The effects of increasing sodium chloride concentration on Mycoplasma gallisepticum vaccine survival in solution

Lyophilized Mycoplasma gallisepticum (MG) vaccines are generally rehydrated and diluted with distilled or chlorine-free water as per manufacturer recommendations. However, as mycoplasma species lack a cell wall, this can lead to decreased viability of live vaccine during administration. The ability of phosphate-buffered saline (PBS) to prevent losses in live vaccine viability was examined. It was shown that a concentration of 1 x PBS prevented the two-fourfold decrease in MG viability seen when the vaccines were diluted with water alone.     

Mitsuokella jalaludinii inhibits growth of Salmonella enterica serovar Typhimurium

Salmonella continues to be a significant human health threat, and the objective of this study was to identify microorganisms with the potential to improve porcine food-safety through their antagonism of Salmonella. Anaerobic culture supernatants of 973 bacterial isolates from the gastrointestinal tract and feces of swine were screened for their capacity to inhibit the growth of Salmonella enterica serovar Typhimurium. Growth inhibition of 1000-fold or greater was observed from 16 isolates, and 16S rRNA sequencing identified the isolates as members of the genera Mitsuokella, Escherichia/Shigella, Anaerovibrio, Selenomonas, and Streptococcus. Four isolates were identified as Mitsuokella jalaludinii, and the mechanism of Salmonella Typhimurium growth inhibition by M. jalaludinii was further investigated. M. jalaludinii stationary phase culture supernatants were observed to significantly inhibit growth, and featured the production of lactic, succinic, and acetic acids. Aerobic and anaerobic S. Typhimurium growth was restored when the pH of the culture supernatants (pH 4.6) was increased to pH 6.8. However, S. Typhimurium growth in fermentation acid-free media was the same at pH 4.6 and pH 6.8 - indicating a synergistic effect between fermentation acid production and low pH as the cause of S. Typhimurium growth inhibition. Furthermore, exposure of S. Typhimurium to M. jalaludinii culture supernatants inhibited Salmonella invasion of HEp-2 cells by 10-fold. The results identify M. jalaludinii as a possible inhibitor of Salmonella growth and invasion in swine, and thus a potential probiotic capable of improving food safety.     

Forestomach epithelial receptor activation by rumen fluids from sheep given intraruminal infusions of volatile fatty acids

Forty-four reticuloruminal epithelial receptors were tested with rumen fluids obtained from 12 sheep before they were intraruminally infused with 4.0M acetic acid (8 sheep) or 4.0M butyric acid (4 sheep; preinfusion rumen fluid) and with rumen fluids obtained at the onset of ruminal stasis (abolition rumen fluid). The preinfusion rumen fluids from the 8 acetic acid-infused sheep (mean pH, 6.55) contained 1.7 mM nondissociated volatile fatty acids (VFA)/L and excited none of the 25 receptors tested. Preinfusion rumen fluids from the 4 butyric acid-infused sheep (mean pH, 6.98) contained 0.3 mM nondissociated VFA/L and also did not evoke responses in any of the 19 receptors tested. Abolition rumen fluids from sheep treated with acetic acid excited 17 of the 25 receptors tested and contained 89.4 mM nondissociated VFA/L, of which nondissociated acetic acid comprised 85.0 mM/L. Abolition rumen fluids from sheep treated with butyric acid activated 14 of the 19 receptors tested and contained 61.1 mM nondissociated VFA/L, of which 38.7 mM/L was nondissociated butyric acid. Preinfusion rumen fluids whose pH values were adjusted to that of abolition rumen fluids with HCl contained nondissociated VFA levels ranging from 16.3 mM/L (acetic acid-treated sheep) to 20.6 mM/L (butyric acid-treated sheep) and elicited responses in 4 of 30 receptors tested. Preinfusion rumen fluids whose pH values were adjusted to the pH value of abolition rumen fluid with acetic acid contained 29.5 mM nondissociated VFA/L and excited 7 of 13 tested receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hydrochloric,acetic, butyric,and propionic acids on pathogenesis of ulcers in the nonglandular portion of the stomach of horses

