Prediction of marbofloxacin dosage for the pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida by pharmacokinetic/pharmacodynamic modelling

Pharmacodynamic Parameters of Pharmacokinetic/Pharmacodynamic (PK/PD) Integration Models

Pharmacokinetic/pharmacodynamic (PK/PD) integration models are used to investigate the antimicrobial activity characteristics of drugs targeting pathogenic bacteria through comprehensive analysis of the interactions between PK and PD parameters. PK/PD models have been widely applied in the development of new drugs, optimization of the dosage regimen, and prevention and treatment of drug-resistant bacteria. In PK/PD analysis, minimal inhibitory concentration (MIC) is the most commonly applied PD parameter. However, accurately determining MIC is challenging and this can influence the therapeutic effect. Therefore, it is necessary to optimize PD indices to generate more rational results. Researchers have attempted to optimize PD parameters using mutant prevention concentration (MPC)-based PK/PD models, multiple PD parameter-based PK/PD models, kill rate-based PK/PD models, and others. In this review, we discuss progress on PD parameters for PK/PD models to provide a valuable reference for drug development, determining the dosage regimen, and preventing drug-resistant mutations.

Clinical Breakpoint of Apramycin to Swine Salmonella and Its Effect on Ileum Flora

The purpose of this study was to establish the clinical breakpoint (CBP) of apramycin (APR) against Salmonella in swine and evaluate its effect on intestinal microbiota. The CBP was established based on three cutoff values of wild-type cutoff value (CO_WT), pharmacokinetic-pharmadynamic (PK/PD) cutoff value (CO_PD) and clinical cutoff value (CO_CL). The effect of the optimized dose regimen based on ex vivo PK/PD study. The evolution of the ileum flora was determined by the 16rRNA gene sequencing and bioinformatics. This study firstly established the CO_WT, CO_PD in ileum, and CO_CL of APR against swine Salmonella, the value of these cutoffs were 32 µg/mL, 32 µg/mL and 8 µg/mL, respectively. According to the guiding principle of the Clinical Laboratory Standards Institute (CLSI), the final CBP in ileum was 32 µg/mL. Our results revealed the main evolution route in the composition of ileum microbiota of diarrheic piglets treated by APR. The change of the abundances of Bacteroidetes and Euryarchaeota was the most obvious during the evolution process. Methanobrevibacter, Prevotella, S24-7 and Ruminococcaceae were obtained as the highest abundance genus. The abundance of Methanobrevibacter increased significantly when APR treatment carried and decreased in cure and withdrawal period groups. The abundance of Prevotella in the tested groups was significantly lower than that in the healthy group. A decreased of abundance in S24-7 was observed after Salmonella infection and increased slightly after cure. Ruminococcaceae increased significantly after Salmonella infection and decreased significantly after APR treatment. In addition, the genera of Methanobrevibacter and Prevotella were defined as the key node. Valine, leucine and isoleucine biosynthesis, D-Glutamine and D-glutamate metabolism, D-Alanine metabolism, Peptidoglycan and amino acids biosynthesis were the top five Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in the ileum microbiota of piglets during the Salmonella infection and APR treatment process. Our study extended the understanding of dynamic shift of gut microbes during diarrheic piglets treated by APR.

Distribution of marbofloxacin within the bronchoalveolar region of healthy pigs

The purpose of this study was to clarify the distribution of marbofloxacin (MBFX) within the bronchoalveolar region of pigs. Four clinically healthy pigs were intramuscularly injected with a single dose of MBFX (2 mg/kg). Samples of plasma and bronchoalveolar lavage fluid (BALF) were obtained for each pig at 0 (before administration), 3, 8 and 24 hr after administration of MBFX. As a result, the MBFX concentrations in pulmonary epithelial lining fluid (ELF) and in alveolar cells showed a similar pattern of concentrations during the experimental period. The MBFX concentrations both in ELF and alveolar cells were higher than in plasma. These results suggest that intramuscularly injected MBFX was well distributed in the bronchoalveolar region.

The antimicrobial peptide MPX kills Actinobacillus pleuropneumoniae and reduces its pathogenicity in mice

Actinobacillus pleuropneumoniae is the causative agent of highly contagious and fatal respiratory infections, causing substantial economic losses to the global pig industry. Due to increased antibiotic resistance, there is an urgent need to find new antibiotic alternatives for treating A. pleuropneumoniae infections. MPX is obtained from wasp venom and has a killing effect on various bacteria. This study found that MPX had a good killing effect on A. pleuropneumoniae and that the minimum inhibitory concentration (MIC) was 16 μg/mL. The bacterial density of A. pleuropneumoniae decreased 1000 times after MPX (1 × MIC) treatment for 1 h, and the antibacterial activity was not affected by pH or temperature. Fluorescence microscopy showed that MPX (1 × MIC) destroyed the bacterial cell membrane after treatment for 0.5 h, increasing membrane permeability and releasing bacterial proteins and Ca²⁺, Na⁺ and other cations. In addition, MPX (1 × MIC) treatment significantly reduced the formation of bacterial biofilms. Quantitative RT-PCR results showed that MPX treatment significantly upregulated the expression of the PurC virulence gene and downregulated that of ApxI, ApxII, and Apa1. In addition, the Sap A gene was found to play an important role in the tolerance of A. pleuropneumoniae to antimicrobial peptides. Therapeutic evaluation in a murine model showed that MPX protects mice from a lethal dose of A. pleuropneumoniae and relieves lung inflammation. This study reports the use of MPX to treat A. pleuropneumonia infections, laying the foundation for the development of new drugs for bacterial infections.

