Pharmacokinetic/pharmacodynamic integration and modelling of oxytetracycline for the porcine pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida

Pharmacokinetic–pharmacodynamic (PK/PD) integration and modelling were used to predict dosage schedules of oxytetracycline for two pig pneumonia pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) were determined in broth and porcine serum. PK/PD integration established ratios of average concentration over 48 h (Cav0–48 h)/MIC of 5.87 and 0.27 µg/mL (P. multocida) and 0.70 and 0.85 µg/mL (A. pleuropneumoniae) for broth and serum MICs, respectively. PK/PD modelling of in vitro time–kill curves established broth and serum breakpoint values for area under curve (AUC0–24 h)/MIC for three levels of inhibition of growth, bacteriostasis and 3 and 4 log10 reductions in bacterial count. Doses were then predicted for each pathogen, based on Monte Carlo simulations, for: (i) bacteriostatic and bactericidal levels of kill; (ii) 50% and 90% target attainment rates (TAR); and (iii) single dosing and daily dosing at steady-state. For 90% TAR, predicted daily doses at steady-state for bactericidal actions were 1123 mg/kg (P. multocida) and 43 mg/kg (A. pleuropneumoniae) based on serum MICs. Lower TARs were predicted from broth MIC data; corresponding dose estimates were 95 mg/kg (P. multocida) and 34 mg/kg (A. pleuropneumoniae)

Appraising the seismic response of a retrofitted adobe historic structure, the role of modal updating and advanced computations

The concepts of structural assessment and retrofit of historical constructions are of particular complexity and require advanced knowledge in material science, conservation techniques and structural analysis. In particular, adobe constructions, given their low mechanical properties and brittle failure modes, are in immense need of comprehensive assessment and retrofitting plans. The current work focuses on the adobe Church of Kuñotambo in Peru, having experienced long periods of deterioration and earthquake-related damage. Under the ongoing Seismic Retrofitting Project (SRP) of the Getty Conservation Institute (GCI), the structural assessment of the church initiated in 2015 confirmed the low lateral capacity of the building and the poor connectivity between the structural parts. Based on the existing cracks and damage, a strengthening scheme was optimized and validated. After the implementation of the retrofitting plan, the quality of its execution and efficiency were assessed in 2019 with a new in situ campaign, which included ambient vibration testing (AVT) and sonic testing. From the acquired field data, the FE model of the retrofitted church was optimized, by updating the stiffness properties of masonry and discontinuities. Moreover, nonlinear static analyses were performed on the updated model in all in-plan directions. Finally, a displacement-based performance assessment was undertaken, under different earthquake limit states, demonstrating the adequacy of the retrofitting.Partial funding by Getty Conservation Institute – Seismic Retrofitting Project

Comparison of standardised versus non-standardised methods for testing the in vitro potency of oxytetracycline against mannheimia haemolytica and pasteurella multocida

The in vitro pharmacodynamics of oxytetracycline was established for six isolates of each of the calf pneumonia pathogens Mannheimia haemolytica and Pasteurella multocida. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and bacterial time-kill curves were determined in two matrices, Mueller Hinton broth (MHB) and calf serum. Geometric mean MIC ratios, serum:MHB, were 25.2:1 (M. haemolytica) and 27.4:1 (P. multocida). The degree of binding of oxytetracycline to serum protein was 52.4%. Differences between serum and broth MICs could not be accounted for by oxytetracycline binding to serum protein. In vitro time-kill data suggested a co-dependent killing action of oxytetracycline. The in vitro data indicate inhibition of the killing action of oxytetracycline by serum factor(s). The nature of the inhibition requires further study. The outcome of treatment with oxytetracycline of respiratory tract infections in calves caused by M. haemolytica and P. multocida may not be related solely to a direct killing action

Efficacy and safety of a novel oral isoxazoline, sarolaner (Simparica™), for the treatment of sarcoptic mange in dogs

