Targeting and arginine-driven synergizing photodynamic therapy with nutritional immunotherapy nanosystems for combating MRSA biofilms.

The resistance and immune escape of methicillin-resistant Staphylococcus aureus (MRSA) biofilms cause recalcitrant infections. Here, we design a targeting and synergizing cascade PDT with nutritional immunotherapy nanosystems (Arg-PCN@Gel) containing PCN-224 as PDT platform for providing reactive oxygen species (ROS), incorporating arginine (Arg) as nitric oxide (NO) donor to cascade with ROS to produce more lethal ONOO- and promote immune response, and coating with gelatin as targeting agent and persistent Arg provider. The nanosystems adhered to the autolysin of MRSA and inhibited Arg metabolism by down-regulating icdA and icaA. It suppressed polysaccharide intercellular adhesin and extracellular DNA synthesis to prevent biofilm formation. The NO broke mature biofilms and helped ROS and ONOO- penetrate into biofilms to inactivate internal MRSA. Arg-PCN@Gel drove Arg to enhance immunity via inducible NO synthase/NO axis and arginase/polyamine axis and achieve efficient target treatment in MRSA biofilm infections. The targeting and cascading PDT synergized with nutritional immunotherapy provide an effective promising strategy for biofilm-associated infections.

Formulation of a rational dosage regimen of ceftiofur hydrochloride oily suspension by pharmacokinetic-pharmacodynamic (PK-PD) model for treatment of swine Streptococcus suis infection.

BACKGROUND: Our previously prepared ceftiofur (CEF) hydrochloride oily suspension shows potential wide applications for controlling swine Streptococcus suis infections, while the irrational dose has not been formulated. OBJECTIVES: The rational dose regimens of CEF oily suspension against S. suis were systematically studied using a pharmacokinetic-pharmacodynamic model method. METHODS: The healthy and infected pigs were intramuscularly administered CEF hydrochloride oily suspension at a single dose of 5 mg/kg, and then the plasma and pulmonary epithelial lining fluid (PELF) were collected at different times. The minimum inhibitory concentration (MIC), minimal bactericidal concentration, mutant prevention concentration (MPC), post-antibiotic effect (PAE), and time-killing curves were determined. Subsequently, the area under the curve by the MIC (AUC0-24h/MIC) values of desfuroylceftiofur (DFC) in the PELF was obtained by integrating in vivo pharmacokinetic data of the infected pigs and ex vivo pharmacodynamic data using the sigmoid Emax (Hill) equation. The dose was calculated based on the AUC0-24h/MIC values for bacteriostatic action, bactericidal action, and bacterial elimination. RESULTS: The peak concentration, the area under the concentration-time curve, and the time to peak for PELF's DFC were 24.76 ± 0.92 µg/mL, 811.99 ± 54.70 µg·h/mL, and 8.00 h in healthy pigs, and 33.04 ± 0.99 µg/mL, 735.85 ± 26.20 µg·h/mL, and 8.00 h in infected pigs, respectively. The MIC of PELF's DFC against S. suis strain was 0.25 µg/mL. There was strong concentration-dependent activity as determined by MPC, PAE, and the time-killing curves. The AUC0-24h/MIC values of PELF's DFC for bacteriostatic activity, bactericidal activity, and virtual eradication of bacteria were 6.54 h, 9.69 h, and 11.49 h, respectively. Thus, a dosage regimen of 1.94 mg/kg every 72 h could be sufficient to reach bactericidal activity. CONCLUSIONS: A rational dosage regimen was recommended, and it could assist in increasing the treatment effectiveness of CEF hydrochloride oily suspension against S. Suis infections.

Discovery of novel nitrogenous heterocyclic-containing quinoxaline-1,4-di-N-oxides as potent activator of autophagy in M.tb-infected macrophages.

