Pharmacokinetic-pharmacodynamic modeling of tylosin against Streptococcus suis in pigs

Effect of theophylline on serum and milk pharmacokinetics of tylosin following intramuscular administration in lactating goats

AIM OF THE WORK

The study was conducted to evaluate the influence of theophylline pre-treatment on serum pharmacokinetics and milk elimination of tylosin following single intramuscular (IM) administrations in lactating goats.

METHODS AND RESULTS

In a cross-over study, tylosin was injected via intramuscular (IM) at a single dose of 15 mg/kg b.wt. After a one-month washout period goats received theophylline at a daily IM dose of 2 mg/kg b.wt. for seven consecutive days then tylosin was injected IM dose of 15 mg/kg b.wt. two hours after the last theophylline dosing. Blood samples were collected before and at 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 10, 12, and 24 h post-injection. Samples were left to clot and then centrifuged to yield serum. Milk samples were collected before and at 0.5, 1, 2, 4, 6, 8, 10, 12, 24, 48, and 72 h post-injection from each goat by hand milking. Tylosin serum concentrations were determined by high-performance liquid chromatography (HPLC). Tylosin concentrations versus time were analyzed by a noncompartmental method. Tylosin Cmax significantly declined from 1.73 ± 0.10 to 1.01 ± 0.11 µg/ml, and attained Tmax values of 2 and 1 h, respectively in theophylline-pretreated goats. Moreover, theophylline pretreatment significantly shortened the elimination half-life (t1/2el) from 6.94 to 1.98 h, t1/2ka from 0.62 to 0.36 h and the mean residence time (MRT) from 8.02 to 4.31 h, also Vz/F and AUCs decreased from 11.91 to 7.70 L/kg and from 12.64 to 4.57 µg*h/ml, respectively, consequently, theophylline enhanced the clearance (Cl/F) of tylosin from the body. Similarly, tylosin milk concentrations were significantly lower in theophylline-pretreated goats than in goats that received tylosin alone and were detected up to 24 and 72 h in both groups, respectively. Moreover, the t1/2el and AUCs were significantly decreased from 14.68 ± 1.97 to 4.72 ± 0.48 h, and from 181 to 67.20 µg*h/ml, respectively.

CONCLUSIONS

The withdrawal period for tylosin in goat milk is at least 72 h. Theophylline pretreatment significantly decreases serum and milk tylosin concentrations to subtherapeutic levels, which could have serious clinical consequences such as failure of therapy. This means that after administering tylosin to goats, milk from these animals should not be consumed for at least 96 h to ensure that the milk is free from residues of the antibiotic.

Flow cytometric assessments of metabolic activity in bacterial assemblages provide insight into ecosystem condition along the Buffalo National River, Arkansas

The Buffalo National River (BNR), on karst terrain in Arkansas, is considered an extraordinary water resource. Water collected in Spring 2017 along BNR was metagenomically analyzed using 16S rDNA, and for 17 months (5/2017-11/2018), bacterial responses were measured in relation to nutrients sampled along a stretch of BNR near a concentrated animal feed operation (CAFO) on Big Creek. Because cell count and esterase activity can increase proportionally with organic enrichment, they were hypothesized to be elevated near the CAFO. Counts (colony forming units; CFUs) were different among sites for 73 % of the months; Big Creek generated highest CFUs 27 % of the time, with the closest downstream site at 13.3 %. Esterase activity was different among sites 94 % of the time, with Big Creek exhibiting lowest activity 71 % of the time. Over the months, activity was similar across sites at ~70 % active, except at Big Creek (56 %). The α-diversity of BNR microbial consortia near a wastewater treatment plant (WWTP) and the CAFO was related to distance from the WWTP and CAFO. The inverse relationship between high CFUs and low esterase activity at Big Creek (r = -0.71) actuated in vitro exposures of bacteria to organic wastewater contaminants (OWC) previously identified in the watershed. Exponential-phase Escherichia coli (stock strain), Streptococcus suis (avirulent, from swine), and S. dysgalactiae (virulent, from silver carp, Hypophthalmichthys molitrix) were incubated with atrazine, pharmaceuticals (17 α-ethynylestradiol and trenbolone), and antimicrobials (tylosin and butylparaben). Bacteria were differentially responsive. Activity varied with exposure time and OWC type, but not concentration; atrazine decreased it most. Taken together - the metagenomic taxonomic similarities along BNR, slightly higher bacterial growth and lower bacterial esterase at the CAFO, and the lab exposures of bacterial strains showing that OWC altered metabolism - the results indicated that bioactive OWC entering the watershed can strongly influence microbial processes in the aquatic ecosystem.

