Influence of diet on the experimental infection of pigs with Brachyspira pilosicoli.

The effects of five different diets on the experimental infection of pigs with a Danish field isolate of Brachyspira pilosicoli were investigated. The diets tested were a pelleted and a non-pelleted standard diet based on wheat and barley, the standard diet supplemented with 2 per cent lactic acid, a fermented liquid feed and a diet based on cooked rice. Two trials were conducted, each with six groups of six pigs; in each, two of the groups were fed the standard diet. One of these groups and the other four groups were challenged after two weeks on the diets and euthanased four weeks later. The clinical signs of B pilosicoli infection varied from loose stools to watery, mucoid diarrhoea. The group fed the rice diet excreted B pilosicoli in their faeces for a significantly shorter period than the group fed the standard diet (P < 0.01), and fewer of them excreted the organism (P < 0.05). All the pigs fed the pelleted diet excreted B pilosicoli in their faeces, and significantly more of them showed clinical signs of disease than the pigs fed the standard diet (P < 0.05). The fermented liquid feed and the diet containing lactic acid had no significant effect on the excretion of B pilosicoli or on the numbers of pigs showing clinical signs of disease.

Subchronic oral toxicity study on the three flavouring substances: octan-3-ol, 2-methylcrotonic acid and oct-3-yl 2-methylcrotonate in Wistar rats.

Groups of 10 male and 10 female rats were administered 0, 25, 100 or 400 mg octan-3-ol/kg body weight per day, 77 mg 2-methylcrotonic acid/kg body weight per day or 163 mg oct-3-yl 2-methylcrotonate/kg body weight per day by gavage for 90 days. Relative liver weights of high-dose octan-3-ol males, and males and females dosed with oct-3-yl 2-methylcrotonate were significantly greater than those of the control. In male and female rats dosed with the highest level of octan-3-ol and in male rats dosed with 2-methylcrotonic acid, incidences of bile duct proliferation were increased. In the kidneys of males dosed with mid- and high level of octan-3-ol and oct-3-yl 2-methylcrotonate, tubular karyomegaly and desquamation of tubular epithelial cells were observed. Based on increased liver weight and microscopic evaluation of the liver and kidney, a no-observed-effect level (NOEL) of 25 mg/kg for octan-3-ol in rats was established. The histopathological evaluation of the liver of rats dosed with oct-3-yl 2-methylcrotonate revealed lesions corresponding to the lesions seen in rats dosed mid-dose with octan-3-ol. This observation is in accordance with the general assumption that oct-3-yl 2-methylcrotonate is completely hydrolysed to octan-3-ol and 2-methylcrotonic acid. However, when comparing the liver histopathology of oct-3-yl 2-methylcrotonate and 2-methylcrotonic acid and the kidney lesions of all three substances, conflicting results were seen and the present study does not allow the conclusion to be drawn that oct-3-yl 2-methylcrotonate and structurally-related esters are completely hydrolysed, at least under the conditions of the present study.

Application of a 5' nuclease assay for detection of Lawsonia intracellularis in fecal samples from pigs.

A 5' nuclease assay was developed to detect Lawsonia intracellularis in porcine fecal samples. The specific probe and primers were chosen by using the 16S ribosomal DNA gene as a target. The 5' nuclease assay was used with a total of 204 clinical samples, and the results were compared to those of immunohistochemistry (IM) on ileal sections of the same animals. There was 91% agreement between the results of IM and the 5' nuclease assay. In the 5' nuclease assay, 111 (54%) of the pigs tested positive for L. intracellularis infection, with a mean cycle threshold (Ct) value of 27.2, whereas 98 (48%) of the pigs tested positive by IM. On average, the Ct and DeltaRn values for the positive samples were 27.2 (standard deviation [SD], 3.7) and 1.6 (SD, 0.7), respectively. A Ct value of 27.2 corresponds to a fecal excretion of approximately 10(7) L. intracellularis cells per g of feces. Furthermore, a total of 40 fecal samples derived from a herd known to be free from infection with L. intracellularis all tested negative, with a Ct value of 40. By using a Ct value of 36 as the cutoff limit, the detection limit of the assay was 1 L. intracellularis cell per PCR tube. In conclusion, the 5' nuclease assay that has been developed represents an applicable fast method for detection of L. intracellularis in fecal samples, with a sensitivity and specificity comparable to those of IM.

Changes in bacterial community structure in the colon of pigs fed different experimental diets and after infection with Brachyspira hyodysenteriae.

