Uptake and intracellular activity of fluconazole in human polymorphonuclear leukocytes

Antifungal Drugs Influence Neutrophil Effector Functions

There is a growing body of evidence for immunomodulatory side effects of antifungal agents on different immune cells, e.g., T cells. Therefore, the aim of our study was to clarify these interactions with regard to the effector functions of polymorphonuclear neutrophils (PMN). Human PMN were preincubated with fluconazole (FLC), voriconazole (VRC), posaconazole (POS), isavuconazole (ISA), caspofungin (CAS), micafungin (MFG), conventional amphotericin B (AMB), and liposomal amphotericin B (LAMB). PMN then were analyzed by flow cytometry for activation, degranulation, and phagocytosis and by dichlorofluorescein assay to detect reactive oxygen species (ROS). Additionally, interleukin-8 (IL-8) release was measured by enzyme-linked immunosorbent assay. POS led to enhanced activation, degranulation, and generation of ROS, whereas IL-8 release was reduced. In contrast, ISA-pretreated PMN showed decreased activation signaling, impaired degranulation, and lower generation of ROS. MFG caused enhanced expression of activation markers but impaired degranulation, phagocytosis, generation of ROS, and IL-8 release. CAS showed increased phagocytosis, whereas degranulation and generation of ROS were reduced. AMB led to activation of almost all effector functions besides impaired phagocytosis, whereas LAMB did not alter any effector functions. Independent from class, antifungal agents show variable influence on neutrophil effector functions in vitro Whether this is clinically relevant needs to be clarified.

Conserved molecular mechanisms underlying the effects of small molecule xenobiotic chemotherapeutics on cells

For proper determination of the apoptotic potential of chemoxenobiotics in synergism, it is important to understand the modes, levels and character of interactions of chemoxenobiotics with cells in the context of predicted conserved biophysical properties. Chemoxenobiotic structures are studied with respect to atom distribution over molecular space, the predicted overall octanol-to-water partition coefficient (Log OWPC; unitless) and molecular size viz a viz van der Waals diameter (vdWD). The Log OWPC-to-vdWD (nm^-1 ) parameter is determined, and where applicable, hydrophilic interacting moiety/core-to-vdWD (nm^-1 ) and lipophilic incorporating hydrophobic moiety/core-to-vdWD (nm^-1 ) parameters of their part-structures are determined. The cellular and sub-cellular level interactions of the spectrum of xenobiotic chemotherapies have been characterized, for which a classification system has been developed based on predicted conserved biophysical properties with respect to the mode of chemotherapeutic effect. The findings of this study are applicable towards improving the effectiveness of existing combination chemotherapy regimens and the predictive accuracy of personalized cancer treatment algorithms as well as towards the selection of appropriate novel xenobiotics with the potential to be potent chemotherapeutics for dendrimer nanoparticle-based effective transvascular delivery.

Immunomodulatory properties of antifungal agents on phagocytic cells

Phagocytic cells, particularly neutrophils and monocytes/macrophages, are the first line and the most effective form of innate host defence against pathogenic fungi. During antifungal therapy these phagocytic cells are also exposed to antifungal agents. In the phagocyte-fungus-antifungal agent interplay, drugs may directly interact with phagocytes through specific pattern recognition receptors, leading to altered antifungal activities. Antifungal agents, through modulation of fungal virulence, may initiate different immune response programs in the phagocytes, leading to antifungal synergism/antagonism or up-regulation of gene expression for a pro-inflammatory response. Additionally, indirect modulation of phagocyte behavior by pretreatment of neutrophils, monocytes, and macrophages with cytokines and exposure to antifungal agents have shown promising findings for combined drug-cytokine therapy that may improve treatment of life-threatening fungal diseases. In this review, we discuss the main in vitro and in vivo immunomodulatory effects of antifungal agents on phagocytes in response to pathogenic fungi, as well as we address underlying immunopharmacologic mechanisms and their potential impact on clinical outcome.