Ultrasound-assisted extraction of emodin from Rheum officinale Baill and its antibacterial mechanism against Streptococcus suis based on CcpA

Emodin was extracted from Rheum officinale Baill by ultrasound-assisted extraction (UAE), and ethanol was chosen as the suitable solvent through SEM and molecular dynamic simulation. Under the optimum conditions (power 541 W, time 23 min, liquid to material ratio 13:1 mL/g, ethanol concentration 83 %) predicted by RSM, the yield of emodin was 2.18 ± 0.11 mg/g. Moreover, ultrasound power and time displayed the significant effects on the extraction process. Extracting dynamics analysis indicated that the extraction process of emodin by UAE conformed to Fick's second diffusion law. The results of antibacterial experiments suggested that emodin can damage cell membrane and inhibit the expression of cps2A, sao, mrp, epf, neu and the hemolytic activity of S. suis. Biolayer interferometry and FT-IR multi-peak fitting assays demonstrated that emodin induced a secondary conformational shift in CcpA. Molecular docking and molecular dynamics confirmed that emodin bound to CcpA through hydrogen bonding (ALA248, GLU249, GLY129 and ASN196) and π-π T-shaped interaction (TYR225 and TYR130), and the mutation of amino acid residues affected the affinity of CcpA to emodin. Therefore, emodin inhibited the sugar utilization of S. suis through binding to CcpA, and CcpA may be a potential target to inhibit the growth of S. suis.

Degradation of veterinary antibiotics by Fenton process: Products identification and toxicity assessment

The aim of the work was primarily to determine the relationship between the doses of Fenton's reagents and the effectiveness of the ecotoxicity removal of aqueous solutions containing selected antibiotics. The degradation process of ampicillin, doxycycline, and tylosin in an acidic environment in the presence of H2O2 and FeSO4 was studied. The effect of reagent doses on the degree of degradation and identification of antibiotic transformation products was measured by the UPLC qTOF method. The degree of mineralisation was determined based on changes in the concentration of total organic carbon. The ecotoxicity of products was determined with commercial MARA® and MICROTOX® bioassays, as well as against unselected microorganisms from polluted rivers and wastewater treatment plant effluent. It was found that the complete degradation of antibiotics and the simultaneous elimination of the toxicity of the Fenton process products required the use of a precisely defined amount of reagents. When an insufficient dose of reactants was used, the post-reaction solutions contained antibiotic derivatives showing antimicrobial activity. On the other hand, the toxicity of the post-reaction solution against to microbiocenoses was observed when too high doses of H2O2 were used in the process. This effect resulted from the presence of unreacted reagent or other unidentified peroxides.

Optimizing tylosin dosage for co-infection of Actinobacillus pleuropneumoniae and Pasteurella multocida in pigs using pharmacokinetic/pharmacodynamic modeling

Formulating a therapeutic strategy that can effectively combat concurrent infections of Actinobacillus pleuropneumoniae (A. pleuropneumoniae) and Pasteurella multocida (P. multocida) can be challenging. This study aimed to 1) establish minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), time kill curve, and post-antibiotic effect (PAE) of tylosin against A. pleuropneumoniae and P. multocida pig isolates and employ the MIC data for the development of epidemiological cutoff (ECOFF) values; 2) estimate the pharmacokinetics (PKs) of tylosin following its intramuscular (IM) administration (20 mg/kg) in healthy and infected pigs; and 3) establish a PK-pharmacodynamic (PD) integrated model and predict optimal dosing regimens and PK/PD cutoff values for tylosin in healthy and infected pigs. The MIC of tylosin against both 89 and 363 isolates of A. pleuropneumoniae and P. multocida strains spread widely, ranging from 1 to 256 μg/mL and from 0.5 to 128 μg/mL, respectively. According to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) ECOFFinder analysis ECOFF value (≤64 µg/mL), 97.75% (87 strains) of the A. pleuropnumoniae isolates were wild-type, whereas with the same ECOFF value (≤64 µg/mL), 99.72% (363 strains) of the P. multicoda isolates were considered wild-type to tylosin. Area under the concentration time curve (AUC), T1/2, and Cmax values were significantly greater in healthy pigs than those in infected pigs (13.33 h × μg/mL, 1.99 h, and 5.79 μg/mL vs. 10.46 h × μg/mL, 1.83 h, and 3.59 μg/mL, respectively) (p < 0.05). In healthy pigs, AUC24 h/MIC values for the bacteriostatic activity were 0.98 and 1.10 h; for the bactericidal activity, AUC24 h/MIC values were 1.97 and 1.99 h for A. pleuropneumoniae and P. multocida, respectively. In infected pigs, AUC24 h/MIC values for the bacteriostatic activity were 1.03 and 1.12 h; for bactericidal activity, AUC24 h/MIC values were 2.54 and 2.36 h for A. pleuropneumoniae and P. multocida, respectively. Monte Carlo simulation lead to a 2 μg/mL calculated PK/PD cutoff. Managing co-infections can present challenges, as it often demands the administration of multiple antibiotics to address diverse pathogens. However, using tylosin, which effectively targets both A. pleuropneumoniae and P. multocida in pigs, may enhance the control of bacterial burden. By employing an optimized dosage of 11.94-15.37 mg/kg and 25.17-27.79 mg/kg of tylosin can result in achieving bacteriostatic and bactericidal effects in 90% of co-infected pigs.

