In vitro complex formation and inhibition of hepatic cytochrome P450 activity by different macrolides and tiamulin in goats and cattle

In humans, clinically relevant drug-drug interactions occur with some macrolide antibiotics via the formation of stable metabolic intermediate (MI) complexes with enzymes of the cytochrome P4503A (CYP3A) subfamily. The formation of such complexes can result in a decreased biotransformation rate of simultaneously administered drugs. In previous studies it was shown that the veterinary antibiotic tiamulin was also able to form a stable MI complex in pigs and rats. In the present study the relative CYP3A inhibiting potency and MI complex formation of a series of macrolide antibiotics and tiamulin were studied in microsomal fractions of goat and cattle and in a cell-line expressing bovine CYP3A. Tiamulin and triacetyloleandomycin (TAO) were found to be effective inhibitors of CYP450 activity in all systems tested. Erythromycin and tilmicosin were found to be relatively less effective inhibitors of CYP450 activity in microsomes, and their activity in the bovine CYP3A4 expressing cell line was relatively weak. Tylosin was shown to be a weak inhibitor in microsomes and not in the cell line, whereas spiramycin had no effect at all. MI-complex formation measured by spectral analysis was seen with TAO, tiamulin, erythromycin and tylosin, but not with tilmicosin and spiramycin. Although additional factors play a role in vivo, these results may explain potential drug-drug interactions and differences between related compounds in this respect.     

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 6β- and 1 lα- positions was sirongly 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 28- position were inhibited to a lesser degree, whereas the ethoxyresorufin-O-deethylation, aniline hydroxylation and testosterone hydroxylations at the 15α- and 15β- 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.     

The use of macrolides, lincomycin and tiamulin as animal feed drugs for pigs in Schleswig-Holstein

An evaluation of production orders for medicated feedingstuffs for pigs given in 1998 in Schleswig-Holstein showed macrolides, lincomycin and tiamulin as frequently used antibiotical ingredients. The presented study analyses the production orders which include macrolides, lincomycin or tiamulin in more detail. There were large deviations to the rules of good clinical practise for the use of antibiotics (2000). The applied dosage was often lower than suggested in the literature.     

In vitro antimicrobial activity against 10 North American and European Lawsonia intracellularis isolates

The objective of this study was to determine the in vitro minimum inhibitory concentration (MIC) of antimicrobials against 10 isolates of Lawsonia intracellularis, the etiological agent of proliferative enteropathy (PE). Antimicrobials tested included carbadox, chlortetracycline, lincomycin, tiamulin, tylosin and valnemulin. The MIC of each antimicrobial against L. intracellularis was determined using a tissue culture system and was identified as the lowest concentration that inhibited 99% of L. intracellularis growth, as compared to the antimicrobial-free control. Each antimicrobial concentration was evaluated for both intracellular and extracellular activity against L. intracellularis, an obligately intracellular bacterium. When tested for intracellular activity, carbadox, tiamulin, and valnemulin were the most active antimicrobials with MICs of < or =0.5microg/ml. Tylosin (MICs ranging from 0.25 to 32microg/ml) and chlortetracycline (MICs ranging from 0.125 to 64microg/ml) showed intermediate activities and lincomycin (MICs ranging from 8 to >128mIcog/ml) showed the least activity. When tested for extracellular activity, valnemulin (MICs ranging from 0.125 to 4microg/ml) was the most active against most L. intracellularis isolates. Chlortetracycline (MICs ranging from 16 to 64microg/ml), tylosin (MICs ranging from 1 to >128microg/ml), and tiamulin (MICs ranging from 1 to 32microg/ml) showed intermediate activities. Lincomycin (MICs ranging from 32 to >128microg/ml) showed the least activity. Our in vitro results showed that each L. intracellularis isolate had a different antimicrobial sensitivity pattern and these data can be utilized as an in vitro guideline for the further antimicrobial evaluation of field L. intracellularis isolates.     

