Immunomodulatory effect of fosfomycin on human B-lymphocyte function

Predicted Environmental Risk Assessment of Antimicrobials with Increased Consumption in Portugal during the COVID-19 Pandemic; The Groundwork for the Forthcoming Water Quality Survey

The environmental release of antimicrobial pharmaceuticals is an imminent threat due to ecological impacts and microbial resistance phenomena. The recent COVID-19 outbreak will likely lead to greater loads of antimicrobials in the environment. Thus, identifying the most used antimicrobials likely to pose environmental risks would be valuable. For that, the ambulatory and hospital consumption patterns of antimicrobials in Portugal during the COVID-19 pandemic (2020–2021) were compared with those of 2019. A predicted risk assessment screening approach based on exposure and hazard in the surface water was conducted, combining consumption, excretion rates, and ecotoxicological/microbiological endpoints in five different regions of Portugal. Among the 22 selected substances, only rifaximin and atovaquone demonstrated predicted potential ecotoxicological risks for aquatic organisms. Flucloxacillin, piperacillin, tazobactam, meropenem, ceftriaxone, fosfomycin, and metronidazole showed the most significant potential for antibiotic resistance in all analysed regions. Regarding the current screening approach and the lack of environmental data, it is advisable to consider rifaximin and atovaquone in subsequent water quality surveys. These results might support the forthcoming monitorisation of surface water quality in a post-pandemic survey.

Fosfomycin, Applying Known Methods and Remedies to A New Era

The exponential increase in the numbers of isolates of Carbapenem-Resistant Enterobacteriaceae (CRE) creates the need for using novel therapeutic approaches to save the lives of patients. Fosfomycin has long been considered a rational option for the treatment of CRE to be used as part of a combined therapy scheme. However, the assessment of fosfomycin susceptibility in the laboratory presents a great challenge due to the discrepancies found between different methodologies. Thus, our goal was to evaluate fosfomycin susceptibility in a group of 150 Enterobacteriaceae bacterial isolates using agar dilution as the gold standard technique to compare the results with those obtained by disk diffusion. We found a fosfomycin susceptibility of 79.3% in general terms. By comparing both methodologies, we reported a categorical agreement of 96% without Very Major Errors (VMEs) or Major Errors (MEs) and 4% of minor Errors (mEs). Our results suggest that fosfomycin could provide a rational alternative treatment for those patients that are infected by a Multidrug-Resistant (MDR) microorganism that is currently untreatable and that the disk diffusion and classical agar dilution techniques are adequate to assess the resistance profile of CRE to fosfomycin.

Novel inhaled combined antibiotic formulations in the treatment of Pseudomonas aeruginosa airways infections in cystic fibrosis

In cystic fibrosis, chronic airways infection caused by Pseudomonas aeruginosa can be treated with inhaled antibiotics such as inhaled tobramycin, aztreonam or colistin. However, biofilm formation induced by this bacterium can reduce the effectiveness of such therapies and can contribute to antibiotic resistance. Inhaled antibiotic combination might represent an optimal antibiofilm strategy in this setting. This review discusses the rationale for combining the antibiotics as well as some emerging or existing combinations. Most of the combinations except for fosfomycin/tobramycin are at an early stage of development. The latter combination was found to be effective in Phase II clinical studies and is planned to be tested in Phase III trials. The clinical data on long-term efficacy are currently missing, but the existing evidence as well as the unmet therapeutic need can prompt the further evaluation of such compounds.

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.

Synergistic effects of aminoglycosides and fosfomycin on Pseudomonas aeruginosa in vitro and biofilm infections in a rat model

OBJECTIVES

To study the in vitro and in vivo efficacy of aminoglycosides against Pseudomonas aeruginosa, either alone or in combination with fosfomycin.

METHODS

Using an in vitro study to assess inhibition of the growth of P. aeruginosa, MIC(90) and MIC(50) values of amikacin, gentamicin, netilmicin, tobramycin and isepamicin were determined, either alone or in combination with fosfomycin, and then the fractional inhibitory concentration index was calculated. In the biofilm-infected rat model, the efficacy and effects of treatment with isepamicin and fosfomycin on infection were studied.