Intracellular concentrations of posaconazole in different compartments of peripheral blood

Therapeutic drug monitoring (TDM) of antifungal plasma concentrations is increasingly recommended. However, data on antifungal concentrations in the other compartments of the peripheral blood are limited. Hence, we collected 23 blood samples from 14 patients receiving posaconazole for prophylaxis of fungal infections. These samples were separated by double-discontinuous Ficoll-Hypaque density gradient centrifugation. The intracellular posaconazole concentrations of the obtained cells, i.e., the peripheral blood mononuclear cells (PBMCs), polymorphonuclear leukocytes (PMNs), and red blood cells (RBCs), were determined by liquid chromatography-tandem mass spectrometry. The intracellular concentrations of the PBMCs and PMNs were significantly higher than those of surrounding media (P < 0.001). The ratios between the intracellular and extracellular concentrations (C/E) were 22.5 +/- 21.2, 7.66 +/- 6.50, and 0.09 +/- 0.05 for the PBMCs, PMNs, and RBCs, respectively. Posaconazole reaches high concentrations within human PBMCs and PMNs and is, to a lesser extent, present in RBCs. The high intracellular concentrations might contribute to posaconazole efficacy and distribution.

Quantitation of azoles and echinocandins in compartments of peripheral blood by liquid chromatography-tandem mass spectrometry

A rapid turnaround is a prerequisite of therapeutic drug monitoring (TDM). For antifungals, this need is still unmet, since hardly any method has been established to simultaneously quantitate concentrations of different antifungal classes. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed allowing quantitation of anidulafungin (ANF), caspofungin (CSF), isavuconazole (ISC), micafungin (MCF), posaconazole (PSC), and voriconazole (VRC). Quantitation was successful with diluted plasma samples, peripheral blood mononuclear cells (PBMC), polymorphonuclear leukocytes (PMN), and erythrocytes (RBC). A triple quadrupole mass spectrometer in selected reaction monitoring mode was used with positive electrospray ionization. Cells and calibration standards were extracted with acetonitrile containing internal standard. Internal standards were a CSF derivate for echinocandins and itraconazole for triazoles. Chromatographic separation of the supernatant was achieved by a gradient method facilitating a BetaBasic C4 column. Analytes were quantified in a single 8-min run. Calibration curves were linear and fitted using least squares with a weighting factor of the reciprocal concentration. Limits of detection (ng/ml) were ANF, 8.3; CSF, 31.5; ISC, 1.5; MCF, 97.7; PSC, 3.3; and VRC, 1.4. The lower limits of quantitation (ng/ml) were ANF, 64; CSF, 108; ISC, 4.5; MCF, 160; PSC, 10; and VRC, 4.2. Intraday precisions ranged from 6.3% to 8.8% for azoles and 8.8% to 15.4% for echinocandins. Intraday and interday accuracies (percent bias) of all analytes were within 13.8%. The method was established as standard practice for the quantitation of intracellular antifungal concentrations and optimizes TDM by applying a rapid single method for 6 antifungals.

In vitro inhibition of fungal activity by macrophage-mediated sequestration and release of encapsulated amphotericin B nanosupension in red blood cells

The efficacy of antifungal treatment has been diminished by the biodistribution limitations of amphotericin B (AmB) due to its pharmacological profile, as well as the severe side effects it causes. A cellular drug-delivery system, which incorporates human erythrocytes (RBCs) loaded with an AmB nanosuspension (AmB-NS), is developed in order to improve antifungal treatment. AmB-NS encapsulation in RBCs is achieved by using hypotonic hemolysis, leading to intracellular AmB amounts of 3.81 +/- 0.47 pg RBC(-1) and an entrapment efficacy of 15-18%. Upon phagocytosis of AmB-NS-RBCs, leukocytes show a slow AmB release over ten days, and no alteration in cell viability. This results in an immediate, permanent inhibition of intra- and extracellular fungal activity. AmB-NS-RBC-leukocyte-mediated delivery of AmB is efficient in amounts 1000 times lower than the toxic dose. This drug-delivery method is effective for the transport of water-insoluble substances, such as AmB, and this warrants consideration for further testing.

Antifungal effect of voriconazole on intracellular Candida glabrata, Candida krusei and Candida parapsilosis in human monocyte-derived macrophages

