Antimicrobial resistance and class 1 and 2 integrons in Escherichia coli from meat turkeys in Northern Italy.

This study is aimed at determining the antimicrobial resistance (AMR) and the presence of class 1 and 2 integrons in 48 avian pathogenic Escherichia coli (APEC) strains isolated from meat turkeys during three sequential production cycles. Thirty avian faecal E. coli (AFEC) strains from the first cycle were also analysed. Strains were tested for AMR against 25 antimicrobials by disk diffusion test and were screened for the presence of integrons and associated gene cassettes by polymerase chain reaction followed by sequencing. Genetic relatedness of isolates was established by pulsed-field gel electrophoresis. High levels of resistance were detected to tetracyclines, penicillins and sulphonamides in APEC and AFEC. Resistance to aminoglycosides, fluoroquinolones, cephalosporins and phenicols was variable, based on the antimicrobial drug and the isolate (APEC vs. AFEC). Full susceptibility to colistin was detected. Multidrug resistance of up to seven antimicrobial classes was exhibited by APEC (93.8%) and AFEC (100%). Nearly 44% of strains tested positive for class 1 and/or class 2 integrons containing the dfrA, aadA and sat2 genes, alone or in combination, coding for streptomycin/spectinomycin, trimethoprim and streptothricin resistance, respectively. The estX and orfF genes of unknown function were also detected. A significant association was found between the presence of integrons and the resistance to aminoglycosides and potentiated sulphonamides. The results of this study showed that AMR, multidrug resistance and class 1 and 2 integrons are widespread among pathogenic and commensal E. coli from Italian turkeys. More attention should be addressed to limit the use of antimicrobials in turkeys and the AMR of turkey E. coli.

Fluoroquinolone resistance and molecular characterization of gyrA and parC quinolone resistance-determining regions in Escherichia coli isolated from poultry.

Escherichia coli are a common inhabitant of the gastrointestinal tract of mammals and birds; nevertheless, they may be associated with a variety of severe and invasive infections. Whereas fluoroquinolones (FQ) have been banned in the United States for use in poultry production, the use of these antimicrobials in poultry husbandry is still possible in the European Union, although with some restrictions. The aim of this study was to investigate the FQ resistance of 235 E. coli isolates recovered from chickens and turkeys. Minimum inhibitory concentrations were determined by a microdilution method, whereas mutations in the quinolone resistance-determining regions of the target genes, gyrA and parC, were detected by a PCR-based method. High resistance rates (>60%) were observed for nalidixic acid, flumequine, and difloxacin, whereas resistance to ciprofloxacin, danofloxacin, enrofloxacin, marbofloxacin, and sarafloxacin was less frequently reported (<40%). Sixty-four isolates (27.2%) showed full susceptibility toward the tested FQ, but 57 isolates (24.2%) were resistant to all tested FQ. The remaining 114 E. coli isolates (48.5%) were grouped in 5 different resistance patterns. Isolates resistant only to flumequine or nalidixic acid or both possessed 1 gyrA mutation, whereas isolates with further resistance to enrofloxacin, difloxacin, danofloxacin, and sarafloxacin had in addition 1 or 2 parC substitutions. Two gyrA mutations coupled with 1 substitution in parC were detected in isolates resistant to all tested FQ. The number of mutations and their correlation with the in vitro activity of FQ reflected the currently accepted model, according to which a single gyrA substitution is associated with resistance or decreased susceptibility to older quinolones, whereas further gyrA or parC substitutions are needed for a higher level of resistance.

Enrofloxacin against Escherichia coli in turkeys: which treatment scheme is effective?

