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Bent Halling-Sørensen

Publications and source records attributed to Bent Halling-Sørensen.

At least 19 recordsLinked to original sources
PubMed2006

Susceptibility of bacteria isolated from pigs to tiamulin and enrofloxacin metabolites.

Susceptibilities to metabolites of tiamulin (TIA) and enrofloxacin (ENR) were tested using selected bacteria with previously defined minimal inhibitory concentrations (MIC). The TIA metabolites tested were: N-deethyl-tiamulin (DTIA), 2beta-hydroxy-tiamulin (2beta-HTIA) and 8alpha-hydroxy-tiamulin (8alpha-HTIA), and the ENR metabolites were: ciprofloxacin (CIP) and enrofloxacin N-oxide (ENR-N). Bacteria, all of porcine origin, were selected as representatives of bacterial infections (Staphylococcus hyicus and Actinobacillus pleuropneumoniae), zoonotic bacteria (Campylobacter coli) and indicator bacteria (Escherichia coli and enterococci). Furthermore the effects of these compounds were tested on the microbial community of active sludge to test any negative effect on colony forming units (CFU). DTIA had a potency of 12.5-50% of the potency of TIA. 2beta-HTIA and 8alpha-HTIA had potencies less than 1% of the potency of TIA. ENR-N had a potency of 0.75-1.5% of the potency of ENR, while CIP and ENR had similar potencies. Results obtained here indicate that CIP and DTIA could contribute to the selective pressure for upholding antimicrobial resistant bacteria in animals under ENR or TIA treatment. The most potent metabolites CIP and DTIA showed considerable potencies against activated sludge bacteria compared to the parent compounds. EC(50) (microg/ml) for ENR, CIP, TIA and DTIA were 0.018 [95% CI: 0.028-0.149], 0.064 [95% CI: 0.007-0.046], 6.0 [95% CI: 3.6-9.8], and 9.7 [95% CI: 5.8-16.3], respectively. This indicates that the compounds can change the bacterial population in the sludge, and hereby alter the properties of the sludge.

Actinobacillus Infections↗
PubMed2006

Effect of tetracycline residues in pig manure slurry on tetracycline-resistant bacteria and resistance gene tet(M) in soil microcosms.

Effects of tetracycline residues from pig manure slurry on the prevalence of tetracycline-resistant bacteria and the tetracycline resistance gene, tet(M), were studied in soil microcosms. Four types of soil microcosms were established for a period of 152 days, supplemented with combinations of pig manure slurry and a tetracycline-resistant Enterococcus faecalis, CG110, containing the tetracycline resistance gene tet(M) (on the conjugative transposon, Tn916). The prevalence of both tetracycline-resistant aerobic bacteria and tetracycline-resistant enterococci declined rapidly until day 45 where no significant differences in the levels of tetracycline-resistant bacteria in any of the four types of microcosms could be detected. tet(M) could be detected in microcosms supplemented with either pig manure slurry and/or E. faecalis CG110 (tet(M)) for the whole period (152 days). tet(M) could be detected longer than tetracycline-resistant enterococci could be isolated (limit of detection 100 CFU/g soil) probably due to viable but not culturable (VBNC) bacteria with tet(M), horizontal gene transfer of tet(M) to indigenous soil bacteria or presence of "free" DNA. The concentration of chlortetracycline and oxytetracycline were almost stable through out the experimental period, but the tetracycline concentrations had no effect on prevalence of tetracycline-resistant bacteria. The presented microcosm approach simulated natural farmland conditions well and supported results from previous field studies.

Animals↗
PubMed2006

Isolation and structural elucidation of tiamulin metabolites formed in liver microsomes of pigs.