The effect of monensin, tiamulin and the simultaneous administration of both substances on the microsomal mixed function oxidases and on the peroxide formation in broilers

The influence of Monensin, Tiamulin and the simultaneous administration of the two substances on the microsomal, mixed function oxidases was studied on cockerels. Monensin was seen to cause a slight depression in the amount of cytochrome P-450 and cytochrome b5 as well as in the activities of aniline-p-hydroxylase, p-nitrophenol-hydroxylase and p-nitroanisole-O-demethylase. Tiamulin induced a moderate increase in the amount of cytochrome P-450 and in the activities of aniline-p-hydroxylase, p-nitrophenol-hydroxylase and aminopyrine-N-demethylase. The combined administration of monensin and tiamulin resulted in marked induction of the microsomal enzymes; the amount of cytochrome P-450 reduced by metyrapone or carbon monoxide increased 2.5 or 2-times, respectively, and the activities of the tested microsomal hydroxylases and demethylases showed also an expressed increase. At the same time the formation of lipid peroxides also markedly increased and the GSH concentration was reduced. In conclusion, the results of the investigations indicate that the simultaneous application of monensin and tiamulin cause a marked induction of the drug-metabolizing microsomal enzymes and a significant increase in the lipid peroxide formation.     

Tiamulin resistance in porcine Brachyspira pilosicoli isolates

There are few studies on antimicrobial susceptibility of Brachyspira pilosicoli, therefore this study was performed to investigate the situation among isolates from pigs. The tiamulin and tylosin susceptibility was determined by broth dilution for 93 and 86 porcine B. pilosicoli isolates, respectively. The isolates came from clinical samples taken in Swedish pig herds during the years 2002 and 2003. The tylosin minimal inhibitory concentration (MIC) was >16 microg/ml for 50% (n=43) of the isolates tested. A tiamulin MIC >2 microg/ml was obtained for 14% (n=13) of the isolates and these were also tested against doxycycline, salinomycin, valnemulin, lincomycin and aivlosin. For these isolates the susceptibility to salinomycin and doxycycline was high but the MICs for aivlosin varied. The relationship between the 13 tiamulin resistant isolates was analyzed by pulsed-field gel electrophoresis (PFGE). Among the 13 isolates 10 different PFGE patterns were identified.     

In vitro susceptibility of 21 antimicrobial agents to 37 isolates of Brachyspira hyodysenteriae isolated from pigs in Okinawa Prefecture

The in vitro susceptibilities to 21 antimicrobial agents, of 37 isolates of Brachyspira (B.) hyodysenteriae isolated from pigs in Okinawa meat center and a pig farm in Okinawa Prefecture, Japan, were determined by the agar dilution method. Carbadox was the most active of all the agents tested against the isolates (MIC: <0.003 to 0.05). All the isolates were highly susceptible to olaquindox, tiamulin, dimetridazole, efrotomycin and valnemulin with MICs ranging from 相似文献   

Oxidative monensin metabolism and cytochrome P450 3A content and functions in liver microsomes from horses, pigs, broiler chicks, cattle and rats

The oxidative metabolism of monensin, an ionophore antibiotic extensively used in veterinary practice as a coccidiostat and a growth promoter, was studied in hepatic microsomal preparations from horses, pigs, broiler chicks, cattle and rats. As assayed by the measurement of the amount of the released formaldehyde, the rate of monensin O-demethylation was nearly of the same order of magnitude in all species, but total monensin metabolism, which was estimated by measuring the rate of substrate disappearance by a high-performance liquid chromatography (HPLC) method, was highest in cattle, intermediate in rats, chicks and pigs, and lowest in horses. When expressed as turnover number (nmol of metabolized monensin/min nmol cytochrome P450-1), the catalytic efficiency (chick > cattle > pig approximately rat > horse) was found to correlate inversely with the well known interspecies differences in the susceptibility to the toxic effects of the ionophore, which is characterized by an oral LD50 of 2-3 mg/kg bodyweight (bw) in horses, 50-80 mg/kg bw in cattle and 200 mg/kg bw in chicks. Chick and cattle microsomes also displayed both the highest catalytic efficiency toward two P450 3A dependent substrates (erythromycin and triacetyloleandomycin) and the highest immunodetectable levels of proteins cross-reacting with anti rat P450 3A1/2. Further studies are required to define the role played by this isoenzyme in the oxidative biotransformation of the drug in food producing species.     

