Evaluation of an on-farm culture system for the detection of subclinical mastitis pathogens in dairy cattle

The purpose of this observational study was to compare the performance of a novel on-farm culture (OFC) test with the reference method (RM) in identifying pathogens, and in particular Staphylococcus aureus, associated with subclinical mastitis (SCM) in dairy cattle. The OFC test (Mastatest HiSCC; Mastaplex Limited) for SCM uses a cartridge with 2 × 12 wells allowing 1 sample to be analyzed in duplicate (24 wells) or 2 samples analyzed simultaneously, each in 12 wells. Results of the milk analyses are reported hierarchically (Staph. aureus → coagulase-negative staphylococci (CNS) → other gram positive or coliform/gram negative → no bacteria present) and emailed within 24 h. Milk samples (617 quarter level from 158 cows and 70 cow level) were collected from 288 cows [individual cow somatic cell count (ICSCC) ≥150,000 cells/mL] on 9 purposefully selected farms known to have a high prevalence of clinical and subclinical Staph. aureus mastitis in Southland New Zealand. Quarter samples were analyzed individually (617 samples) and after animal-level pooling, providing 228 (158 + 70) cow-level samples. Samples were analyzed by the OFC test (in duplicate) and the RM (culture agar medium and latex test based on the recommendation by the National Mastitis Council) and identifications confirmed with MALDI-TOF mass spectrometry. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) for detection of Staph. aureus were all ∼90% with tight 95% confidence limits, and Cohen's kappa (κ) for agreement between the OFC test and RM was 0.81. Kappa for agreement between the OFC test duplicates was 0.93. About 35% of cows had only one quarter infected with Staph. aureus and all these animals could still be identified when pooled cow-level milk was analyzed. Although the high prevalence of Staph. aureus in the herds used in this study does not affect the Se and Sp values, it does elevate the PPV value (and decrease the NPV) and therefore use of PPV to extrapolate to a population with lower prevalence is not appropriate. For CNS, Sp, PPV, and NPV were all >0.8, κ was ≥0.6, and Se was >0.7. Kappa for agreement between the OFC test duplicates was 0.83. A result of "no bacteria detected" was reported in 13% of the cows with 93% agreement between OFC test and RM. We conclude that the OFC test provides a reliable method for detecting Staph. aureus in pooled cow-level milk even if only one quarter is infected; in the absence of Staph. aureus in the milk, it reliably identified CNS in pooled cow-level milk; it reliably identified cows with <10 cfu/10 µL of their milk. Compared with the RM, the method was rapid with results returned in 24 h of loading the cartridge.

Modeling the interaction of polymeric nanoparticles functionalized with cell penetrating peptides at the nano-bio interface

The interaction of nanoparticles with Caco-2 monolayers in cell culture underpins our predictions of the uptake of nanoformulations in vivo for drug delivery. Cell-penetrating peptides (CPP), such as oligoarginine, are currently of interest to enhance cellular uptake of bioactives and nanoparticles. This paper assesses the cellular association of poly(ethyl-cyanoacrylate) nanoparticles functionalized with di-arginine-histidine (RRH) in a Caco-2 cell model. We applied a computational model of particokinetics, In vitro Sedimentation, Diffusion and Dosimetry (ISDD) to predict the accumulation of nanoparticles on the cell surface. An important finding is that the proportion of nanoparticles associated with cells was less than 5 %. This has important implications for interpreting nanoparticle uptake in vitro. RRH-decoration does not appear to alter nanoparticle deposition, but increases association of nanoparticles with Caco-2 cells. Immediate deposition of nanoparticles on the cell surface was apparent and similar between formulations, but underestimated by the ISDD model. Key to understanding the nano-bio interface for drug delivery, nanoparticles that reach the cells were not necessarily absorbed by them, but can become detached. This variable of nanoparticle release from cells was incorporated into a new mathematical model presented here.

Studies on the safety and the tissue distribution of inhaled high-dose amorphous and crystalline rifampicin in a rat model

Inhaled delivery of rifampicin has the potential to achieve high drug concentrations in the lung and the blood for efficient treatment of tuberculosis (TB). Due to its existence as polymorphs, in vivo evaluation of the respiratory tract safety of inhalable amorphous and crystalline rifampicin particles, at clinically relevant high-dose, is necessary. This study investigates the lung and liver safety and the tissue distribution of rifampicin after intra-tracheal administration of high (≥25 mg/kg) doses of amorphous and crystalline powder formulations to Sprague Dawley rats. Powder formulations were administered by intra-tracheal insufflation to rats. Lung and liver safety were evaluated by histopathology. Serum alanine transaminase (ALT) and aspartate aminotransferase (AST) assays were performed to study the hepatic effects. Rifampicin was quantified in the tissues using LC-MS/MS. Intra-tracheal administration of rifampicin decreased the drug burden on the liver compared to oral administration based on its lower serum ALT activity. Repeated-dose intra-tracheal rifampicin was well tolerated by rats, confirmed by the absence of drug or delivery induced complexities. The histopathological evaluation of rat lungs, after both single and repeated drug administration for seven days, suggested the absence of drug-induced toxicity. Following single intra-tracheal delivery of 50 mg/kg doses, comparable rifampicin concentrations to that from same oral dose were observed in lung, liver, heart and brain. Inhaled delivery of high-dose rifampicin was safe to rat lungs and liver suggesting its potential for localized as well as systemic drug delivery without toxicity concerns.