AbstractThe efficacy of the novel isoxazoline, sarolaner (Simparica™) was investigated in dogs with clinical signs consistent with sarcoptic mange and harbouring natural infestations of Sarcoptes scabiei. One placebo-controlled laboratory study and one multi-centred field study with a commercial comparator containing imidacloprid/moxidectin (Advocate® spot-on) were conducted. Oral or topical treatments were administered on Days 0 and 30. Up to 10 skin scrapings were taken for the assessment of S. scabiei infestations from each dog before treatment and on Days 14, 30, 44 and 60 in the laboratory study, and on Days 30 and 60 in the field study. In the laboratory study, efficacy was calculated based on the percent reduction of mean live mite counts compared to the placebo group. In the field study parasitological cure rate (% dogs free of mites) was determined and non-inferiority of sarolaner to the control product was assessed.In the laboratory study 44 mixed breed dogs were enrolled in four batches. Due to decreasing mite counts in the placebo treated dogs, immunosuppression with dexamethasone (0.4mg/kg three times per week for two weeks) was initiated in all dogs on study at that time (n=6) and those subsequently enrolled (n=14). In the field study, dogs were enrolled in a 2:1 ratio (sarolaner:comparator); 79 dogs were assessed for efficacy and safety, and an additional 45 dogs were assessed for safety only. There were no treatment related adverse events in either study.In the laboratory study, no mites were found on any sarolaner-treated dogs 14 days after the first treatment except for one dog that had a single mite on Day 44. In the field study, the parasitological cure rate was 88.7% and 100% in the sarolaner group and 84.6% and 96.0% in the imidacloprid/moxidectin group, on Days 30 and 60, respectively. Statistical analysis showed that sarolaner was non-inferior to imidacloprid/moxidectin at both time points. The clinical signs of sarcoptic mange, including hair loss, papules, pruritus, erythema, and scaling/crusting improved throughout the study.Sarolaner was safe, achieved 100% reduction in the numbers of S. scabiei detected and resulted in marked improvement of the clinical signs of sarcoptic mange in dogs following two monthly oral administrations

Pharmacokinetic–pharmacodynamic integration and modelling of oxytetracycline for the calf pathogens Mannheimia haemolytica and Pasteurella multocida

A calf tissue cage model was used to study the pharmacokinetics (PK) and pharmacodynamics (PD) of oxytetracycline in serum, inflamed (exudate) and noninflamed (transudate) tissue cage fluids. After intramuscular administration, the PK was characterized by a long mean residence time of 28.3 hr. Based on minimum inhibitory concentrations (MICs) for six isolates each of Mannheimia haemolytica and Pasteurella multocida, measured in serum, integration of in vivo PK and in vitro PD data established area under serum concentration–time curve (AUC0–∞)/MIC ratios of 30.0 and 24.3 hr for M. haemolytica and P. multocida, respectively. Corresponding AUC0–∞/MIC ratios based on MICs in broth were 656 and 745 hr, respectively. PK-PD modelling of in vitro bacterial time–kill curves for oxytetracycline in serum established mean AUC0–24 hr/MIC ratios for 3log10 decrease in bacterial count of 27.5 hr (M. haemolytica) and 60.9 hr (P. multocida). Monte Carlo simulations predicted target attainment rate (TAR) dosages. Based on the potency of oxytetracycline in serum, the predicted 50% TAR single doses required to achieve a bacteriostatic action covering 48-hr periods were 197 mg/kg (M. haemolytica) and 314 mg/kg (P. multocida), respectively, against susceptible populations. Dosages based on the potency of oxytetracycline in broth were 25- and 27-fold lower (7.8 and 11.5 mg/kg) for M. haemolytica and P. multocida, respectively

Impact of growth matrix on pharmacodynamics of antimicrobial drugs for pig pneumonia pathogens

Abstract Background The most widely used measure of potency of antimicrobial drugs is Minimum Inhibitory Concentration (MIC). MIC is usually determined under standardised conditions in broths formulated to optimise bacterial growth on a species-by-species basis. This ensures comparability of data between laboratories. However, differences in values of MIC may arise between broths of differing chemical composition and for some drug classes major differences occur between broths and biological fluids such as serum and inflammatory exudate. Such differences must be taken into account, when breakpoint PK/PD indices are derived and used to predict dosages for clinical use. There is therefore interest in comparing MIC values in several broths and, in particular, in comparing broth values with those generated in serum. For the pig pneumonia pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida, MICs were determined for three drugs, florfenicol, oxytetracycline and marbofloxacin, in five broths [Mueller Hinton Broth (MHB), cation-adjusted Mueller Hinton Broth (CAMHB), Columbia Broth supplemented with NAD (CB), Brain Heart Infusion Broth (BHI) and Tryptic Soy Broth (TSB)] and in pig serum. Results For each drug, similar MIC values were obtained in all broths, with one exception, marbofloxacin having similar MICs for three broths and 4–5-fold higher MICs for two broths. In contrast, for both organisms, quantitative differences between broth and pig serum MICs were obtained after correction of MICs for drug binding to serum protein (fu serum MIC). Potency was greater (fu serum MIC lower) in serum than in broths for marbofloxacin and florfenicol for both organisms. For oxytetracycline fu serum:broth MIC ratios were 6.30:1 (P. multocida) and 0.35:1 (A. pleuropneumoniae), so that potency of this drug was reduced for the former species and increased for the latter species. The chemical composition of pig serum and broths was compared; major matrix differences in 14 constituents did not account for MIC differences. Bacterial growth rates were compared in broths and pig serum in the absence of drugs; it was concluded that broth/serum MIC differences might be due to differing growth rates in some but not all instances. Conclusions For all organisms and all drugs investigated in this study, it is suggested that broth MICs should be adjusted by an appropriate scaling factor when used to determine pharmacokinetic/pharmacodynamic breakpoints for dosage prediction