The effects of Mannheimia haemolytica and albendazole on marbofloxacin pharmacokinetics in lambs

The study aimed to define the effects of M. haemolytica and a single oral dose of albendazole on the single-dose pharmacokinetics of marbofloxacin in lambs. The pharmacokinetic-pharmacodynamic integration of marbofloxacin was applied to describe a 3 mg/kg intramuscular dose in lambs. The 6 healthy and 12 naturally infected with M. haemolytica lambs (Akkaraman, males weighing 10-15 kg and aged 2-3 months) were used in this study. In the marbofloxacin group, 6 healthy lambs received marbofloxacin. In the albendazole group after 2 weeks washout period, the same animals received marbofloxacin on 1 h after albendazole. In the diseased marbofloxacin group, 6 lambs naturally infected with M. haemolytica received marbofloxacin. In the diseased albendazole group, 6 lambs naturally infected with M. haemolytica received marbofloxacin on 1 h after albendazole. The marbofloxacin and albendazole were administered each as a single dose of 3 mg/kg intramuscular and 7.5 mg/kg oral, respectively, in the respective groups. Plasma concentration of marbofloxacin was measured with HPLC-UV and pharmacokinetic parameters were analyzed by non-compartmental model. Albendazole did not change the pharmacokinetic profiles of marbofloxacin in healthy and diseased lambs. However, M. haemolytica affected the pharmacokinetics of marbofloxacin in diseased lambs, AUC_0-24/MIC₉₀ ratio was not found to be higher than 125, but C_max/MIC₉₀ ratios was found to be higher than 10 for an MIC value of 0.25 μg/mL in all groups. The marbofloxacin dose described in this study may not be effective for the treatment of infections due to M. haemolytica in lambs, with MIC ≤ 0.25 μg/mL.

Pharmacokinetic-pharmacodynamic relationship of marbofloxacin for Escherichia coli and Pasturella multocida following repeated intramuscular administration in goats

The pharmacokinetics (PK) and pharmacodynamics (PD) of marbofloxacin (MBF) were determined in six healthy female goats of age 1.00-1.25 years after repeated administration of MBF. The MBF was administered intramuscularly (IM) at 2 mg kg^-1  day^-1 for 5 days. Plasma concentrations of MBF were determined by high-performance liquid chromatography, and PK parameters were obtained using noncompartmental analysis. The MBF concentrations peaked at 1 hr, and peak concentration (C_max ) was 1.760 µg/ml on day 1 and 1.817 µg/ml on day 5. Repeated dosing of MBF caused no significant change in PK parameters except area under curve (AUC) between day 1 (AUC_0-∞ D1 = 7.67 ± 0.719 µg × hr/ml) and day 5 (AUC_0-∞ D5 = 8.70 ± 0.857 µg × hr/ml). A slight difference in mean residence time between 1st and 5th day of administration and accumulation index (AI = 1.13 ± 0.017) suggested lack of drug accumulation following repeated IM administration up to 5 days. Minimum inhibitory concentration (MIC) demonstrated that Escherichia coli (MIC = 0.04 µg/ml) and Pasturella multocida (MIC = 0.05 µg/ml) were highly sensitive to MBF. Time-kill kinetics demonstrated rapid and concentration-dependent activity of MBF against these pathogens. PK/PD integration of data for E. coli and P. multocida, using efficacy indices: C_max /MIC and AUC_0-24hr /MIC, suggested that IM administration of MBF at a dose of 2 mg kg^-1  day^-1 is appropriate to treat infections caused by E. coli. However, a dose of 5 mg kg^-1  day^-1 is recommended to treat pneumonia caused by P. multocida in goats. The study indicated that MBF can be used repeatedly at dosage of 2 mg/kg in goats without risk of drug accumulation up to 5 days.

Establishment and comparison of Actinobacillus pleuropneumoniae experimental infection model in mice and piglets

Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia, a disease responsible for substantial losses in the worldwide pig industry. In this study, outbred Kunming (KM) and Institute of Cancer Research (ICR) mice were evaluated as alternative mice models for APP research. After intranasal infection of serotype 5 reference strain L20, there was less lung damage and a lower clinical sign score in ICR compared to KM mice. However, ICR mice showed more obvious changes in body weight loss, the amount of immune cells (such as neutrophils and lymphocytes) and cytokines (such as IL-6, IL-1β and TNF-α) in blood and bronchoalveolar lavage fluid (BALF). The immunological changes observed in ICR mice closely mimicked those found in piglets infected with L20. While both ICR and KM mice are susceptible to APP and induce pathological lesions, we suggest that ICR and KM mice are more suitable for immunological and pathogenesis studies, respectively. The research lays the theoretical basis for determine that mice could replace pigs as the APP infection model and it is of significance for the study of APP infection in the laboratory.