Mitotic index is predictive for survival for canine cutaneous mast cell tumors

Mitotic index (MI) is an indirect measure of cell proliferation that has been demonstrated to be a strong predictor of outcome for several human and canine cancers. The purpose of this study was to evaluate the utility of MI as a predictor of biologic behavior and survival in dogs with cutaneous mast cell tumors (MCTs). Medical records from 148 dogs with histologically confirmed MCTs were reviewed. Information regarding tumor grade, local recurrence, metastatic disease, date of death/last follow-up, and outcome was obtained. The region of the tumor with the highest overall mitotic activity was chosen for evaluation, and the MI value was defined as the number of mitotic figures/10 high-power fields (400x, 2.7 mm(2)). A Cox proportional hazards regression model was used to compare MI with survival data. A Mann-Whitney test was used to compare MI on the basis of the development of local recurrence and metastatic disease. The MI correlated directly with tumor grade (P < .0001). The median survival time for dogs with an MI < or =5 was significantly longer (70 months) than for those with an MI >5 (2 months), regardless of grade (P < .001). For grade II tumors with an MI < or =5, the median survival time (MST) was 70 months, compared with 5 months for those with an MI >5 (P < .001). For grade III tumors with an MI < or =5, the MST was not reached, compared with <2 months for those with an MI >5 (P < .001). In conclusion, MI is a strong predictor of overall survival for dogs with cutaneous MCTs and should be included as a prognostic indicator when determining therapeutic options.     

In vitro development of resistance to enrofloxacin,erythromycin, tylosin,tiamulin and oxytetracycline in Mycoplasma gallisepticum,Mycoplasma iowae and Mycoplasma synoviae

The in vitro emergence of resistance to enrofloxacin, erythromycin, tylosin, tiamulin, and oxytetracycline in three avian Mycoplasma species, Mycoplasma gallisepticum, Mycoplasma synoviae and Mycoplasma iowae was studied. Mutants were selected stepwise and their MICs were determined after 10 passages in subinhibitory concentrations of antibiotic. High-level resistance to erythromycin and tylosin developed within 2-6 passages in the three Mycoplasma species. Resistance to enrofloxacin developed more gradually. No resistance to tiamulin or oxytetracycline could be evidenced in M. gallisepticum or M. synoviae after 10 passages whereas, resistant mutants were obtained with M. iowae. Cross-sensitivity tests performed on mutants demonstrated that mycoplasmas made resistant to tylosin were also resistant to erythromycin, whereas mutants made resistant to erythromycin were not always resistant to tylosin. Some M. iowae tiamulin-resistant mutants were also resistant to both macrolide antibiotics. Enrofloxacin and oxytetracycline did not induce any cross-resistance to the other antibiotics tested. These results show that Mycoplasma resistance to macrolides can be quickly selected in vitro, and thus, providing that similar results could be obtained under field conditions, that development of resistance to these antibiotics in vivo might also be a relatively frequent event.     

Studies on the toxic interaction between monensin and tiamulin in rats: effects on P450 activities

Studies were carried out to investigate the effects of monensin and tiamulin, and the simultaneous administration of both compounds on microsomal enzymes in rats. In Phase I of the experiments the effects of monensin and tiamulin were studied separately (monensin 10, 30, and 50 mg/kg or tiamulin 40, 120, and 200 mg/kg body weight, respectively), while in Phase II the two compounds were administered simultaneously (monesin 10 mg/kg and tiamulin 40 mg/kg b.w., respectively). When monensin was administered by itself, it exerted no significant effect on microsomal liver enzymes. In a few cases, slight inhibition of certain enzyme activities was seen. Tiamulin provoked a dose-dependent hepatic enzyme induction. The combined administration of monensin and tiamulin at low doses (10 and 40 mg/kg, respectively) resulted in marked elevation of P450-related enzyme activities. The enzyme induction was more pronounced in females than in males. The results suggest that the simultaneous administration of tiamulin may influence the biotransformation of monensin, possibly increasing the amount of reactive metabolite(s) of the ionophore antibiotic.     