As a continuation of our research on antimycobacterial agents, a series of novel quinoxaline-1,4-di-N-oxides (QdNOs) containing various nitrogenous heterocyclic moieties at the R6 position were designed and synthesized. Antimycobacterial activities, as well as the cytotoxic effects, of the compounds were assayed. Four compounds (6b, 6f, 6n, and 6o), characterized by 2-carboxylate ethyl or benzyl ester, 6-imidazolyl or 1,2,4-triazolyl, and a 7-fluorine group, exhibited the most potent antimycobacterial activity against M.tb strain H37Rv (MIC ≤ 0.25 µg/mL) with low toxicity in VERO cells (SI = 169.3-412.1). Compound 6o also exhibited excellent antimycobacterial activity in an M.tb-infected macrophage model and was selected for further exploration of the mode of antimycobacterial action of QdNOs. The results showed that compound 6o was capable of disrupting membrane integrity and disturbing energy homeostasis in M.tb. Furthermore, compound 6o noticeably increased cellular ROS levels and, subsequently, induced autophagy in M.tb-infected macrophages, possibly indicating the pathways of QdNOs-mediated inhibition of intracellular M.tb replication. The in vivo pharmacokinetic (PK) profiles indicated that compounds 6o was acceptably safe and possesses favorable PK properties. Altogether, these findings suggest that compound 6o is a promising antimycobacterial candidate for further research.

Dosage Regimen Formulation and Therapeutic Effect Evaluation of Cyadox Nanosuspension Against Dairy Cow Mastitis Caused by Staphylococcus aureus.

AIMS: In this study, the dosage regimen establishment of cyadox nanosuspension against dairy cow mastitis caused by Staphylococcus aureus (S. aureus) was used as example to provide a general reference for the other novel nanocrystal preparations. METHODS: The effect of cyadox against S. aureus isolates from dairy cows were firstly estimated and then the dosing regimen of nanosuspension after intramammary administration was optimized according to the model of ex vivo pharmacokinetic (PK) and pharmacodynamic (PD). The therapeutic efficacy of the predicted dosage regimen was evaluated. RESULTS: The results demonstrated that cyadox has a concentration-dependent effect on S. aureus. The smallest and highest values of minimum inhibitory concentration (MIC) against 80 isolates was 8 and 64 µg/mL, respectively. The corresponding MIC 50 and MIC 90 was 16 and 32 µg/mL, respectively. The MIC against the pathogenic S. aureus SAHZ156001 in broth and milk were 16 and 32 µg/mL, respectively. The AUC 0-last and C max of cyadox in milk were 4442.877 µg*h/mL and 753.052 µg/mL, respectively. According to the inhibitory sigmoid E max modeling and dosage equation, the daily doses were predicted 1.6, 6.6, and 12.2 mL/gland to achieve bacteriostatic, bactericidal, and elimination effects. The dosage internal was daily administration for continuous three days. CONCLUSION: The clinical experiment showed that the efficient rates were 100, 100, and 90.9%, and the curative rates were 100, 81.8, and 63.6% in 12.2, 6.6 and 1.6 ml/gland groups, respectively. These results showed that cyadox nanosuspension had a good prospect as intramammary infusion to cure dairy cow mastitis infected by S. aureus. This study will be helpful for providing reference for nanocrystal preparation dosage regimen formulation.

The antibacterial activities of aditoprim and its efficacy in the treatment of swine streptococcosis.