RESULTS

The combinations of amikacin and fosfomycin or isepamicin and fosfomycin showed the most significant synergistic effects against P. aeruginosa as compared with other treatments. In the biofilm-infected rat model, as a single agent, neither isepamicin nor fosfomycin reduced C-reactive protein level and numbers of white blood cells, or reduced the colony counts of the bacteria from both tissue and silica gel tubes. However, the combination of these two agents resulted in a good therapeutic effect.

CONCLUSIONS

Combination of aminoglycosides and fosfomycin not only showed a positive effect in vitro but also improved the therapeutic effect in a biofilm-infected rat model. This offers an effective treatment strategy against some therapy-resistant infections.

Inhibition of sulfur mustard-induced cytotoxicity and inflammation by the macrolide antibiotic roxithromycin in human respiratory epithelial cells

BACKGROUND

Sulfur mustard (SM) is a potent chemical vesicant warfare agent that remains a significant military and civilian threat. Inhalation of SM gas causes airway inflammation and injury. In recent years, there has been increasing evidence of the effectiveness of macrolide antibiotics in treating chronic airway inflammatory diseases. In this study, the anti-cytotoxic and anti-inflammatory effects of a representative macrolide antibiotic, roxithromycin, were tested in vitro using SM-exposed normal human small airway epithelial (SAE) cells and bronchial/tracheal epithelial (BTE) cells. Cell viability, expression of proinflammatory cytokines including interleukin (IL)-1beta, IL-6, IL-8 and tumor necrosis factor (TNF), and expression of inducible nitric oxide synthase (iNOS) were examined, since these proinflammatory cytokines/mediators are import indicators of tissue inflammatory responses. We suggest that the influence of roxithromycin on SM-induced inflammatory reaction could play an important therapeutic role in the cytotoxicity exerted by this toxicant.

RESULTS

MTS assay and Calcein AM/ethidium homodimer (EthD-1) fluorescence staining showed that roxithromycin decreased SM cytotoxicity in both SAE and BTE cells. Also, roxithromycin inhibited the SM-stimulated overproduction of the proinflammatory cytokines IL-1beta, IL-6, IL-8 and TNF at both the protein level and the mRNA level, as measured by either enzyme-linked immunosorbent assay (ELISA) or real-time RT-PCR. In addition, roxithromycin inhibited the SM-induced overexpression of iNOS, as revealed by immunocytochemical analysis using quantum dots as the fluorophore.

CONCLUSION

The present study demonstrates that roxithromycin has inhibitory effects on the cytotoxicity and inflammation provoked by SM in human respiratory epithelial cells. The decreased cytotoxicity in roxithromycin-treated cells likely depends on the ability of the macrolide to down-regulate the production of proinflammatory cytokines and/or mediators. The results obtained in this study suggest that macrolide antibiotics may serve as potential vesicant respiratory therapeutics through mechanisms independent of their antibacterial activity.

Synergistic effect of fosfomycin and arbekacin on a methicillin-resistant Staphylococcus aureus-induced biofilm in a rat model

Biofilms are a major concern for clinicians in the treatment of infectious disease because of the resistance to a wide range of antibiotics. Using a rat air pouch model, methicillin-resistant Staphylococcus aureus (MRSA) growing as a biofilm was treated with a combination of fosfomycin (FOM) and arbekacin (ABK) or by the agents alone. This model has the advantage of permitting frequent sampling of exudates for bacterial counts and anti-bacterial activity, and morphological examination of the biofilm structure and inflammatory process in the pouch tissues. A clear synergistic effect was observed in the rats treated with a combination of fosfomycin and arbekacin. Morphological studies using scanning electron microscopy and histological staining showed dramatic changes of the biofilm structure as well as the inflammatory response in the rats. These results suggested an enhancement of bactericidal activity of arbekacin penetrating through the biofilm layer by virtue of fosfomycin. A possible mechanism of the synergistic effect is discussed.