The efficacy of enrofloxacin (ENRO) was evaluated against multidrug-resistant avian pathogenic Escherichia coli correlating the minimum inhibitory concentrations (MIC) of 235 E. coli field strains with its pharmacokinetics (PK) in 50 healthy turkeys (5 groups) with a PK/pharmacodynamic approach. The treatments were as follows: a) single oral gavage and b) single subcutaneous (SC) treatment at the recommended dose of 10 mg/kg; c) single oral gavage, d) 5 d of 10-h pulsed water medication, and e) 5 d of 24-h continuous water medication at the doubled dose of 20 mg/kg. Blood samples were collected at established times over 24 h. Plasma was analyzed using a liquid chromatography tandem mass spectrometry method that was validated in house. A monocompartmental and a noncompartmental model were applied to the data to obtain the PK results. After gavage administration, the mean maximum concentration Cmax/MIC50 and area under the curve AUC0-24/MIC50 ratios were, respectively, 3.07 ± 0.62 and 7.01 ± 1.03 and 25.48 ± 3.04 and 57.2 ± 3.73 for the 10 and 20 mg/kg doses, respectively. After SC administration of 10 mg/kg, Cmax/MIC50 and AUC0-24/MIC50 ratios were 3.45 ± 0.75 and 33.96 ± 7.46, respectively. After the administration of 10-h pulsed or 24-h continuous medicated water at 20 mg/kg, lower values of Cmax/MIC50 (10-h pulsed: 3.45 ± 0.7; 24-h continuous: 3.05 ± 0.48) and AUC0-24/MIC50 (10-h pulsed: 42.42 ± 6.17; 24-h continuous: 53.32 ± 5.55) were obtained. Based on these results, the European Union-recommended dosage of 10 mg/kg seems ineffective to achieve adequate drug plasma concentrations and even the 20 mg/kg by 10 h pulsed or continuous medicated water administration did not reach completely efficacious concentrations in plasma against colibacillosis. Although the results obtained were not completely encouraging, the medicated water should preferably be provided continuously. To conclude about the efficacy of ENRO treatment against colibacillosis, target tissue concentration should be extensively considered.

Pharmacokinetic/pharmacodynamic evaluation of the efficacy of flumequine in treating colibacillosis in turkeys.

Flumequine (FLU) is used in the treatment of systemic bacterial infections in poultry, including colibacillosis, which is a common disease in turkeys. The pharmacokinetic (PK) behavior of FLU administered to 32 healthy turkeys as an oral bolus via gavage or as 10-h pulsed administration in drinking water were compared, using the authorized dose of 15 mg/kg and the double dose of 30 mg/kg. The minimum inhibitory concentrations (MIC) of 235 Escherichia coli field strains isolated from poultry were determined for pharmacodynamics (PD) to develop a PK/PD model. Blood samples were collected at established times over 24 h, and the obtained plasma was analyzed using a liquid chromatography tandem mass spectrometry method that was validated in-house. A monocompartmental model and a noncompartmental model were applied to the data to obtain the PK results. For both types of administration and both dosages, the ratios of the maximum concentration (Cmax)/MIC50 and the area under the plasma concentration-time curve (AUC)/MIC50 achieved were considerably lower than the fluoroquinolone breakpoints usually adopted for efficacy. The Cmax/MIC50 and AUC0-24/MIC50 ratios were, respectively, 0.67 ± 0.09 and 4.76 ± 0.48 and 1.18 ± 0.35 and 7.05 ± 2.40 for the 15 and 30 mg/kg bolus doses, respectively. After 10-h pulsed administration of 15 mg/kg, values of Cmax/MIC50, 0.19 ± 0.02 on d 1 and 0.30 ± 0.08 on d 5 of therapy were obtained, the AUC/MIC50 ratios were 2.09 ± 0.29 and 3.22 ± 0.93 on d 1 and 5, respectively. Higher values were obtained with the doubled dose of 30 mg/kg: the Cmax/MIC50 ratios were 0.49 ± 0.11 on d 1 and 0.69 ± 0.18 on d 5; the AUC/MIC50 ratios were 5.15 ± 1.15 and 6.57 ± 1.92 on d 1 and 5, respectively. Based on these results, FLU administration should be adopted when specific diagnostic findings indicate its efficacy, and revising the dosage scheme to comply with the prudent and responsible use of antimicrobials in veterinary medicine is advisable.