In vivo pharmacokinetic/Pharmacodynamic modeling of Enrofloxacin against Escherichia coli in broiler chickens

Background

Systemic Escherichia coli infections cause early mortality of commercial broiler chickens. Although enrofloxacin has long been used in poultry, the in vivo pharmacokinetic/pharmacodynamic (PK/PD) relationship of enrofloxacin against E. coli is unclear. The present study aimed to establish an in vivo PK/PD model of enrofloxacin against E. coli in seven-day-old chicks and to ascertain whether the selection of target organ for PD determination is critical for parameter magnitude calculation in enrofloxacin PK/PD modeling.

Results

The in vivo effectiveness of enrofloxacin against E. coli in different organs varied, with the E_max ranging from − 4.4 to − 5.8 Log₁₀ colony forming units (cfu)/mL or cfu/g. Both the surrogate AUC_0–24/MIC of enrofloxacin or AUC_0–24/MIC of the combination of enrofloxacin and ciprofloxacin correlated well with effectiveness in each organ. The AUC_0–24/MIC ratio of the combination of enrofloxacin and ciprofloxacin producing bactericidal and elimination effects were 21.29 and 32.13 in blood; 41.68, and 58.52 in the liver; and 27.65 and 46.22 in the lung, respectively.

Conclusions

The in vivo effectiveness of enrofloxacin against E. coli in different organs was not identical after administration of the same dosage. To describe the magnitude of PK/PD parameter exactly, bacterial loading reduction in different organs as PD endpoints should be evaluated and compared in PK/PD modeling. The selection of a target organ to evaluate PDs is critical for rational dosage recommendation.

Pharmacokinetic/pharmacodynamic assessment of cefquinome against Actinobacillus Pleuropneumoniae in a piglet tissue cage infection model

To evaluate the relationship between the pharmacokinetic/pharmacodynamic (PK/PD) parameters and the antibacterial effect of cefquinome against Actinobacillus pleuropneumoniae, a tissue cage infection model was established in piglets. In this model, an initial count of A. pleuropneumoniae of approximately 10⁶ CFU/mL was exposed to different concentrations of cefquinome after multiple administration at dosages of 0.2, 0.4, 0.8, 1, 2, 4 mg/kg body weight once a day for 3 days. Concentration of cefquinome and bacterial numbers of A. pleuropneumoniae in the tissue-cage fluid (TCF) were monitered. An inhibitory form of sigmoid maximum effect (E_max) model was used to estimate the relationship between the antibacterial effect and PK/PD indices of cefquinome against A. pleuropneumoniae. The minimum inhibitory concentration of cefquinome against A. pleuropneumoniae was 0.016 μg/mL in TCF. The total maximum antibacterial effect was a 3.96 log₁₀ (CFU/mL) reduction. In addition, the cumulative percentage of time over a 24 h period that the drug concentration exceeds the MIC (%T > MIC) was the pharmacokinetic-pharmacodynamic (PK-PD) index that best correlated with the antibacterial efficacy (R² = 0.967). The estimated %T > MIC values were 11.59, 27.49, and 59.81% for a 1/3-log₁₀ (CFU/mL) reduction, a 2/3-log₁₀ (CFU/mL) reduction, and a 1-log₁₀ (CFU/mL) reduction, respectively, during the 24h administration period of cefquinome. In conclusion, cefquinome exhibits excellent antibacterial activity and time-dependent characteristics against A. pleuropneumoniae in vivo. Furthermore, these data provide meaningful guidance to optimize regimens of cefquinome to treat respiratory tract infections caused by A. pleuropneumoniae.

Update on Actinobacillus pleuropneumoniae-knowledge, gaps and challenges

Porcine pleuropneumonia, caused by the bacterial porcine respiratory tract pathogen Actinobacillus pleuropneumoniae, leads to high economic losses in affected swine herds in most countries of the world. Pigs affected by peracute and acute disease suffer from severe respiratory distress with high lethality. The agent was first described in 1957 and, since then, knowledge about the pathogen itself, and its interactions with the host, has increased continuously. This is, in part, due to the fact that experimental infections can be studied in the natural host. However, the fact that most commercial pigs are colonized by this pathogen has hampered the applicability of knowledge gained under experimental conditions. In addition, several factors are involved in development of disease, and these have often been studied individually. In a DISCONTOOLS initiative, members from science, industry and clinics exchanged their expertise and empirical observations and identified the major gaps in knowledge. This review sums up published results and expert opinions, within the fields of pathogenesis, epidemiology, transmission, immune response to infection, as well as the main means of prevention, detection and control. The gaps that still remain to be filled are highlighted, and present as well as future challenges in the control of this disease are addressed.