OBJECTIVE: To identify the pathogenesis of gastric ulcers by comparing injury to the nonglandular gastric mucosa of horses caused by hydrochloric acid (HCl) or volatile fatty acids (VFAs). SAMPLE POPULATION: Gastric tissues from 30 horses. PROCEDURE: Nonglandular gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference were measured and electrical resistance calculated for tissues after addition of HCl and VFAs to normal Ringer's solution (NRS). Tissues were examined histologically. RESULTS: Mucosa exposed to HCl in NRS (pH, 1.5) had a significant decrease in Isc, compared with Isc for mucosa exposed to NRS at pH 4.0 or 7.0. Also, exposure to 60mM acetic, propionic, and butyric acids (pH, 4.0 or 1.5) caused an immediate significant decrease in Isc. Recovery of sodium transport was detected only in samples exposed to acetic acid at pH 4.0. Recovery of sodium transport was not seen in other mucosal samples exposed to VFAs at pH < or = 4.0. CONCLUSIONS AND CLINICAL RELEVANCE: Acetic, butyric, and propionic acids and, to a lesser extent, HCl caused decreases in mucosal barrier function of the nonglandular portion of the equine stomach. Because of their lipid solubility at pH < or = 4.0, undissociated VFAs penetrate cells in the nonglandular gastric mucosa, which causes acidification of cellular contents, inhibition of sodium transport, and cellular swelling. Results indicate that HCl alone or in combination with VFAs at gastric pH < or = 4.0 may be important in the pathogenesis of gastric ulcers in the nonglandular portion of the stomach of horses.     

添加糖蜜和乙酸对西藏发酵全混合日粮青贮发酵品质及有氧稳定性影响

为研究乙酸和糖蜜对发酵全混合日粮(FTMR)品质及有氧稳定性的影响,试验以全混合日粮(TMR)为发酵原料,设对照组、乙酸(A)、糖蜜(M)、乙酸和糖蜜组合添加(AM)4个处理,发酵45 d后分析FTMR的发酵品质,同时将所有FTMR暴露到空气中,分别在第6,9和12天取样评定其有氧稳定性。结果表明,与对照相比,A和AM组降低了乳酸含量(P>0.05),各组仅检测到微量的丙酸、少量的丁酸和较低的氨态氮/总氮,表明各组FTMR发酵品质均良好。有氧暴露6 d后,各组乳酸、乙酸和水溶性碳水化合物含量均呈不同程度的下降,对照和M组pH值在第12 天显著(P<0.05)上升至5.70和6.50,具有较高的氨态氮/总氮和酵母菌数量。而A和AM组乳酸含量均呈先上升后下降的变化趋势,且好氧性微生物和酵母菌数量在整个有氧暴露的过程中始终维持在较低水平,有氧暴露12 d后pH值仍维持在4.50左右,延长了有氧稳定时间。综合考虑,为了获得品质优良的FTMR饲料,可在TMR中添加0.3%乙酸,既不影响发酵品质,也可提高其有氧稳定性。     

Susceptibility of Salmonella isolated from fish feed factories to disinfectants and air-drying at surfaces

The objective of this work was to determine whether persistence of certain Salmonella isolates in fish feed factories involved enhanced resistance to disinfectants or air-drying. Salmonella isolates known to be persistent in fish feed factories and Salmonella isolates from other origins were tested for their sensitivity to nine disinfectants by using a suspension test. More than 5log(10)reduction in viable count for all isolates was only achieved by two of the disinfectants at 80% of the lowest recommended user concentration. However, Salmonella isolates from fish feed factories were not more resistant to disinfectants compared to Salmonella from other origins. For four of the disinfectants, presence of fish feed had a more adverse effect on disinfection efficacy compared to the protein bovine serum albumin (BSA). In general, the Salmonella isolates were more resistant to disinfection than Escherichia coli DSM 682, a strain recommended in testing of disinfectants. The Salmonella isolates were also tested for their ability to survive air-drying at stainless steel surfaces, but there were no differences in survival of isolates from fish feed factories compared to isolates of other origin. In conclusion the Salmonella isolates from fish feed factories were not particularly resistant to disinfection or air-drying at surfaces. The data show that disinfectants to be used against Salmonella should be thoroughly tested and selected, since not all disinfectants appear to be effective against Salmonella.     