Infections caused by Candida species other than Candida albicans are increasingly common, and decreased susceptibility to azoles has made them more difficult to treat. Since phagocytic killing is important in elimination of Candida infections, intracellular killing of fluconazole-resistant Candida glabrata, Candida krusei and Candida parapsilosis (four strains each) by voriconazole was investigated in human monocyte-derived macrophages (MDMs). MDMs were infected with Candida, and voriconazole was then added. MDMs were lysed at 0, 24 or 48 h after infection, and viable Candida in the lysates enumerated. Compared to the starting inoculum, the number of viable intracellular C. parapsilosis and C. glabrata in untreated MDMs increased to 28,121 and 351 %, respectively, in 48 h. In contrast, the number of C. krusei decreased to 42 %. In MDMs treated with voriconazole, the decrease in viable count was dependent upon drug concentration. At 48 h, C. glabrata was killed only at 5x MIC (P < 0.05), C. krusei was killed at all voriconazole concentrations, while C. parapsilosis was inhibited at 0.5 and 1x MIC and killed at > or = 2.5x MIC (P < 0.05). The data show that intracellular growth and survival of these Candida species in the absence or presence of voriconazole vary markedly. The activity of voriconazole depends on the concentration of the drug and the time of exposure. For the 12 Candida strains studied, regression curves show that the maximum intracellular anticandidal activity of voriconazole was reached at 3.5-5x MIC.

Effects of voriconazole, granulocyte-macrophage colony-stimulating factor, and interferon γ on intracellular fluconazole-resistant Candida glabrata and Candida krusei in human monocyte-derived macrophages

Infections caused by fluconazole-resistant Candida glabrata and Candida krusei are increasingly common causes of morbidity and mortality. We investigated the intracellular killing of fluconazole-resistant C. glabrata and C. krusei by cytokine-activated human monocyte-derived macrophages (MDM) in the presence and absence of voriconazole. For C. glabrata, MDM were activated with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or interferon gamma (IFN-gamma) before infection, after infection, or both before and after infection, whereas for C. krusei MDM were activated with cytokines both before and after infection. Activated MDM were infected, treated with voriconazole, and then lysed, and viable yeast in the lysates enumerated at 0, 24, or 48 h after infection. In the presence of voriconazole (2.5 x MIC), the best activity against C. glabrata occurred when MDM were activated with GM-CSF for 24 h before infection as well as after infection or when they were activated for 24 h before infection alone. A lesser effect was observed when MDM were activated for at least 1 h before infection or when they were treated with cytokines only after infection. IFN-gamma activation had a significant but lesser effect than GM-CSF. Activity against C. krusei in the presence of voriconazole was greatest when MDM were activated with IFN-gamma rather than GM-CSF. Our results suggest that cytokines increase the intracellular anticandidal effect of voriconazole and may be useful as therapeutic adjuvants to voriconazole for treatment of infections caused by fluconazole-resistant C. glabrata and C. krusei.

Uptake and intracellular activity of voriconazole in human polymorphonuclear leucocytes

OBJECTIVES

The intracellular penetration of voriconazole into human polymorphonuclear leucocytes (PMNs) and its intracellular activity against Candida spp. were evaluated.

METHODS

The intracellular penetration of voriconazole into PMNs was evaluated by a radiometric assay. The effect of cell viability, environmental conditions, metabolic inhibitors and membrane stimulation was also studied. The intracellular activity was determined by incubation of PMNs containing intracellular blastospores in the presence of voriconazole for 3 h.

RESULTS

The uptake of voriconazole by PMNs was rapid and not saturable. The cellular to extracellular concentration (C/E) ratio for voriconazole was 8.5+/-1.3. Voriconazole was rapidly released from loaded PMNs. The uptake of voriconazole was not affected by environmental temperature and cell viability. Neither the external pH nor the metabolic inhibitors affected the uptake of voriconazole. The ingestion of opsonized zymosan, but not of opsonized Candida spp., significantly decreased the levels of PMN-associated voriconazole. At the extracellular concentrations evaluated, voriconazole did not affect the intracellular survival of Candida.

CONCLUSIONS

Voriconazole reached high intracellular concentrations within human PMNs. The uptake was rapid and not saturable but it did not affect the intracellular killing of Candida spp.

