Effects of dietary sodium butyrate on hepatic biotransformation and pharmacokinetics of erythromycin in chickens.

Butyrate, a commonly applied feed additive in poultry nutrition, can modify the expression of certain genes, including those encoding cytochrome P450 (CYP) enzymes. In comparative in vitro and in vivo experiments, the effect of butyrate on hepatic CYP genes was examined in primary cultures of chicken hepatocytes and in liver samples of chickens collected from animals that had been given butyrate as a feed additive. Moreover, the effect of butyrate on the biotransformation of erythromycin, a marker substance for the activity of enzymes of the CYP3A family, was investigated in vitro and in vivo. Butyrate increased the expression of the avian-specific CYP2H1 both in vitro and in vivo. In contrast, the avian CYP3A37 expression was decreased in hepatocytes following butyrate exposure, but not in the in vivo model. CYP1A was suppressed by butyrate in the in vitro experiments, and overexpressed in vivo in butyrate-fed animals. The concomitant incubation of hepatocytes with butyrate and erythromycin led to an increased CYP2H1 expression and a less pronounced inhibition of CYP3A37. In in vivo pharmacokinetic experiments, butyrate-fed animals given a single i.m. injection of erythromycin, a slower absorption phase (longer T(half-abs) and delayed T(max)) but a rapid elimination phase of this marker substrate was observed. Although these measurable differences were detected in the pharmacokinetics of erythromycin, it is unlikely that a concomitant application of sodium butyrate with erythromycin or other CYP substrates will cause clinically significant feed-drug interaction in chickens.

Detection of Pseudomonas aeruginosa in water samples using a novel synthetic medium and impedimetric technology.

AIMS: To investigate whether the use of a novel synthetic medium in conjunction with impedimetric technology could provide a rapid and automated detection of Pseudomonas aeruginosa in water samples. METHODS AND RESULTS: A selective synthetic medium (Z-broth) in which the only carbon and nitrogen source is acetamide was applied in direct impedimetric examination for the selective isolation of P. aeruginosa. A total of 1036 tap-water, well-water, swimming-pool water and dialysis water samples were investigated, and any P. aeruginosa contamination was detected in 7-24 h. Neither false-negative nor false-positive results were observed. CONCLUSIONS: The results of the present evaluation demonstrate that impedance measurement with the use of Z-broth is suitable for the rapid and automatic detection of P. aeruginosa in water. SIGNIFICANCE AND IMPACT OF THE STUDY: The main advantages of the method: 240 samples can be examined in one step, the procedure is fully automated, the results are obtained quickly and the labour and media requirements are low.

Tiamulin selectively inhibits oxidative hepatic steroid and drug metabolism in vitro in the pig.

The simultaneous use of the antibiotic tiamulin with certain ionophoric antibiotics (monensin, salinomycin) may give rise to a toxic interaction in pigs and poultry. In the present study, effects of tiamulin on hepatic cytochrome P450 activities in vitro were studied using pig liver microsomes. When tiamulin was added to the incubation medium the N-demethylation rate of ethylmorphine and the hydroxylation of testosterone at the 6 beta- and 11 alpha-positions was strongly inhibited. Tiamulin inhibited these activities more than SKF525A or cimetidine, but less than ketoconazole. The microsomal N-demethylation rate of erythromycin and the hydroxylation of testosterone at the 2 beta-position were inhibited to a lesser degree, whereas the ethoxyresorufin-O-deethylation, aniline hydroxylation and testosterone hydroxylations at the 15 alpha- and 15 beta-positions were not affected by tiamulin. No in vitro complexation by tiamulin of cytochrome P450 resulting in a loss of CO-binding capacity could be demonstrated. Results from the present study suggest a selective inhibition of cytochrome P450 enzymes in pigs, probably belonging to the P4503A subfamily. The mechanism of this interaction is still unclear. However, interactions between tiamulin and those veterinary drugs or endogenous compounds which undergo oxidative metabolism by P450 enzymes must be considered. More research is needed to reveal which of the P450 enzymes are affected by tiamulin in order to improve the understanding and probably the predictability of this interaction.