Pharmacokinetics of sulfadimethoxine and sulfamethoxazole in combination with trimethoprim after oral single- and multiple-dose administration to healthy pigs

Tissue residue distribution and withdrawal time estimation of trimethoprim and sulfachloropyridazine in Yugan black-bone fowl (Gallus gallus domesticus Brisson)

Black-bone fowl are different from ordinary broilers in appearance and are considered to have rich nutritional properties. However, the metabolism of therapeutic drugs in black-bone fowl remains unclear. This study aimed to determine the tissue residue depletion kinetics of trimethoprim and sulfachloropyridazine in Yugan black-bone fowl, after daily oral administrations for 5 days at 4 mg/kg bw/day trimethoprim and 20 mg/kg bw/day sulfachloropyridazine, and to calculate the withdrawal times. After consecutive oral administrations, the tissues (liver, kidney, muscle and skin/fat) were collected at each of the following time points (0.16, 1, 3, 5, 7, 9, 20, 30 and 40 days). A newly-devised LC-MS/MS method was used to analyse the concentrations of trimethoprim and sulfachlorpyridazine in target tissues. The results showed that sulfachloropyridazine was rapidly metabolised in broilers, and there was no residue in all tissues 3 days post-administration. The concentration of trimethoprim in black-bone fowl skin/fat is the highest, and its metabolism rate is low. After 40 days, the concentration of trimethoprim in skin/fat is still as high as 140.1 ± 58.0 μg/kg, exceeding the maximum residue limit. In order to protect consumers' health, it is suggested that the withdrawal time of TMP in Yugan black-bone fowl is 69 days.

Dosing Regimen of Aditoprim and Sulfamethoxazole Combination for the Glaesserella parasuis Containing Resistance and Virulence Genes

Glaesserella parasuis (G. parasuis) causes Glasser’s disease in pigs and causes high mortality in piglets. The new drug Aditoprim (ADP) alone or combined with Sulfamethoxazole (SMZ) is one of the good choices for treating respiratory infections. The objective of this study was to recommend the optimal dosing regimen for the treatment of G. parasuis infection which contains resistance and virulence genes by ADP/SMZ compound through pharmacokinetics–pharmacodynamics (PK-PD) modeling. The whole genome of the virulent strain G. parasuis H78 was obtained and annotated by whole genome sequencing. The results show that G. parasuis H78 consists of a unilateral circular chromosome with prophages in the genome. The annotation results of G. parasuis H78 showed that the genome contained a large number of virulence-related genes and drug resistance-related genes. The in vitro PD study showed that the antibacterial effect of ADP/SMZ compound against G. parasuis was time-dependent, and AUC/MIC was selected as the PK-PD modeling parameter. The PK study showed that the content of ADP/SMZ compound in pulmonary epithelial lining fluid (PELF) was higher than plasma, and there were no significant differences in ADP and SMZ PK parameters between the healthy and infected group. The dose equation to calculate the optimal dosing regimen of ADP/SMZ compound administration for control of G. parasuis infection was 5/25 mg/kg b.w., intramuscular injection once a day for 3~5 consecutive days. The results of this study provide novel therapeutic options for the treatment of G. parasuis infection to decrease the prevalence and disease burden caused by G. parasuis.

Antibacterial activity of combined aditoprim and sulfamethoxazole against Escherichia coli from swine and a dose regimen based on pharmacokinetic-pharmacodynamic modeling