Although the antimicrobial tiamulin is extensively metabolized in pigs, the metabolism is not well investigated. In this work the NADPH dependent metabolism of tiamulin in liver microsomes from pigs has been studied. The tiamulin metabolites formed in the incubations were analysed using LC-MS, and three major metabolites were isolated using solid phase extraction and preparative HPLC. The final structure elucidations were performed by tandem mass spectrometry and (1)H and (13)C NMR. The structures of the metabolites were found to be 2beta-hydroxy-tiamulin, 8alpha-hydroxy-tiamulin and N-deethyl-tiamulin. In addition, the LC-MS chromatograms revealed two other minor metabolites. From their chromatography and from MS(2) analysis the structures were estimated to be 2beta-hydroxy-N-deethyl-tiamulin and 8alpha-hydroxy-N-deethyl-tiamulin, but the structures were not confirmed by NMR. In these studies approximately 20% of tiamulin was deethylated, 10% was hydroxylated in the 2beta-position and 7% was hydroxylated in the 8alpha-position. About 40% of tiamulin was metabolized during the incubation conditions used. The protein precipitation in the incubations was performed using perchloric acid, and the preparative purification was performed under alkaline conditions. Therefore, the stability of the metabolites under these conditions was studied. The metabolites were found to be stable in the acid solution, but under alkaline conditions, particularly at room temperature, the stability of especially 8alpha-hydroxy-tiamulin was considerably reduced (40% loss after 1 week).

Animals↗
PubMed2006

Distribution of the UV filter 3-benzylidene camphor in rat following topical application.

A straightforward analytical method for determination of 3-benzylidene camphor (3-BC) in rat adipose tissue, brain, liver, muscle, plasma and testis following topical application was developed and validated. Three exposure levels (60, 180 and 540 mg kg(-1) day(-1)) were tested for 65 days in male Sprague-Dawley rats (24 days postnatal). Sample preparation involving homogenization and n-heptane or methanol extraction of the tissue was applied before injection into the LC-ESI-MS-MS system. The response was linear from 2 to 100 microg l(-1) for the qualifier and the quantifier MRM transitions (R(2) (quantifier) > 0.994). Detection limit of the method corresponded to 0.005 microg g(-1) tissue and 12.5 microg l(-1) plasma, respectively. Recovery was determined for all tissues (adipose tissue: 40%; all other tissues: 80-100%) at three individual levels. 3-(4-Methyl benzylidene camphor) (4-MBC) was used throughout the study as internal standard. 3-Benzylidene camphor was detected in all tissues at all exposure levels at concentrations between 0.05 microg g(-1) (liver) and 36 microg g(-1) (adipose tissue) and in plasma at 16-89 microg l(-1). The method allowed for the quantification of 3-benzylidene camphor in all tested tissues following topical application. Furthermore, it was shown that 3-benzylidene camphor can be found in various tissues in the rat following topical application. These findings may suggest that following use of 3-benzylidene camphor containing sunscreen, similar disposition and distribution may occur in humans.

Administration, Topical↗
PubMed2006

Multi-component analysis of tetracyclines, sulfonamides and tylosin in swine manure by liquid chromatography-tandem mass spectrometry.

A multi-component method focussing on thorough sample preparation has been developed for simultaneous analysis of swine manure for three classes of antibiotic-tetracyclines, sulfonamides, and tylosin. Liquid manure was initially freeze-dried and homogenised by pulverization before extraction by pressurised liquid extraction. The extraction was performed at 75 degrees C and 2,500 psig in three steps using two cycles with 0.2 mol L(-1) citric acid buffer (pH 4.7) and one cycle with a mixture of 80% methanol with 0.2 mol L(-1) citric acid (pH 3). After liquid-liquid extraction with heptane to remove lipids, the pH of the manure was adjusted to 3 with formic acid and the sample was vacuum-filtered through 0.6 mum glass-fibre filters. Finally the samples were pre-concentrated by tandem SPE (SAX-HLB). Recoveries were determined for manure samples spiked at three concentrations (50-5,000 microg kg(-1) dry matter); quantification was achieved by matrix-matched calibration. Recoveries were >70% except for oxytetracycline (42-54%), sulfadiazine (59-73%), and tylosin (9-35%) and did not vary with concentration or from day-to-day. Limits of quantification (LOQ) for all compounds, determined as a signal-to-noise ratio of 10, were in the range 10-100 microg kg(-1) dry matter. The suitability of the method was assessed by analysis of swine manure samples from six different pig-production sites, e.g. finishing pigs, sows, or mixed production. Residues of antibiotics were detected in all samples. The largest amounts were found for tetracyclines (up to 30 mg kg(-1) dry matter for the sum of CTC and ECTC). Sulfonamides were detected at concentrations up to 2 mg kg(-1) dry matter (SDZ); tylosin was not detected in any samples.