In vitro effects of hydrochloric acid and various concentrations of acetic, propionic, butyric, or valeric acids on bioelectric properties of equine gastric squamous mucosa

OBJECTIVE: To compare the effects of hydrochloric acid (HCl) and various concentrations of volatile fatty acids (VFAs) on tissue bioelectric properties of equine stomach nonglandular (NG) mucosa. SAMPLE POPULATION: Gastric tissues obtained from 48 adult horses. PROCEDURES: NG gastric mucosa was studied by use of Ussing chambers. Short-circuit current (Isc) and potential difference (PD) were measured and electrical resistance (R) and conductance calculated for tissues after addition of HCl and VFAs (5, 10, 20, and 40 mM) in normal Ringer's solution (NRS). RESULTS: Mucosa exposed to HCl in NRS (pH of 1.5 and, to a lesser extent, 4.0) had a significant decrease in Isc, PD, and R, whereas tissues exposed to acetic acid at a pH of < 4.0, propionic and butyric acids at a pH of 相似文献   

Antibacterial activity of milk-fermenting bacteria

Factors influencing salmonella survival in fermented milk products were investigated. Filtrates of yoghurt and cream cultures and a filtrate from milk precipitated by lactic acid were inoculated by salmonellas. The pH value was adjusted within the range of 7.0 to 4.5. The content of nondissociated lactic acid was determined. The filtrates were incubated 24 and 48 hours at a temperature of 37 degrees C. In comparison with the milk filtrate, great inhibitory (at pH 6.5) and bactericidal (at pH 5.5) effects of the yoghurt culture on salmonellas were proved. The filtrate from the cream culture inactivated salmonellas at pH 4.5, the growth ceased at pH 5.5. The effects of lactic and acetic acids on salmonellas at a concentration of 0.5% and pH 3.3, and acetic acid at a concentration of 0.05% and pH 5.1 were also studied.     

猪链球菌2型分离株对野生斑马鱼的致病性

以野生斑马鱼为模式动物,对6株mrp＋epf＋sly＋猪链球菌2型（SS2）分离株进行致病性比较。斑马鱼经腹腔接种不同稀释度的SS2分离株,连续观察5d,Kaplan-Meier生存曲线分析并统计半数致死量（LD50）。结果显示,6个分离株对斑马鱼的LD50在10^5cfu-10^6cfu之间,临床株与非临床株的毒力差异不显著（P〉0.05）。从攻毒后死亡的鱼腹腔和脑可分离到SS2,并伴有腹腔出血及肝、肠、脑部炎性病变。表明SS2可感染斑马鱼,为进一步研究SS2的体内感染机制及毒力因子功能等奠定了基础。     

壳聚糖对5种细菌体外的抑制试验

为开发利用壳聚糖,选择两种不同性质壳聚糖进行体外抑菌试验。将白色壳聚糖(Ⅰ组)和褐色壳聚糖(Ⅱ组)的乙酸溶液、褐色壳聚糖水溶液(Ⅲ组)用无菌蒸馏水分别稀释至10,5,2.5,1.25 g/L和0.625 g/L,用相应稀释度乙酸溶液(Ⅳ组)作对照组。对大肠埃希菌、金黄色葡萄球菌、蜡样芽孢杆菌、绿脓杆菌、鸡伤寒沙门菌进行体外抑菌试验。结果表明,在体外,壳聚糖对上述5种细菌的生长均有不同程度的抑制作用,不同性质的壳聚糖和同一性质不同浓度的壳聚糖抑菌效果不同。     