Susceptibility of Actinobacillus pleuropneumoniae, Pasteurella multocida and Streptococcus suis Isolated from Pigs in Hungary between 2018 and 2021

Porcine respiratory disease complex (PRDC) has been a major animal health, welfare, and economic problem in Hungary; therefore, great emphasis should be put on both the prevention and control of this complex disease. As antibacterial agents are effective tools for control, antibiotic susceptibility testing is indispensable for the proper implementation of antibacterial therapy and to prevent the spread of resistance. The best method for this is to determine the minimum inhibitory concentration (MIC) by the broth microdilution method. In our study, we measured the MIC values of 164 Actinobacillus pleuropneumoniae, 65 Pasteurella multocida, and 118 Streptococcus suis isolates isolated from clinical cases against the following antibacterial agents: amoxicillin, ceftiofur, cefquinome, oxytetracycline, doxycycline, tylosin, tilmicosin, tylvalosin, tulathromycin, lincomycin, tiamulin, florfenicol, colistin, enrofloxacin, and sulfamethoxazole-trimethoprim. Outstanding efficacy against A. pleuropneumoniae isolates was observed with ceftiofur (100%) and tulathromycin (100%), while high levels of resistance were observed against cefquinome (92.7%) and sulfamethoxazole-trimethoprim (90.8%). Ceftiofur (98.4%), enrofloxacin (100%), florfenicol (100%), and tulathromycin (100%) were found to be highly effective against P. multocida isolates, while 100% resistance was detected against the sulfamethoxazole-trimethoprim combination. For the S. suis isolates, only ceftiofur (100%) was not found to be resistant, while the highest rate of resistance was observed against the sulfamethoxazole-trimethoprim combination (94.3%). An increasing number of studies report multi-resistant strains of all three pathogens, making their monitoring a high priority for animal and public health.

Bioactivity of bacteria associated with Red Sea nudibranchs and whole genome sequence of Nocardiopsis dassonvillei RACA-4

Microorganisms associated with marine invertebrates consider an important source of bioactive products. This study aimed to screen for antimicrobial and anticancer activity of crude extracts of bacteria associated with Red sea nudibranchs and molecular identification of the bioactive isolates using 16Sr RNA sequencing, in addition to whole-genome sequencing of one of the most bioactive bacteria. This study showed that bacteria associated with Red sea nudibranchs are highly bioactive and 16Sr RNA sequencing results showed that two isolates belonged to Firmicutes, and two isolates belonged to Proteobacteria, and Actinobacteria. The whole genome sequence data of the isolated Nocardiopsis RACA4 isolate has an estimated genome length of 6,721,839 bp and the taxonomy showed it belongs to the bacteria Nocardiopsis dassonvillei. The De novo assembly of RACA-4 paired reads using Unicycler v0.4.8 initially yielded 97 contigs with an N50 value of 214,568 bp and L50 value of 10, The resulting assembly was further mapped to the reference genome Nocardiopsis dassonvillei strain NCTC10488 using RagTag software v.2.1.0 and a final genome assembly resulted in 39 contigs and N50 value of 6,726,007 and L50 of 1. Genome mining using anti-smash showed around 9.1% of the genome occupied with genes related to secondary metabolites biosynthesis. A wide variety of secondary metabolites belonging to Polyketides, Terpenes, and nonribosomal peptides were predicted with high degree of similarity to known compounds. Non-characterized clusters were also found which suggest new natural compounds discovered by further studies.

Antimicrobial susceptibility profiles of Mycoplasma hyorhinis strains isolated from five European countries between 2019 and 2021

Mycoplasma hyorhinis is an emerging swine pathogen bacterium causing polyserositis and polyarthritis in weaners and finishers. The pathogen is distributed world-wide, generating significant economic losses. No commercially available vaccine is available in Europe. Therefore, besides improving the housing conditions for prevention, antimicrobial therapy of the diseased animals is the only option to control the infection. Our aim was to determine the minimal inhibitory concentrations (MIC) of ten antimicrobials potentially used against M. hyorhinis infection. The antibiotic susceptibility of 76 M. hyorhinis isolates from Belgium, Germany, Hungary, Italy and Poland collected between 2019 and 2021 was determined by broth micro-dilution method and mismatch amplification mutation assay (MAMA). Low concentrations of tiamulin (MIC₉₀ 0.312 μg/ml), doxycycline (MIC₉₀ 0.078 μg/ml), oxytetracycline (MIC₉₀ 0.25 μg/ml), florfenicol (MIC₉₀ 2 μg/ml) and moderate concentrations of enrofloxacin (MIC₉₀ 1.25 μg/ml) inhibited the growth of the isolates. For the tested macrolides and lincomycin, a bimodal MIC pattern was observed (MIC₉₀ >64 μg/ml for lincomycin, tulathromycin, tylosin and tilmicosin and 5 μg/ml for tylvalosin). The results of the MAMA assay were in line with the conventional method with three exceptions. Based on our statistical analyses, significant differences in MIC values of tiamulin and doxycycline were observed between certain countries. Our results show various levels of antimicrobial susceptibility among M. hyorhinis isolates to the tested antibiotics. The data underline the importance of susceptibility monitoring on pan-European level and provides essential information for proper antibiotic choice in therapy.

