Poly(D,L-lactide-coglycolide) particles containing gentamicin: pharmacokinetics and pharmacodynamics in Brucella melitensis-infected mice

Drug delivery systems containing gentamicin were studied as a treatment against experimental brucellosis in mice. Micro- and nanoparticles prepared by using poly(D,L-lactide-coglycolide) (PLGA) 502H and microparticles made of PLGA 75:25H were successfully delivered to the liver and the spleen, the target organs for Brucella melitensis. Both polymers have the same molecular weight but have different lactic acid/glycolic acid ratios. Microparticles of PLGA 502H and 75:25H released their contents in a sustained manner, in contrast to PLGA 502H nanoparticles, which were degraded almost completely during the first week postadministration. The values of the pharmacokinetic parameters after administration of a single intravenous dose of 1.5 mg/kg of body weight of loaded gentamicin revealed higher areas under the curve (AUCs) for the liver and the spleen and increased mean retention times (MRTs) compared to those for the free drug, indicating the successful uptake by phagocytic cells in both organs and the controlled release of the antibiotic. Both gentamicin-loaded PLGA 502H and 75:25H microparticles presented similar pharmacokinetic parameter values for the liver, but those made of PLGA 75:25 H were more effective in targeting the antibiotic to the spleen (higher AUCs and MRTs). The administration of three doses of 1.5 mg/kg significantly reduced the load associated with the splenic B. melitensis infection. Thus, the formulation made with the 75:25H polymer was more effective than that made with 502H microspheres (1.45-log and 0.45-log reductions, respectively, at 3 weeks posttreatment). Therefore, both, pharmacokinetic and pharmacodynamic parameters showed the suitability of 75:25H microspheres to reduce the infection of experimentally infected mice with B. melitensis.     

Intracellular killing of Brucella melitensis in human macrophages with microsphere-encapsulated gentamicin

OBJECTIVES: Treatment of human brucellosis demands antibiotic targeting into the mononuclear-phagocytic system. The aim of this work was to prepare and characterize particulate carriers containing gentamicin and to study their interactions with phagocytic cells and bactericidal activity against intracellular Brucella melitensis. METHODS: Different poly(lactide-co-glycolide) (PLGA) polymers with free carboxylic end-group were used to formulate micro- and nanoparticles containing gentamicin, by a water-oil-water solvent-evaporation technique. PLGA 502H and 75:25H microparticles were selected because they showed the highest gentamicin loadings as well as good physico-chemical properties and sustained release in vitro. RESULTS: Gentamicin-containing microspheres of both polymers were successfully phagocytosed by infected THP-1 human monocytes, and immunocytochemistry studies revealed that the antibiotic reached Brucella-specific compartments. A dose of 30 microg of encapsulated gentamicin was able to reduce intracellular Brucella infection by 2.2 log. CONCLUSIONS: Altogether, these results suggest that 502H and 75:25H microspheres are suitable carriers for gentamicin targeting inside human macrophages and thus for brucellosis treatment.     

Gentamicin-loaded microspheres for reducing the intracellular Brucella abortus load in infected monocytes

OBJECTIVES: The intracellular antibiotic efficiency of gentamicin-loaded microspheres in the context of Brucella-infected murine monocytes was examined in vitro with a view to developing improved therapies for the treatment of brucellosis. METHODS: Biodegradable microspheres made of end-group capped and uncapped poly(lactide-co-glycolide) 50:50 (PLGA 50:50 and PLGA 50:50H) and containing gentamicin sulphate were used to target Brucella abortus-infected J774 monocyte-macrophages. The infected cells were treated with 15 micro g of free or microencapsulated gentamicin and the efficacy of the treatments was measured after 24 h. RESULTS: The particle sizes were below 8 micro m and in vitro release of gentamicin from the microspheres followed a continuous (PLGA 50:50H) or a multiphasic (PLGA 50:50) pattern over 50 days. Treatment with gentamicin microencapsulated into the end-group uncapped PLGA 50:50H microspheres, decreased significantly the number of intracellular bacteria (typically by 2 log(10)) in comparison with untreated infected cells. Addition of 2% poloxamer 188 to the microsphere dispersion medium further reduced the infection (3.5 log(10)). Opsonization of the particles with non-immune mouse serum had no effect on the antibacterial efficacy of the microspheres. End-group capped PLGA 50:50 type microspheres containing the antibiotic were less effective at reducing intracellular bacteria ( approximately 1 log(10) reduction), although addition of poloxamer 188 to the dispersion medium again enhanced their intracellular antibacterial activity. Placebo PLGA 50:50 and PLGA 50:50H microspheres had no bactericidal activity. CONCLUSIONS: The results indicate that PLGA 50:50-microencapsulated gentamicin sulphate may be suitable for efficient drug targeting and delivery to reduce intracellular Brucella infections.     