Cell-based, animal and H1 receptor binding studies relative to the sedative effects of ketotifen and norketotifen atropisomers

OBJECTIVES

Ketotifen (K) and its active metabolite norketotifen (N) exist as optically active atropisomers. They both have antihistaminic and anti-inflammatory properties but the S-atropisomer of N (SN) causes less sedation than K and RN in rodents. This study investigated whether this could be related to a lower concentration of SN in brain or a lower affinity of SN for rat brain H₁ receptors.

METHODS

Ketotifen and norketotifen atropisomers were quantified using a validated chiral HPLC assay. RBE4 and Caco-2 cell monolayers were used in uptake and permeability studies, respectively. Free and total brain-to-plasma (B/P) ratios were determined after injecting racemic K and N into rat tail veins. Affinity for rat brain H₁ receptors (K_I ) was determined using the [³ H]mepyramine binding assay.

KEY FINDINGS

Uptake and permeation studies indicate no stereoselective transport for K or N. B/P ratios reveal the brain concentration of N is lower than K with no stereoselective transport into brain. Finally, the [³ H]mepyramine binding assay shows SN has the lowest affinity for rat brain H₁ receptors.

CONCLUSION

The lower sedative effect of SN in rodents is probably due to a combination of a lower uptake of N than K into the brain and less affinity of SN for CNS H₁ receptors.

A STELLA simulation model for in vitro dissolution testing of respirable size particles

In vitro dissolution testing is a useful quality control tool to discriminate the formulations and to approximate the in vivo drug release profiles. A dissolution apparatus has been custom-made for dissolution testing of dry powder formulations in a small volume of stationary medium (25 μL spread over 4.91 cm² area i.e. ~50 μm thick). To understand the system and predict the key parameters which influence the dissolution of respirable size particles, a simulation model was constructed using STELLA modeling software. Using this model, the permeation (dissolution followed by diffusion through the membrane) of two anti-tubercular drugs of differing solubilities, moxifloxacin (17.68 ± 0.85 mg mL^-1) and ethionamide (0.46 ± 0.02 mg mL^-1), from the respirable size particles and their diffusion from a solution were simulated. The simulated permeation profiles of moxifloxacin from solution and respirable size particles were similar, indicating fast dissolution of the particles. However, the simulated permeation profile of ethionamide from respirable size particles showed slower permeation compared to the solution indicating the slow dissolution of the respirable size particles of ethionamide. The sensitivity analysis suggested that increased mucus volume and membrane thickness decreased the permeation of drug. While this model was useful in predicting and distinguishing the dissolution behaviours of respirable size moxifloxacin and ethionamide, further improvement could be made using appropriate initial parameter values obtained by experiments.

Crystalline adduct of moxifloxacin with trans-cinnamic acid to reduce the aqueous solubility and dissolution rate for improved residence time in the lungs

A crystalline adduct of the anti-tubercular drug, moxifloxacin and trans-cinnamic acid (1:1 molar ratio (MCA_1:1)) was prepared to prolong the residence time of the drug in the lungs by reducing its solubility and dissolution rate. Whether the adduct is a salt or cocrystal has not been unequivocally determined. Equilibrium solubility and intrinsic dissolution rate measurements for the adduct (MCA_1:1) in phosphate buffered saline (PBS, pH 7.4) revealed a significant decrease in the solubility of moxifloxacin (from 17.68 ± 0.85 mg mL^-1 to 6.10 ± 0.05 mg mL^-1) and intrinsic dissolution rate (from 0.47 ± 0.04 mg cm^-2 min^-1 to 0.14 ± 0.03 mg cm^-2 min^-1) compared to the supplied moxifloxacin. The aerosolization behaviour of the adduct from an inhaler device, Aerolizer^®, using a Next Generation Impactor showed a fine particle fraction of 30.4 ± 1.2%. The dissolution behaviour of the fine particle dose of respirable particles collected was assessed in a small volume of stationary mucus fluid using a custom-made dissolution apparatus. The respirable adduct particles showed a lower dissolution (microscopic observation) and permeation compared to the supplied moxifloxacin. The crystalline adduct MCA_1:1 has a lower solubility and dissolution rate than moxifloxacin and could improve the local residence time and therapeutic action of moxifloxacin in the lungs.

Carrier-free combination dry powder inhaler formulation of ethionamide and moxifloxacin for treating drug-resistant tuberculosis

This study aimed to develop a combination dry powder formulation of ethionamide and moxifloxacin HCl as this combination is synergistic against drug-resistant Mycobacterium tuberculosis (Mtb). L-leucine (20% w/w) was added in the formulations to maximize the process yield. Moxifloxacin HCl and/or ethionamide powders with/without L-leucine were produced using a Buchi Mini Spray-dryer. A next generation impactor was used to determine the in vitro aerosolization efficiency. The powders were also characterized for other physicochemical properties and cytotoxicity. All the spray-dried powders were within the aerodynamic size range of <5.0 µm except ethionamide-only powder (6.0 µm). The combination powders with L-leucine aerosolized better (% fine particle fraction (FPF): 61.3 and 61.1 for ethionamide and moxifloxacin, respectively) than ethionamide-only (%FPF: 9.0) and moxifloxacin-only (%FPF: 30.8) powders. The combination powder particles were collapsed with wrinkled surfaces whereas moxifloxacin-only powders were spherical and smooth and ethionamide-only powders were angular-shaped flakes. The combination powders had low water content (<2.0%). All the powders were physically stable at 15% RH and 25 ± 2 °C during 1-month storage and tolerated by bronchial epithelial cell-lines up to 100 µg/ml. The improved aerosolization of the combination formulation may be helpful for the effective treatment of drug-resistant tuberculosis. Further studies are required to understand the mechanisms for improved aerosolization and test the synergistic activity of the combination powder.

