagellar human monoclonal antibody on gut-derived Pseudomonas aeruginosa sepsis. Mice were given a suspension of P. aeruginosa SP10052 in their drinking water and were simultaneously treated with ampicillin (200 mg/kg of body weight) to disrupt the normal bacterial flora. Cyclophosphamide was then administered to induce leukopenia and translocation of the P. aeruginosa that had colonized the gastrointestinal tract, thereby producing gut-derived generalized sepsis. In this model, intraperitoneal injection of 100 microg of antiflagellar human monoclonal antibody (SC-1225) per mouse for 5 consecutive days significantly (P < 0.01) increased the survival rate compared with that for mice treated with bovine serum albumin (BSA). Treatment with SC-1225 significantly reduced the average number of viable bacteria in portal blood, liver, and heart blood compared with the average number after treatment with BSA. Furthermore, the presence in serum of the inflammatory cytokines tumor necrosis factor alpha and interleukin 6 were evaluated as markers of severity of infection, and the results showed that the levels of these cytokines in mice treated with SC-1225 were significantly decreased in comparison with those in BSA-treated control mice. Although there was no significant difference in the number of bacteria that colonized the intestine, SC-1225 treatment significantly increased bacterial opsonophagocytosis by cultured peritoneal macrophages from mice with or without cyclophosphamide pretreatment. Our results indicate that antiflagellar human monoclonal antibody SC-1225 protects mice against gut-derived sepsis caused by P. aeruginosa and suggest that such an effect is due to its opsonophagocytic activity and the reduced motility of the translocated bacteria once the bacteria move from the intestine into the bloodstream.

Paradoxical synergistic effects of tumour necrosis factor and interleukin 1 in murine gut-derived sepsis with Pseudomonas aeruginosa

The authors evaluated the synergistic effect of tumour necrosis factor (TNF) and interleukin 1 (IL-1) in gut-derived sepsis in mice. After colonization of Pseudomonas aeruginosa strain D4 in the gastrointestinal tract, cyclophosphamide was administered to induce bacterial translocation of the P. aeruginosa and thereby to cause gut-derived sepsis. In this model, treatment either with 8 microg/kg of recombinant human TNF-alpha (rhTNF-alpha) or 2 microg/kg of recombinant human interleukin 1alpha (rhIL-1alpha) solely did not affect the mortality, whereas combined administration of the same doses of rhTNF-alpha and rhIL-1alpha significantly increased the mortality rate in comparison with saline-treated mice. Bacterial counts in liver and blood were significantly higher in rhTNF-alpha and rhIL-1alpha treated mice than in saline-treated mice. Endogenous TNF-alpha and IL-1beta productions were stimulated after combined treatment with rhTNF-alpha and rhIL-1alpha. On the contrary to these adverse effects, combined treatment with 500 microg/kg of rhTNF-alpha and 50 microg/kg of rhIL-1alpha on the day before the administration of cyclophosphamide significantly reduced the mortality from septic infection. We conclude that TNF and IL-1 synergistically affect the mortality of mice after gut-derived sepsis due to P. aeruginosa in mice and the timing of treatment with these cytokines causes both extremes in their effects.

Fosfomycin alters lipopolysaccharide-induced inflammatory cytokine production in mice

To determine the mechanisms of immunomodulating action of fosfomycin (FOF), we examined its effect on the production of inflammatory cytokines in mice injected with lipopolysaccharide (LPS). Treatment with FOF significantly lowered the peak serum levels of tumor necrosis factor alpha and interleukin-1 beta, indicating that FOF alters inflammatory cytokine production after LPS stimulation.

Fosfomycin, an antibiotic, possessed TGF-beta-like immunoregulatory activities

The regulatory effects of fosfomycin (FOM) were correlated closely with the multifunction of TGF-beta in the modulation of immune responses in vivo and in vitro. LPS-induced polyclonal IgM and IgG antibody responses were depressed at 3 days after the initial culture and subsequently enhanced at day 10 by FOM or TGF-beta. Neither FOM nor TGF-beta inhibited LPS-induced IgA antibody responses, whereas dexamethasone (DX) reduced polyclonal IgM, IgG and IgA antibody responses wholly. The suppression of antibody responses and Mv1Lu cell proliferation induced by FOM or TGF-beta was partly overcome with soluble TFG-beta receptors (sRIII). Oral, i.v. and i.p. administration of FOM exhibited similar enhanced SRBC-specific antibody responses to that seen after oral administration of TGF-beta. The addition of FOM and latent TGF-beta inhibited the proliferation of Mv1Lu cells, but FOM did not lead to an increase in plasmin activities, which convert latent to active TGF-beta, and further the expression of TGF-beta receptors on the cell surface. In addition, FOM failed to enhance TGF-beta secretion. These findings suggest that immunomodulation of FOM results in increased sensitivity of cells to TGF-beta.

Effect of interleukin-10 on gut-derived sepsis caused by Pseudomonas aeruginosa in mice

We evaluated the protective effect of interleukin-10 (IL-10) against murine gut-derived sepsis caused by Pseudomonas aeruginosa. Gut-derived sepsis was induced by administering cyclophosphamide and ampicillin while feeding P. aeruginosa to specific-pathogen-free mice. Treating mice with recombinant human IL-10 (rhIL-10) at 1.0 or 5.0 microg/mouse twice a day following the second cyclophosphamide administration significantly increased the survival rate compared to that of control mice treated with saline; however, treatment with rhIL-10 at 0.1 microg/mouse did not result in significant protection. Bacterial counts in the liver, spleen, and blood were all significantly lower in mice treated with rhIL-10 than in saline-treated control mice. Treatment with rhIL-10 significantly suppressed tumor necrosis factor alpha, interleukin-1beta, interleukin-6, and gamma interferon levels in the serum of mice following induction of gut-derived sepsis. We also studied the effect of IL-10 on leukocyte recovery after cyclophosphamide treatment of mice. Administration of rhIL-10 intraperitoneally at 1. 0 microg/mouse significantly accelerated the recovery of leukocytes in comparison with that of the group of saline-treated controls. These results indicate that IL-10 shows a protective effect against gut-derived P. aeruginosa sepsis. We suspect that the mechanism of this effect is that IL-10 regulates in vivo production of inflammatory cytokines. Furthermore, acceleration of leukocyte recovery by IL-10 after cyclophosphamide-induced depression may also play an important role in this protection.