Oxytetracycline Pharmacokinetics in Rainbow Trout during and after an Orally Administered Medicated Feed Regimen

Abstract

The pharmacokinetic–pharmacodynamic predictor of antimicrobial activity for tetracyclines is reported to be the area under the concentration–time curve at steady state (AUC_ss) divided by the minimal inhibitory concentration of the targeted pathogen. Here, we estimate AUC_ss values for oxytetracycline (OTC) in serum of rainbow trout Oncorhynchus mykiss by using a destructive sampling study design. Seventy-two rainbow trout were fed OTC-medicated feed at 74.7 ± 1.5 mg/kg (mean ± SD) body weight (BW) by oral gavage for 10 consecutive days. Serum was collected from nine fish at 1, 3, 6, 8, 10, 12, 15, and 22 d after dosing began. Serum OTC concentrations were measured by high-performance liquid chromatography with a 0.01-μg/mL limit of detection. The average OTC AUC_ss was 29.2 μg × h/mL and was estimated using nonlinear mixed-effects modeling and bootstrap resampling techniques. The elimination half-life was estimated as 85.0 h, and the fraction of steady state achieved was estimated as 0.85. The calculated AUC_ss (24.8 μg × h/mL) following 10 d of oral dosing with 75 mg OTC/kg BW was less than the estimated AUC_ss. Results suggest that the pharmacokinetics of OTC exposure, including the AUC_ss, is better evaluated by using multiday dosimetry than by using a standard single-dose protocol.

Received September 29, 2011; accepted January 30, 2012     

Evaluation of a commercially available hyperimmune plasma product for prevention of naturally acquired pneumonia caused by Rhodococcus equi in foals

OBJECTIVE: To determine efficacy of a commercially available hyperimmune plasma product for prevention of naturally acquired pneumonia caused by Rhodococcus equi in foals. DESIGN: Randomized clinical trial. ANIMALS: 165 foals. PROCEDURE: Foals were randomly assigned to 1 of 2 groups (hyperimmune plasma or nontreated controls). Foals with failure of passive transfer (FPT) of immunity were treated with hyperimmune plasma and evaluated as a third group. Foals that received plasma were given 950 ml between 1 and 10 days of age and between 30 and 50 days of age. A tracheobronchial aspirate was obtained from foals with clinical signs of respiratory tract disease for bacteriologic culture. RESULTS: A significant difference in incidence of pneumonia caused by R equi in foals with adequate passive transfer was not detected between foals that received plasma (19.1%) and nontreated foals (30%). Of 13 foals without FPT that received plasma and developed pneumonia caused by R equi, 12 developed disease prior to administration of the second dose of hyperimmune plasma. Incidence of undifferentiated pneumonia of all causes was not different between groups. CONCLUSION AND CLINICAL RELEVANCE: Intravenous administration of the commercially available hyperimmune plasma was safe, and the product contained high concentrations of anti-R equi antibodies. However, within this limited foal population, the difference in incidence of pneumonia caused by R equi observed between foals that received plasma and control foals was not significant.     

Fluorouracil as a treatment for corneal papilloma in a Malayan tapir

A 26-year-old, wild caught, male Malayan tapir at the Miami Metrozoo with bilateral corneal papillomas was serially immobilized and given subconjunctival injections of fluorouracil. Over the course of 17 weeks five bilateral injections of 25 mg fluorouracil were given. This treatment caused regression of the corneal lesions as evidenced by decreased lesion diameter, decreased corneal vascularity, increased corneal clarity, and improved visual function. No adverse drug effects were observed.     

Two-step and random regression analyses of weight gain of station-tested beef bulls