Animals↗
PubMed2005

Determination of bisphenol diglycidyl ethers in topical dosage forms.

A method involving extraction and LC-ESI-MS-MS detection of BADGE, BFDGE, BADGE*H2O, BADGE*2H2O, BADGE*HCl, BADGE*H2O*HCl, BADGE.2HCl and BFDGE*2HCl in aqueous cream was developed and validated. Initially, empty internally lacquered aluminum container closure systems were extracted with isopropanol as an attempt to estimate the upper limit of extractable bisphenol diglycidyl ethers present in lacquer. Six of the eight potential bisphenol diglycidyl ethers were quantified. In an accelerated experiment, on aqueous cream stored in lacquered aluminum tubes at 70 degrees C, all derivatives except BADGE*2HCl and BFDGE*2HCl were extracted from cream samples and quantified as an attempt to estimate the upper limit of compounds leaching to the cream. Detection limits were from 0.3+/-0.2 to 3.4+/-0.7 microgl(-1). Recoveries were determined for all compounds at three concentration levels (mean 63+/-6%). Mean inter-day and mean intra-day precision was 7+/-2 and 13+/-6%, respectively. Three commercially available creams were obtained from a local community pharmacy and analysed for bisphenol diglycidyl ethers. BADGE, BADGE*H2O, BADGE*2H2O and BADGE*H2O*HCl were detected and quantified. In conclusion, the developed method allows for the extraction and detection of bisphenol diglycidyl ethers originating from the epoxy phenol lacquer used in aluminum tubes. This study does not indicate that they leach into aqueous cream in significant amounts under normal storage conditions.

Benzhydryl Compounds↗
PubMed2005

Assessment of the importance of sorption for steroid estrogens removal during activated sludge treatment.

Distribution coefficients (K(d)) between water and activated sludge particles (f(oc)=27.7+/-0.1%) were measured for the steroid estrogens (SE), estrone (E1), 17beta-estradiol (E2) and 17alpha-ethinylestradiol (EE2) in batch experiments. Experimental concentration levels ranged from environmentally realistic low ng/l to the high microg/l. In this range K(d)s were independent of their water concentration. The experimentally obtained K(d)s (with 95% confidence intervals) were 402+/-126 l/kg, 476+/-192 l/kg and 584+/-136 l/kg for E1, E2 and EE2, respectively. K(d)s were used to estimate the fraction of the total SE concentration that is expected to be sorbed in the activated sludge treatment tanks of a typical STP assuming equilibrium conditions. Assuming a suspended solids concentration of 4 g/l dissolved solids (ds), it was estimated that 61+/-9%, 66+/-13% and 70+/-6% of the total concentration of E1, E2 and EE2, respectively, would be sorbed during activated sludge treatment. The fraction of the SEs that was expected to be sorbed to suspended sludge particles in the effluents from a typical Danish STP was estimated to be only 0.20+/-0.06%, 0.24+/-0.10% and 0.29+/-0.07% of the total concentration of E1, E2 and EE2, respectively, at a suspended solids concentration of 5 mg/lds. For a typical STP the removal of steroid estrogens with excess sludge was estimated to be only 1.5-1.8% of the total loading if equilibrium conditions exists. Sorption is therefore not important for the fate of SEs in STPs compared to biodegradation.