Effects of moxifloxacin in zymogen A or S. aureus stimulated human THP-1 monocytes on the inflammatory process and the spread of infection

Antimicrobial agents have been reported to exhibit immunomodulatory and anti-inflammatory activities, both in vivo and in vitro (e.g., in human lymphocytes, macrophages and monocytes). The effects of moxifloxacin on cytokine immunomodulatory mediators, free radical generation and hydrolytic enzyme activities in zymogen A-stimulated human THP-1 monocytes were evaluated. An increase in c-AMP levels, protein kinase C activity, and the release of nitric oxide and hydrogen peroxide with a decrease in pH occurred within the first hour. Further, the effects of moxifloxacin were reduced by agents which blocked the oxygen burst, lysosome-phagosome fusion, and the energy generation within the cell. After 4 h, there was a decrease in NAG and cathepsin D activities, lipid peroxidation and the release of pro-inflammatory cytokines. These data indicate that moxifloxacin may modify the acute-phase inflammatory responses through inhibition of cytokine release in monocytes. Moxifloxacin inhibited the release of TNFalpha, IL-1, IL-6, and IL-8 in a concentration-dependent manner across a range of 0.004 to 4 microg/mL. After 4 h, there was a decrease in the release of these cytokines, thus interfering with the inflammation process to reduce infection and its spread. The effects of moxifloxacin appear initially to activate monocytes to kill bacteria through the innate immune process by releasing ROS and lysosomal hydrolytic enzymes as well as phagocytosis of the organism. At a later time the bacteria are killed through a Bacterialstatic mechanism of protein synthesis inhibition and there is a reversal of the effects of moxifloxacin on cytokine release, free radical generation and hydrolytic enzymes so that lipid peroxidation and tissue destruction by the infection process is suppressed.

Effects of alatrofloxacin, the parental prodrug of trovafloxacin, on phagocytic, anti-inflammatory and immunomodulation events of human THP-1 monocytes

Alatrofloxacin functions similar to other fluoroquinolone antibiotics in that it not only has antibiotic activity to kill invading organisms by interfering with DNA synthesis, it possesses immunosuppressive activity. In the first hour after bacteria have been phagocytosed by THP-1 monocytes, the drug activates a lytic mechanism involving the release of c-AMP, tumor necrosis factor (TNFalpha), interleukin-1 (IL-1), IL-6 and nitric oxide, with elevations in lysosomal hydrolytic enzyme activities. This effect reverses between 2 and 4 h. At this time, all of these inflammatory processes are returned to normal values or below suggesting that alatrofloxacin reduces the spread of infection and destruction of tissue related to inflammation.

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.

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.

Modulatory effect of macrolide antibiotics on the Th1- and Th2-type cytokine production

The effect of the macrolide antibiotics, clarithromycin, midecamycin acetate and josamycin, on the generation of Th1- and Th2-type cytokines by mitogen-stimulated human T lymphocytes was compared with that of fosfomycin. The following results were obtained. These drugs demonstrated potent inhibitory activity on the release and gene expression of TNF-alpha and IL-2. Their inhibitory effect on IFN-alpha, IL-4, IL-5, IL-6 was less marked. The release of IL-10 was poorly suppressed. Clarithromycin had the most potent inhibitory effect of the drugs used. The present results suggested that anti-bacterial agents might modify the host's immunological response by interfering with the activity of T helper cells.

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 antibiotics, levofloxacin and fosfomycin, on a mouse model with Escherichia coli O157 infection

There have been some reservations about the treatment of enterohemorrhagic Escherichia coli (EHEC) infection with antibiotics to prevent the occurrence of hemolytic uremic syndrome (HUS). However, the administration of antimicrobial agents for EHEC infection is under discussion. Therefore, we used an experimental mouse model to assess the advantage/disadvantage of two major antibiotics, levofloxacin (LVFX) and fosfomycin (FOM). Germ-free IQI mice were inoculated with EHEC O157 strain EDL931 or #7. Bacteria colonized feces at 10(9)-10(10) CFU/g, and Shiga toxins (STXs) were detected in the feces. From 1 day after infection, mice were assigned to LVFX (20 mg/kg) once daily or FOM (400 mg/kg) once daily. A significant decrease in overall mortality was observed after treatment of LVFX, with EHEC disappearing immediately from the feces of mice. FOM also reduced mortality for one strain, the STX level decreased gradually. LVFX exhibited higher therapeutic efficacy than FOM. Strain differences were observed in the model during the treatment.

