In vitro dynamic pharmacokinetic/pharmacodynamic(PK/PD) modeling and PK/PD cutoff of cefquinome against Haemophilus parasuis.

BACKGROUND: Haemophilus parasuis (H. parasuis) causes Glässer's disease and multisystem infectious disease. It is one of the major causes of nursery mortality in swine herds. Cefquinome (CEQ) is proposed for the treatment of pigs against respiratory tract infection. However, few studies have investigated the PK/PD characteristics and PK/PD cutoff of this drug against H. parasuis. RESULTS: A total of 213 H. parasuis strains were isolated from diseased pigs in China. The minimal inhibitory concentrations (MICs) of CEQ against these isolates were determined. The MIC(50) and MIC(90) values were 0.125 and 8 mg/L, respectively. An in vitro dynamic PK/PD infection model was used to investigate the antimicrobial effect of CEQ against H. parasuis strain of serotype 5. The target values of CEQ for 3-log(10)-unit and 4-log10-unit decreases effects were the percent time that CEQ concentrations were above the minimum inhibitory concentration (T% > MIC) of 61 and 71 respectively. According to Monte Carlo simulation, the PK/PD cutoff for CEQ against H. parasuis was 0.06 mg/L. The suggested dose regimen was 4 mg/kg/12 h BW. CONCLUSIONS: The value of PK/PD surrogate marker T% > MIC is of great utility in CEQ clinical usage. The very first CEQ PK/PD cutoff provide fundamental data for CEQ breakpoint determination. A more desirable dose regimen against H. parasuis was provided for CEQ using in China district.

Systems biology for organotypic cell cultures.

Translating in vitro biological data into actionable information related to human health holds the potential to improve disease treatment and risk assessment of chemical exposures. While genomics has identified regulatory pathways at the cellular level, translation to the organism level requires a multiscale approach accounting for intra-cellular regulation, inter-cellular interaction, and tissue/organ-level effects. Tissue-level effects can now be probed in vitro thanks to recently developed systems of three-dimensional (3D), multicellular, "organotypic" cell cultures, which mimic functional responses of living tissue. However, there remains a knowledge gap regarding interactions across different biological scales, complicating accurate prediction of health outcomes from molecular/genomic data and tissue responses. Systems biology aims at mathematical modeling of complex, non-linear biological systems. We propose to apply a systems biology approach to achieve a computational representation of tissue-level physiological responses by integrating empirical data derived from organotypic culture systems with computational models of intracellular pathways to better predict human responses. Successful implementation of this integrated approach will provide a powerful tool for faster, more accurate and cost-effective screening of potential toxicants and therapeutics. On September 11, 2015, an interdisciplinary group of scientists, engineers, and clinicians gathered for a workshop in Research Triangle Park, North Carolina, to discuss this ambitious goal. Participants represented laboratory-based and computational modeling approaches to pharmacology and toxicology, as well as the pharmaceutical industry, government, non-profits, and academia. Discussions focused on identifying critical system perturbations to model, the computational tools required, and the experimental approaches best suited to generating key data.

Integration of pharmacokinetic and pharmacodynamic indices of valnemulin in broiler chickens after a single intravenous and intramuscular administration.

The antibacterial efficacy of valnemulin against Staphylococcus aureus was studied ex vivo in broiler chickens after intravenous and intramuscular administration at a dose of 10 mg/kg bodyweight (BW). The minimum inhibitory concentrations (MICs) of valnemulin against S. aureus strains ATCC 25923 in broth and serum were 0.12 and 1 µg/mL, respectively. The MIC50 and MIC90 of valnemulin against all susceptible S. aureus strains isolated from chickens in the test population were 0.06 and 0.12 µg/mL, respectively. Protein binding, which greatly influences the efficacy of valnemulin, was assayed by equilibrium dialysate in vitro. A high binding fraction of 86.2% was found, which seems in good agreement with the difference of bacterial susceptibility tests observed in broth and serum. The surrogate index of AUC0-24/MIC required for the lowest bacteriostatic effect, and 2 log10CFU reduction in bacterial count were 24.4 h and 38.0 h, respectively. The required daily dose of valnemulin for a bacteriostatic activity was calculated to be 15 mg/kg BW based on the MIC90 of 0.12 µg/mL. Considering the slow disposition process of valnemulin and an AUC0-24 h value of more than 10-fold obtained from diseased animals, a suggested dose of 3 mg/kg BW is sufficient to achieve a satisfactory therapeutic efficacy in infected broilers. Due to the time-dependent antibacterial characteristics of valnemulin, the recommended daily dose should be split into two or three sub-doses to achieve the highest effectiveness while diminishing the risk of development of bacterial resistance.