The mortality of livestock caused by pathogenic Escherichia coli (E. coli) still accounts for a large proportion of deaths in large-scale production and reproduction, which causes devastating economic losses to the pig breeding industry. The aims of this study were to investigate the antibacterial activity of combined aditoprim (ADP) and sulfamethoxazole (SMZ) against clinical isolates of E. coli from pigs and to develop a pharmacokinetic-pharmacodynamic (PK-PD) model to formulate the optimal dose of ADP/SMZ for the treatment of pig colibacillosis. Blood and ileum fluid samples were collected at different times after single intramuscular injection of ADP/SMZ (5/25 mg/kg b.w.) to healthy pigs and E. coli-infected pigs. Concentrations of ADP and SMZ in plasma and ileum fluid were analyzed by HPLC. The peak concentration (C_max ) and the area under the concentration-time curve (AUC_0-24h ) in ileum fluid of healthy pigs were 1.76 ± 0.27 µg/ml and 18.92 ± 2.87 µg·h/ml for ADP and 19.15 ± 2.63 µg/ml and 125.70 ± 11.86 µg·h/ml for SMZ, respectively. C_max and AUC_0-24h in ileum fluid of infected pigs were 1.88 ± 0.13 µg/ml and 15.12 ± 0.75 µg·h/ml for ADP and 19.71 ± 3.68 µg/ml and 133.92 ± 17.14 µg·h/ml for SMZ, respectively. The minimum inhibitory concentrations (MICs) of combined ADP and SMZ (ADP/SMZ) against 185 strains of E. coli from pigs were determined. The MIC₅₀ and MIC₉₀ of ADP/SMZ were 0.5/2.5 and 4/20 µg/ml, respectively. The MIC of the selected pathogenic E. coli SHC28 was 0.5/2.5 µg/ml in Mueller-Hinton broth and 0.25/1.25 µg/ml in ileum fluid, respectively. In vitro, the mutant prevention concentration, the post-antibiotic effect, growth, and time-killing curves in vitro and ex vivo of ADP/SMZ against the isolate SHC28 were assayed for PD studies. The results showed that ADP/SMZ exhibited strong concentration-dependent antimicrobial activity against E. coli. After integrating the in vivo pharmacokinetic parameters of infected pigs and ex vivo PD data using the sigmoid E_max (Hill) equation, the AUC_24h /MIC values in ileum fluid for bacteriostatic, bactericidal, and bacterial eradication were 18.84, 65.39, and 110.68 h, respectively. In conclusion, a dosage of 3.45/17.25 mg/kg ADP/SMZ by intramuscular injection daily for 3 consecutive days may be sufficient to treat swine colibacillosis due to E. coli with a MIC of 0.5/2.5 µg/ml.

Antibacterial Residue Excretion via Urine as an Indicator for Therapeutical Treatment Choice and Farm Waste Treatment

Many of the infectious diseases that affect livestock have bacteria as etiological agents. Thus, therapy is based on antimicrobials that leave the animal's tissues mainly via urine, reaching the environment through slurry and waste water. Once there, antimicrobial residues may lead to antibacterial resistance as well as toxicity for plants, animals, or humans. Hence, the objective was to describe the rate of antimicrobial excretion in urine in order to select the most appropriate molecule while reducing harmful effects. Thus, 62 pigs were treated with sulfamethoxypyridazine, oxytetracycline, and enrofloxacin. Urine was collected through the withdrawal period and analysed via LC-MS/MS. Oxytetracycline had the slowest rate of degradation (a half-life time of 4.18 days) and the most extended elimination period in urine (over 2 months), followed by enrofloxacin (a half-life time of 1.48 days, total urine elimination in ca. 3 weeks) and sulfamethoxypyridazine (a half-life time of 0.49 days, total urine elimination in ca. 1 week). Bacterial sensitivity and recommendations for responsible use are limiting when selecting the treatment. Nevertheless, with similar effectiveness, sulfamethoxypyridazine would be the choice, as waste treatment would only need to be implemented for 1 week after treatment. Thus, more in-depth knowledge regarding antibacterial elimination would improve resource management, while protecting animals and consumers' health.

A history of antimicrobial drugs in animals: Evolution and revolution

The evolutionary process of antimicrobial drug (AMD) uses in animals over a mere eight decades (1940-2020) has led to a revolutionary outcome, and both evolution and revolution are ongoing, with reports on a range of uses, misuses and abuses escalating logarithmically. As well as veterinary therapeutic perspectives (efficacy, safety, host toxicity, residues, selection of drug, determination of dose and measurement of outcome in treating animal diseases), there are also broader, nontherapeutic uses, some of which have been abandoned, whilst others hopefully will soon be discontinued, at least in more developed countries. Although AMD uses for treatment of animal diseases will continue, it must: (a) be sustainable within the One Health paradigm; and (b) devolve into more prudent, rationally based therapeutic uses. As this review on AMDs is published in a Journal of Pharmacology and Therapeutics, its scope has been made broader than most recent reviews in this field. Many reviews have focused on negative aspects of AMD actions and uses, especially on the question of antimicrobial resistance. This review recognizes these concerns but also emphasizes the many positive aspects deriving from the use of AMDs, including the major research-based advances underlying both the prudent and rational use of AMDs. It is structured in seven sections: (1) Introduction; (2) Sulfonamide history; (3) Nontherapeutic and empirical uses of AMDs (roles of agronomists and veterinarians); (4) Rational uses of AMDs (roles of pharmacologists, clinicians, industry and regulatory controls); (5) Prudent use (residue monitoring, antimicrobial resistance); (6) International and inter-disciplinary actions; and (7) Conclusions.