Host HSPD1 Translocation from Mitochondria to the Cytoplasm Induced by Streptococcus suis Serovar 2 Enolase Mediates Apoptosis and Loss of Blood–Brain Barrier Integrity

Streptococcus suis serovar 2 (S. suis serovar 2) is a zoonotic pathogen that causes meningitis in pigs and humans, and is a serious threat to the swine industry and public health. Understanding the mechanism(s) by which S. suis serovar 2 penetrates the blood–brain barrier (BBB) is crucial to elucidating the pathogenesis of meningitis. In a previous study, we found that expression of the virulence factor enolase (Eno) by S. suis serovar 2 promotes the expression of host heat shock protein family D member 1 (HSPD1) in brain tissue, which leads to the apoptosis of porcine brain microvascular endothelial cells (PBMECs) and increased BBB permeability, which in turn promotes bacterial translocation across the BBB. However, the mechanism by which HSPD1 mediates Eno-induced apoptosis remains unclear. In this study, we demonstrate that Eno promotes the translocation of HSPD1 from mitochondria to the cytoplasm, where HSPD1 binds to β-actin (ACTB), the translocated HSPD1, and its interaction with ACTB led to adverse changes in cell morphology and promoted the expression of apoptosis-related proteins, second mitochondria-derived activator of caspases (Smac), and cleaved caspase-3; inhibited the expression of X-linked inhibitor of apoptosis protein (XIAP); and finally promoted cell apoptosis. These results further elucidate the role of HSPD1 in the process of Eno-induced apoptosis and increased BBB permeability, increasing our understanding of the pathogenic mechanisms of meningitis, and providing a framework for novel therapeutic strategies.

Quantification and Determination of Stability of Tylvalosin in Pig Plasma by Ultra-High Liquid Chromatography with Ultraviolet Detection

Tylvalosin (TV) is a macrolide antibiotic that is used for treating respiratory and enteric bacterial infections in swine and in poultry. In the coming years, the use of this drug will probably be widely studied in different species, but before its use in each veterinary species, macrolide analytical determination in various biological fluids is a pre-requisite step for the rational dose calculation of TV based on specific pharmacokinetic information. Its quantification is essential for detecting and avoiding the appearance of residues in animal products intended for human consumption. Therefore, a robust chromatographic method coupled with an ultraviolet detector was fully validated for the quantification of TV in pig plasma. A mixture (78:22) of (A) 0.3% formic acid in water and (B) acetonitrile was used as the mobile phase. TV and enrofloxacin (internal standard) were eluted at 14.1 and 5.9 min, respectively. Calibration curves ranged from 0.1 to 5 μg/mL. The accuracy and precision parameters for the quality controls were always <13.0%. Recovery ranged from 89.66 to 96.92%. The detection and quantification limits were found to be 0.05 μg/mL and 0.1 μg/mL, respectively. This method could be applied to develop pharmacokinetic studies.

Optimization and Validation of Dosage Regimen for Ceftiofur against Pasteurella multocida in Swine by Physiological Based Pharmacokinetic-Pharmacodynamic Model

Model informed drug development is a valuable tool for drug development and clinical application due to its ability to integrate variability and uncertainty of data. This study aimed to determine an optimal dosage of ceftiofur against P. multocida by ex vivo pharmacokinetic/pharmacodynamic (PK/PD) model and validate the dosage regimens by Physiological based Pharmacokinetic-Pharmacodynamic (PBPK/PD) model. The pharmacokinetic profiles of ceftiofur both in plasma and bronchoalveolar lavage fluid (BALF) are determined. PD performance of ceftiofur against P. multocida was investigated. By establishing PK/PD model, PK/PD parameters and doses were determined. PBPK model and PBPK/PD model were developed to validate the dosage efficacy. The PK/PD parameters, AUC_{0–24 h}/MIC, for bacteriostatic action, bactericidal action and elimination were determined as 44.02, 89.40, and 119.90 h and the corresponding dosages were determined as 0.22, 0.46, and 0.64 mg/kg, respectively. AUC_{24 h}/MIC and AUC _{72 h}/MIC are simulated by PBPK model, compared with the PK/PD parameters, the therapeutic effect can reach probability of target attainment (PTA) of 90%. The time-courses of bacterial growth were predicted by the PBPK/PD model, which indicated the dosage of 0.46 mg/kg body weight could inhibit the bacterial growth and perform good bactericidal effect.