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.

Fosfomycin (FOM: 1 R-2S-epoxypropylphosphonic acid) suppress the production of IL-8 from monocytes via the suppression of neutrophil function

We investigated the influence of fosfomycin (FOM) on the production and the mRNA expression of interleukin-8 (IL-8) by monocytes. In the incubation of whole blood stimulated by N-Formyl-Met-Leu-Phe (FMLP), FOM significantly suppressed the production and the mRNA expression of IL-8 by monocytes and its inhibitory action was concentration-dependent (FOM: 50-200 microg/ml). However, FOM did not influence the production and the mRNA expression of IL-8 in the incubation of fractionated mononuclear cell stimulated by FMLP. The supernatant of FMLP-stimulated polymorphonuclear leukocyte (PMNL) could induce the mRNA expression of IL-8 by monocyte. The supernatant of FMLP-stimulated PMNL which was pre-treated with FOM significantly (P < 0.05) inhibited the expression of IL-8 mRNA by monocyte. Moreover, FOM suppressed the production of leukotriene B4 (LTB4) from neutrophil in a concentration-dependent manner. When LTB4 was added to the fractionated mononuclear cells directory, the expression of IL-8 mRNA was enhanced (P < 0.05). The present study indicated that FOM suppress the production of LTB4 from neutrophils and suppress the expression of IL-8 mRNA by LTB4 from monocytes. It was also demonstrated that LTB4 produced by neutrophil is one of the factor which promotes the expression of IL-8 mRNA in monocytes.

Alteration of cytokine levels by fosfomycin and prednisolone in spontaneous proliferation of cultured lymphocytes from patients with HTLV-I-associated myelopathy (HAM/TSP)

Fosfomycin has recently been reported as an antibiotic with immunomodulatory activities. To evaluate the possibility of clinical administration of fosfomycin in patients with human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), the effects of this agent on the HTLV-I-induced in vitro phenomenon were studied. The influence of fosfomycin on in vitro spontaneous proliferation (SP) of peripheral blood mononuclear cells (PBMCs) from four patients with HAM/TSP was measured by thymidine incorporation into the cells, and the concentration of several cytokines in the culture supernatants was examined in three HAM/TSP patients. Enzyme-linked immunosorbent assays (ELISAs) were employed to detect the concentrations of interleukin-4 (IL-4), IL-6, IL-10, interferon-gamma (IFN-gamma), transforming growth factor-beta1 (TGF-beta1), and macrophage inflammatory protein-1alpha (MIP-1alpha). The data were compared to the changes by prednisolone which is known to regulate the HTLV-I-associated in vitro phenomenon and to have a therapeutic benefit in patients with HAM/TSP. Production of IL-6, IFN-gamma and MIP-1alpha from the spontaneously proliferating cells were demonstrated. Fosfomycin could not suppress the HTLV-I-associated SP, but had the properties to decrease the levels of TGF-beta1 and MIP-1alpha. It was also demonstrated that the concentrations of IFN-gamma and MIP-1alpha in the cultures in the presence of prednisolone were apparently decreased, suggesting a possible involvement of these cytokines in the pathogenesis of HAM/TSP. These findings support the hypothesis that fosfomycin may have immunomodulatory potentials in HTLV-I-related cellular interactions in a different manner from ordinary immunomodulatory agents.