Aniracetam does not improve working memory in neurologically healthy pigeons

Understanding the effects of cognitive enhancing drugs is an important area of research. Much of the research, however, has focused on restoring memory following some sort of disruption to the brain, such as damage or injections of scopolamine. Aniracetam is a positive AMPA-receptor modulator that has shown promise for improving memory under conditions when the brain has been damaged, but its effectiveness in improving memory in neurologically healthy subjects is unclear. The aim of the present study was to examine the effects of aniracetam (100mg/kg and 200 mg/kg) on short-term memory in "neurologically healthy" pigeons. Pigeons were administered aniracetam via either intramuscular injection or orally, either 30 or 60 minutes prior to testing on a delayed matching-to-sample task. Aniracetam had no effect on the pigeons' memory performance, nor did it affect response latency. These findings add to the growing evidence that, while effective at improving memory function in models of impaired memory, aniracetam has no effect in improving memory in healthy organisms.

The influence of storage relative humidity on aerosolization of co-spray dried powders of hygroscopic kanamycin with the hydrophobic drug rifampicin

The purpose of this study was to investigate the influence of storage humidity on in vitro aerosolization and physicochemical properties of co-spray dried powders of kanamycin with rifampicin. The powders were stored for one-month in an open Petri dish at different relative humidities (RHs) (15%, 43%, and 75%) and 25 ± 2 °C. The in vitro aerosolization (fine particle fraction, FPF) of the powders was determined by a next generation impactor (NGI). The moisture content, particle morphology and crystallinity of the powders were determined by Karl Fischer titration, scanning electron microscopy, and X-ray powder diffractometry, respectively. At all RH, the FPF of hydrophobic rifampicin-only powder was unaffected but the FPF of hygroscopic kanamycin-only powder significantly decreased even at 43% RH. The kanamycin-only particles fused together, crystallized and formed hard cakes at 75% RH. The aerosolization of kanamycin and rifampicin in the combination powders remained unaffected at 15% and 43% RH, but aerosolization significantly decreased at 75% RH. Enrichment of the surface of the particles with hydrophobic rifampicin did not protect the combination powders from moisture uptake but it prevented particle agglomeration up to 43% RH. At 75% RH, the moisture uptake led to agglomeration of the particles of the combination powder particles and consequently an increase in aerodynamic diameter. Further studies are required to investigate how rifampicin enrichment prevents particle agglomeration, the possible mechanisms (e.g. particle interactions due to capillary forces or electrostatic forces) for the changes in the aerosolization and changes in surface composition during storage.

In vitro dissolution testing of respirable size anti-tubercular drug particles using a small volume dissolution apparatus

A dissolution apparatus that uses a small volume of stationary medium (25 μL) has been developed for in vitro dissolution testing of respirable drug particles and used to evaluate the dissolution of two anti-tubercular drugs, moxifloxacin and ethionamide. Solubilities of moxifloxacin and ethionamide in phosphate buffered saline (PBS, pH 7.4) were 17.68 ± 0.85 mg mL^-1 and 0.46 ± 0.02 mg mL^-1 whereas in the presence of lung surfactant (0.4% w/v Curosurf^® in PBS) solubilities were 20.76 ± 0.35 mg mL^-1 and 0.56 ± 0.03 mg mL^-1, respectively. A fine particle dose (∼50 µg) of aerodynamically separated moxifloxacin or ethionamide particles (<6.4 µm) was collected onto a glass coverslip using a modified Twin Stage Impinger. The dissolution behaviour of the fine particle dose was evaluated at various perfusate flow rates (0.2, 0.4 and 0.8 mL min^-1 of PBS), mucus simulant concentrations (1.0, 1.5 and 2.0% w/v polyethylene oxide in PBS), and in the presence of lung surfactant. The dissolution behaviour of the respirable size particles was observed under an optical microscope and the dissolved drug that diffused into the perfusate was quantified by HPLC. The moxifloxacin particles disappeared quickly and showed faster permeation (<30 min) compared to the ethionamide particles at all the dissolution conditions evaluated. This study demonstrated the differences in the dissolution rates of moxifloxacin and ethionamide particles and may be useful to estimate the residence time of the inhaled dry powder particles in the lungs.

Translational studies on a ready-to-use intramuscular injection of penethamate for bovine mastitis

Bovine mastitis caused by bacterial infections of the mammary gland (udder) of dairy cows is a costly pathology for the dairy industry due to direct and indirect losses in production. Penethamate, a pro-drug of benzylpenicillin, is used by intramuscular injection (IM). The existing products are powders which must be reconstituted in water-for-injection and this presents difficulties in the field. Penethamate is too unstable to be formulated as an aqueous formulation but a chemically stable suspension formulation was possible in certain oils; however, some literature suggests that such formulations would have unacceptable prolonged release. The translational research proceeded iteratively from lab to the target species, rather than via laboratory animal trials. Pilot studies in cows suggested that some oily suspensions would give concentrations of benzylpenicillin, (in both blood and milk) comparable with those of the reconstituted product. A physicochemical screen and a low level in vitro-in vivo correlation (IVIVC) was cautiously used to guide selection of formulations for subsequent animal trials which have resulted in a lead formulation for good laboratory practices (GLP), good clinical practices (GCP) studies.

Preadmission predictors of academic performance in a pharmacy program: A longitudinal, multi-cohort study

INTRODUCTION

This study examined the extent to which a preadmission health science program and demographic variables predicted academic performance throughout an undergraduate pharmacy degree (BPharm) program.

METHODS

A longitudinal, multi-cohort study was undertaken of 557 students admitted to the University of Otago School of Pharmacy BPharm program between 2008 and 2012, from a preceding health science year (HSFY). Preadmission baseline data including health science grade point average (GPA), sex, age, ethnicity, residency status, and high school qualifications were matched against outputs of GPA performances in all three years of the BPharm program using regression analyses.