Endocrine evaluation after an intra-articular therapeutic dosage of dexamethasone in horses.

This study investigated whether a single intra-articular administration (IA) of dexamethasone (DEX) in horses at therapeutic dosage could exert a systemic effect by influencing the hypothalamic-pituitary-adrenal axis activity as a consequence of (limited) absorption and systemic distribution. The results indicated that DEX was detectable in urine collected 12-48 h after IA administration and that injection was accompanied by a reduced urine excretion of cortisol, 6ß-hydroxycortisol (6ßOHF) and two other metabolites of cortisol lasting up to 48 h post-DEX administration. The systemic effects in horses treated with DEX by IA route are similar to those that typically occur with short-term treatment including the reduction in urinary cortisol concentration.

Pharmacokinetics of ketamine and propofol combination administered as ketofol via continuous infusion in cats.

The pharmacokinetics of the extemporaneous combination of low doses of ketamine and propofol, known as 'ketofol', frequently used for emergency procedures in humans to achieve safe sedation and analgesia was studied in cats. The study was performed to assess propofol, ketamine and norketamine kinetics in six female cats that received ketamine and propofol (1:1 ratio) as a loading dose (2 mg/kg each, IV) followed by a continuous infusion (10 mg/kg/h each, IV, 25 min of length). Blood samples were collected during the infusion period and up to 24 h afterwards. Drug quantification was achieved by HPLC analysis using UV-visible detection for ketamine and fluorimetric detection for propofol. The pharmacokinetic parameters were deduced by a two-compartment bolus plus infusion model for propofol and ketamine and a monocompartmental model for norketamine. Additional data were derived by a noncompartmental analysis. Propofol and ketamine were quantifiable in most animals until 24 and 8 h after the end of infusion, respectively. Propofol showed a long elimination half-life (t(1/2λ2) 7.55 ± 9.86 h), whereas ketamine was characterized by shorter half-life (t(1/2λ2) 4 ± 3.4 h) owing to its rapid biotransformation into norketamine. The clinical significance of propofol's long elimination half-life and low clearance is negligible when the drug is administered as short-term and low-dosage infusion. The concurrent administration of ketamine and propofol in cats did not produce adverse effects although it was not possible to exclude interference in the metabolism.

Testosterone hydroxylation in bovine liver: enzyme kinetic and inhibition study.

In order to sort out the involvement of cytochrome P450 (CYP) 3A and possibly CYP2B in testosterone hydroxylation in cattle, enzyme kinetic and inhibition studies were performed. Most relevant kinetic constants (Km and Vmax) for 6beta-, 16beta- and 2beta-testosterone hydroxylase (OHT) activities were determined and accounted for 93.4 +/- 13.8, 36.4 +/- 6.1 and 110.8 +/- 15.2 muM, respectively, for Km and 0.558 +/- 0.03, 0.280 +/- 0.013, and 0.338 +/- 0.017 nmol min-1 mg-1 protein, respectively, for Vmax. Eadie-Hofstee plot analysis pointed out how these enzymatic activities in cattle follow a monophasic kinetic pattern. Preliminary inhibition studies conducted with the CYP3A inhibitor ketoconazole and the CYP2B inhibitors orphenadrine and 9-ethynylphenanthrene seemed to suggest the major involvement of CYP3A in testosterone hydroxylation in cattle. Immuno-inhibition studies with an anti-peptide antibody against bovine CYP3A4 confirmed the predominant role of CYP3A in testosterone hydroxylation in bovine liver, proving the usefulness of anti-peptide antibodies in defining the contribution of specific P450 isoforms in drug metabolism in veterinary species.

Benzydamine as a useful substrate of hepatic flavin-containing monooxygenase activity in veterinary species.