Aditoprim (ADP) has potential use as an antimicrobial agent in animals. However, its pharmacodynamic properties have not been systematically studied yet. In this study, the in vitro antibacterial activities of ADP and its main metabolites were assayed, and the in vivo antibacterial efficacy of ADP for the treatment of swine streptococcosis was evaluated. It was shown that Salmonella and Streptococcus from swine, Escherichia coli and Salmonella from chickens, E. coli, Streptococcus, Mannheimia, Pasteurella from calves, Streptococcus and Mannheimia from sheep, and E. coli, Flavobacterium columnare, Acinetobacter baumannii and Yersinia ruckeri from fishes were highly susceptible to ADP. Haemophilus parasuis from swine, Staphylococcus aureus, Aeromonas punctate, Mycobacterium tuberculosis, Streptococcus agalactiae from fishes, and Klebsiella from calves and sheep showed moderate susceptibility to ADP, whereas E. coli, Actinobacillus pleuropneumonia, Pasteurella, S. aureus, Clostridium perfringens from swine, S. aureus, C. perfringens from chickens, and S. aureus from calves were resistant to ADP. The main metabolites of ADP showed equal activity to that of their parent compound, and the prevention and therapeutic dosages of ADP recommended for swine streptococcosis were 10 and 20~40 mg/kg b.w., respectively. This study firstly showed that ADP had strong antibacterial activity and had potential to be used as a single drug in the treatment of bacterial infectious diseases.

Antibiotic alternatives: the substitution of antibiotics in animal husbandry?

It is a common practice for decades to use of sub-therapeutic dose of antibiotics in food-animal feeds to prevent animals from diseases and to improve production performance in modern animal husbandry. In the meantime, concerns over the increasing emergence of antibiotic-resistant bacteria due to the unreasonable use of antibiotics and an appearance of less novelty antibiotics have prompted efforts to develop so-called alternatives to antibiotics. Whether or not the alternatives could really replace antibiotics remains a controversial issue. This review summarizes recent development and perspectives of alternatives to antibiotics. The mechanism of actions, applications, and prospectives of the alternatives such as immunity modulating agents, bacteriophages and their lysins, antimicrobial peptides, pro-, pre-, and synbiotics, plant extracts, inhibitors targeting pathogenicity (bacterial quorum sensing, biofilm, and virulence), and feeding enzymes are thoroughly discussed. Lastly, the feasibility of alternatives to antibiotics is deeply analyzed. It is hard to conclude that the alternatives might substitute antibiotics in veterinary medicine in the foreseeable future. At the present time, prudent use of antibiotics and the establishment of scientific monitoring systems are the best and fastest way to limit the adverse effects of the abuse of antibiotics and to ensure the safety of animal-derived food and environment.

Solid lipid nanoparticle suspension enhanced the therapeutic efficacy of praziquantel against tapeworm.

Hydatid disease caused by tapeworm is an increasing public health and socioeconomic concern. In order to enhance the therapeutic efficacy of praziquantel (PZQ) against tapeworm, PZQ-loaded hydrogenated castor oil solid lipid nanoparticle (PZQ-HCO-SLN) suspension was prepared by a hot homogenization and ultrasonication method. The stability of the suspension at 4°C and room temperature was evaluated by the physicochemical characteristics of the nanoparticles and in-vitro release pattern of the suspension. Pharmacokinetics was studied after subcutaneous administration of the suspension in dogs. The therapeutic effect of the novel formulation was evaluated in dogs naturally infected with Echinococcus granulosus. The results showed that the drug recovery of the suspension was 97.59% ± 7.56%. Nanoparticle diameter, polydispersivity index, and zeta potential were 263.00 ± 11.15 nm, 0.34 ± 0.06, and -11.57 ± 1.12 mV, respectively and showed no significant changes after 4 months of storage at both 4°C and room temperature. The stored suspensions displayed similar in-vitro release patterns as that of the newly prepared one. SLNs increased the bioavailability of PZQ 5.67-fold and extended the mean residence time of the drug from 56.71 to 280.38 hours. Single subcutaneous administration of PZQ-HCO-SLN suspension obtained enhanced therapeutic efficacy against tapeworm in infected dogs. At the dose of 5 mg/kg, the stool-ova reduction and negative conversion rates and tapeworm removal rate of the suspension were 100%, while the native PZQ were 91.55%, 87.5%, and 66.7%. When the dose reduced to 0.5 mg/kg, the native drug showed no effect, but the suspension still got the same therapeutic efficacy as that of the 5 mg/kg native PZQ. These results demonstrate that the PZQ-HCO-SLN suspension is a promising formulation to enhance the therapeutic efficacy of PZQ.