Stimulating effect of an oral polybacterial immunomodulator on the proliferative activity of guinea pig lymphocytes

A preparation for the prophylaxis and treatment of inflammations of oral mucosa and parodont Dentavax (D) was investigated in guinea pigs. Animals were given orally D for 5 consecutive days and a month later the procedure was repeated. On day 3, 10, 21, and 28 after immunization and reimmunization lymphoproliferative responses to PHA, rIL-2, LPS and D were measured by the radiometric blast transformation assay in peripheral blood, spleen, mesenteric lymph nodes (MLN) and Peyer's patches (PP). The percentage of cells entering S and G2/M-phases of cell cycle was assessed by the flow cytometric DNA analysis. A correlation in proliferative activity of cells after in vitro stimulation with PHA and LPS has been established by both methods. Peak values of lymphocyte stimulation were found on day 10, especially after the second administration of D in all organs tested, mainly in MLNs and spleen. Electron-microscopic studies demonstrated an extensive development of the endoplasmatic reticulum in plasmatic cells from spleen, PPs, mesenteric, bronchial and inguinal lymph nodes. The results obtained may be considered a proof of the immunostimulating effect of Dentavax.

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

We evaluated the protective effect of fosfomycin (FOM) and an enantiomer of fosfomycin [FOM (+); an isomer of FOM with no bactericidal activity] on murine gut-derived sepsis caused by Pseudomonas aeruginosa. Endogenous bacteremia was induced by administering cyclophosphamide (CY) and ampicillin to specific-pathogen-free mice fed P. aeruginosa. Treatment of mice with FOM at 250 mg/kg of body weight per day twice a day after the second CY administration significantly increased the survival rate compared to that for control mice treated with saline. Treatment with FOM (+) at 20 and 100 mg/kg also significantly increased the survival rate (from 30% for control mice to 80% for treated mice). The bacterial counts in the liver and blood were both significantly lower in FOM(+)-treated mice in comparison with those in liver and blood of saline-treated control mice. FOM(+) administration affected neither the bacterial colonization in the intestinal tract nor the leukocyte counts in the peripheral blood of the mice. After intravascular inoculation of P. aeruginosa, treatment of mice with FOM (+) did not enhance bacterial clearance from the blood of mice pretreated or not enhance bacterial clearance from the blood of mice pretreated or not pretreated with CY, FOM(+) significantly suppressed tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 levels in the serum of mice after gut-derived sepsis. These results indicate that both FOM and FOM(+) have protective effects against P. aeruginosa bacteremia, despite a lack of specific activity of FOM(+), and suggest that FOM may possess immunomodulating activity and that it induces a protective effect. The protective mechanism is speculated to be that FOM modulates the vivo production of inflammatory cytokines.

Immunomodulating effects of antibiotics: literature review

Antibiotics can interact directly with the immune system. This is a review of the immunomodulating effects of antibiotics. The Medline database on CD-ROM was searched for the years 1987 to 1994 using the following search string: "thesaurus explode antibiotics/all AND (thesaurus explode immune-system/drug effects OR thesaurus immune-tolerance/drug effects)." Aspects of the immune system studied were aspects of phagocyte functions: phagocytosis and killing, and chemotaxis and aspects of lymphocyte functions: lymphocyte proliferation, cytokine production, antibody production, delayed hypersensitivity and natural killer-cell activity. In order to quantify and to compare immunomodulatory properties of antibiotics we calculated an "immune index," defined as: number of positive statements--number of negative statements/total number of statements. Concerning phagocytosis, positive effects were observed for cefodizime, imipenem, cefoxitin, amphotericin B and clindamycin and negative effects for erythromycin, roxithromycin, cefotaxime, tetracycline, ampicillin and gentamicin. Clindamycin, cefoxition and imipenem induce enhancement of chemotaxis, whereas cefotazime, rifampicin and teicoplanin decrease chemotaxis. Regarding lymphocyte proliferation, cefodizime has the strongest stimulating effect, whereas tetracycline has the strongest negative effect. Except for erythromycin and amphotericin B the number of statements reported is too small to be conclusive for the interpretation of effects on cytokine production. Erythromycin and amphotericin B appear to stimulate cytokine production. As to antibody production, cefodizime has the strongest positive effect, whereas josamycin, rifampicin and tetracycline have marked negative effects. For delayed hypersensitivity and the natural killer-cell activity the number of statements is too small for any single antibiotic to be conclusive. There are three markedly immuno-enhancing antibiotics (imipenem, cefodizime and clindamycin) and eight markedly immuno-depressing antibiotics (erythromycin, roxithromycin, cefotaxime, tetracycline, rifampicin, gentamicin, teicoplanin and ampicillin).