Preparation of Aditoprim Injection against Streptococcus suis in Pigs and a Dose Regimen Based on Pharmacokinetic-Pharmacodynamic Modeling

In order to effectively treat the infection of Streptococcus suis and reduce the emergence of drug-resistant bacteria, an aditoprim (ADP) injection was developed in this study. The pharmaceutical property investigation results demonstrated that ADP injection was a clear yellow liquid with 10 g ADP distributing in every 100 mL solution uniformly. Its pH value and drug content were around 6.20 and 99.35~100.40%, respectively. And quality assessment preliminarily indicated its reliable quality and stability. Additionally, the bronchoalveolar lavage fluid method was first applied to evaluate accurate ADP concentration at infection site in this study. Through pharmacodynamic assay, the MIC, MBC and MPC of ADP against Streptococcus suis CVCC 607 was 2 μg/mL, 4 μg/mL and 12.8 μg/mL, respectively. The bacteria growth inhibition curves showed that ADP was a concentration-dependent antibacterial drug, and the PK-PD model parameter of AUC/MIC was selected. The pharmacokinetic parameters of alveolar fluid evaluated by WinNonlin software revealed similar pharmacokinetic process of ADP in healthy pigs and infected pigs. Combined with pharmacokinetics-pharmacodynamics (PK-PD) modeling, the dosage regimen of 3~5 days with an interval of 12 h at 4.10 mg/kg or 5.91 mg/kg could be adopted to treat the infection of Streptococcus suis. Consequently, this ADP injection with a multi-dose protocol would be a promising antimicrobial product for efficient treatment of S. suis infection of pigs.

Tylosin Inhibits Streptococcus suis Biofilm Formation by Interacting With the O-acetylserine (thiol)-lyase B CysM

Streptococcus suis (S. suis) can decrease its virulence or modify local conditions through biofilm formation, which promotes infection persistence in vivo. Biofilm formation is an important cause of chronic drug-resistant S. suis infection. The aim of this study was to evaluate whether tylosin effectively inhibits S. suis biofilm formation by interacting with O-acetylserine (thiol)-lyase B (CysM), a key enzymatic regulator of cysteine synthesis. Biofilm formation of the mutant (ΔcysM) strain was significantly lower compared to the wild-type ATCC 700794 strain. Tylosin inhibited cysM gene expression, decreased extracellular matrix contents, and reduced cysteine, homocysteine, and S-adenosylmethionine levels, indicating its potential value as an effective inhibitor of S. suis biofilm formation. Furthermore, using biolayer interferometry technology and fourier-transform infrared spectroscopy, we found that tylosin and CysM could be combined directly. Overall, these results provide evidence that tylosin inhibits S. suis biofilm formation by interacting with CysM.

Prudent Use of Tylosin for Treatment of Mycoplasma gallisepticum Based on Its Clinical Breakpoint and Lung Microbiota Shift

The aim of this study was to explore the prudent use of tylosin for the treatment of chronic respiratory infectious diseases in chickens caused by Mycoplasma gallisepticum (MG) based on its clinical breakpoint (CBP) and its effect on lung microbiota. The CBP was established based on the wild-type/epidemiological cutoff value (CO_WT/ECV), pharmacokinetics-pharmacodynamics (PK-PD) cutoff value (CO_PD), and clinical cutoff value (CO_CL) of tylosin against MG. The minimum inhibitory concentration (MIC) of tylosin against 111 MG isolates was analyzed and the CO_WT was 2 μg/ml. M17 with MIC of 2 μg/ml was selected as a representative strain for the PK-PD study. The CO_PD of tylosin against MG was 1 μg/ml. The dosage regimen formulated by the PK-PD study was 3 days administration of tylosin at a dose of 45.88 mg/kg b.w. with a 24-h interval. Five different MIC MGs were selected for clinical trial, and the CO_CL of tylosin against MG was 0.5 μg/ml. According to the CLSI decision tree, the CBP of tylosin against MG was set up as 2 μg/ml. The effect of tylosin on lung microbiota of MG-infected chickens was analyzed by 16S rRNA gene sequencing. Significant change of the lung microbiota was observed in the infection group and treatment group based on the principal coordinate analysis and the Venn diagrams of the core and unique OTU. The phyla Firmicutes and Proteobacteria showed difference after MG infection and treatment. This study established the CBP of tylosin against MG. It also provided scientific data for the prudent use of tylosin based on the evaluation of MG infection and tylosin treatment on the lung microbiota.

Pharmacokinetic/Pharmacodynamic Modeling of Spiramycin against Mycoplasma synoviae in Chickens

This research aimed to assess the pharmacokinetics/pharmacodynamics (PK/PD) and tissue residues of spiramycin in chickens. The PK of spiramycin were determined in 12 chickens using a parallel study design in which each group of chickens (n = 6) received a single dose of spiramycin at 17 mg/kg intravenously (IV) or orally. Plasma samples were collected at assigned times for up to 48 h to measure spiramycin concentrations. Additionally, a tissue depletion study was performed in 42 chickens receiving spiramycin at 17 mg/kg/day orally for 7 days. The area under the plasma concentration–time curve values were 29.94 ± 4.74 and 23.11 ± 1.83 µg*h/mL after IV and oral administrations, respectively. The oral bioavailability was 77.18%. The computed withdrawal periods of spiramycin were 11, 10, and 7 days for liver, muscle, and skin and fat, respectively. The minimum inhibitory concentration for spiramycin against Mycoplasma synoviae (M. synoviae) strain 1853 was 0.0625 µg/mL. Using the PK/PD integration, the appropriate oral dose of spiramycin against M. synoviae was estimated to be 15.6 mg/kg. Thus, we recommend an oral dose of 15.6 mg spiramycin/kg against M. synoviae in chickens and a withdrawal period of 11 days following oral treatment with 17 mg spiramycin/kg/day for 7 days.