Quantitative risk model to estimate the level of antimicrobial residues that can be transferred to soil via manure, due to oral treatments of pigs

Veterinary antimicrobials can spread via manure onto agricultural fields, representing an emission of these products or their active metabolites into the environment. This causes concerns regarding the role of antimicrobial residues in the development, selection and spread of resistance. Aiming to approach this issue quantitatively, first a literature review was performed on the bioavailability and extent of in vivo biotransformation of twelve antimicrobials commonly used in pigs orally, and on the level of their persistence in manure. This information was then used in a model estimating the level of each of these administered antimicrobials that is present in manure at the end of common storage durations in pits and, thus, readily applied onto soil. From the studied antimicrobials, the highest level of residues in stored manure was estimated for doxycycline (55% of the initial amount of doxycycline administered orally to pigs after six months of manure storage), as a combining result of its high use in pigs, low bioavailability and high stability in manure. Other antimicrobials (e.g. amoxicillin) are readily degraded and therefore pose less threat. The results of this study highlight the importance of rational antimicrobial use and of further research on pharmacokinetics of antimicrobials and their degraded products in different environmental compartments, to efficiently control the spread of residues and/or resistance genes from manure to these matrices.

Pharmacokinetics and pharmacodynamics of sulfamethoxazole and trimethoprim in swimming crabs (Portunus trituberculatus) and in vitro antibacterial activity against Vibrio: PK/PD of SMZ-TMP in crabs and antibacterial activity against Vibrio

Serious bacterial pathogens have recently become a major cause of massive mortality in swimming crabs (Portunus trituberculatus). In this study, the antibacterial activity against Vibrio and the pharmacokinetics (PK) of sulfamethoxazole (SMZ)-trimethoprim (TMP) in crabs were estimated to explore the pharmacokinetics/pharmacodynamics (PK/PD) properties of the SMZ-TMP combination. The in vitro bacteriostatic activity and the anti-Vibrio infection activity of the SMZ-TMP combination at various ratios in crabs were studied. A degree of synergism was observed in the SMZ-TMP combination at ratios ranging from 50:1 to 1:5. The results showed that the MIC50 and MIC90 values for different SMZ-TMP combinations were in the ranges of 0.62-5 and 0.62-10μg/mL, respectively. The distribution of the MIC values of the SMZ-TMP combination at ratios of 1:1 and 5:1 were 0.31-5 and 0.31-10μg/mL, respectively. Crabs were then fed the SMZ-TMP combination (at ratios of 5:1 and 1:1) six successive times and then challenged with Vibrio parahaemolyticus at 1×10(5), 1×10(6), and 5×10(6) colony forming units (cfu) per crab. The results showed that the number of surviving crabs administered SMZ-TMP at a ratio of 1:1 was greater than that of the crabs given SMZ-TMP at a ratio of 5:1. In addition, the tissue distribution and absorption of SMZ-TMP (ratios of 5:1 and 1:1) in crabs were studied through high-performance liquid chromatography (HPLC). In the crabs fed SMZ-TMP at a ratio of 5:1, the CmaxSMZ/TMP values in the hemolymph, hepatopancreas, muscle and gill were 104:1. 0.57:1, 19:1 and 6:1, respectively. In contrast, the corresponding CmaxSMZ/TMP values in these tissues in the crabs fed SMZ-TMP at a ratio of 1:1 were 34:1, 0.14:1, 4:1 and 3:1, respectively. The results showed that TMP was better absorbed and eliminated in the crabs fed SMZ-TMP at a ratio of 1:1 than in the crabs fed this combination at a ratio of 5:1. In addition, TMP was absorbed and eliminated more rapidly in the hepatopancreas than in the gill, muscle and hemolymph. The distribution volume of TMP in the hepatopancreas exceeded that of SMZ observed in the experiments. The results indicated that the PK/PD effect of the SMZ-TMP at a ratio of 1:1 was greater than that of the combination at a ratio of 5:1. Our study suggests that a SMZ-TMP ratio of 1:1 may be used to control bacterial disease in aquatic animals.