添加乙酸对西藏燕麦和紫花苜蓿混合青贮发酵品质和有氧稳定性的影响

为探讨不同水平乙酸对燕麦和紫花苜蓿(7∶3)混合青贮发酵品质和有氧稳定性的影响,试验设对照组和3个乙酸添加组(0.3%,0.4%,0.5%),青贮后第30,45和60天开窖取样,测定青贮饲料的发酵品质,同时60 d后打开剩余的所有实验室青贮窖,将青贮饲料暴露于空气中,测定青贮饲料有氧稳定性。结果表明,添加乙酸显著(P<0.05)降低了混合青贮饲料的pH,其中0.4%与0.5%乙酸处理组pH显著(P<0.05)低于0.3%乙酸处理组。青贮60 d后乙酸添加组乳酸含量显著(P<0.05)高于对照组,但处理组间差异不显著(P>0.05)。添加乙酸显著(P<0.05)降低了青贮过程中氨态氮/总氮,且氨态氮/总氮随着乙酸添加量的增加呈下降趋势(P>0.05)。各乙酸添加组水溶性碳水化合物均显著(P<0.05)高于对照组,其中0.4%乙酸添加组最高。在有氧暴露前10 d,各组pH和氨态氮/总氮基本保持稳定,其中乙酸添加组低于对照组。暴露10 d后各组pH均有上升,其中对照组显著(P<0.05)上升。在整个有氧暴露阶段,乳酸和水溶性碳水化合物含量逐渐下降,但各乙酸添加组均显著(P<0.05)高于对照组,其中0.4%乙酸添加组乳酸含量始终保持最高。综合考虑发酵品质和有氧稳定性,0.4%乙酸添加量最适宜。     

青稞秸秆替代苇状羊茅对全混合日粮青贮早期发酵品质及有氧稳定性的影响

本试验旨在研究不同比例青稞秸秆替代苇状羊茅对全混合日粮青贮早期发酵品质及有氧稳定性的影响。试验设对照组(TH₀)和3个青稞秸秆不同比例替代组TH₅、TH₁₀和TH₁₅。青贮14 d开窖取样,分析其发酵品质、化学成分及微生物数量,将剩余的发酵TMR暴露于空气,用多通道温度记录仪记录温度变化;并分别在有氧暴露的第2,5和8天取样评定其有氧稳定性。结果表明,与对照组(TH₀)相比,TH₅的pH、乳酸、乙酸、总挥发性脂肪酸和乙醇含量无显著(P>0.05)差异;TH₁₀和对照相比pH差异不显著(P>0.05),但乳酸、乙酸、总挥发性脂肪酸和乙醇含量显著(P<0.05)低于对照组;TH₁₅ pH显著(P<0.05)高于对照组,乳酸、乙酸、总挥发性脂肪酸和乙醇含量显著(P<0.05)低于对照组;各组氨态氮/总氮和乳酸/乙酸无显著(P>0.05)差异,均以乳酸发酵为主,发酵品质良好。有氧暴露第2天后各组pH和氨态氮/总氮持续上升;乳酸、乙酸和水溶性碳水化合物含量持续下降;酵母菌和好氧细菌数量显著(P<0.05)升高。除TH₁₅外,其他各组温度在第35 h开始上升,TH₁₅温度上升延迟,并且温度上升峰值最小。和其他组相比,TH₁₅有氧稳定性最好。综合考虑发酵品质、有氧稳定性及对青稞秸秆资源的最大化利用,建议采用TH₁₅设计配方最为适宜。     

Biofilm formation in Haemophilus parasuis: relationship with antibiotic resistance,serotype and genetic typing