RESULTS

Five hundred thirty-eight students (96.6%) completed their BPharm degree. The regression models were significantly predictive of performance in the BPharm program with 57%, 43% and 38% of variances explained for GPA performance across years two, three and four, respectively (p < 0.001). Demographic variables including being male, being from certain minority ethnic groups or not having a specific domestic high school qualification were associated with lower GPA performances across the BPharm program compared to reference groups.

DISCUSSION AND CONCLUSIONS

Determining admission from performance rankings as the single selection tool holds reasonable predictive value early in progression, however additional measures may be warranted to better predict performances extending beyond the first year of the BPharm program.

A real-time in vitro assay to evaluate the release of macromolecules from liposomes

The availability of a real-time assay to experimentally investigate the release of encapsulated proteins would be beneficial given the interest in the use of liposomes as a drug delivery vehicle. Although simple assays for small molecular weight substances exist, assays to evaluate macromolecules do not. Here we describe a method that detects the release of model macromolecules from liposomes in real time. The assay employs the intermolecular distance-dependent phenomenon of fluorescence resonance energy transfer (FRET) between the fluorophore donor, fluorescein (FITC), and fluorescent quencher, QSY^® 9. The macromolecular species were conjugated to the markers fluorescein (44kDa dextran) and QSY^® 9 (67 kDa bovine serum albumin, BSA). Following confirmation of quenching between FITC-Dex and QSY^® 9-BSA, liposomes were loaded with the macromolecular markers and subjected to various treatments (high-pressure extrusion and Triton X solubilisation) to cause release from liposomes. An increase in FITC fluorescence was observed when liposomes were subjected to extrusion cycles. Surprisingly, the addition of Triton X did not cause an increase in fluorescence probably because the FRET pair became associated with mixed micelles. This assay method should be useful in studies to investigate the mechanisms by which macromolecules are released from liposomes, particularly when liposomes are exposed to release-triggers (eg, temperature change, pH change, ultrasound). Such understanding will underpin the formulation of triggered liposomal delivery systems for macromolecules.

Pharmacokinetics of Abamectin/Levamisole Combination in a Medium Chain Mono and Diglyceride-Based Vehicle and an In Vitro Release and In Vitro In Vivo Correlation Study for Levamisole

A combination of lipophilic and hydrophilic drugs in a single solution is a challenge due to their different physicochemical properties. In vitro and in vivo release studies are useful to optimize this solution. The in vitro (Franz diffusion cell) release rate of levamisole phosphate from an isotropic vehicle of medium chain mono and diglycerides (MCMDG) was significantly slower than the release from water. The injectable solution of the isotropic MCMDG-based system was prepared with 13.65% of levamisole phosphate and 0.5% of abamectin. Two milliliters/50 kg (0.04 ml/kg) was injected subcutaneously into five healthy adult sheep. None of the animals showed the signs of inflammation at injection site. Both drugs were assayed using validated HPLC methods. The absorption rates for levamisole (0.71 ± 0.32 h^-1) and abamectin (0.24 ± 0.08 day^-1) from the MCMDG-based formulation were considerably slower than those of other studies conducted on the commercial products. The t_max was delayed for levamisole (2.20 ± 0.45 h) and abamectin (4.20 ± 1.64 days) compared with those in published studies. Longer MRT values for levamisole (6.14 ± 1.14 h) and abamectin (8.80 ± 1.39 days) were found in this study compared to those reported. A correlation was observed between in vivo fraction absorbed and in vitro fraction released for levamisole phosphate in the MCMDG-based formulation. The injection vehicle of isotropic MCMDG-based system delayed the subcutaneous absorption of levamisole phosphate and abamectin compared to the commercial subcutaneous injection products for levamisole and abamectin. Notably, this isotropic MCMDG-based vehicle system is prepared with a combination of two drugs with different physicochemical properties.

An observational study of the effect of vibration on the caking of suspensions in oily vehicles

An oily suspension of penethamate (PNT) that was physically stable on storage, caked solidly during road/air transport. This paper reports on the caking behaviour of PNT oily suspension formulations exposed to vibrations in a lab-based test designed to simulate road/air transport. The lab-test was used to study the effects of container type (glass v PET) and formulation (oil, surfactant type and concentration) on the physical stability of suspension under vibration. Redispersibility of the sediment was lower at longer vibrations times and at higher intensity of vibration. Caking on vibration was strongly influenced by the type of container (caking in glass but not in PET) possibly due to tribo-charging of particles. Caking on vibration was dependent on the formulation: type and concentration of surfactant; type of oil. The physical stability of oily suspensions, and the effect of vibration are two areas which have been largely neglected in the pharmaceutical literature. This paper discusses some potential mechanisms for the observations but studies using fully characterised materials are required. Finally we conclude that static testing of physical stability of oily suspensions is not sufficient and that a vibrational stress test is required.

Quantification of Cell-Penetrating Peptide Associated with Polymeric Nanoparticles Using Isobaric-Tagging and MALDI-TOF MS/MS

High sensitivity quantification of the putative cell-penetrating peptide di-arginine-histidine (RRH) associated with poly (ethyl-cyanoacrylate) (PECA) nanoparticles was achieved without analyte separation, using a novel application of isobaric-tagging and high matrix-assisted laser desorption/ionization coupled to time-of-flight (MALDI-TOF) mass spectrometry. Isobaric-tagging reaction equilibrium was reached after 5 min, with 90% or greater RRH peptide successfully isobaric-tagged after 60 min. The accuracy was greater than 90%, which indicates good reliability of using isobaric-tagged RRH as an internal standard for RRH quantification. The sample intra- and inter-spot coefficients of variations were less than 11%, which indicate good repeatability. The majority of RRH peptides in the nanoparticle formulation were physically associated with the nanoparticles (46.6%), whereas only a small fraction remained unassociated (13.7%). The unrecovered RRH peptide (~40%) was assumed to be covalently associated with PECA nanoparticles. Graphical Abstract ᅟ.