Pharmacokinetic-Pharmacodynamic Profile, Bioavailability, and Withdrawal Time of Tylosin Tartrate Following a Single Intramuscular Administration in Olive Flounder (Paralichthys olivaceus)

Simple Summary

Fishes usually stop eating food when they are sick, and treating diseased fish with oral drugs is a serious hurdle in the aquaculture industry. Tylosin tartrate is a potent bacterial-killing agent useful against frequently occurring bacterial fish infections. We tested the effectiveness against pathogenic bacteria and the human safety of the drug for possible application to cultured olive flounder, one of the most important culture species in far eastern Asian countries. Tylosin tartrate was very effective in killing the pathogenic bacteria grown in artificial culture media, and it was also demonstrated that the drug reached body concentrations in olive flounder, high enough to kill the pathogen. In addition, we also determined how long to wait until the fish clears the injected drug out and it is possible for human consumption. These results will pave a new method for disease treatment useful for olive flounder farming.

Abstract

The objective of this study was to demonstrate the pharmacokinetic–pharmacodynamic profile, bioavailability, and withdrawal time of tylosin tartrate (TT) administered to olive flounder via intramuscular (IM, 10 or 20 mg/kg, n = 240) and intravascular (IV, 10 mg/kg, n = 90) injections. Serum concentrations of tylosin were determined using a validated liquid chromatography-tandem mass spectrometry method. According to the non-compartmental analysis, the bioavailability of TT was 87%. After the IV injection, the terminal half-life, total body clearance, volume of distribution, and mean residence time of TT were 21.07 h, 0.07 L/kg/h, 2.15 L/kg, and 16.39 h, respectively. Rapid absorption (T_max 0.25 h), prolonged action (terminal half-life, 33.96 and 26.04 h; MRT, 43.66 and 33.09 h), and linear dose–response relationship (AUC_0-inf, 123.55 and 246.05 µg/mL*h) were monitored following 10 and 20 mg/kg IM injection. The withdrawal time of TT from muscle (water temperature, 22 °C) was 9.84 days, rounded up to 10 days (220 degree days). Large C_max/MIC₉₀, AUC_0-inf/MIC₉₀, and T > MIC₉₀ values were obtained for Streptococcus isolates and these PK/PD indices satisfied the criteria required for efficacy evaluation. This study lays a foundation for the optimal use of TT and provides valuable information for establishing therapeutic regimens.

Evaluating a tylosin dosage regimen for treatment of Staphylococcus delphini infection in mink (Neovison vison): a pharmacokinetic-pharmacodynamic approach

Staphylococcus delphini is one of the most common pathogens isolated from mink infections, especially dermatitis. Tylosin (TYL) is used frequently against these infections, although no evidence-based treatment regimen exists. This study aimed to explore the dosage of TYL for infections caused by S. delphini in mink. Two animal experiments with a total of 12 minks were conducted to study the serum pharmacokinetic (PK) characteristics of TYL in mink after 10 mg/kg IV and oral dosing, respectively. The concentration of TYL in serum samples collected before and eight times during 24 h after TYL administration was quantitated with liquid chromatography quadrupole time-of-flight mass spectrometry, and the TYL disposition was analyzed using non-linear mixed effect analysis. The pharmacodynamics (PD) of TYL against S. delphini were studied using semi-mechanistic modeling of in vitro time-kill experiments. PKPD modeling and simulation were done to establish the PKPD index and dosage regimen. The disposition of TYL was described by a two-compartmental model. The area under the free concentration-time curve of TYL over the minimum inhibitory concentration of S. delphini (fAUC/MIC) was determined as PKPD index with breakpoints of 48.9 and 98.7 h for bacteriostatic and bactericidal effect, respectively. The calculated daily oral dose of TYL was 2378 mg/kg, which is 238-fold higher than the currently used TYL oral dosage regimen in mink (10 mg/kg). Accordingly, sufficient TYL concentrations are impossible to achieve in mink plasma, and use of this drug for extra-intestinal infections in this animal species must be discouraged.

Streptococcus suis serotype 2 enolase interaction with host brain microvascular endothelial cells and RPSA-induced apoptosis lead to loss of BBB integrity

Host proteins interacting with pathogens are receiving more attention as potential therapeutic targets in molecular medicine. Streptococcus suis serotype 2 (SS2) is an important cause of meningitis in both humans and pigs worldwide. SS2 Enolase (Eno) has previously been identified as a virulence factor with a role in altering blood brain barrier (BBB) integrity, but the host cell membrane receptor of Eno and The mechanism(s) involved are unclear. This study identified that SS2 Eno binds to 40S ribosomal protein SA (RPSA) on the surface of porcine brain microvascular endothelial cells leading to activation of intracellular p38/ERK-eIF4E signalling, which promotes intracellular expression of HSPD1 (heat-shock protein family D member 1), and initiation of host-cell apoptosis, and increased BBB permeability facilitating bacterial invasion. This study reveals novel functions for the host-interactional molecules RPSA and HSPD1 in BBB integrity, and provides insight for new therapeutic strategies in meningitis.