Effect of fluconazole on phagocytic response of polymorphonuclear leukocytes in a rat model of acute sepsis

Recently, fluconazole (FLZ) has been shown to improve survival and reduce multiorgan failure in experimental and clinical septic shock. The mechanism by which FLZ affords protection against sepsis remains obscure. This study examines the effect of FLZ on phagocytic activity of polymorphonuclear leukocytes (PMNs) in a rat model of septic shock by inducing fecal peritonitis in male Wistar rats using intraperitoneal instillation (1 mL/kg) of fecal suspension in saline (1:1 w/v). Sham control rats received sterile fecal suspension and vehicle treatment. FLZ was administered in the doses of 0, 3, 10, and 30 mg/kg by gavage 30 minutes before fecal instillation. The samples of peritoneal fluid were collected 8 hours following fecal inoculation for the evaluation of phagocytic response of PMNs using zymosan-induced luminol-dependent chemiluminescence (CL). Fecal peritonitis caused massive infiltration of PMNs in the peritoneal cavity (ANOVA F(4,45) = 6.322, P < .001). Although FLZ reduced the infiltration of PMNs, this effect was neither significant nor dose dependent. The actual CL response was significantly higher in the peritoneal fluid of rats subjected to peritonitis, which was significantly and dose dependently attenuated by FLZ treatment (ANOVA F(4,45) = 11.048, P < .001). Normalization of CL response for 1000 PMNs revealed that FLZ dose-dependently albeit insignificantly reduced the activity of PMNs. The high dose of FLZ caused 2.29-fold decrement in the area under curve (AUC) pertaining to cumulative CL response. The findings of this study suggest that FLZ protects rats against septic shock by inhibiting PMN-mediated inflammatory cascade without compromising their phagocytic activity.

Pharmacokinetics/pharmacodynamics of echinocandins

The novel class of echinocandins represents a milestone in antifungal drug research that has further expanded our therapeutic options. The favorable pharmacokinetic profile of the echinocandins has been elucidated in animal and human studies. The echinocandins are targeted for once-daily dosing and are not metabolized through the cytochrome P450 enzyme system, and they are generally well tolerated due to lack of mechanism-based toxicity. Little is known, however, about the disposition of these compounds in tissues and body fluids and the relationships between dosage, concentrations in the body, and antifungal efficacy in vivo. Many unanswered questions remain, including the importance of the high protein binding and the concentrations of free antifungal agents at target sites. Although recent attempts have been made to ensure the reproducibility of in vitro tests, the clinical usefulness of these tests is still unreliable and their relevance remains controversial. In vitro activity must be correlated with achievable concentrations at the site of infection. As little is known about the relationship between the pharmacokinetics and the pharmacodynamics of the echinocandins, increased incorporation of these principles in experimental and clinical studies is an important objective that will benefit the treatment and prophylaxis of life-threatening invasive fungal infections in immunocompromised patients.

Treatment of intra-abdominal abscesses caused by Candida albicans with antifungal agents and recombinant murine granulocyte colony-stimulating factor

The aim of the present study was to assess the influence of immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (rmG-CSF) on intra-abdominal abscesses caused by Candida albicans. Mice received prophylaxis or therapy with 1 microg of rmG-CSF/day in the presence or absence of antifungal treatment consisting of amphotericin B (0.75 mg/kg of body weight/day) or fluconazole (50 mg/kg/day). The number of Candida CFU in abscesses was significantly reduced (P<0.05) in mice receiving rmG-CSF prophylaxis (day -1 or day -1 through 2) compared with controls on day 8 of infection. Administration of rmG-CSF therapy alone (for 5 days starting on day 4 of infection) had no influence on the number of Candida CFU in abscesses. Amphotericin B treatment was significantly more effective than fluconazole treatment (3.41 log CFU/abscesses; 95% confidence interval [CI], 3.17 log CFU/abscesses; 3.65 versus 3.90 log CFU/abscesses; 95% CI, 3.66 log CFU/abscesses, 4.16 log CFU/abscesses; P<0.05). Therapeutic administration of rmG-CSF in conjunction with an antifungal agent showed a tendency towards a further reduction of Candida CFU in abscesses than antifungal treatment only. In conclusion, in this experimental model of intra-abdominal Candida abscesses, rmG-CSF administration did not have a detrimental influence on the course of infection. Amphotericin B treatment was most effective, and additional rmG-CSF therapy did not antagonize the effect of antifungal treatment. In contrast, addition of rmG-CSF therapy to antifungal treatment might further enhance the beneficial effect of the antifungal agent.

Effects of cytokines and fluconazole on the activity of human monocytes against Candida albicans

This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular Candida albicans in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), gamma interferon (IFN-gamma), or IL-4 had no effect on the growth of C. albicans. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (P < 0.05), while the addition of IL-10 resulted in increased growth (P < 0.01). In the presence of fluconazole, only the addition of IFN-gamma resulted in an increase in the growth of C. albicans. In the presence or absence of fluconazole, all cytokine combinations except IFN-gamma plus GM-CSF caused significant decreases in growth (P < 0.01). IL-10 and IL-4 did not influence the activity of TNF-alpha or IL-1beta. In the absence or presence of C. albicans the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (P < 0.01). Similar observations were made for superoxide (O(2)(-)) only in the presence of C. albicans. The greatest concentrations of NO and O(2)(-) were produced when C. albicans alone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular C. albicans.

