Bacterial community analysis of purulent material from liver abscesses of crossbred cattle and Holstein steers fed finishing diets with or without tylosin

Liver abscesses in feedlot cattle are polymicrobial infections. Culture-based studies have identified Fusobacterium necrophorum as the primary causative agent, but a number of other bacterial species are frequently isolated. The incidence of liver abscesses is highly variable and is affected by a number of factors, including cattle type. Holstein steers raised for beef production have a higher incidence than crossbred feedlot cattle. Tylosin is the commonly used antimicrobial feed additive to reduce the incidence of liver abscesses. The objective of this study was to utilize 16S ribosomal RNA amplicon sequence analyses to analyze the bacterial community composition of purulent material of liver abscesses of crossbred cattle (n = 24) and Holstein steers (n = 24), each fed finishing diet with or without tylosin. DNA was extracted and the V3 and V4 regions of the 16S rRNA gene were amplified, sequenced, and analyzed. The minimum, mean, and maximum sequence reads per sample were 996, 177,070, and 877,770, respectively, across all the liver abscess samples. Sequence analyses identified 5 phyla, 14 families, 98 genera, and 102 amplicon sequence variants (ASV) in the 4 treatment groups. The dominant phyla identified were Fusobacteria (52% of total reads) and Proteobacteria (33%). Of the top 25 genera identified, 17 genera were Gram negative and 8 were Gram positive. The top 3 genera, which accounted for 75% of the total reads, in the order of abundance, were Fusobacterium, Pseudomonas, and Bacteroides. The relative abundance, expressed as percent of total reads, of phyla, family, and genera did not differ (P > 0.05) between the 4 treatment groups. Generic richness and evenness, determined by Shannon–Weiner and Simpson’s diversity indices, respectively, did not differ between the groups. The UniFrac distance matrices data revealed no clustering of the ASV indicating variance between the samples within each treatment group. Co-occurrence network analysis at the genus level indicated a strong association of Fusobacterium with 15 other genera, and not all of them have been previously isolated from liver abscesses. In conclusion, the culture-independent method identified the bacterial composition of liver abscesses as predominantly Gram negative and Fusobacterium as the dominant genus, followed by Pseudomonas. The bacterial community composition did not differ between crossbred and Holstein steers fed finishing diets with or without tylosin.     

“泰乐星”牌酒石酸泰乐菌素对鸡支原体抑菌效果及增重试验

选用14日龄AA雏鸡149只，分为6组，除阴性对照外，其余试验组均用鸡支原体强毒人工接种，24h后给药，试验期为20天，综合评价试验结果：以“泰乐星”牌酒石酸泰乐菌素500mg/L组效果最好，其效果与进口产品差异不显著（P〉0．05），成活率达96％，增重率达155．9％。     

泰乐菌素药渣残留量的测定

采用高效液相色谱-紫外检测方法,建立了泰乐菌素药渣残留量测定的分析方法。泰乐菌素在6min内完全检出。线性范围为0.5～20.0mg/L,相关系数为0.999 8,最小检出浓度为0.1mg/L。将该方法应用于泰乐菌素测定上,回收率介于98.3%～100.3%,效果较好。     

二氧化锰改性碳纳米管对四环素和泰乐菌素的吸附

采用氧化还原法制备二氧化锰负载碳纳米管(Mn O2/MWNT),通过批次吸附实验研究其对所选四环素和泰乐菌素的吸附行为及其影响因素。研究结果表明:与未处理的碳纳米管相比,二氧化锰负载后显著提高了碳纳米管对四环素和泰乐菌素的吸附,约提高了5~8倍;两种抗生素在Mn O2/MWNT上的强吸附机制可解释为π-π电子交互作用、阳离子-π键作用和路易斯酸碱对作用;随着p H升高,四环素和泰乐菌素在Mn O2/MWNT上的吸附显著降低,两种抗生素所含官能团的去质子化作用,以及Mn O2/MWNT表面含氧官能团的解离,导致Mn O2/MWNT与两种抗生素之间的吸附作用减弱。可溶性腐植酸降低了泰乐菌素在Mn O2/MWNT上的吸附,而对四环素影响很小,主要原因是大分子腐植酸不能有效地与四环素竞争Mn O2/MWNT孔道内部的吸附位点。     