Needle-Free Delivery of Acetalated Dextran-Encapsulated AR-12 Protects Mice from Francisella tularensis Lethal Challenge

Francisella tularensis causes tularemia and is a potential biothreat. Given the limited antibiotics for treating tularemia and the possible use of antibiotic-resistant strains as a biowarfare agent, new antibacterial agents are needed. AR-12 is an FDA-approved investigational new drug (IND) compound that induces autophagy and has shown host-directed, broad-spectrum activity in vitro against Salmonella enterica serovar Typhimurium and F. tularensis. We have shown that AR-12 encapsulated within acetalated dextran (Ace-DEX) microparticles (AR-12/MPs) significantly reduces host cell cytotoxicity compared to that with free AR-12, while retaining the ability to control S. Typhimurium within infected human macrophages. In the present study, the toxicity and efficacy of AR-12/MPs in controlling virulent type A F. tularensis SchuS4 infection were examined in vitro and in vivo. No significant toxicity of blank MPs or AR-12/MPs was observed in lung histology sections when the formulations were given intranasally to uninfected mice. In histology sections from the lungs of intranasally infected mice treated with the formulations, increased macrophage infiltration was observed for AR-12/MPs, with or without suboptimal gentamicin treatment, but not for blank MPs, soluble AR-12, or suboptimal gentamicin alone. AR-12/MPs dramatically reduced the burden of F. tularensis in infected human macrophages, in a manner similar to that of free AR-12. However, in vivo, AR-12/MPs significantly enhanced the survival of F. tularensis SchuS4-infected mice compared to that seen with free AR-12. In combination with suboptimal gentamicin treatment, AR-12/MPs further improved the survival of F. tularensis SchuS4-infected mice. These studies provide support for Ace-DEX-encapsulated AR-12 as a promising new therapeutic agent for tularemia.     

Treatment of Staphylococcus aureus skin infection in vivo using rifampicin loaded lipid nanoparticles

We have previously reported on a novel nanoparticle formulation that was effective at killing Staphylococcus aureus in vitro. Here, we report for the first time, the antibacterial effects of a lipidic nano-carrier containing rifampicin (NanoRIF) which can be used to successfully treat Methicillin-Resistant S. aureus (MRSA) infection at a reduced antibiotic dosage compared to the free drug in a skin wound model in mice. The formulation used contains the lipid monoolein, a cationic lipid N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (DOTAP) and the antibiotic. We have shown that rifampicin-loaded nanoparticles are more effective at treating infection in the skin wound model than the antibiotic alone. Cryo-TEM was used to capture for the first time, interactions of the formed nanoparticles with the cell wall of an individual bacterium. Our data strongly indicate enhanced binding of these charged nanoparticles with the negatively charged bacterial membrane. The efficacy we have now observed in vivo is of significant importance for the continued development of nanomedicine-based strategies to combat antibiotic resistant bacterial skin infections.

We report a novel cubosome formulation that is effective at killing Staphylococcus aureus in vitro.     

Gentamicin-loaded microspheres for treatment of experimental Brucella abortus infection in mice

OBJECTIVES: To evaluate the efficacy of gentamicin-loaded poly (lactide-co-glycolide) 50:50H (PLGA 50:50H) microspheres for the treatment of mice experimentally infected with Brucella abortus 2308. METHODS: The microspheres were dispersed in either 2% (w/v) poloxamer 188 saline solution, or deionized water with the help of a cell homogenizer to break up particle aggregates, and were administered intravenously or intraperitoneally to B. abortus-infected mice 7 days post-infection. RESULTS: Neither a single intravenous or intraperitoneal dose of 67 microg of gentamicin per mouse, nor three intraperitoneal doses of 100 microg of gentamicin per mouse, reduced the Brucella infection in the spleen compared with untreated mice 1 and 3 weeks post-treatment. Histological examination revealed granulation and tissue reaction in the periphery of spleen and liver of animals given three doses of the gentamicin-loaded microspheres. CONCLUSIONS: The lack of therapeutic activity of the gentamicin-loaded microspheres might be related to inappropriate microsphere size and aggregation, resulting also in a poor distribution of the microspheres in the spleen. The results might provide an example of practical problems related to particle size and aggregation for in vivo therapy with PLGA microspheres.     