Biofilms are surface-associated microbial communities, which are encased in self-synthesized extracellular environment. Biofilm formation may trigger drug resistance and inflammation, resulting in persistent infections. Haemophilus parasuis is the etiological agent of a systemic disease, Glässer's disease, characterized by fibrinous polyserositis, arthritis and meningitis in pigs. The purpose of this study was to examine the correlation between biofilm and antibiotic resistance among the clinical isolates of H. parasuis. In the present study, we tested biofilm-forming ability of 110 H. parasuis isolates from various farms using polystyrene microtiter plate assays. Seventy-three isolates of H. parasuis (66.4%) showed biofilm formation and most of them performed weak biofilm-forming ability (38/73). All isolates were tested for antimicrobial susceptibility to 18 antimicrobial agents by the broth microdilution method. H. parasuis isolates showed very high resistance (>90%) to sulfanilamide, nalidixic acid, and trimethoprim. Resistance to eight antibiotics such as penicillin (41.1% vs 8.1%), ampicillin (31.5% vs 8.1%), amoxicillin (28.8% vs 5.4%), gentamicin (46.6% vs 24.3%), cefazolin (19.2% vs 2.7%), doxycycline (19.2% vs 8.1%), cefotaxime (11% vs 2.7%), and cefaclor (13.7% vs 5.4%) was comparatively higher among biofilm producers than non-biofilm producers. Pulsed-field gel electrophoresis (PFGE) analyses could distinguish various isolates. Our data indicated that H. parasuis field isolates were able to form biofilms in vitro. In addition, biofilm positive strains had positive correlation with resistance to β-lactams antibiotics. Thus, biofilm formation may play important roles during H. parasuis infections.     

Factors affecting the in vitro production of volatile fatty acids by mixed bacterial populations from the bovine rumen

Factors affecting in vitro ruminal bacterial VFA production were examined. Treatments consisted of high and low initial pH (6.7, 5.7), osmolality (600, 400 mOsm) and concentrations of acetic (40, 0 mM) and propionic acids (20, 0 mM). Response variables measured included the production of acetic, propionic and total VFA, total gas and methane. Initial pH affected (P less than .05) most variables either independently or in combination with one or more of the other factors. Acetic acid production was reduced 40% (P = .03) when initial acetic acid concentrations were 40 mM compared with 0 mM. Also, acetic acid production was less (P less than .01) at low initial pH (5.7) than at high initial pH (6.7). Propionic acid production was greater (P = .05) at high vs low initial acetic acid concentrations. Propionic acid production was greater in response to low vs high initial osmolality, although the magnitude of this difference depended on initial pH (interaction P = .02). Total production of VFA was greater (P less than .01) at high than at low initial pH; however, at low initial pH, no difference (P greater than .05) was observed due to initial osmolality, whereas at high pH, production was greater (interaction P = .04) for low than for high initial osmolality. The diminished production of total VFA at pH 5.7 occurred primarily due to reduced acetic acid production, although increased production of propionic and butyric acids was noted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Infusion of sodium bicarbonate in experimentally induced metabolic acidosis does not provoke cerebrospinal fluid (CSF) acidosis in calves

In a crossover study, 5 calves were made acidotic by intermittent intravenous infusion of isotonic hydrochloric acid (HCl) over approximately 24 h. This was followed by rapid (4 h) or slow (24 h) correction of blood pH with isotonic sodium bicarbonate (NaHCO(3)) to determine if rapid correction of acidemia produced paradoxical cerebrospinal fluid (CSF) acidosis. Infusion of HCl produced a marked metabolic acidosis with respiratory compensation. Venous blood pH (mean ± S(x)) was 7.362 ± 0.021 and 7.116 ± 0.032, partial pressure of carbon dioxide (Pco(2), torr) 48.8 ± 1.3 and 34.8 ± 1.4, and bicarbonate (mmol/L), 27.2 ± 1.27 and 11 ± 0.96; CSF pH was 7.344 ± 0.031 and 7.240 ± 0.039, Pco(2) 42.8 ± 2.9 and 34.5 ± 1.4, and bicarbonate 23.5 ± 0.91 and 14.2 ± 1.09 for the period before the infusion of hydrochloric acid and immediately before the start of sodium bicarbonate correction, respectively. In calves treated with rapid infusion of sodium bicarbonate, correction of venous acidemia was significantly more rapid and increases in Pco(2) and bicarbonate in CSF were also more rapid. However, there was no significant difference in CSF pH. After 4 h of correction, CSF pH was 7.238 ± 0.040 and 7.256 ± 0.050, Pco(2) 44.4 ± 2.2 and 34.2 ± 2.1, and bicarbonate 17.8 ± 1.02 and 14.6 ± 1.4 for rapid and slow correction, respectively. Under the conditions of this experiment, rapid correction of acidemia did not provoke paradoxical CSF acidosis.     