Biodegradation, Environmental↗
PubMed2005

Dissipation of oxytetracycline, chlortetracycline, tetracycline and doxycycline using HPLC-UV and LC/MS/MS under aquatic semi-field microcosm conditions.

A mixture of four tetracyclines; oxytetracycline (OTC), chlortetracycline (CTC), tetracycline (TC), and doxycycline (DC) was applied in fifteen 12000l outdoor microcosms at four treatment levels plus controls each with three replicates (n = 3). The dissipation times of parent compounds were monitored and half-lives (DT50) of 1-4 days, depending on treatment level were recorded. This is in accordance with half-lives from previous findings in bench-top experiments. Parent compound DT50, were determined using HPLC-UV. Furthermore, the samples were analyzed for ten different tetracycline products using LC/MS/MS. Two products were found for chlortetracycline; 4-epi-anh-chlortetracyline and the iso-chlortetracycline. Iso-forms were only found for CTC and only at the highest treatment (300 microg l(-1)). The half-lives, trajectories, and relative amounts of the products were analogous for all four tetracyclines. DT50 for products were less than 1.2 days. Formation of 4-epi-anh-tetracyclines, occurred at neutral to weak alkaline conditions.

Chromatography, High Pressure Liquid↗
PubMed2005

Dissipation and effects of chlortetracycline and tylosin in two agricultural soils: a field-scale study in southern Denmark.

Presently, there is a basic lack of information concerning the accumulation of antibacterial agent residues in agricultural soils. In this field study, performed in southern Denmark, we assess the dissipation of chlortetracycline (CTC), and tylosin A (TYL A) as a function of time. Field soils were classified as a sandy loam soil (field A) and a sandy soil (field B) and each field was sampled on six occasions during the 155-d experimental period from May to October 2000 for chemical analysis and counts of colony-forming units (CFU) detecting the level of aerobic bacteria surviving antibiotic exposure. Colony-forming units and TYL A were detected throughout the entire sampling period, with respective starting soil concentrations of 30 and 50 microg kg(-1) soil declining to 1 and 5 microg kg(-1) soil, on day 155. Compound half-lives (95% confidence limits in parentheses) were estimated for both fields and T1/2 for CTC was 25 d (20-34) and 34 d (28-42) in fields A and B, respectively, and T1/2 for TYL A was 67 d (54-86) and 49 d (40-64) in fields A and B, respectively. No significant difference was determined between compound half-lives on the two fields. The level of aerobic antibiotic-resistant bacteria in the soil over time and soil fauna community was assessed in relation to application of manure containing antibacterial agents to the agricultural fields. The level of both CTC- and TYL-resistant bacteria was affected in the soil by amendment of manure, but declined during the study to the same level as observed at the beginning.

Agriculture↗
PubMed2004

Fast and robust simultaneous determination of three veterinary antibiotics in groundwater and surface water using a tandem solid-phase extraction with high-performance liquid chromatography-UV detection.

A simple and robust analytical method is presented in which the three veterinary antibiotics oxytetracycline (OTC), sulfachloropyridazine (SCP) and tylosin (TYL) were simultaneously determined in surface water and groundwater. The three compounds were simultaneously extracted from the water samples using a mixture of methanol, EDTA and McIlvaine buffer (citric acid and sodium orthophosphate) and then cleaned-up and pre-concentrated by solid-phase extraction using sacrificial Isolute strong anion-exchange cartridges, to remove interfering organic material, and Waters Oasis hydrophilic-liphophilic balance polymer cartridges, to retain the compounds, in tandem. Analysis was performed using liquid chromatography with ultraviolet detection. Recoveries for river water samples spiked at 10 and 1 microgl(-1) were respectively 99.6+/-4.6 and 99.4+/-8.4% for OTC; 99.9+/-2.2 and 105.0+/-5.7% for SCP; and 94.9+/-2.4 and 71.6+/-8.2% for TYL. Overall limits of detection based on pre-concentrating 400 ml of sample were 0.35 microgl(-1) for OTC and TYL and 0.25 microgl(-1) for SCP.