Dry powders based on PLGA nanoparticles for pulmonary delivery of antibiotics: Modulation of encapsulation efficiency, release rate and lung deposition pattern by hydrophilic polymers

Although few experimental studies have been handled so far to exploit the potential of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) in the production of dry powders for antibiotic inhalation, there has been no comprehensive study on the role played by NP composition. In this work, we try to shed light on this aspect by designing and developing a pulmonary delivery system for antibiotics, such as tobramycin (Tb), based on PLGA NPs embedded in an inert microcarrier made of lactose, referred to as nano-embedded micro-particles (NEM). At nanosize level, helper hydrophilic polymers were used to impart the desired surface, bulk and release properties to PLGA NPs prepared by a modified emulsion-solvent diffusion technique. Results showed that poly(vinyl alcohol) (PVA) and chitosan (CS) are essential to optimise the size and modulate the surface properties of Tb-loaded PLGA NPs, whereas the use of alginate (Alg) allows efficient Tb entrapment within NPs and its release up to one month. Optimized formulations display good in vitro antimicrobial activity against P. aeruginosa planktonic cells. Furthermore, spray-drying of the NPs with lactose yielded NEM with peculiar but promising flow and aerosolization properties, while preserving the peculiar NP features. Nonetheless, in vivo biodistribution studies showed that PVA-modified Alg/PLGA NPs reached the deep lung, while CS-modified NPs were found in great amounts in the upper airways, lining lung epithelial surfaces. In conclusion, PLGA NP composition appears to play a crucial role in determining not only the technological features of NPs but, once processed in the form of NEM, also their in vitro/in vivo deposition pattern.     

Gallium Potentiates the Antibacterial Effect of Gentamicin against Francisella tularensis

The reasons why aminoglycosides are bactericidal have not been not fully elucidated, and evidence indicates that the cidal effects are at least partly dependent on iron. We demonstrate that availability of iron markedly affects the susceptibility of the facultative intracellular bacterium Francisella tularensis strain SCHU S4 to the aminoglycoside gentamicin. Specifically, the intracellular depots of iron were inversely correlated to gentamicin susceptibility, whereas the extracellular iron concentrations were directly correlated to the susceptibility. Further proof of the intimate link between iron availability and antibiotic susceptibility were the findings that a ΔfslA mutant, which is defective for siderophore-dependent uptake of ferric iron, showed enhanced gentamicin susceptibility and that a ΔfeoB mutant, which is defective for uptake of ferrous iron, displayed complete growth arrest in the presence of gentamicin. Based on the aforementioned findings, it was hypothesized that gallium could potentiate the effect of gentamicin, since gallium is sequestered by iron uptake systems. The ferrozine assay demonstrated that the presence of gallium inhibited >70% of the iron uptake. Addition of gentamicin and/or gallium to infected bone marrow-derived macrophages showed that both 100 μM gallium and 10 μg/ml of gentamicin inhibited intracellular growth of SCHU S4 and that the combined treatment acted synergistically. Moreover, treatment of F. tularensis-infected mice with gentamicin and gallium showed an additive effect. Collectively, the data demonstrate that SCHU S4 is dependent on iron to minimize the effects of gentamicin and that gallium, by inhibiting the iron uptake, potentiates the bactericidal effect of gentamicin in vitro and in vivo.     