An In Silico Knockout Model for Gastrointestinal Absorption Using a Systems Pharmacology Approach - Development and Application for Ketones

Gastrointestinal absorption and disposition of ketones is complex. Recent work describing the pharmacokinetics (PK) of d-β-hydroxybutyrate (BHB) following oral ingestion of a ketone monoester ((R)-3-hydroxybutyl (R)-3-hydroxybutyrate) found multiple input sites, nonlinear disposition and feedback on endogenous production. In the current work, a human systems pharmacology model for gastrointestinal absorption and subsequent disposition of small molecules (monocarboxylic acids with molecular weight < 200 Da) was developed with an application to a ketone monoester. The systems model was developed by collating the information from the literature and knowledge gained from empirical population modelling of the clinical data. In silico knockout variants of this systems model were used to explore the mechanism of gastrointestinal absorption of ketones. The knockouts included active absorption across different regions in the gut and also a passive diffusion knockout, giving 10 gut knockouts in total. Exploration of knockout variants has suggested that there are at least three distinct regions in the gut that contribute to absorption of ketones. Passive diffusion predominates in the proximal gut and active processes contribute to the absorption of ketones in the distal gut. Low doses are predominantly absorbed from the proximal gut by passive diffusion whereas high doses are absorbed across all sites in the gut. This work has provided mechanistic insight into the absorption process of ketones, in the form of unique in silico knockouts that have potential for application with other therapeutics. Future studies on absorption process of ketones are suggested to substantiate findings in this study.

Susceptibility to antimicrobials of mastitis-causing Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae from New Zealand and the USA as assessed by the disk diffusion test

OBJECTIVE

To compare the antimicrobial susceptibility patterns of three common mastitis pathogens (Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae) isolated from milk samples from New Zealand and the USA.

METHODS

A total of 182 S. aureus, 126 Str. uberis and 89 Str. dysgalactiae isolates from New Zealand (107, 106 and 41, respectively) and the USA (75, 20 and 48, respectively) were assessed using the disk diffusion test.

RESULTS

Susceptibility varied among the bacterial species. All isolates were susceptible to the amoxicillin-clavulanic acid combination. Resistance to lincomycin was most frequent (susceptibility of 8.6%) across all species. Non-susceptible (i.e. resistant or intermediate) isolates of S. aureus were identified for the three non-isoxazolyl penicillins (amoxicillin, ampicillin and penicillin: 20.6% and 36.0%) and lincomycin (99.9% and 94.6%) for NZ and the USA, respectively. Resistance to erythromycin (5.3%) and tetracyclines (6.7%) was detected only in isolates from the USA. There were differences in susceptibility between Str. uberis and Str. dysgalactiae; all streptococcal isolates demonstrated resistance to aminoglycosides (neomycin 52.4% and streptomycin 27.9%) and enrofloxacin (28%). Resistance of Str. dysgalactiae to tetracycline was almost 100.0% and to oxytetracycline 89.9%.

CONCLUSION AND CLINICAL RELEVANCE

Most of the isolates tested were susceptible to most of the antimicrobials commonly used for treatment of bovine mastitis, with the exception of the lincosamides. Susceptibility to a selected class-representative antimicrobial and at the genus level should be interpreted with caution. Differences between NZ and the USA confirm the value of national surveys to determine the susceptibility patterns of mastitis pathogens.

Surface Energy Determined by Inverse Gas Chromatography as a Tool to Investigate Particulate Interactions in Dry Powder Inhalers

Dry powder inhalers (DPIs) usually contain drug particles <6 µm which agglomerate and/ or adhere on the surfaces of large carriers particles. The detachment of drug particles from carriers and de-agglomeration of drug particles into primary particles is essential for drug deposition in the deep lung. These processes are influenced by the surface energy of particles. Inverse gas chromatography (IGC) has been used to determine the surface energy of powder particles used in DPI to characterize materials and to understand aerosolization behaviour. Early studies used an infinite dilution technique to determine nonpolar surface energy and free energy of adsorption for polar interactions separately. Although some correlations were observed with the change in nonpolar surface energy before and after micronization, milling and storage, a lack of consistency in the change of free energy of adsorption was common. Moreover, a consistent relationship between complex de-agglomeration behaviour and surface energy has not been established and there are even some examples of negative correlation. In fact, nonpolar surface energy at infinite dilution is an incomplete representation of powder surface characteristics. The techniques for measuring polar surface energy, total surface energy and surface energy distribution have provided more revealing information about surface energetics of powders. Surface energy distributions determined by IGC or surface energy analyser have been successfully used to understand energetic heterogeneity of surfaces, characterize different polymorphs and understand changes due to micronization, structural relaxation, dry coating and storage. Efforts have been made to utilize surface energy distribution data to calculate powder strength distribution and to explain complex de-agglomeration behaviour of DPI formulations.