Tissue Residues and Pharmacokinetic/Pharmacodynamic Modeling of Tiamulin Against Mycoplasma anatis in Ducks

The pharmacokinetics of tiamulin were studied in 2 groups of ducks (n = 6) after its oral administration at 2 different doses (30 and 60 mg/kg, respectively). Plasma concentrations of tiamulin were measured by high performance liquid chromatography at different time points up to 24 h post-administration. The maximum plasma concentrations were 0.77 and 2.32 μg/mL attained at 2 h (T_max) for 30 and 60 mg/kg, respectively. The elimination half-lives for these 2 doses were 3.54 and 6.34 h, respectively. The minimum inhibitory concentration for tiamulin against Mycoplasma anatis (M. anatis) strain 1340 was determined to be 0.06 μg/mL. The proper oral dose of tiamulin against M. anatis in ducks was calculated to be 35 mg/kg/day using the pharmacokinetic/pharmacodynamic modeling. Tiamulin was administered orally (40 mg/kg/day) to 30 ducks for 3 successive days to determine its residues in edible tissues and its preslaughter withdrawal time. The highest tiamulin residues were detected in the liver, followed by the muscle, whereas lower concentrations were detected in the skin and fat. The estimated withdrawal periods of tiamulin were 6, 5, 3, and 3 days for liver, muscle, skin, and fat, respectively. Therefore, an oral dosage regimen of 35 mg/kg/day should be adequate for tiamulin against M. anatis. We recommend a preslaughter withdrawal period of 6 days when ducks are treated with 40 mg tiamulin/kg/day, orally, for 3 days.

Tackling Antibiotic Resistance with Compounds of Natural Origin: A Comprehensive Review

Drug-resistant bacteria pose a serious threat to human health worldwide. Current antibiotics are losing efficacy and new antimicrobial agents are urgently needed. Living organisms are an invaluable source of antimicrobial compounds. The antimicrobial activity of the most representative natural products of animal, bacterial, fungal and plant origin are reviewed in this paper. Their activity against drug-resistant bacteria, their mechanisms of action, the possible development of resistance against them, their role in current medicine and their future perspectives are discussed. Electronic databases such as PubMed, Scopus and ScienceDirect were used to search scientific contributions until September 2020, using relevant keywords. Natural compounds of heterogeneous origins have been shown to possess antimicrobial capabilities, including against antibiotic-resistant bacteria. The most commonly found mechanisms of antimicrobial action are related to protein biosynthesis and alteration of cell walls and membranes. Various natural compounds, especially phytochemicals, have shown synergistic capacity with antibiotics. There is little literature on the development of specific resistance mechanisms against natural antimicrobial compounds. New technologies such as -omics, network pharmacology and informatics have the potential to identify and characterize new natural antimicrobial compounds in the future. This knowledge may be useful for the development of future therapeutic strategies.

Modeling the Effect of Tylosin Phosphate on Macrolide-Resistant Enterococci in Feedlots and Reducing Resistance Transmission

Tylosin phosphate (TYL) is administered to more than 50% of U.S. beef cattle to reduce the incidence of liver abscesses but may increase the risk of macrolide-lincosamide-streptogramin-resistant bacteria disseminating from the feedlot. Limited evidence has been collected to understand how TYL affects the proportion of resistant bacteria in cattle or the feedlot environment. We created a mathematical model to investigate the effects of TYL administration on Enterococcus dynamics and examined preharvest strategies to mitigate the impact of TYL administration on resistance. The model simulated the physiological pharmacokinetics of orally administered TYL and estimated the pharmacodynamic effects of TYL on populations of resistant and susceptible Enterococcus within the cattle large intestine, feedlot pen, water trough, and feed bunk. The model parameters' population distributions were based on the available literature; 1000 Monte Carlo simulations were performed to estimate the likely distribution of outcomes. At the end of the simulated treatment period, the median estimated proportion of macrolide-resistant enterococci was only 1 percentage point higher within treated cattle compared with cattle not fed TYL, in part because the TYL concentrations in the large intestine were substantially lower than the enterococci minimum inhibitory concentrations. However, 25% of the simulated cattle had a >10 percentage point increase in the proportion of resistant enterococci associated with TYL administration, termed the TYL effect. The model predicts withdrawing TYL treatment and moving cattle to an antimicrobial-free terminal pen with a low prevalence of resistant environmental enterococci for as few as 6 days could reduce the TYL effect by up to 14 percentage points. Additional investigation of the importance of this subset of cattle to the overall risk of resistance transmission from feedlots will aid in the interpretation and implementation of resistance mitigation strategies.