PLGA/xylitol nanoparticles enhance antibiofilm activity via penetration into biofilm extracellular polymeric substances

Biofilms are gelatinous masses of microorganisms attached to wound surfaces. Previous studies suggest that biofilms generate resistance towards antibiotic treatments. It was reported that hydrogels containing xylitol and antibiotic combinations produced additive antibiofilm inhibition. However, hydrogel formulations lack specificity, due to which xylitol cannot penetrate into the biofilm matrix and gets easily degraded by bacterial beta lactamase enzymes. It was hypothesized that the incorporation of xylitol in PLGA (polylactic-co-glycolic acid) nanoparticles will enhance penetration into the EPS (extra polymeric substance) component of the biofilm matrix and potentially overcome the antibiotic resistance associated with the biofilms. The purpose of this study was to develop PLGA nanoparticles loaded with xylitol, which will enhance bacterial biofilm penetration. The nanoparticles were loaded with different amounts of xylitol (0.5–5% w/w) and characterized for physiochemical and drug release properties. The metabolic antibiofilm activity of the PLGA nanoparticles containing xylitol was demonstrated by an XTT assay using as references the cultures of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) and the polymicrobial biofilms of both bacterial strains. Live/dead viability staining was also performed to investigate the viability ratio of bacterial cells present in the biofilms. The biofilm penetration study of the PLGA nanoparticles was assessed by combining the nanoparticles with conjugated concanavalin A (Con A)-fluorescein isothiocyanate (FITC) and by viewing using confocal laser scanning electron microscopy (CLSM). In conclusion, the PLGA nanoparticles loaded with xylitol were successfully developed and were found to promote the antibiofilm activity of xylitol in infected wounds.

Biofilms are gelatinous masses of microorganisms attached to wound surfaces.     

Evaluation of the In Vitro Activity of Voriconazole As Predictive of In Vivo Outcome in a Murine Aspergillus fumigatus Infection Model

We have evaluated the in vitro activity of voriconazole against 61 strains of Aspergillus fumigatus by using broth microdilution, disk diffusion, and minimal fungicidal concentration procedures. We observed an excellent correlation between the results obtained with the three methods. Five percent of the strains showed MICs greater than or equal to the epidemiological cutoff value (ECV; 1 μg/ml). To assess whether MICs were predictive of in vivo outcome, we tested the efficacy of voriconazole at 25 mg/kg of body weight daily in an immunosuppressed murine model of disseminated infection using 10 strains representing various patterns of susceptibility to the drug as determined by the in vitro study. Voriconazole prolonged survival and reduced fungal load in the kidneys and brain in those mice infected with strains with MICs of ≤0.25 μg/ml, while in mice infected with strains with MICs of 0.5 to 2 μg/ml, the efficacy was varied and strain dependent and in mice infected with the strain with a MIC of 4 μg/ml, the antifungal did not show efficacy. Voriconazole reduced galactomannan antigenemia against practically all strains with a MIC of <4 μg/ml. Our results demonstrate that some relationship exists between voriconazole MICs and in vivo efficacy; however, further studies testing additional strains are needed to better ascertain which MIC values can predict clinical outcome.     

Pharmacodynamic Evaluation of the Activities of Six Parenteral Vancomycin Products Available in the United States

A recent report found that generic parenteral vancomycin products may not have in vivo efficacies equivalent to those of the innovator in a neutropenic murine thigh infection model despite having similar in vitro microbiological activities and murine serum pharmacokinetics. We compared the in vitro and in vivo activities of six of the parenteral vancomycin products available in the United States. The in vitro assessments for the potencies of the vancomycin products included MIC/minimal bactericidal concentration (MBC) determinations, quantifying the impact of human and murine serum on the MIC values, and time-kill studies. Also, the potencies of the vancomycin products were quantified with a biological assay, and the human and mouse serum protein binding rates for the vancomycin products were measured. The in vivo studies included dose-ranging experiments with the 6 vancomycin products for three isolates of Staphylococcus aureus in a neutropenic mouse thigh infection model. The pharmacokinetics of the vancomycin products were assessed in infected mice by population pharmacokinetic modeling. No differences were seen across the vancomycin products with regard to any in vitro evaluation. Inhibitory sigmoid maximal bacterial kill (E_max) modeling of the relationship between vancomycin dosage and the killing of the bacteria in mice in vivo yielded similar E_max and EC₅₀ (drug exposure driving one-half E_max) values for bacterial killing. Further, there were no differences in the pharmacokinetic clearances of the 6 vancomycin products from infected mice. There were no important pharmacodynamic differences in the in vitro or in vivo activities among the six vancomycin products evaluated.     