The Population Pharmacokinetics of D-β-hydroxybutyrate Following Administration of (R)-3-Hydroxybutyl (R)-3-Hydroxybutyrate

The administration of ketones to induce a mild ketosis is of interest for the alleviation of symptoms associated with various neurological disorders. This study aimed to understand the pharmacokinetics (PK) of D-β-hydroxybutyrate (BHB) and quantify the sources of variability following a dose of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (ketone monoester). Healthy volunteers (n = 37) were given a single drink of the ketone monoester, following which, 833 blood BHB concentrations were measured. Two formulations and five dose levels of ketone monoester were used. A nonlinear mixed effect modelling approach was used to develop a population PK model. A one compartment disposition model with negative feedback effect on endogenous BHB production provided the best description of the data. Absorption was best described by two consecutive first-order inputs and elimination by dual processes involving first-order (CL = 10.9 L/h) and capacity limited elimination (V max = 4520 mg/h). Covariates identified were formulation (on relative oral bioavailable fraction and absorption rate constant) and dose (on relative oral bioavailable fraction). Lean body weight (on first-order clearance) and sex (on apparent volume of distribution) were also significant covariates. The PK of BHB is complicated by complex absorption process, endogenous production and nonlinear elimination. Formulation and dose appear to strongly influence the kinetic profile following ketone monoester administration. Further work is needed to quantify mechanisms of absorption and elimination of ketones for therapeutic use in the form of ketone monoester.

Signaled drug delivery and transport across the blood-brain barrier

We use a mathematical model to describe the delivery of a drug to a specific region of the brain. The drug is carried by liposomes that can release their cargo by application of focused ultrasound (US). Thereupon, the drug is absorbed through the endothelial cells that line the brain capillaries and form the physiologically important blood-brain barrier (BBB). We present a compartmental model of a capillary that is able to capture the complex binding and transport processes the drug undergoes in the blood plasma and at the BBB. We apply this model to the delivery of levodopa (L-dopa, used to treat Parkinson's disease) and doxorubicin (an anticancer agent). The goal is to optimize the delivery of drug while at the same time minimizing possible side effects of the US.

Stability of penethamate, a benzylpenicillin ester prodrug, in oily vehicles

Penethamate (PNT) is an ester prodrug of benzylpenicillin which is marketed as dry powder for reconstitution with aqueous vehicle prior to injection. The purpose of this paper was to investigate the chemical stability of PNT in oily formulations to provide a basis for a ready-to-use (RTU) oil-based PNT formulation. The chemical stability of PNT solutions and suspensions in light liquid paraffin (LP), medium chain triglyceride (MIG), ethyl oleate (EO) and sunflower oil (SO) was investigated at 30 °C. Solid state stability of PNT powder and stability of PNT in EO suspensions with different moisture contents were also evaluated. The solubility of PNT in the oils was in order SO > EO > MIG > LP. Degradation of PNT was rapid in oily solutions and less than 10% remained after 7-15 days. Stability of PNT decreased with increase in moisture content in ethyl oleate suspensions. PNT was stable over four weeks in the solid state. Hydrolysis, due to moisture in the oil formulation is not the only degradation mechanism. PNT stability (% drug remaining) in oily suspensions after 3.5 months was in the order LP (96.2%) > MIG (95.4%) > EO (94.1%) > SO (86%). A shelf-life of up to 5.5 years at 30 °C may be achieved for PNT suspension in these oils.

Kinetic and equilibrium studies of bile salt-liposome interactions

Research has suggested that exposure to sub-micellar concentrations of bile salts (BS) increases the permeability of lipid bilayers in a time-dependent manner. In this study, incubation of soy phosphatidylcholine small unilamellar vesicles (liposomes) with sub-micellar concentrations of cholate (C), deoxycholate (DC), 12-monoketocholate (MKC) or taurocholate (TC) in pH 7.2 buffer increased membrane fluidity and negative zeta potential in the order of increasing BS liposome-pH 7.2 buffer distribution coefficients (MKC < C ≈ TC < DC). In liposomes labeled with the dithionite-sensitive fluorescent lipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine (NBD-PE) in both leaflets and equilibrated with sub-micellar concentrations of BS, fluorescence decline during continuous exposure to dithionite was biphasic involving a rapid initial phase followed by a slower second phase. Membrane permeability to dithionite as measured by the rate of the second phase increased in the order control < MKC < TC ∼ C < DC. In liposomes labeled with NBD-PE in the inner leaflet only and incubated with the same concentrations of C, DC and MKC, membrane permeability to dithionite initially increased very rapidly in the order MKC < C < DC before impermeability to dithionite was restored after which fluorescence decline was consistent with NBD-PE flip-flop. For liposomes incubated with TC, membrane permeability to dithionite was only slightly increased and the decline in fluorescence was mainly the result of NBD-PE flip-flop. These results provide evidence that BS interact with lipid bilayers in a time-dependent manner that is different for conjugated and unconjugated BS. MKC appears to cause least disturbance to liposomal membranes but, when the actual MKC concentration in liposomes is taken into account, MKC is actually the most disruptive.

Parameterisation affects identifiability of population models

Identifiability is an important aspect of model development. In this work, using a simple one compartment population pharmacokinetic model, we show that identifiability of the variances of the random effects parameters are affected by the parameterisation of the fixed effects parameters.

Effect of 12-oxochenodeoxycholate on the pharmacokinetics and pharmacodynamics of morphine 6-glucuronide in Wistar rats

Objectives

The semi-synthetic bile salt, 12-oxochenodeoxycholate (OCDC also known as 12-monoketocholate), has been shown to enhance drug permeation across biological membranes with low cytotoxicity. Its effect on the analgesic potency and brain concentration of morphine 6-glucuronide (M6G) was studied in male Wistar rats.