Fluconazole in cats: pharmacokinetics following intravenous and oral administration and penetration into cerebrospinal fluid, aqueous humour and pulmonary epithelial lining fluid

The pharmacokinetics of fluconazole following intravenous (i.v.) and oral (p.o.) administration and the penetration of fluconazole into cerebrospinal fluid, aqueous humour and epithelial lining fluid (ELF) of the lungs were evaluated in adult male cats. Pharmacokinetic parameters were calculated from serum concentration-time data obtained following i.v. and p.o. administration of 50 mg per cat using a cross-over study design. Fluconazole concentrations were measured using a high-performance liquid chromatography assay. Mean total body clearance of fluconazole was 37.7 mL/h.kg, mean volume of distribution at steady state was 1.14 L/kg, mean residence time was 31.0 h and mean half-life of elimination was 25 h as derived by non-compartmental analysis of data. Absorption was complete. Mean ratios of fluid:serum fluconazole concentrations following administration of 50 mg fluconazole per day for 8 days were as follows: cerebrospinal fluid, 0.88; aqueous humour 0.79; ELF, 1.20. Fluconazole concentrations in cerebrospinal fluid, aqueous humour and ELF exceeded reported minimum inhibitory concentrations of fluconazole for pathogenic fungi. Results of this study suggest fluconazole can effectively be administered to cats at 50 mg per cat per day.

Cytotoxic activity of doxorubicin "loaded" neutrophils against human mammary carcinoma (HTB-19)

Neutrophils were intra-cellularly "loaded" with the chemotherapeutic agent, doxorubicin applying a variety of incubation conditions in order to identify parameters which maximize chemotherapeutic incorporation, while simultaneously preserving optimal viability and chemotactic responsiveness. Doxorubicin "loaded" neutrophils (DLN) were produced in triplicate at different combinations of incubation conditions such as temperature (4 degrees C, 37 degrees C); duration (0, 1, 2 hours); and doxorubicin concentration (20, 40, 60 micrograms/ml). Chemotactic responsiveness of rinsed DLN preparations was subsequently assessed against the neutrophil peptide chemotactic agent, formyl methionyl leucyl phenylalanine (fMLP, 10(-6) M) utilizing a modified 96-well Boyden chemotactic chamber apparatus. Viable, fMLP-responsive DLN preparations were subsequently detected with MTT vitality staining reagent. At sub-physiological incubation temperatures (4 degrees C), profound declines in the viability of DLN preparations were detected when simultaneously incubated with doxorubicin formulated at concentrations greater than 10 micrograms/ml. In contrast, DLN preparations incubated at 37 degrees C displayed diminished viability only when incubated with doxorubicin formulated at a concentration of 60 micrograms/ml. Viable DLN populations were subsequently evaluated to determine their ability to exert in vitro cytotoxic activity against monolayer populations of human mammary carcinoma (HTB-19) propagated in a tissue culture environment. The lethal effect which DLN preparations inflicted towards HTB-19 populations was substantially greater than was observed with an equivalent population of untreated neutrophils. Maximal in vitro cytotoxic activity was detected with DLN preparations produced at 37 degrees C in the presence of doxorubicin formulated at a concentration of 40 micrograms/ml. In contrast, DLN preparations produced at an incubation temperature of 37 degrees C, and a doxorubicin concentration of 20 micrograms/ml displayed relatively lower levels of in vitro cytotoxic activity against HTB-19 monolayer populations. The degree of in vitro cytotoxic activity exerted against HTB-19 monolayer populations by DLN preparations was directly influenced by the duration of the challenge period. Maximal in vitro cytotoxic activity was observed when HTB-19 monolayer populations were challenged with DLN preparations for a period of 96-hours duration at 37 degrees C. Challenge periods of 48-hours duration produced levels of in vitro cytotoxic activity which were substantially lower than those observed for challenge periods of 96-hours duration. Optimal in vitro cytotoxic activity was recognized when DLN preparations were allowed to establish direct contact with HTB-19 monolayer populations at an estimated DLN:HTB-19 cellular ratio of approximately 5:1 (37 degrees C, CO2, 6%). Significantly less in vitro cytotoxic activity was recognized when DLN preparations were only permitted indirect cellular contact with HTB-19 monolayer populations which was achieved through the application of a semi-permeable 3 microM pore membrane partition. In vitro cytotoxic activity of DLN populations was not inhibited by the anti-oxidant agent, dimethyl sulfoxide (DMSO), but was inhibited in the presence of glutathione (GSH), superoxide dismutase (SOD), and vitamin E (alpha-tocopherol). Similarly, in vitro cytotoxic activity of DLN populations was also inhibited in the presence of sodium heparin (serine esterase inhibitor), and dexamethasone (inhibitor of neutrophil activation-degranulation phenomenon). Experimental results observed in these investigations collectively imply that the in vitro cytotoxic activity exerted by DLN preparations against HTB-19 populations is in part attributable to neutrophil-mediated cytotoxic immunity. This innate property of neutrophil populations involves their capacity to generate highly reactive oxygen "free" radical species (O2, HO, H2O2), and synthes