Host-based Prophylaxis Successfully Targets Liver Stage Malaria Parasites

Eliminating malaria parasites during the asymptomatic but obligate liver stages (LSs) of infection would stop disease and subsequent transmission. Unfortunately, only a single licensed drug that targets all LSs, Primaquine, is available. Targeting host proteins might significantly expand the repertoire of prophylactic drugs against malaria. Here, we demonstrate that both Bcl-2 inhibitors and P53 agonists dramatically reduce LS burden in a mouse malaria model in vitro and in vivo by altering the activity of key hepatocyte factors on which the parasite relies. Bcl-2 inhibitors act primarily by inducing apoptosis in infected hepatocytes, whereas P53 agonists eliminate parasites in an apoptosis-independent fashion. In combination, Bcl-2 inhibitors and P53 agonists act synergistically to delay, and in some cases completely prevent, the onset of blood stage disease. Both families of drugs are highly effective at doses that do not cause substantial hepatocyte cell death in vitro or liver damage in vivo. P53 agonists and Bcl-2 inhibitors were also effective when administered to humanized mice infected with Plasmodium falciparum. Our data demonstrate that host-based prophylaxis could be developed into an effective intervention strategy that eliminates LS parasites before the onset of clinical disease and thus opens a new avenue to prevent malaria.     

Characterization of Mouse Models of Mycobacterium avium Complex Infection and Evaluation of Drug Combinations

The Mycobacterium avium complex is the most common cause of nontuberculous mycobacterial lung disease worldwide; yet, an optimal treatment regimen for M. avium complex infection has not been established. Clarithromycin is accepted as the cornerstone drug for treatment of M. avium lung disease; however, good model systems, especially animal models, are needed to evaluate the most effective companion drugs. We performed a series of experiments to evaluate and use different mouse models (comparing BALB/c, C57BL/6, nude, and beige mice) of M. avium infection and to assess the anti-M. avium activity of single and combination drug regimens, in vitro, ex vivo, and in mice. In vitro, clarithromycin and moxifloxacin were most active against M. avium, and no antagonism was observed between these two drugs. Nude mice were more susceptible to M. avium infection than the other mouse strains tested, but the impact of treatment was most clearly seen in M. avium-infected BALB/c mice. The combination of clarithromycin-ethambutol-rifampin was more effective in all infected mice than moxifloxacin-ethambutol-rifampin; the addition of moxifloxacin to the clarithromycin-containing regimen did not increase treatment efficacy. Clarithromycin-containing regimens are the most effective for M. avium infection; substitution of moxifloxacin for clarithromycin had a negative impact on treatment efficacy.     

Estradiol loaded PLGA nanoparticles for oral administration: Effect of polymer molecular weight and copolymer composition on release behavior in vitro and in vivo

The present investigation was aimed at optimization of estradiol loaded PLGA nanoparticulate formulations resulting in improved oral bioavailability and sustained release of estradiol by varying the molecular weight and copolymer composition of PLGA. Nanoparticles were prepared following emulsion–diffusion–evaporation method employing didodecyldimethyl ammonium bromide (DMAB) as stabilizer. The effect of polymer molecular weight and copolymer composition on particle properties and release behavior (in vitro and in vivo) has been reported. Drug release in vitro decreased with increase in molecular weight and lactide content of PLGA. Zero order release was obtained with low molecular weight (14,500 and 45,000 Da) PLGA, while high molecular weight (85,000 and 213,000 Da) and different copolymer compositions followed square root of time (Higuchi's pattern) dependent release. The bioavailability of estradiol from nanoparticles was assessed in male Sprague Dawley (SD) rats at a dose of 1 mg estradiol/rat. The in vivo performance of the nanoparticles was found to be dependent on the particle size, polymer molecular weight and copolymer composition. The C_max of drug in the plasma was dependent on the polymer molecular weight and composition while particle size was found to influence the duration of release, suggesting smaller is better. The histopathological examination revealed absence of any inflammatory response with the formulations prepared of low/high molecular weight or high lactide content polymers for the studied period. Together, these results indicate that nanoparticulate formulations are ideal carriers for oral administration of estradiol having great potential to address the dose related issues of estradiol.     