Differential susceptibility to tetracycline, oxytetracycline and doxycycline of the calf pathogens Mannheimia haemolytica and Pasteurella multocida in three growth media

For clinical isolates of bovine Mannheimia haemolytica and Pasteurella multocida, this study reports minimum inhibitory concentration (MIC) differences for tetracycline, oxytetracycline and doxycycline between cation‐adjusted Mueller‐Hinton broth (CAMHB), foetal bovine serum (FBS) and Roswell Park Memorial Institute (RPMI) medium. MICs were determined according to CLSI standards and additionally using five overlapping sets of twofold dilutions. Matrix effect: (a) free drug MICs and minimum bactericidal concentrations (MBC) for all drugs were significantly higher in FBS than in CAMHB for both pathogens (p < 0.001); (b) MICs and MBCs were higher for CAMHB and FBS compared to RPMI for P. multocida only. Net growth rate for P. multocida in CAMHB was significantly slower than in FBS and higher than in RPMI, correlating to MIC and MBC ranking. Drug effect: doxycycline MICs and MBCs were significantly lower (p < 0.001) in both CAMHB and FBS than tetracycline and oxytetracycline for both pathogens. Only for M. haemolytica were oxytetracycline MIC and MBC significantly lower than tetracycline, precluding the use of tetracycline to predict oxytetracycline susceptibility in this species. Determining potencies of tetracyclines in a physiological medium, such as FBS, is proposed, when the objective is correlation with pharmacokinetic data for dosage determination

VetCAST method for determination of the pharmacokineticpharmacodynamic cut-off values of a long-acting formulation of florfenicol to support clinical breakpoints for florfenicol Antimicrobial Susceptibility Testing in cattle

The PK/PD cut-off (PK/PDCO ) value of florfenicol for calf pathogens was determined for long acting formulations (MSD Nuflor® and a bioequivalent generic product). PK/PDCO is one of the three MICs considered by VetCAST, a sub-committee of the European Committee on Susceptibility Testing, to establish a Clinical Breakpoint for interpreting Antimicrobial Susceptibility Testing. A population model was built by pooling three pharmacokinetic data sets, obtained from 50 richly sampled calves, receiving one of two formulations (the pioneer product and a generic formulation). A virtual population of 5000 florfenicol disposition curves was generated by Monte Carlo Simulations over the 96 h of the assumed duration of action of the formulations. From this population, the maximum predicted MIC, for which 90% of calves can achieve some a priori selected critical value for two PK/PD indices, AUC/MIC and T>MIC, was established. Numerical values were established for two bacterial species of the bovine respiratory disease complex, Pasteurella multocida and Mannheimia haemolytica. It was concluded that the PK/PDCO of florfenicol for both AUC/MIC and T>MIC was 1 mg/L

Pharmacokinetic/pharmacodynamic integration and modelling of florfenicol for the pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida

Pharmacokinetic-pharmacodynamic (PK/PD) integration and modelling were used to predict dosage schedules for florfenicol for two pig pneumonia pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Pharmacokinetic data were pooled for two bioequivalent products, pioneer and generic formulations, administered intramuscularly to pigs at a dose rate of 15 mg/kg. Antibacterial potency was determined in vitro as minimum inhibitory concentration (MIC) and Mutant Prevention Concentration in broth and pig serum, for six isolates of each organism. For both organisms and for both serum and broth MICs, average concentration:MIC ratios over 48 h were similar and exceeded 2.5:1 and times greater than MIC exceeded 35 h. From in vitro time-kill curves, PK/PD modelling established serum breakpoint values for the index AUC24h/MIC for three levels of inhibition of growth, bacteriostasis and 3 and 4log10 reductions in bacterial count; means were 25.7, 40.2 and 47.0 h, respectively, for P. multocida and 24.6, 43.8 and 58.6 h for A. pleuropneumoniae. Using these PK and PD data, together with literature MIC distributions, doses for each pathogen were predicted for: (1) bacteriostatic and bactericidal levels of kill; (2) for 50 and 90% target attainment rates (TAR); and (3) for single dosing and daily dosing at steady state. Monte Carlo simulations for 90% TAR predicted single doses to achieve bacteriostatic and bactericidal actions over 48 h of 14.4 and 22.2 mg/kg (P. multocida) and 44.7 and 86.6 mg/kg (A. pleuropneumoniae). For daily doses at steady state, and 90% TAR bacteriostatic and bactericidal actions, dosages of 6.2 and 9.6 mg/kg (P. multocida) and 18.2 and 35.2 mg/kg (A. pleuropneumoniae) were required. PK/PD integration and modelling approaches to dose determination indicate the possibility of tailoring dose to a range of end-points