Tylosin exposure reduces the susceptibility of Salmonella Typhimurium to florfenicol and tetracycline

BACKGROUND

Antibiotics exposure has been implicated in the emergence of bacterial strains that are resistant to structurally related or unrelated antibiotics. Tylosin is a macrolide antibiotic that has been administered to treat respiratory pathogenic bacteria in swine. Thus, this study was undertaken to evaluate the impact of exposure to a constant (3 μg/mL) and decreasing concentrations of tylosin on the susceptibility of Salmonella enterica serovar Typhimurium to various antibiotics.

RESULTS

S. Typhimurium strains exposed to tylosin for 12 and 24 h in the in vitro dynamic model demonstrated at least an eight-fold increase in the minimum inhibitory concentrations (MICs) of florfenicol and tetracycline. Exposure to tylosin extended the lag-time of the growth curve and enhanced the generation of reactive oxygen species. Gene expression analysis demonstrated up-regulation of the acrAB and tolC Salmonella efflux pump genes and its global regulators (marA and soxS). Besides, the expression of ompC gene was down-regulated in tylosin exposed S. Typhimurium.

CONCLUSION

Exposure to decreasing concentrations of tylosin could reduce the susceptibility of S. Typhimurium to florfenicol and tetracycline.

Pharmacokinetics, tissue residues, and ex vivo pharmacodynamics of tylosin against Mycoplasma anatis in ducks

The pharmacokinetics of tylosin were investigated in 3 groups of ducks (n = 6). They received a single dose of tylosin (50 mg/kg) by intravenous (IV), intramuscular (IM), and oral administrations, respectively. Plasma samples were collected at various time points to 24 hr post-administration to evaluate tylosin concentration over time. Additionally, tylosin residues in tissues and its withdrawal time were assessed using 30 ducks which received tylosin orally (50 mg/kg) once daily for 5 consecutive days. After IV administration, the volume of distribution, elimination half-life, area under the plasma concentration-time curve, and the total body clearance were 7.07 ± 1.98 L/kg, 2.04 hr, 19.47 µg hr/ml, and 2.82 L hr^-1  kg^-1 , respectively. After IM and oral administrations, the maximum plasma concentrations were 3.70 and 2.75 µg/ml achieved at 1 and 2 hr, and the bioavailability was 93.95% and 75.77%, respectively. The calculated withdrawal periods of tylosin were 13, 8, and 5 days for kidney, liver, and muscle, respectively. For the pharmacodynamic profile, the minimum inhibitory concentration for tylosin against M. anatis strain 1,340 was 1 µg/ml. The calculated optimal oral dose of tylosin against M. anatis in ducks based on the ex vivo pharmacokinetic/pharmacodynamic modeling was 61 mg kg^-1  day^-1 .

PK/PD modeling of Ceftiofur Sodium against Haemophilus parasuis infection in pigs

BACKGROUND

Ceftiofur Sodium is widely used in China. Our aim was to determine Ceftiofur Sodium activity and optimize dosing regimens against the pathogen Haemophilus parasuis using an in vitro and ex vivo pharmacokinetics/pharmacodynamics modeling approach. By adopting these strategies, we wanted to extend the effective life of Ceftiofur Sodium in reduce drug-resistance in pigs.

RESULTS

We established an H. parasuis infection model in pigs, and assessed the pharmacokinetics of Ceftiofur Sodium in both healthy and infected animals. After Ceftiofur Sodium (10 mg/kg, i.m.) administration to healthy and H. parasuis-infected pigs, plasma based desfuroylceftiofur (a metabolite of Ceftiofur Sodium) was measured by High Performance Liquid Chromatography. The pharmacokinetics of Ceftiofur Sodium (desfuroylceftiofur) was consistent with a two-compartment open model, with first-order absorption. We observed no significant differences (P > 0.05) in pharmacokinetic parameters between healthy and infected pigs. Pharmacodynamics data showed that Ceftiofur Sodium was highly inhibitory against H. parasuis, with MIC, MBC, and MPC values of 0.003125, 0.0125 and 0.032 μg/mL, respectively. Desfuroylceftiofur in plasma also had strong bactericidal activity. Almost all H. parasuis cultured in plasma medium of Ceftiofur Sodium-inoculated healthy pigs, at each time point, were killed within 24 h. A weaker antibacterial activity was measured in infected-pig plasma medium at 18, 24, 36, and 48 h, after Ceftiofur Sodium inoculation. Pharmacokinetic parameters were combined with ex vivo pharmacodynamic parameters, and the bacteriostatic effect (36.006 h), bactericidal effect (71.637 h) and clearance (90.619 h) within 24 h, were determined using the Hill equation. Dose-calculation equations revealed the optimal dose of Ceftiofur Sodium to be 0.599-1.507 mg/kg.

CONCLUSIONS

There were no significant differences in Ceftiofur Sodium pharmacokinetic parameters between healthy and infected pigs, although pharmacokinetics/pharmacodynamics fitting curves showed obviously differences. The optimal dose of Ceftiofur Sodium was lower than recommended (3 mg/kg), which may provide improved treatments for Glässers disease, with lower drug-resistance possibility.