Benzydamine (BZ), a weak base and an indazole derivative with analgesic and antipyretic properties used in human and veterinary medicine, is metabolized in human, rat, cattle and rabbit to a wide range of metabolites. One of the main metabolites, BZ N-oxide (BZ-NO), is produced in the liver and brain by flavin-containing monooxygenases (FMOs), by liver and brain enzymes. To evaluate the suitability of BZ as an FMO probe in veterinary species, BZ metabolism was studied in vitro using liver microsomes from bovine, rabbit and swine. Kinetic parameters, K(m) and V(max), of BZ-NO production, were evaluated to corroborate the pivotal role of FMOs. Inhibition studies were carried out by heat inactivation and by specific FMO chemical inhibitors: trimethylamine and methimazole. The results confirmed the presence of FMO activity in the liver and the role of BZ as a suitable marker of FMO enzyme activities for the veterinary species considered.

Expression profiling of skeletal muscle in young bulls treated with steroidal growth promoters.

Dexamethasone (Dex), alone or in association with estrogens, is often illegally administered per os at very low dosage as a growth promoter in beef cattle, with effects that are opposite to the muscle wasting and atrophy induced by repeated administration at therapeutic dosages. In vitro and in vivo studies have investigated the catabolic effects of Dex at therapeutic doses on skeletal muscle, demonstrating an increase in the expression of GDF8 (myostatin) gene, a well-known negative regulator of skeletal muscle mass, in a dose-dependent way. This suggested a direct role of myostatin in Dex-induced muscle wasting. In the present study, an oligonucleotide microarray platform was used to compare expression profiles of beef cattle muscle in animals treated with either Dex or Dex plus 17-beta estradiol (Estr) administered at subtherapeutic dosage, against untreated controls. Data analysis demonstrates that the expression profiles were strongly affected by Dex treatment with hundreds of genes upregulated with relevant fold-change, whereas seven genes were downregulated including the myostatin gene. On the contrary, the number of differentially regulated genes was lower in response to the addition of Estr to the Dex treatment. Differentially regulated genes were analyzed to describe the effects of these treatments on muscle physiology, highlighting the importance of specific pathways (e.g., Wnt or cytokine signaling) and cellular processes (e.g., cell shape and motility). Finally, the observed differences in the expression profile will allow the development of indirect bio-markers to detect illegal Dex treatments in beef cattle using quantitative RT-PCR.

Microbiological, chemical and physical quality of drinking water for commercial turkeys: a cross-sectional study.

Drinking water for poultry is not subject to particular microbiological, chemical and physical requirements, thereby representing a potential transmission route for pathogenic microorganisms and contaminants and/or becoming unsuitable for water-administered medications. This study assessed the microbiological, chemical and physical drinking water quality of 28 turkey farms in North-Eastern Italy: 14 supplied with tap water (TW) and 14 with well water (WW). Water salinity, hardness, pH, ammonia, sulphate, phosphate, nitrate, chromium, copper and iron levels were also assessed. Moreover, total bacterial count at 22°C, presence and enumeration of Enterococcus spp. and E. coli, presence of Salmonella spp. and Campylobacter spp. were quantified. A water sample was collected in winter and in summer at 3 sampling sites: the water source (A), the beginning (B) and the end (C) of the nipple line (168 samples in total). Chemical and physical quality of both TW and WW sources was mostly within the limits of TW for humans. However, high levels of hardness and iron were evidenced in both sources. In WW vs. TW, sulphate and salinity levels were significantly higher, whilst pH and nitrate levels were significantly lower. At site A, microbiological quality of WW and TW was mostly within the limit of TW for humans. However, both sources had a significantly lower microbiological quality at sites B and C. Salmonella enterica subsp. enterica serotype Kentucky was isolated only twice from WW. Campylobacter spp. were rarely isolated (3.6% of farms); however, Campylobacter spp. farm-level prevalence by real-time PCR was up to 43% for both water sources. Winter posed at higher risk than summer for Campylobacter spp. presence in water, whereas no significant associations were found with water source, site, recirculation system, and turkey age. Low salinity and high hardness were significant risk factors for C. coli and C. jejuni presence, respectively. These results show the need of improving sanitization of drinking water pipelines for commercial turkeys.