Interaction of Candida albicans, macrophages and fluconazole: in vitro and ex vivo observations

In recent years, medical interest in evaluating the interaction among mycetes, phagocytes, and antimycotic drugs has increased notably due to higher incidences of fungal infections in immunocompromised subjects and to the long-term therapy they require. In this study the in vitro and ex vivo interaction of fluconazole, at plasma concentrations, with mouse macrophages was evaluated in the presence of different inocula of Candida albicans. The results showed that fluconazole did not interfere negatively with phagocyte functions; conversely, according to different experimental conditions, it was able to increase both phagocytosis and intracellular killing of candida, probably exerting its action on the yeast rather than on the phagocyte. A higher enhancement of macrophage functions was observed in vitro when the drug was present in the medium with macrophages and candida in a 1:1 ratio.

Penetration of brodimoprim into human neutrophils and intracellular activity

The entry of an antibiotic into phagocytes is a prerequisite for its intracellular bioactivity against susceptible facultative or obligatory intracellular microorganisms. Brodimoprim is a dimethoxybenzylpyrimidine that has recently entered into clinical use, and its uptake into and elimination from human polymorphonuclear neutrophils (PMNs), together with its effects on normal phagocytic and antimicrobial mechanisms, have been investigated. Brodimoprim uptake by PMNs was determined by a velocity-gradient centrifugation technique under various experimental conditions and was expressed as the ratio of the intracellular to the extracellular drug concentration (C/E) in comparison with the C/E of trimethoprim, which was used as a control drug. After incubation with 7.5 micrograms of brodimoprim per ml, PMNs accumulated brodimoprim (C/E, 74.43 +/- 12.35 at 30 min) more avidly than trimethoprim (C/E, 20.97 +/- 6.61 at 30 min). The cellular uptake of brodimoprim was not affected by temperature, 2,4-dinitrophenol, or potassium fluoride and was increased with an increase in the pH of the medium. It was reduced in formaldehyde-killed PMNs. The efflux of brodimoprim was very rapid (46% after 5 min). The liposolubility of brodimoprim was about three times that of trimethoprim, as was the uptake. Therefore, a possible passive transmembrane diffusion mechanism might be proposed. Brodimoprim did not decrease either phagocytosis or phagocyte-mediated bactericidal activity, nor did it affect oxidative burst activity, as investigated by luminol-amplified chemiluminescence. On the basis of the pharmacokinetic data for brodimoprim, the concentration of 7.5 micrograms/ml was chosen as the highest concentration attainable in serum by oral therapy, and at this concentration of brodimoprim, the amount of drug that penetrated into PMNs was able to maintain its antimicrobial activity without interfering with the functions of the PMNs.

Fluconazole increases bactericidal activity of neutrophils

BACKGROUND

Candida infections after injury are associated with significant mortality. Death often results from gram negative sepsis. Because antifungal therapy lowers mortality seen with Candida infections, this study was undertaken to determine whether fluconazole (FCZ) augments host response against bacteria, specifically, the bactericidal activity of polymorphonuclear neutrophils (PMN).

METHODS

PMN from 23 volunteers were incubated with phosphate-buffered saline or FCZ (20 micrograms/mL or 40 micrograms/mL). Bactericidal activity of these PMN, as well as FCZ alone, was determined using Escherichia coli and a colony forming unit protocol.