Effect of acid and alkali treatment of soybean meal on nitrogen utilization by ruminants

Soybean meal (SBM) was treated with acid or alkali to determine effects on N solubility, in vitro NH3-N accumulation, in situ N degradability, and N digestion and retention in growing lambs. The following SBM treatments resulted in decreased (P less than .05) N solubility and in vitro NH3-N accumulation compared with control SBM: spraying with 2.5 or 5% acetic or propionic acid, soaking in .5 N HCl, .5 N NaOH or .5 N propionic acid followed by air drying, and soaking in H2O, .5 N HCl or .5 N propionic acid followed by drying at 100 C. In situ residual N was determined for SBM subjected to the above treatments. Soybean meal sprayed with 2.5 or 5% acetic or propionic acid had greater (P less than .05) in situ residual N after 4, 8 and 12 h of incubation than control SBM. Soybean meal soaked in .5 N HCl or .5 N NaOH and air-dried, and soaked in H2O, .5 N propionic acid or .5 N HCl and dried at 100 C had greater (P less than .05) in situ residual N after 4, 8, 12 and 24 h of incubation than control SBM. In a lamb N balance trial, SBM treated by spraying with 5% acetic or propionic acid or by soaking in .5 N NaOH did not result in reduced N digestion compared to control SBM. Feeding SBM soaked in .5 N NaOH resulted in a 39% increase (P less than .05) in N retention compared with control SBM (5.21 vs 3.74 g/d, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

混合乳酸菌制剂对芦苇低水分青贮品质的影响

将成熟期芦苇晾晒成30%和40%2个水分组,并分别添加3%、6%、9%和12%混合乳酸菌制剂(LABs)发酵20 d,研究水分含量和混合乳酸菌制剂对芦苇青贮品质的影响。结果表明:添加混合乳酸菌制剂显著降低了30%和40%水分条件下,青贮后CF和NDF含量(P<0.05)。同等水分下,添加乳酸菌制剂可以显著降低pH值、提高青贮料乳酸、乙酸生成量以及乳酸菌数量(P<0.05)。随水分含量的升高,pH值显著下降,乳酸、总酸生成量以及乳酸菌数量显著增加(P<0.05)。各种试验处理组均获得较理想的发酵效果。     

牛初乳乳清制备工艺研究

为优化乳清制备工艺,以脱脂牛初乳为原料,研究通过酸沉酪蛋白方法制备高质量乳清。综合考虑酸的种类、强弱和乳清中IgG的活性变化,确定了酸沉酪蛋白的最佳工艺条件为：0．8mol／L乳酸调脱脂乳pH值至4．3,加水至干物质终质量分数为10％,45℃水浴15min,4000r／min离心5min。经检测所制备的乳清中IgG活性含量仅损失3．05％。     

玉米、小麦、水稻秸秆自然发酵的生化变化

测定玉米、小麦、水稻干秸秆在自然发酵中的生化变化.结果表明:玉米秸秆气味香甜,pH下降迅速并保持在4.2以下,挥发性发酵产物种类有13种,主要为乙醇、乙酸、乳酸及甘油等利于提高饲料品质的物质;而小麦和水稻秸秆质地生硬,生料气味,pH下降困难,挥发性发酵产物多达20种,其中乳酸和乙酸较少,而产生丁酸等影响发酵品质的物质较多;发酵物中可溶性糖含量的变化在一定程度上反映其优劣;当发酵初期可溶性糖较多时,pH下降迅速,后期可溶性糖含量平稳;而当初期可溶性糖含量较低时,pH下降缓慢,后期可溶性糖含量则一直下降.     

高效液相色谱法测定水产品中孔雀石绿残留量方法的改进

水产品中残留的隐色孔雀石绿经后氧化铅柱氧化为显色孔雀石绿,采用高效液相色谱-紫外检测器对显色孔雀石绿进行了检测.样品提取净化采用乙腈在乙酸铵缓冲溶液条件下提取,10 000 r/min离心,上清液转入50 mL离心管,再加入15 mL蒸馏水,10 000 r/min离心,取上清液过固相萃取柱,再用3mL蒸馏水洗柱,1 ...