Boldenone, boldione, and milk replacers in the diet of veal calves: the effects of phytosterol content on the urinary excretion of boldenone metabolites.

Twenty-six veal calves were split into two groups and fed two milk replacers with a different content of phytosterols for 26 days; then, 14 calves (7 animals from each diet) were kept as controls and 12 calves (6 per diet) received daily, per os, a combination of 17beta-boldenone (17beta-Bol) and androsta-1,4-dien-3,17-dione (ADD) for 38 days. The urinary elimination of 17 alpha-/17beta-boldenone conjugates (17 alpha/beta-Bol) and androsta-1,4-dien-3,17-dione (ADD) was followed by liquid chromatography-tandem mass spectrometry from all of the animals until slaughtering. In urine from treated animals, 17 alpha-Bol concentrations, despite a great variability, were greater than 17beta-Bol, both detected always as conjugates. At days 1, 2, and 3, the mean urine concentration of 17 alpha-Bol was higher than 12 ng/mL. A remarkable decrease was observed during the following days, but the 17 alpha-Bol concentration was still higher than the attention level of 2 ng/mL in 58% of the samples; the concentration of 17beta-Bol was around the action level of 1 ng/mL; two days after treatment withdrawal, no 17beta-Bol was detected in the urine. In urine from control animals, the 17 alpha-Bol concentration was strictly related to the phytosterol content of the diet, while, in urine from treated animals, the much higher 17 alpha-Bol levels were not modified by the production from diet precursors. The results confirmed that a 17 alpha-Bol level higher than 2 ng/mL should be considered as evidence of suspected illegal treatment and that the urinary excretion of 17beta-Bol is due to exogenous administration of 17beta-Bol. The discontinuous rate of elimination of both 17 alpha- and 17beta-Bol, despite the daily administration of 17beta-Bol plus ADD, indicates the necessity for further research to detect other urinary boldenone metabolites to strength surveillance strategy.

Expression analysis of androgen-responsive genes in the prostate of veal calves treated with anabolic hormones.

In order to identify indirect molecular biomarkers of anabolic treatments in veal calves, an animal experiment was performed using two combinations of growth promoters (consisting of boldenone undecylenate and estradiol benzoate, and of testosterone enantate and estradiol benzoate). We selected a set of 12 genes that are known to be androgen responsive in other mammalian species. The expression profile of this set of genes was analysed on prostate samples of veal calves using a real-time RT-PCR approach. For each selected gene the corresponding bovine sequence was obtained and a gene specific real-time assay was optimised and validated. The amplification was shown to be highly specific, linear and efficient. High reproducibility (<1%) and low-test variability (<2.5%) were also been achieved. Messenger RNA levels were quantified in prostate samples, non-parametric analysis of variance showed significant up-regulation of three genes (MAF, ESR1 and AR) and significant down-regulation of four genes (HMGCS1, HPGD, DBI, and LIM) in treated samples when compared with untreated controls. To assess the possibility of identifying hormone-treated animals by molecular means we performed a discriminant analysis that was effective in classifying treated and non-treated samples with an accuracy of 93%. Our results indicate that identification of treatment with steroid hormones in veal calves by means of gene expression analysis is a feasible approach and could be improved increasing both the number of genes and the number of controls analysed.

In vitro febantel transformation by sheep and cattle ruminal fluids and metabolism by hepatic subcellular fractions from different animal species.

Febantel and one of its main metabolites, febantel sulphoxide, are chemically modified to only a slight extent when incubated in vitro with sheep and cattle ruminal fluids; other major metabolites, fenbendazole and oxfendazole, are respectively, oxidized to oxfendazole and reduced to fenbendazole. Febantel is negligibly metabolized by hepatic cytosol fractions but microsome preparations effect more extensive metabolic transformations. Important differences in this respect were found between microsome preparations from rat, horse, pig, cattle, sheep, chicken and trout livers.