Our objectives were to compare a two-step model and a joint procedure via random regression model for evaluating weight gain of beef bulls, weighed every 28 d on 140-d test, and to estimate genetic, environmental, and phenotypic parameters. Two-step analysis consisted of fitting fixed linear regressions to weights of each bull to determine weight gain on test. In the second step, gain on test was analyzed by a mixed model that included fixed effects of breed, test group, and starting age and random effects of weaning herd-year group and animal (additive genetic). The random regression model included the same effects as the two-step mixed-model analysis with an additional random animal permanent environment effect. Fourth-order Legendre polynomials of days on test were fitted for all fixed and random effects in the random regression model, except for breed. Breed effects and residual variances varied for each measurement period. Variance components and EBV for gain were obtained from the covariance function and estimates of random regression coefficients for weight, respectively. Random regression heritability estimates for gain on test increased over time, being maximum at end of test (0.38) and equal to two-step estimate. Permanent environment variance ratio estimates also increased over time and were greater than heritability estimates. Estimate of weaning herd-year variance ratio was approximately constant over time, being equal to 0.07 at end of test and similar to two-step estimate. Genetic correlations between gain through different periods on test given by random regression model were high (from 0.81, between 28 and 140-d gain on test, to 0.99, between 112 and 140-d gain on test). Genetic correlations between gain on discrete 28-d intervals were moderate to high (e.g., 0.49 and 0.99 between the last 28 d on test and the first and fourth 28 d, respectively). Rank correlations between EBV for 140-d gain by the two procedures were 0.98, 0.84, and 0.73 for all bulls and the 5% and 1% of bulls with highest random regression EBV, respectively. Results indicated that the two procedures rank top bulls quite differently for 140-d gain on test. Random regression model accounted for changes over time of genetic and environmental effects on the test weight gain curve of the bulls. Use of 112-d instead of a 140-d test provided similar ranking of bulls on the basis of EBV for gain on test.     

益生素在养猪生产中是否有效

在食品中加入某些活的微生物早已被证明对人类健康有积极的影响,这一方法已拓展到食品动物生产领域,且已涉及到许多微生物菌种,特别是乳酸菌、芽孢杆菌和酿酒酵母菌。对益生素兴趣的增加基本上是由于微生物耐药性问题的出现,同时自禁止在动物生产中使用抗生素后,益生素被认为是一种可减少病原菌感染并可提高猪、尤其是断奶期间仔猪的健康。然而,仍有必要阐明益生素在猪生产中的作用及潜在作用机制。在评价益生菌功效时,必须考虑所用的特定菌株和治疗猪对应的生长阶段。在实际的养猪生产中,重复益生素的功效还存在问题,因为维持其活性对它们的有益功效极为关键,但利用常规的饲料加工技术难以实现。益生素微生物能够被有效投喂的一种情况是在利用液体发酵饲料的生产系统中。液体饲料可以用活的野生乳酸菌进行发酵,也可将特定分离株作为＂启动子＂刺激其发酵,后一种方法对发酵的可重复性及其速度有益处。养猪场的微生物应用条件对其发挥正常功效很可能是至关重要的。给利用非理想条件饲养的猪饲喂益生素,所增加的经济效益远大于采用最佳福利条件和管理措施饲养的猪。如果猪出生时使其肠道内建立一个有益的微生物菌群,就有可能会产生较为健康的猪。实现这一效果的最有效方法是给母猪服用益生素,这提供了一个扩大益生菌的手段,使新生仔猪的生活环境中到处都是值得拥有的有益菌株。相比之下,它也许足以在仔猪断奶前后向其提供一个有支持作用和保护作用的肠道菌群,因为就某些肠道菌群的不稳定和损失来说,此时期是一个重要的决定性时刻。     

Characterization of anti-channel catfish MHC class IIbeta monoclonal antibodies

This study characterizes four monoclonal antibodies (mAb) developed against the major histocompatibility complex (MHC) class II beta chain of the channel catfish, Ictalurus punctatus. Immunoprecipitations using catfish clonal B cells revealed that each of these mAbs immunoselected proteins of approximately 32 and 36 kD, which are of the appropriate sizes for MHC class II alpha and beta chains, respectively. Cell distribution studies using a fluorescence-activated cell sorter (FACS) combined with RT-PCR analyses demonstrated that MHC class II beta is expressed at a high density on catfish clonal macrophage, B and T cell lines, on alloantigen stimulated leukocytes, and on lipopolysaccharide-induced B-cell blasts. Collectively, these results demonstrate the potential importance of these antibodies as reagents in future studies dealing with the functional role of MHC class II molecules in immune recognition of self from non-self.     

Recovery of Mycoplasma spp. from the Reproductive Tract of the Mare during the Estrous Cycle

The sites in the genital tract from which mycoplasmas could be recovered at various stages of the estrous cycle were studied in five Standardbred mares naturally infected with Mycoplasma. Mycoplasma equigenitalium and Mycoplasma subdolum were most frequently isolated from the clitoral fossa as compared to the vagina, cervix, and uterus. The lowest isolation prevalence was observed in the uterus. The recovery of Mycoplasma spp. from the clitoral fossa did not differ at any stage of the estrous cycle; however, recovery from the vagina, cervix, and uterus was variable during the cycle and more organisms were recovered on the day of ovulation than at any other time. From these results it was concluded that the clitoral fossa is the most likely “ecological niche” for Mycoplasma spp. in the mare. Ureaplasmas were not isolated.