猪肉和牛奶源葡萄球菌耐药性调查

2010年从贵州省猪肉和牛奶样品中分离鉴定出73株葡萄球菌,其中金黄色葡萄球菌50株,凝固酶阴性葡萄球菌23株。采用琼脂稀释法检测其对18种抗菌药物的敏感性,运用统计学方法比较分析金黄色葡萄球菌与凝固酶阴性葡萄球菌的耐药性差异。结果显示,动物性食品源葡萄球菌耐药较严重,对临床上常用药物耐药率较高,且为多重耐药,其中乳源葡萄球菌的多重耐药现象较猪肉源葡萄球菌严重;猪肉源金黄色葡萄球菌主要对青霉素类、四环素和大环内酯类耐药,乳源金黄色葡萄球菌主要对青霉素类、头孢菌素类、大环内酯类、四环素、克林霉素、泰妙菌素及利福平耐药;猪肉源凝固酶阴性葡萄球菌主要对氨苄西林、苯唑西林和泰妙菌素耐药,乳源凝固酶阴性葡萄球菌的耐药谱与乳源金黄色葡萄球菌类似。     

The effect of antibiotics against bovine mycoplasmas and ureaplasmas.

A combination of lincomycin-spectinomycin-tylosin was tested against several strains of mycoplasmas and acholeplasmas as might be encountered in bovine semen and shown to be effective against them. This combination as well as minocin , rosaramicin, rosoxacin, tiamulin, gentamicin and declomycin were tested in vitro against 58 isolates of ureaplasma from the bovine urogenital tract. The lincomycin-spectinomycin-tylosin combination, minocin , rosaramicin, tiamulin and declomycin were quite active, while rosoxacin and gentamicin were much less active against the test strains.     

Comparison of methods for antimicrobial susceptibility testing and MIC values for pleuromutilin drugs for Brachyspira hyodysenteriae isolated in Germany

In Germany treatment of swine dysentery is hampered by Brachyspira hyodysenteriae strains showing elevated MIC values to the few antibiotics licensed. Therefore, susceptibility testing of clinical isolates is an important service to the swine practitioner. This study compares the established agar dilution procedure for antimicrobial susceptibility testing of this fastidious anaerobe to the broth microdilution test newly developed [Anim. Health Res. 2 (2001) 59; Vet. Microbiol. 84 (2002) 123; J. Clin. Microbiol. 41 (2003) 2596]. A total of 221 isolates were examined twice with either test procedure using tiamulin and valnemulin as antibiotics. Both methods gave reproducible results, and the MIC values for the reference strains B. hyodysenteriae B204 and Staphylococcus aureus ATCC 29213 corresponded to previously published data. However, the results for individual strains differed significantly for both tests (P < 0.001) with MIC values being on average one dilution step lower in the broth dilution method. The 221 strains used for comparing test procedures were isolated between 1989 and 2001. An additional 102 strains isolated in 2002 were tested only with the broth dilution procedure. A significant rise in the average MIC value for both pleuromutilins could be demonstrated when comparing earlier isolates to those from 2000 to 2001 (P < 0.05), while in 2002 the average MIC significantly decreased when compared to the value in 2000 (P < 0.05). However, strains with MIC values for tiamulin as high as 8 microg/ml (broth dilution) could still be isolated.     