Potent in vivo antimalarial activity of water-soluble artemisinin nano-preparations

Artemisinin is a remarkable compound whose derivatives and combinations with multiple drugs have been utilized at the forefront of malaria treatment. However, the inherent issues of the parent compound such as poor bioavailability, short serum half-life, and high first-pass metabolism partially limit further applications of this drug. In this study, we enhanced the aqueous phase solubility of artemisinin by encapsulating it in two nanocarriers based on the polymer polycaprolactone (ART-PCL) and lipid-based Large Unilamellar Vesicles (ART-LIPO) respectively. Both nanoformulations exhibit in vitro parasite killing activity against Plasmodium falciparum with the ART-LIPO performing at comparable efficacy to the control drug solubilized in ethanol. These water-soluble formulations showed potent in vivo antimalarial activity as well in the mouse model of malaria at equivalent doses of the parent drug. Additionally, the artemisinin-PCL nanoformulation used in combination with either pyrimethamine or chloroquine increased the survival of the Plasmodium berghei infected mice for more than 34 days and effectively cured the mice of the infection. We highlight the potential for polymer and liposome-based nanocarriers in improving not only the aqueous phase solubility of artemisinin but also concomitantly retaining its therapeutic efficacy in vivo as well.

Polymer and liposome-based nanocarriers not only improve the aqueous phase solubility of artemisinin but also helps to retain its therapeutic efficacy in vivo as well.     

Pharmacokinetics,Trypanosoma brucei gambiense Efficacy,and Time of Drug Action of DB829, a Preclinical Candidate for Treatment of Second-Stage Human African Trypanosomiasis

Human African trypanosomiasis (HAT, also called sleeping sickness), a neglected tropical disease endemic to sub-Saharan Africa, is caused by the parasites Trypanosoma brucei gambiense and T. brucei rhodesiense. Current drugs against this disease have significant limitations, including toxicity, increasing resistance, and/or a complicated parenteral treatment regimen. DB829 is a novel aza-diamidine that demonstrated excellent efficacy in mice infected with T. b. rhodesiense or T. b. brucei parasites. The current study examined the pharmacokinetics, in vitro and in vivo activity against T. b. gambiense, and time of drug action of DB829 in comparison to pentamidine. DB829 showed outstanding in vivo efficacy in mice infected with parasites of T. b. gambiense strains, despite having higher in vitro 50% inhibitory concentrations (IC₅₀s) than against T. b. rhodesiense strain STIB900. A single dose of DB829 administered intraperitoneally (5 mg/kg of body weight) cured all mice infected with different T. b. gambiense strains. No cross-resistance was observed between DB829 and pentamidine in T. b. gambiense strains isolated from melarsoprol-refractory patients. Compared to pentamidine, DB829 showed a greater systemic exposure when administered intraperitoneally, partially contributing to its improved efficacy. Isothermal microcalorimetry and in vivo time-to-kill studies revealed that DB829 is a slower-acting trypanocidal compound than pentamidine. A single dose of DB829 (20 mg/kg) administered intraperitoneally clears parasites from mouse blood within 2 to 5 days. In summary, DB829 is a promising preclinical candidate for the treatment of first- and second-stage HAT caused by both Trypanosoma brucei subspecies.     

In Vitro and In Vivo Antimicrobial Activities of Minocycline in Combination with Azithromycin,Clarithromycin, or Tigecycline against Pythium insidiosum

The present study investigated the in vitro and the in vivo interactions among azithromycin, clarithromycin, minocycline, and tigecycline against Pythium insidiosum. In vitro antimicrobial activities were determined by the broth microdilution method in accordance with CLSI document M38-A2, and the antibiotic interactions were assayed using the checkerboard MIC format. In vivo efficacy was determined using a rabbit infection model. The geometric mean MICs of azithromycin, clarithromycin, minocycline, and tigecycline against P. insidiosum were, respectively, 1.91, 1.38, 0.91, and 0.79 μg/ml. By checkerboard testing, all combinations resulted in in vitro synergistic interactions (>60%). Antagonism was not observed. The in vivo studies showed that azithromycin (20 mg/kg/day twice daily) alone or in combination with minocycline (10 mg/kg/day twice daily) significantly decreased the fungal burden. This study demonstrates that azithromycin possesses potent curative efficacy against subcutaneous pythiosis in the rabbit model.     

