共基质对10株细菌降解苯并芘的作用研究

从石油污染的污泥中分离驯化出10株细菌（SB01-SB10）,利用生物摇床实验对其降解苯并芘（BaP）的效能进行试验,研究了有（或无）共基质（葡萄糖Glu,或菲PHE）对细菌降解BaP的影响,并采用ANOVA和Tukey多重比较进行分析。结果表明,（1）当以BaP为惟一碳源和能源且BaP初始浓度为50mg·L^-1时（MS1）,SB01的降解率最高,5d可降解31．0％;以Glu为共代谢基质时（MS2）,SB09的降解率最高,可达36．9％;以PHE为共代谢基质时（MS3）,SB01对BaP的降解率为46．0％。（2）Glu对SB01、SB02、SB03、SB07、SB10降解BaP有抑制作用,对SB01抑制作用最明显,使SB01的降解率降低了13．1％,Glu对SB05,SB08降解率无明显促进或抑制作用。（3）PHE对细菌降解BaP均表现出促进作用,对SB01的促进作用最明显,使其降解率提高15．0％。（4）Glu对SB09的促进作用大于PHE的促进作用。而对SB06,PHE的促进作用大于Glu。     

Neuraminidase production by Erysipelothrix rhusiopathiae

In order to characterise neuraminidase activity by Erysipelothrix, 85 isolates of Erysipelothrix spp. from a variety of sources including human clinical, marine and terrestrial animals, and the environment were investigated for neuraminidase production. Neuraminidase activity was detected by a peanut lectin haemagglutination method. The effects of media, incubation conditions and pH on the production and activity of neuraminidase were also investigated. Enzyme activity was detected only in the supernatants of the isolates of Erysipelothrix rhusiopathiae which had been incubated in cooked meat broth and Todd Hewitt broth supplemented with horse serum after 16 and 36 h incubation at 37 degrees C. The maximum titres were reached at 40 h in cooked meat broth and 56 h in Todd Hewitt broth supplemented with horse serum. All 58 isolates and the type strain (ATCC 19414) of E. rhusiopathiae produced detectable neuraminidase activity with titres between 10 and 320. The optimal pH for the enzyme activity varied among the isolates with a pH between 6.0 and 7.0 covering the highest enzyme activity of the most. There was no statistically significant difference in the level of neuraminidase activity between isolates from different sources (p > 0.05). Neuraminidase activity was not detected in the non-pathogenic Erysipelothrix spp. such as E. tonsillarum. Neuraminidase was detected only in E. rhusiopathiae suggesting its possible role as a virulence factor. Enzyme production and activity were medium and pH dependent. The peanut lectin haemagglutination assay is a simple, rapid and sensitive method and is particularly useful for the analysis of multiple samples.     

Pharmacodynamics of amoxicillin against Mannheimia haemolytica and Pasteurella multocida and pharmacokinetic/pharmacodynamic (PK/PD) correlation in sheep

Silicone-made tissue cages were implanted in sheep. Blood serum (SBS) and tissue cage fluid (TCF) samples were collected after amoxicillin intravenous and intramuscular administrations, at the dose of 15 mg/kg. Amoxicillin pharmacodynamics were studied in an artificial culture medium, SBS and TCF with use of a Mannheimia haemolytica and a Pasteurella multocida strain. A concentration-independent antimicrobial activity of amoxicillin was confirmed for levels higher than 0.79–1.75 × MIC. This result favored the use of the percentage of the 24 h dosing interval during which drug levels remain above MIC as the appropriate pharmacokinetic/pharmacodynamic index. The subsequent correlation revealed that intravenous administration could be considered effective against “deep” infections caused by bacteria with MICs < 1 μg/mL or “shallow” infections caused by bacteria with MICs < 0.1 μg/mL. Intramuscular administration could be safely considered effective against both “deep” and “shallow” infections when the MICs of the targeted pathogens are lower than 1 μg/mL.     

Nutritional interventions to prevent and rear low‐birthweight piglets

Selection for hyperprolific sows, as a means of increasing litter size and profit, has resulted in an increased number of low‐birthweight (LBW) piglets. These LBW piglets might suffer from increased morbidity and mortality during the early neonatal period. In addition, they show reduced growth performance, meat and carcass quality, which leads to an important economic loss for the farmer in the post‐natal period. Therefore, nutritional interventions can be undertaken to prevent and rear LBW piglets. In the first part of this review, the preventive strategies at the sow level will be discussed. Approaches in preventing LBW piglets are to optimize the intrauterine environment via supplementing the sow during gestation. In the second part of this review, the interventions at the piglet level will be described. To increase the survival and growth rates of LBW piglets, one must focus on ensuring adequate colostrum and milk intake. Interventions include supplementing piglets, split nursing, split weaning and cross‐fostering. Additional interventions increasing the probability of optimal post‐natal food intake will be discussed.