‘Pink eye’ or ‘zere oogjes’ or Keratoconjunctivitis Infectiosa Ovis (KIO)

In a comparative study the clinical efficacy of five different treatments of keratoconjunctivitis infectiosa ovis (KIO) were tested, namely an intramuscular injection of chloramphenicol base (dosage 15 mg/kg), spiramycin base (Suanovil^® dosages 10 to 25 mg/kg), oxytetracycline (Engemycine^® Forte, Terramycin^® LA, dosages respectively 5 and 10 mg/kg), tiamulin (Dynamutulin^®, dosage 10 mg/kg) and subcutaneous injection of procaine penicillin G, benzathine penicillin G, and dihydrostreptomycin in the lower eyelid.

It appeared from these field trials that spiramycin base, oxytetracycline and tiamulin had a clearly positive effect on the clinical course of ‘pink eye’, although with tiamulin there was only a temporary effect (high percentage of relapses).

In view of the field data the following dosage schemes are, for the time being, advised: spiramycin. base (Suanovil^®), and oxytetracycline (formulation with a good biological availability) both 20 to 30 mg/kg and, if necessary, to be repeated on days 5 and 10 after the first intramuscular injection. The dosage scheme advised for tiamulin is 20–30 mg/kg to be repeated on day 3 and if necessary on days 6 and 9 after the intramuscular injection. In mild cases it is sufficient to rub the eyes with for example oxytetracycline eye‐ointment, a few times a day.     

Failure of 3-methylindole to contract the bovine pulmonary vein or to release mediators of anaphylaxis from the bovine lung in vitro

Strips of smooth muscle from the pulmonary vein, pulmonary artery, trachea and bronchus of calves were incubated in an organ bath with 3-methylindole (3MI) and 3-methyloxindole (3MOI). 3MI and 3MOI (5–640 g/ml) did not cause contraction of any of the isolated smooth muscle preparations. No evidence for the release of mediators of anaphylaxis was obtained when chopped bovine lung preparations were incubated with 3MI (20 g/ml) and 3MOI (25 g/ml). Results of the present work diminish the possibility that the pneumotoxic effect of 3MI is due to a primary hydrodynamic imbalance across the alveolocapillary membrane resulting in excess filtration over reabsorption.     

Effect of acute salinomycin-tiamulin toxicity on the lipid peroxide and antioxidant status of broiler chicken.

The combined effect, if any, of salinomycin poisoning and salinomycin-tiamulin interaction on lipid-peroxidative processes and the antioxidative defence system of the liver was studied in domestic fowl. Male broilers (28-day-old), reared on a diet containing 60 mg/kg salinomycin, were treated intraoesophageally with salinomycin (140 mg/kg body mass) or tiamulin (50 mg/kg body mass). Malondialdehyde, reduced glutathione and cytochrome P-450 concentrations as well as glutathione peroxidase and catalase activities of the liver were determined. Liver malondialdehyde concentration rose in the salinomycin-treated group while the amount of cytochrome P-450 increased in both groups treated. Glutathione concentration and glutathione peroxidase activity of the liver decreased rapidly but hepatic catalase activity increased in both groups after the treatment. Manifestation of the effect exerted by salinomycin and salinomycin-tiamulin on lipid-peroxidative processes nearly coincided with the onset of clinical signs and preceded the increase of hepatic cytochrome P-450 concentration. According to the results, the background of the previously reported incompatibility between salinomycin and tiamulin is the synergistic effect exerted on the antioxidant (glutathione) system.     