Full and Broad-Spectrum In Vivo Eradication of Catheter-Associated Biofilms Using Gentamicin-EDTA Antibiotic Lock Therapy

Biofilms that develop on indwelling devices are a major concern in clinical settings. While removal of colonized devices remains the most frequent strategy for avoiding device-related complications, antibiotic lock therapy constitutes an adjunct therapy for catheter-related infection. However, currently used antibiotic lock solutions are not fully effective against biofilms, thus warranting a search for new antibiotic locks. Metal-binding chelators have emerged as potential adjuvants due to their dual anticoagulant/antibiofilm activities, but studies investigating their efficiency were mainly in vitro or else focused on their effects in prevention of infection. To assess the ability of such chelators to eradicate mature biofilms, we used an in vivo model of a totally implantable venous access port inserted in rats and colonized by either Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, or Pseudomonas aeruginosa. We demonstrate that use of tetrasodium EDTA (30 mg/ml) as a supplement to the gentamicin (5 mg/ml) antibiotic lock solution associated with systemic antibiotics completely eradicated Gram-positive and Gram-negative bacterial biofilms developed in totally implantable venous access ports. Gentamicin-EDTA lock was able to eliminate biofilms with a single instillation, thus reducing length of treatment. Moreover, we show that this combination was effective for immunosuppressed rats. Lastly, we demonstrate that a gentamicin-EDTA lock is able to eradicate the biofilm formed by a gentamicin-resistant strain of methicillin-resistant S. aureus. This in vivo study demonstrates the potential of EDTA as an efficient antibiotic adjuvant to eradicate catheter-associated biofilms of major bacterial pathogens and thus provides a promising new lock solution.     

Guanabenz Repurposed as an Antiparasitic with Activity against Acute and Latent Toxoplasmosis

Toxoplasma gondii is a protozoan parasite that persists as a chronic infection. Toxoplasma evades immunity by forming tissue cysts, which reactivate to cause life-threatening disease during immune suppression. There is an urgent need to identify drugs capable of targeting these latent tissue cysts, which tend to form in the brain. We previously showed that translational control is critical during infections with both replicative and latent forms of Toxoplasma. Here we report that guanabenz, an FDA-approved drug that interferes with translational control, has antiparasitic activity against replicative stages of Toxoplasma and the related apicomplexan parasite Plasmodium falciparum (a malaria agent). We also found that inhibition of translational control interfered with tissue cyst biology in vitro. Toxoplasma bradyzoites present in these abnormal cysts were diminished and misconfigured, surrounded by empty space not seen in normal cysts. These findings prompted analysis of the efficacy of guanabenz in vivo by using established mouse models of acute and chronic toxoplasmosis. In addition to protecting mice from lethal doses of Toxoplasma, guanabenz has a remarkable ability to reduce the number of brain cysts in chronically infected mice. Our findings suggest that guanabenz can be repurposed into an effective antiparasitic with a unique ability to reduce tissue cysts in the brain.     

PLGA-coated methylene blue nanoparticles for photoacoustic imaging and photodynamic/photothermal cascaded precisely synergistic therapy of tumor

Photodynamic therapy (PDT) and photothermal therapy (PTT) are synergetic treatment strategies in antitumor treatment to achieve the best anticancer efficacy. Although traditional photosensitizer materials such as methylene blue (MB) have been widely studied for PDT, the photothermal effect is rarely reported. Herein, mono-component nanoparticles lactic-co-glycolic acid-coated methylene blue (MBNPs) based on methylene blue (MB) and lactic-co-glycolic acid (PLGA) were prepared by a facile solution-based emulsification method at room temperature. The resulting nanoparticles possess high photothermal conversion efficiency and excellent photodynamic effect. For the first time, the in vitro and in vivo tests indicated an enhanced antitumor efficacy for MBNPs with combined PDT and PTT. This study provides an efficient approach to fabricate nano-MB and also demonstrates the great potential of lactic-co-glycolic acid-coated MB for biomedical applications. Most importantly, the strong tumor growth inhibition by synergistic PTT and PDT demonstrates an excellent cascaded synergistic effect of MBNPs for the tumor therapy.

Photodynamic therapy (PDT) and photothermal therapy (PTT) are synergetic treatment strategies in antitumor treatment to achieve the best anticancer efficacy.