RESULTS

PMN possess potent bactericidal activity while FCZ possesses minimal inherent bactericidal activity. PMN bactericidal activity is significantly augmented by preincubation with FCZ. This enhanced bactericidal state is greater than the combined individual bactericidal properties of either FCZ concentration and PMN.

CONCLUSIONS

FCZ augments PMN bactericidal activity. This augmentation may help to explain the improved survival of critically injured patients receiving FCZ.

Monoclonal antibodies to Cryptococcus neoformans glucuronoxylomannan enhance fluconazole efficacy

Monoclonal antibody (MAb) 2H1, which binds to the capsular glucuronoxylomannan (GXM) of the fungus Cryptococcus neoformans, prolonged survival and decreased fungal burden in an experimental murine infection. Fluconazole (FLU) is a triazole antibiotic which is effective against C. neoformans. The efficacy of MAb 2H1 in combination with FLU was studied in vitro with the murine macrophage-like cell line J7741.16 and in vivo in mice infected intravenously. In vitro, the combination of MAb 2H1 and FLU was more effective than either agent alone in reducing the number of CFU of C. neoformans cocultured with J774.16 cells. In combination with FLU, GXM-binding MAbs of the immunoglobulin M (IgM), IgG1, IgG2a, IgG2b, IgG3, and IgA isotypes were effective in reducing the numbers of CFU in C. neoformans-J774.16 cocultures. For the in vivo experiments, A/JCr mice were infected intravenously with 5 x 10(5) organisms treated with MAb and FLU. The therapeutic effect of MAb 2H1 was primarily to reduce the number of CFU in the lung and the serum GXM level, whereas FLU was most effective in reducing the number of CFU in the brain. Mice receiving combination therapy had lower numbers of CFU in the lung and serum GXM levels than mice treated with FLU alone. Administration of MAb 2H1 with or without FLU had little or no effect on the number of CFU in the brain. The results provide support for combined therapy.

Fluconazole penetration into the human prostate

Fluconazole concentrations in the serum and prostate of human volunteers undergoing transurethral resection for benign prostatic hypertrophy were measured. There was a high correlation (r = 0.783) between serum (mean = 6.6 micrograms/ml) and tissue (mean = 1.9 micrograms/g) fluconazole concentrations, and these data were used to construct a model for local tissue concentrations.

Novel aspect of amphotericin B action: accumulation in human monocytes potentiates killing of phagocytosed Candida albicans

The influence of low doses of amphotericin B on the capacity of human monocytes to kill Candida albicans was investigated. Killing rates were quantified by a novel flow cytometric assay and were found to be 37% +/- 3% (standard error of the mean) after 3 h. Preincubation of monocytes for 6 to 20 h with low concentrations of amphotericin B (0.2 microgram/ml) resulted in a markedly augmented fungicidal capacity. Enhancement of killing was 80% +/- 11% (standard error of the mean) over that by the controls. This effect did not appear to be due to amphotericin B-dependent monocyte activation; the respiratory burst and expression of human leukocyte antigen-DR were unaltered, and no stimulation of interleukin-1 beta release occurred. Cell-associated amphotericin B was extracted with acetonitrile and was quantified by scanning spectrophotometry. Amphotericin B appeared to accumulate in the cells, and intracellular concentrations attained after overnight incubation in 1 microgram of the drug per ml were estimated to be in the range of 50 fg per cell. The fact that intracellular accumulation was responsible for the enhanced fungicidal capacity of monocytes was supported by the findings that killing of Staphylococcus aureus remained normal and enhancement of killing of an amphotericin B-resistant C. albicans strain was minimal. Dramatic enhancement of monocyte fungicidal capacity probably extends to other amphotericin B-susceptible fungi and could represent a hitherto unrecognized determinant underlying the curative properties and prophylactic efficacy of this drug.

Effect of antimicrobial and antineoplastic drugs on the uptake of fluconazole by human neutrophils and tissue culture cells

The effect of eight antimicrobial and three antineoplastic drugs on the uptake of fluconazole by human neutrophils and culture epithelial cells was evaluated. Fluconazole reached higher concentrations intracellularly than extracellularly (cellular to extracellular concentration ratio C/E > or = 1.3) in the presence of therapeutical concentrations of the antimicrobial and antineoplastic agents evaluated.