Biotransformation of genistein in the rat: elucidation of metabolite structure by product ion mass fragmentology.

Biotransformation of the phytoestrogen [14C]genistein was investigated in male and female rats by application of narrow-bore radio-HPLC-MSn (LCQ, Finnigan) to determine intermediates in metabolism. Urine contained five metabolites, Gm1-Gm5, 24 h after dosing by gavage with [14C]genistein (4 mg kg(-1)). Structural analysis following ESI revealed molecular ions [M+H]+ of m/z 447, 449, 273, and 271 for metabolites Gm2, Gm3, Gm5 and genistein, respectively and an [M-H]- of m/z 349 for Gm4. Metabolite structure was deduced by evaluation of product ion spectra derived from unlabelled and [14C]-labelled ions and sensitivity to treatment with beta-glucuronidase. These studies indicated identity of metabolites with genistein glucuronide (Gm2), dihydrogenistein glucuronide (Gm3), genistein sulphate (Gm4) and dihydrogenistein (Gm5). Detection of the beta-glucuronidase resistant major metabolite Gm1 by ESI was poor and so was analysed by negative ion APCI; this revealed a deprotonated molecular ion of m/z 165 which had chromatographic and mass spectral properties consistent with authentic 4-hydroxyphenyl-2-propionic acid, a novel metabolite of genistein. In vitro metabolism studies with anaerobic caecal cultures derived from male and female rats revealed metabolism of genistein to Gm1 via Gm5 and an additional metabolite (Gm6) which was identified from product ion spectra as 6'-hydroxy-O-desmethylangolensin. Biotransformation of genistein by both isolated hepatocytes and precision-cut liver slices was limited to glucuronidation of parent compound. Commonality of genistein metabolites found in rats with those reported in man suggest similar pathways of biotransformation, primarily involving gut micro-flora.

The metabolism of zearalenone in subcellular fractions from rabbit and hen hepatocytes and its estrogenic activity in rabbits.

The in vitro reduction of zearalenone (ZEN) by subcellular fractions from hen and rabbit hepatocytes clearly shows species-specific differences in the cofactor requirements, rate of metabolism and production of metabolites. The presence of NADH as cofactor in the reaction mixtures enhanced only the reducing activity of the microsomal fraction from rabbit hepatocytes, while NADPH enhanced the reducing activities of the cytosolic fraction from rabbit and both the microsomal and cytosolic fractions from hen hepatocytes. Furthermore, we observed that hen hepatocytes metabolize faster and produce beta-zearalenol (ZEL) as the major metabolite, whereas rabbit hepatocytes metabolize ZEN slowly and mainly into alpha-ZEL, the more uterotrophic metabolite. These last findings are closely related to the higher sensitivity to ZEN estrogenic effects observed in rabbits during the toxicity test involving p.o. administration of the mycotoxin to the animals at 3 dosage levels (0.1, 1, 2 mg/kg body wt).

Pharmacokinetics of sodium amoxicillin in horses.

The pharmacokinetics of sodium amoxicillin were investigated after intravenous and intramuscular administration of a single dose of 15 mg kg-1 body-weight to five horses. A rapid distribution phase was noted after intravenous administration (t1/2 alpha about 20 minutes). The t1/2 beta values obtained after the intravenous and the intramuscular administration were significantly different (P less than 0.05). The bioavailability obtained was about 67 per cent. Plasma protein binding, evaluated in vitro, showed that the percentage of bound fraction was 37 to 38 per cent. It was concluded that sodium amoxicillin administration at 15 mg kg-1 four times a day should be effective in the treatment of several systemic infections in the horse.

Pharmacokinetic profile of sulphamonomethoxine-trimethoprim in horses after intravenous, intramuscular and oral administration.