Modulatory effect of antibiotics on cytokine production by human monocytes in vitro

Some antimicrobial agents have been reported to modify the host immune and inflammatory responses both in vivo and in vitro. Fosfomycin (FOM) and clarithromycin (CAM) have immunomodulatory activity on human lymphocyte function. In the present study, we examined the effects of FOM and CAM on cytokine synthesis by lipopolysaccharide (LPS)-stimulated human monocytes in comparison with that of dexamethasone in vitro. The three drugs demonstrated positive or negative effects on the synthesis of various cytokines by LPS-primed monocytes. They suppressed the synthesis of tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-1 beta, the IL-1 receptor antagonist, and granulocyte-macrophage colony-stimulating factor in a concentration-dependent manner at concentrations between 1.6 and 40 micrograms/ml. On the contrary, the drugs showed different actions on the synthesis of IL-6 and IL-10. Namely, FOM enhanced both IL-6 and IL-10 synthesis, CAM enhanced only IL-10 synthesis, but dexamethasone deeply suppressed the synthesis of both cytokines. These data indicate that antibacterial agents may modify acute-phase inflammatory responses through their effects on cytokine synthesis by monocytes.

Immunosuppressive activity of fosfomycin on human T-lymphocyte function in vitro

Recent investigations have shown that some antibiotics also work as immunomodulators. We have recently reported that fosfomycin (FOM) has an immunomodulatory effect on human B-cell activation. FOM is a unique antibiotic which is chemically unrelated to any other known antibacterial agent. In the present study, we examined the effect of FOM on human T-cell function. FOM inhibited the proliferation of human lymphocytes induced by polyclonal T-cell mitogens in a dose-dependent manner. FOM also strongly suppressed mixed lymphocyte reaction and interleukin-2 (IL-2) production by T cells. Moreover, FOM inhibited the expressions of IL-2 receptor (CD25) and transferrin receptor (CD71) on the activated T-cell surfaces. These data suggest that FOM may block the T-cell division during the transition from G1 to S phase of the cell cycle. Combined treatment with FOM and low-dose cyclosporin A or FK506 caused additive or synergistic suppression of T-cell proliferation, but not on IL-2 receptor expression. It seems that the mode of action of FOM on T-cell function involves a specific suppression of IL-2 production.

Immunosuppressive property of bromocriptine on human B lymphocyte function in vitro

Bromocriptine (BRC), a dopamine ergot alkaloid, inhibits the release of pituitary prolactin (PRL). Hypoprolactinaemia induced in rat by treatment with BRC produces a similar immunosuppressive effect as observed in hypophysectomized rats. The effect of immunosuppression by the administration of BRC has been interpreted as the result of hypoprolactinaemia produced by BRC. However, the direct effect of BRC on lymphocyte function has never been evaluated. The purpose of this study was to investigate the in vitro effect of BRC on human B cell functions. Highly purified B cells from tonsil samples were isolated by Percoll density gradient from non-rosetted cells, and were used as target cells. BRC significantly suppressed the proliferative response of resting and activated B cells in vitro. It suppressed immunoglobulin generation of activated B cells. The inhibition of BRC was manifested in the early stage of the proliferation and differentiation of B cells. The conditioned medium from the polyclonal B cell mitogen-stimulated B cell cultures did not contain PRL as detected by immunoradiometric assay. Treatment with low-dose cyclosporin A or FK506 in conjunction with BRC has proved more effective than either drug alone in suppression of B cell proliferation. Thus, the combined therapy of BRC and immunosuppressants may be effective with decreased toxicity for clinical use.