Methods

Four groups of animals (n = 8) were given 5, 10 or 20 mg/kg OCDC or normal saline (control) by subcutaneous injection 30 min before a subcutaneous injection of 5 mg/kg M6G after which the hotplate test was performed on each rat at various times. After a 2 week wash-out period, the same rats (n = 30) were randomized to two equal groups and given OCDC (20 mg/kg) or normal saline 30 min before 5 mg/kg M6G. At five time points up to 3 h after M6G administration, three rats from each group were euthanized and blood and brain analyzed for M6G.

Key findings

The area under the analgesic effect versus time curve (AUAE) was found to be significantly (P &lt; 0.05) greater in rats given 20 mg/kg OCDC than in control rats. Area under the curve (AUC) for M6G in both plasma and brain was greater in OCDC-treated rats than in control rats, but the brain : plasma AUC ratio was lower.

Conclusions

OCDC enhances the analgesic effect of M6G but gives a lower brain : plasma ratio due to increasing M6G plasma levels probably by reducing its renal clearance.

Delivery of drugs to the brain via the blood brain barrier using colloidal carriers

Delivering drugs to the brain is challenging given the selective permeability of the blood brain barrier (BBB). Targeted colloidal carriers containing drug payloads offer some promise for enhanced and perhaps selective delivery to brain. This review examines the recent literature and identifies issues to be addressed if these systems are to be rationally designed. These include opsonization of nanoparticles and off-target clearance; the cerebral microvasculature, flow of nanoparticles in capillaries and binding to the capillary wall; and transcytosis. Capillary architecture, blood flow and BBB permeability are affected by disease and age and there are species differences. These complexities caution against making extravagant claims for a particular nanosystem but they also highlight the rich opportunities and need for critical research in this field.

Effects of bile salts on propranolol distribution into liposomes studied by capillary electrophoresis

The objective of this study was to study the effect of four different bile salts, cholate (C), deoxycholate (DC), taurocholate (TC), monoketocholate (MKC), on the membrane binding of a cationic model drug, propranolol, using capillary electrophoresis. The apparent distribution coefficient of propranolol in a buffer/liposome system, in the absence and presence of various concentrations of the bile salts, was measured using capillary electrophoresis frontal analysis. At bile salt concentrations which did not disrupt the liposomes, the bile salts increased the apparent distribution coefficient of propranolol in a concentration-dependent manner, to various extents (DC>C>TC>MKC). The mechanisms for these increases were inferred from studies of ion pairing between bile salts and propranolol using mobility shift affinity capillary electrophoresis and from zeta potential measurements. The bile salts ion-paired with propranolol to different extents as indicated by the estimated complexation constants (K range: 30-58 M(-1)). This was found to have a minor effect on the membrane distribution of propranolol only. The major effect is proposed to be due to the insertion of bile salt into the liposomal membranes leading to a more negatively charged membrane surface thereby providing stronger electrostatic interactions with the positively charged propranolol.

Formulation and stability of pilocarpine oral solution

The stability of four formulations of pilocarpine oral solution containing glycerol, hydroxybenzoate preservatives and lemon spirit was studied on storage for 90 days at 4, 25 and 38C using a stability-indicating high performance liquid chromatography assay. The solutions were prepared from pilocarpine hydrochloride powder (0.2 and 3mg/ml) in citrate buffer pH 5.5, or from eyedrops (3mg/ml) in citrate buffer pH 5.5 or phosphate buffer pH 7.5. Significant decomposition of pilocarpine occurred in the pH 7.5 formulation at all three temperatures. The data were adequately described by a first order model. Degradation in the pH 5.5 formulations was not significant over 90 days at 4C or 60 days at 25C. Decomposition at 38C was significant and adequately described by a zero order model. The lower 95 per cent confidence limits for 10 per cent decomposition were 36 days for the eye-drop formulation and 27 and 32 days for the 0.2 and 3mg/ml powder formulations respectively. Pilocarpine oral solution prepared from powder or eye-drops in pH 5.5 buffer is chemically stable for 60 or 90 days at 25C or 4C, respectively, and provides a stable dosage form.

Anin situsingle-pass perfusion model for assessing absorption across the intestinal mucosa of the brushtail possum

AIM

To develop an in situ animal model for assessing absorption of molecules across the intestinal mucosa of possums.

METHODS

A surgical preparation was used to perfuse known concentrations of reference compounds (fluorescein and luteinising hormone-releasing hormone; LHRH) through measured sections of selected regions (jejunum, caecum, proximal colon) of the intestinal tract of 19 possums, over a 2-h period. Plasma concentrations of the compounds, which were perfused either with or without co-administration of a permeation enhancer (sodium deoxycholic acid; SDA), were determined in the perfusion effluent, peripheral and in some instances in the pre-hepatic circulation by spectrofluorometry (fluorescein) or radioimmunoassay (LHRH). Pharmacokinetic parameters of both compounds in the possum were determined over a period of up to 4 h in a further 30 animals (fluorescein, n = 6; LHRH n = 24), from their plasma profiles following intravenous (I/V) administration of a bolus dose.

RESULTS

In animals perfused with 25 mg/ml fluorescein (Perfusion Experiment (PE) 1), the mean plasma concentration was 2.8 (SE 0.12) microg/ml in post-hepatic blood samples. When possums were perfused with 2.5 mg/ml fluorescein and 7 microg/ml LHRH (PE 2), mean plasma concentrations were 0.3 (SE 0.01) and 7.8 (SE 1.64) microg/ml fluorescein and 0.1 (SE 0.02) and 6.3 (SE 0.45) ng/ml LHRH, in the absence and presence of permeation enhancer, respectively. There was a poor correlation between pre-hepatic and post-hepatic concentrations.

CONCLUSIONS

The single-pass in situ perfusion technique provided a useful model for investigating basic information on the absorption of biocontrol agents across the intestinal tract of possums, but had limitations that must be recognised.