The pharmacokinetic profile of a sulphamonomethoxine-trimethoprim (SMM-TMP) combination was investigated in five horses. The combination was administered intravenously, intramuscularly and orally at a constant dose of 20 mg SMM plus 4 mg TMP kg-1 bodyweight. Following intravenous administration both drugs dispersed rapidly with distribution half-lives of about 12 minutes for SMM and about 18 minutes for TMP. Elimination half-lives for intravenous, intramuscular and oral administration were closely similar, indicating that elimination was independent of administration route. Bioavailability of the drugs in aqueous solution was good: about 72 per cent and 84 per cent for SMM and about 84 per cent and 98 per cent for TMP following intramuscular and oral administration, respectively. It is concluded that SMM-TMP administered orally once a day at 20 mg and 4 mg kg-1 bodyweight, respectively, maintains therapeutic concentrations, whereas twice daily intramuscular administration would be more effective for treating systemic infections in the horse than the once a day regimen usually adopted in veterinary practice.

Comparative pharmacokinetics of amikacin sulphate in calves and sheep.

The pharmacokinetics of amikacin sulphate were investigated in calves and sheep. Five animals of each species were given 7.5 mg kg-1 intravenously and intramuscularly. After intravenous administration the pharmacokinetic parameters significantly different (P less than 0.01) between calves (first value) and sheep (second value), were: the initial concentration (87.05, 146.6 micrograms ml-1), the apparent distribution volume (350, 200 ml kg-1), the area under curve (5512, 11,018 min micrograms ml-1) and the clearance (1.5, 0.7 ml min-1 kg-1). After dosing intramuscularly the peak concentration (23.5, 34.36 micrograms ml-1), the peak time (45, 75 min) and the area under curve (5458, 9191 min micrograms ml-1) were significantly different (P less than 0.01). No significant differences were observed in the terminal halflife values, suggesting that elimination rate was independent of both route of administration and animal species. The drug in aqueous solution showed a good bioavailability in both animal species (about 0.87 in sheep and greater than 0.99 in calves) despite the greater serum concentrations always attained in sheep.

The oxidative metabolism of aldicarb in pigs: in vivo-in vitro comparison.

Aldicarb was administered (1 mg/kg b.w.) to four female pigs and the kinetics of its major oxidized metabolites (sulfoxide and sulfone) was followed for 6 hours. The in vitro transformations of the carbamate pesticide into these two still active metabolites were also investigated in hepatocytes and in microsomes from pig livers. In all cases, aldicarb was quickly oxidized to the sulfoxide (major metabolite) and only a minor quantity of sulfone was produced. The in vivo toxic symptomatology was related to the peak serum concentration of sulfoxide, suggesting that this metabolite is principally responsible for the aldicarb toxicity. Selective in vitro inhibition of flavin-containing and cytochrome P-450 monooxygenases confirmed that the former enzymes catalyze mainly sulfoxide production whereas the latter that of sulfone.

Disposition of antimony and aminosidine in dogs after administration separately and together: implications for therapy of leishmaniasis.

The pharmacokinetic behaviour of aminosidine (15 mg kg-1) and antimony (25.65 mg kg-1 as N-methylglucamine antimoniate), administered subcutaneously either separately or together was studied on four dogs. The results demonstrated that antimony (Sb) did not significantly modify the kinetics of aminosidine (AM) but that the kinetic behaviour of the metal was markedly influenced by the antibiotic, as shown by the differences in mean residence time (MRT), elimination rate constant (Kel) and area under the curve (AUC) with and without the antibiotic (MRT[Sb] = 243.8 +/- 29.5 minutes, MRT[Sb+AM] = 1067.9 +/- 199.2 minutes; Kel[Sb] = 0.008 +/- 0.001 min-1, Kel[Sb+AM] = 0.0015 +/- 0.0003 min-1; AUC[Sb] = 21,024.6 +/- 4448.5 micrograms min ml-1, AUC[Sb+AM] = 130,478.5 +/- 30,481.7 micrograms min ml-1). The persistence of high serum concentrations of antimony when it was administered with aminosidine suggests that the therapeutic doses commonly used should be reduced and that the interval between administration should be increased to avoid the metal reaching toxic concentrations.