Efficacy of tiamulin as a growth promotant for growing swine

A study involving 244 pigs initially averaging 13 kg was conducted at two stations to evaluate tiamulin as a growth promotant for growing swine. In each experiment, four replicate pens of five (Exp. 1) or six (Exp. 2) pigs/pen were used to evaluate each treatment. In Exp. 1, pigs were fed 0, 11, 22 or 44 ppm tiamulin from 15 to 58 kg, then fed a nonmedicated control diet for the remainder of the experiment (to 95 kg). In Exp. 2, pigs were fed 0, 2.75, 5.5, 11 or 22 ppm tiamulin from 11 to 56 kg, followed by the nonmedicated control diet (to 95 kg). In each experiment, carbadox (55 ppm) was included as a positive control and was fed to an average weight of 35 kg, followed by the control diet. Averaged across all dietary levels, tiamulin resulted in a 14.1% improvement in gain and a 5.7% improvement in feed:gain ratio during the first 28 to 35 d of the experiment (to 30 kg). These improvements were slightly less than those resulting from the feeding of carbadox during the same period (21.5 and 6.9%, respectively). From 13 to 57 kg, pigs fed tiamulin gained 11.6% faster and 3.1% more efficiently than did controls. Over the entire experiment (13 to 95 kg), tiamulin-fed pigs gained 5.7% faster than did controls, even though the tiamulin was withdrawn at 57 kg body weight. Growth rate from 13 to 57 kg plateaued at the 11-ppm dietary level of tiamulin; whereas, feed:gain ratio plateaued at the 22-ppm level. The results indicate that tiamulin is an effective growth promotant for growing swine.     

Immunolocalization of steroidogenic cells in small follicles of the chicken ovary: Anatomical arrangement and location of steroidogenic cells change during follicular development

Previous anatomical and histochemical studies suggested that interstitial cells were the only steroidogenic cells in the theca layer of small follicles of the chicken ovary. However, the precise cellular site of steroid production in the small follicles is not certain. Therefore, our goal was to identify steroidogenic cells in small follicles (< 10 mm in diameter) of the chicken ovary which have not entered the follicular hierarchy by localizing steroidogenic enzymes with immunocytochemistry. Polyclonal antisera used were anti-cholesterol side-chain-cleavage cytochrome P450 (P450scc), anti-17-hydroxylase cytochrome P450 (P450c17), and anti-aromatase cytochrome P450 (P450arom) for pregnenolone-, androgen-, and estrogen-producing cells, respectively. Ovaries were collected 2 hr after oviposition and embedded in Paraplast after fixation with 4% paraformaldehyde, 10% formaldehyde, or Bouin's solution. Tissues were sectioned (4–6 μm) and sections were mounted on poly-L-lysine coated slides. Sections were incubated overnight at room temperature with each specific antiserum raised in rabbits against cytochrome P450 steroidogenic enzymes or normal rabbit serum as a control and were immunostained with an avidin-biotin-peroxidase complex. Immunoreactivity for the P450 enzymes was absent in the granulosa layer but was present in the theca layer of the small follicles (< 10 mm in diameter). Interstitial cells in the single theca layer of cortical follicles embedded in the ovarian cortex (less than 1 mm in diameter) contained P450scc and P450c17. Cells which contained P450arom, identified as aromatase cells, surrounded the interstitial cells in the theca layer. In small white follicles (approximately 1 mm in diameter), large white follicles (approximately 2–4 mm in diameter), and small yellow follicles (approximately 5–10 mm in diameter) which protruded from the surface of the ovary, the theca layer is divided into the theca interna and the theca externa. P450scc and P450c17 were localized in interstitial cells in the theca interna and externa whereas P450arom was localized in aromatase cells of the theca externa. With follicular development, more interstitial cells staining for P450scc and P450c17 appeared in the theca interna than in the theca externa whereas aromatase cells staining for P450arom were localized only in the theca externa. The distance between interstitial cells and aromatase cells within the theca layer increased as the follicles matured, resulting in a change in the anatomical relationship of steroidogenic cells. Our results of immunolocalization of cytochrome P450 steroidogenic enzymes in developing small follicles suggest that: 1) granulosa cells in small follicles are steroidogenically inactive; 2) steroids are produced in two distinct cell populations in the theca layer of small follicles, namely interstitial cells and aromatase cells; and 3) the anatomical relationship and location of interstitial cells and aromatase cells in the theca layer change with follicular maturation (a two-cell model for steroidogenesis in small follicles during follicular development).