Acute toxicity study of tilmicosin-loaded hydrogenated castor oil-solid lipid nanoparticles.

BACKGROUND: Our previous studies demonstrated that tilmicosin-loaded hydrogenated castor oil solid lipid nanoparticles (Til-HCO-SLN) are a promising formulation for enhanced pharmacological activity and therapeutic efficacy in veterinary use. The purpose of this work was to evaluate the acute toxicity of Til-HCO-SLN. METHODS: Two nanoparticle doses were used for the study in ICR mice. The low dose (766 mg/kg.bw) with tilmicosin 7.5 times of the clinic dosage and below the median lethal dose (LD(50)) was subcutaneously administered twice on the first and 7th day. The single high dose (5 g/kg.bw) was the practical upper limit in an acute toxicity study and was administered subcutaneously on the first day. Blank HCO-SLN, native tilmicosin, and saline solution were included as controls. After medication, animals were monitored over 14 days, and then necropsied. Signs of toxicity were evaluated via mortality, symptoms of treatment effect, gross and microscopic pathology, and hematologic and biochemical parameters. RESULTS: After administration of native tilmicosin, all mice died within 2 h in the high dose group, in the low dose group 3 died after the first and 2 died after the second injections. The surviving mice in the tilmicosin low dose group showed hypoactivity, accelerated breath, gloomy spirit and lethargy. In contrast, all mice in Til-HCO-SLN and blank HCO-SLN groups survived at both low and high doses. The high nanoparticle dose induced transient clinical symptoms of treatment effect such as transient reversible action retardation, anorexy and gloomy spirit, increased spleen and liver coefficients and decreased heart coefficients, microscopic pathological changes of liver, spleen and heart, and minor changes in hematologic and biochemical parameters, but no adverse effects were observed in the nanoparticle low dose group. CONCLUSIONS: The results revealed that the LD50 of Til-HCO-SLN and blank HCO-SLN exceeded 5 g/kg.bw and thus the nanoparticles are considered low toxic according to the toxicity categories of chemicals. Moreover, HCO-SLN significantly decreased the toxicity of tilmicosin. Normal clinic dosage of Til-HCO-SLN is safe as evaluated by acute toxicity.

Formulation, characterization and pharmacokinetics of praziquantel-loaded hydrogenated castor oil solid lipid nanoparticles.

AIM: The purpose of this study was to formulate praziquantel (PZQ)-loaded hydrogenated castor oil (HCO) solid lipid nanoparticles (SLN) to enhance the bioavailability and prolong the systemic circulation of the drug. MATERIALS & METHODS: PZQ was encapsulated into HCO nanoparticles by a hot homogenization and ultrasonication method. The physicochemical characteristics of SLN were investigated by optical microscope, scanning electron microscopy and photon correlation spectroscopy. Pharmacokinetics were studied after oral, subcutaneous and intramuscular administration in mice. RESULTS: The diameter, polydispersivity index, zeta potential, encapsulation efficiency and loading capacity of the nanoparticles were 344.0 +/- 15.1 nm, 0.31 +/- 0.08, -16.7 +/- 0.5 mV, 62.17 +/- 6.53% and 12.43 +/- 1.31%, respectively. In vitro release of PZQ-loaded HCO-SLN exhibited an initial burst release followed by a sustained release. SLN increased the bioavailability of PZQ by 14.9-, 16.1- and 2.6-fold, and extended the mean residence time of the drug from 7.6, 6.6 and 8.2 to 95.9, 151.6 and 48.2 h after oral, subcutaneous and intramuscular administration, respectively. CONCLUSION: The PZQ-loaded HCO-SLN could be a promising formulation to enhance the pharmacological activity of PZQ.