利用响应面法优化泰乐菌素发酵培养基

用响应面法对弗氏链霉菌发酵产泰乐菌素的培养基进行优化。首先用Plackett-Burman法对11个培养基因素进行筛选,结果发现,三个对泰乐菌素效价影响较大的重要因素分别为鱼粉、黄豆饼粉、油,然后进行最陡爬坡实验逼近最佳响应面区域,最后通过Box-Behnken设计,利用Design-Expert V8.0.5软件进行回归分析,得到各因素的最佳浓度,并验证响应面预测值与实测值的一致性。结果表明,在鱼粉10.64 g/L、黄豆饼粉14.69 g/L、油58 g/L的最优培养基下,泰乐菌素的产量可达14915 U/mL,实测值与响应面预测值拟合良好,说明通过响应面实验设计对泰乐菌素发酵培养基的优化是有效的,比优化前提高了15%。     

几种常用酸稀释液测定泰乐菌素精制液效价的方法比较

分别采用0．1mol／L盐酸溶液、0．05mol／L硫酸溶液、0．033mol／L磷酸溶液作稀释液测定泰乐菌素精制液化学效价,从曲线线性关系、准确度及检验结果对比方面进行分析比较。结果显示：三种溶液吸收度与浓度均呈良好的线性关系（R盐酸2=0．9997,R硫酸2=1．0000,R磷酸2=1．0000;n=5）,准确度高,测定结果无明显差异,在质量控制中可以选择不同的酸稀释液进行测定。     

Macrolides and lincosamides

Macrolides and lincosamides are first choice bacteriostatic antibiotics used in veterinary dermatology. The main antibiotics in these classes are erythromycin, lincomycin, clindamycin and tylosin. They are well absorbed if given orally and are able to penetrate well into infected skin. Their spectrum of action comprises bacteria commonly associated with skin infections, including staphylococci. Their main disadvantages are the rapid development of bacterial resistance and occasional gastroenteric upset, most often seen with erythromycin. More recently developed macrolides, such as azithromycin and clarithomycin, are bactericidal, have a larger spectrum of action, a longer endurance, less resistance and may be given once a day instead of two or three times daily.     

安泰粉针剂治疗犊牛腹泻的临床试验

采用临床对比观察的方法,试验安泰粉针剂对83头犊牛腹泻的治疗效果.治疗组口服安泰粉针剂1.5万单位/kg体重,1次/d,连用3～5 d;对照组肌肉注射氟哌酸注射液4.0～8.0 mg/kg体重,2次/d,连用3～5 d,或口服氟哌酸片,10片/次,2～3次/d,连用3～5 d.安泰粉针剂对犊牛腹泻的治疗效果好于临床常用药物氟哌酸,但无统计学意义(P＞0.05).     

双波长紫外分光光度法测定酒石酸泰乐菌素-盐酸多西环素可溶性粉的含量

建立了双波长紫外分光光度法同时测定酒石酸泰乐菌素-盐酸多西环素可溶性粉中酒石酸泰乐菌素和盐酸多西环素含量的检测方法。结果显示，吸收度与浓度呈良好线性关系。酒石酸泰乐菌素的平均回收率为99．90％，RSD为0．42％n=5）；盐酸多西环素的平均回收率为100．07％，RSD为0．74％（n=5）。     

Some Comparative Aspects of the Pharmacokinetics of Tylosin in Buffaloes and Cattle

The pharmacokinetics of tylosin were compared in cattle (Bos taurus) and buffaloes (Bubalus bubalis). Six animals received each a single dose of 10 mg/kg of tylosin tartrate by the intramuscular route. The serum concentration (C _max) and the volume of distribution (V _d) presented significant differences between the two species. C _max was 0.40 ± 0.046 µg/ml for buffaloes and 0.64 ± 0.068 µg/ml for cattle. V _d was 1.91 ± 0.12 L/kg and 1.33 ± 0.09 L/kg for buffaloes and cattle, respectively. However, as the present study did not show considerable differences in the pharmacokinetics of tylosin in buffaloes and cattle, similar dosage regimes of this drug can be recommended for both species.