Effect of bile salts on the transport of morphine-6-glucuronide in rat brain endothelial cells

Bile salts are known to enhance the permeability of biological barriers but little is known about their effects on drug permeability across the blood-brain barrier (BBB). In this paper, the rat brain endothelial 4 (RBE4) cell monolayer incubated with astrocyte-conditioned medium was used as an in vitro model of the BBB to investigate the effects of cholate (C), 12-monoketocholate (MKC), deoxycholate (DC), and taurocholate (TC) on the transport of the hydrophilic drug, morphine-6-glucuronide (M6G). C, MKC, and TC at a concentration of 5 mM each and DC at 1 mM increased the permeability of M6G through the paracellular pathway based on a similar permeability pattern to that of sucrose. RBE4 cell uptake of M6G was unaffected by 5 mM C and TC, whereas 1 mM DC dramatically increased it due to an effect shown to be cytotoxicity as measured by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. Surprisingly, 1 mM MKC significantly increased M6G uptake without any cytotoxicity. In summary, all bile salts increased paracellular permeation of M6G but MKC also enhanced transcellular transport with little cytotoxicity. MKC appears to have the potential to modulate biophysical properties of the cell membrane or membrane-bound transporters and may therefore enhance drug delivery to the brain.

Transport and metabolism of MitoQ10, a mitochondria-targeted antioxidant, in Caco-2 cell monolayers

Mitoquinone (MitoQ10 mesylate) is a mitochondria-targeted antioxidant formulated for oral administration in the treatment of neurodegenerative diseases. We have investigated the absorption and metabolism of MitoQ10 in Caco-2 cell monolayers. The intracellular accumulation of MitoQ10 was 18–41% of the total amount of MitoQ10 added. Some of the intracellular MitoQ10 was reduced to mitoquinol and subsequently metabolized to glucuronide and sulfate conjugates. Transport of MitoQ10 was polarized with the apparent permeability (Papp) from basolateral (BL) to apical (AP) (PappBL→AP) being &gt;2.5-fold the Papp from apical to basolateral (PappAP→BL). In the presence of 4% bovine serum albumin on the basolateral side, the PappAP→BL value increased 7-fold compared with control. The PappBL→AP value decreased by 26, 31 and 61% in the presence of verapamil 100 μM, ciclosporin 10 and 30 μM, respectively, whereas the PappAP→BL value increased 71% in the presence of ciclosporin 30 μM. Apical efflux of mitoquinol sulfate and mitoquinol glucuronide conjugates was significantly decreased by ciclosporin 30 μM and the breast cancer receptor protein (BCRP) inhibitor, reserpine 25 μM, respectively. These results suggested that the bioavailability of MitoQ10 may be limited by intracellular metabolism and the action of P-glycoprotein and BCRP. However, the dramatic increase in absorptive Papp in the presence of bovine serum albumin on the receiver side suggests these barrier functions may be less significant in-vivo.

Hypromellose films for the delivery of growth factors for wound healing

Hypromellose was investigated as a carrier for extending topical growth factor delivery to wounds. Films of hypromellose (E4M, K4M and E10M) containing a model protein horseradish peroxidase (1 % w/w HRP, MW 40 000) were cast from aqueous solutions and dried at 37°C. In-vitro release was determined using Franz-type diffusion cells and films were mounted directly into the Franz cell or cast onto a wound dressing (Melolin) backing. There was an initial burst release then an extended release over 5 h. The Melolin backing significantly reduced the burst but not the extended release rates (P &lt; 0.05). Release of HRP was also determined from 7% w/v hypromellose gels and was significantly lower for E10M than E4M, suggesting that, once hydrated, the E10M hypromellose provides the greatest resistance to HRP release. The release profile of basic fibroblast growth factor from Melolin-backed films made from E4M hypromellose was not significantly different at any time point to that of HRP release from the same formulation. Hypromellose may be incorporated into a wound dressing such as Melolin to provide a prolonged release of an incorporated protein active.

Monoketocholate can decrease transcellular permeation of methotrexate across Caco-2 cell monolayers and reduce its intestinal absorption in rat

Objectives

Bile salts have been shown to decrease the absorption of methotrexate in the rat intestine by an unknown mechanism. We aimed to examine this effect.

Methods

We assessed apical-to-basolateral (AP-BL) permeation of methotrexate (5 μM) across Caco-2 cell monolayers pretreated with various concentrations (0, 0.25, 0.5, 1, 3 and 5 mm) of sodium cholate or its semisynthetic analogue, sodium 12-monoketocholate. We also determined the effect of orally administered 12-monoketocholate on the intestinal absorption of methotrexate in rats to evaluate a possible in-vitro–in-vivo correlation.

Key findings

It was found that sodium cholate and sodium 12-monoketocholate decreased the AP-BL permeation of methotrexate at low concentrations (maximal inhibition at 0.25 and 1 mm, respectively) and increased it at higher concentrations. Determination of [14C] mannitol permeation and electrical resistance of monolayers during experiments showed that membrane integrity was not compromised at low concentrations of bile salts but was disrupted at higher concentrations. Subsequently, we examined the effect of the simultaneous oral administration of sodium 12-monoketocholate (4, 20, 40 and 80 mg/kg) on the intestinal absorption of methotrexate in rats after an oral dose (5 mg/kg). The pharmacokinetic study showed that 12-monoketocholate at 4 and 20 mg/kg did not change the methotrexate area under the serum concentration–time curve whereas sodium 12-monoketocholate at 40 and 80 mg/kg significantly reduced it.

Conclusions

Sodium 12-monoketocholate appears to decrease the intestinal absorption of methotrexate in rats by inhibition of transcellular active transport.