Bacterial communities in the large intestines of pigs were compared using terminal restriction fragment length polymorphism (T-RFLP) analysis targeting the 16S ribosomal DNA. The pigs were fed different experimental diets based on either modified standard feed or cooked rice supplemented with dietary fibers. After feeding of the animals with the experimental diets for 2 weeks, differences in the bacterial community structure in the spiral colon were detected in the form of different profiles of terminal restriction fragments (T-RFs). Some of the T-RFs were universally distributed, i.e., they were found in all samples, while others varied in distribution and were related to specific diets. The reproducibility of the T-RFLP profiles between individual animals within the diet groups was high. In the control group, the profiles remained unchanged throughout the experiment and were similar between two independent but identical experiments. When the animals were experimentally infected with Brachyspira hyodysenteriae, causing swine dysentery, many of the T-RFs fluctuated, suggesting a destabilization of the microbial community.

Pharmacokinetics and penetration of danofloxacin into the gastrointestinal tract in healthy and in Salmonella typhimurium infected pigs.

The pharmacokinetics and penetration of danofloxacin into the gastrointestinal tract in healthy pigs and in pigs experimentally infected with Salmonella typhimurium were studied. In the infected pigs, a decrease in body clearance and an increase in mean elimination half-life was observed (P < 0.01). Moreover a significant reduction in the volume of the peripheral compartment was found. Danofloxacin distributed well to the gastrointestinal tract achieving high AUC / AUC(plasma)ratios in both groups of pigs. However, compared to the healthy pigs AUC / AUC(plasma)ratios decreased in the infected pigs. Salmonella infection led to an increase in mean residence time (MRT) in the small intestines and lymph nodes and a decrease in MRT in caecum and colon.

The pharmacodynamic effect of amoxicillin and danofloxacin against Salmonella typhimurium in an in-vitro pharmacodynamic model.

The pharmacodynamic effect of amoxicillin and danofloxacin against two strains of Salmonella typhimurium was examined in an in-vitro pharmacodynamic model. For amoxicillin, peak concentrations of 1, 2 and 4 microg ml(-1)and half-lives (t12) of 3 and 15 hours were evaluated. For danofloxacin peak concentrations of 0.25, 0.50 and 1. 50 microg ml(-1)and half-lives of 7 and 15 hours were examined. For amoxicillin both the peak concentration and the half-life influenced the pharmacodynamic effect (P < 0.001). Maximal pharmacodynamic effect was observed when the antibiotic concentration was greater than minimum inhibitory concentration for 79 per cent or more of the dosing interval. The MICS of the isolates increased when the amoxicillin concentrations were close to the MIC during the first hours of exposure. For danofloxacin the pharmacodynamic effect was dependent on the peak concentration only (P < 0.001). Increases in MIC were found in two cases with the less susceptible strain, where peak concentration/ MIC ratios were equal to or less than 4.

The pharmacodynamic effect of amoxycillin and danofloxacin against Actinobacillus pleuropneumoniae in an in-vitro pharmacodynamic model.

The pharmacodynamic effect of amoxycillin and danofloxacin against two strains of Actinobacillus pleuropneumoniae was evaluated in an in-vitro pharmacodynamic model. For amoxycillin peak concentrations of 0.5, 1, and 4 microg ml(-1)and half-lives of 3 and 15 hours were examined. For danofloxacin peak concentrations of 0.125, 0.5, and 1. 5 microg ml(-1)and half-lives of 1.5 and 7 hours were evaluated. The initial bactericidal effect was measured as the reduction in colony count (log CFU ml(-1)) during the first three hours, and the overall pharmacodynamic effect as the area under the bacterial growth versus time curve (AUBC). The initial bactericidal effect of amoxycillin was maximal at peak concentrations of two to four times the MIC. Peak concentration and half-life only influenced the pharmacodynamic effect of amoxycillin if the antibiotic concentration fell below the MIC during the experiments, which is consistent with time >MIC as the most important parameter of pharmacodynamic effect of beta-lactam drugs. For danofloxacin maximal bactericidal effect initially was observed at peak concentrations of at least eight times the MIC. The pharmacodynamic effect was dependent on the peak concentration. The half-life only influenced the pharmacodynamic effect of danofloxacin in experiments with a peak concentration MIC ratio of less than eight. This indicated that for danofloxacin the peak concentration was the major determinant of pharmacodynamic effect.