Anti-Bacterial Agents↗
PubMed2004

Simultaneous extraction of tetracycline, macrolide and sulfonamide antibiotics from agricultural soils using pressurised liquid extraction, followed by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

The veterinary antibacterial agents chlortetracycline (CTC), oxytetracycline (OTC), sulfadiazine (SDZ), erythromycin (ERY) and tylosin (TYL A, B, C and D) were extracted from soil using pressurized liquid extraction (PLE). Citric acid (pH 4.7) and methanol was used as extraction buffer, followed by tandem-solid-phase extraction (SPE) clean-up (SAX + HLB) for all compounds. For quantification two slightly different methods were employed using LC-MS-MS with MRM detection. The soil extraction method was validated using a loamy sand soil and a sandy soil, representing two typical Danish agricultural soils. Recoveries were 50-80% for the tetracyclines (CTC and OTC) and sulfadiazine (SDZ) and 60-100% for the macrolides (TYL and ERY). Limits of detection for the soil extraction method (LOD(soil)) were 0.6-5.6 microg kg(-1) soil for CTC and OTC, 0.9-2.9 microg kg(-1) soil for SDZ and 2.4-5.5 microg kg(-1) soil for TYL A and ERY. Furthermore, the method was applied to field samples taken from two agricultural fields fertilised with liquid manure containing CTC and TYL A. These results showed a decline in the content of antibacterial agents throughout the sampling period of 155 days from 10 to 15 microg CTC kg(-1) soil and 20-55 microg TYL A kg(-1) soil to below or near the LOD(soil) listed above. Finally, the method was applied to barley grains harvested from the fields. None of the antibacterial agents were measured in grain samples, but recoveries for spiked grain samples were similar to soil recoveries.

Anti-Bacterial Agents↗
PubMed2004

Isolation, structural elucidation and in vitro activity of 2-acetyl-2-decarboxamido-oxytetracycline against environmental relevant bacteria, including tetracycline-resistant bacteria.

2-Acetyl-2-decarboxamido-oxytetracycline (ADOTC) is a major impurity of oxytetracycline (OTC) produced as a side product during fermentation. ADOTC was isolated from OTC and other impurities using preparative HPLC. The preparative column was an Xterra MS, C18 chromatographic column (100 mm x 19 mm i.d., 5 microm), and the mobile phase contained methanol-water (27:73 (v/v)) with 0.08 M formic acid added. The flow rate was 9.0 ml/min. It was possible to isolate few milligram ADOTC in a day. The compound was unambiguously identified using NMR and MS-MS. The anti-microbial activity against activated sludge bacteria was determined giving a potency of only 3% of that of OTC. With tetracycline-resistant bacteria, no anti-microbial activity was observed, indicating a mode of action similar to that of OTC.

Animals↗
PubMed2004

Quantitative analysis of oxytetracycline and its impurities by LC-MS-MS.

A liquid chromatographic-tandem mass spectrometric method using an Xterra MS C(18) chromatographic column ( 100 mm x 2.1 mm i.d., 3.5microm) that allows complete separation of oxytetracycline (OTC) and the impurities: 4-epi-oxytetracycline (EOTC), tetracycline (TC), 4-epi-tetracycline (ETC), 2-acetyl-2-decarboxamido-oxytetracycline (ADOTC), alpha-apo-oxytetracycline (alpha-AOTC) and beta-apo-oxytetracycline (beta-AOTC) was developed. Gradient elution was used and calibration curves were obtained using the scan mode selected reaction monitoring (SRM). Acceptable correlations were obtained for OTC, TC, EOTC and ADOTC whereas the correlations of alpha-AOTC and beta-AOTC were less accurate resulting in higher limits of quantification (LOQ) and limits of detection (LOD) relative to the other compounds. The intraday and interday accuracy varied for all the compounds from 90 to 112% and the intraday and interday precision were lower than 7.1%. The method was applied for analysis of commercial available ointments containing OTC resulting in an acceptable quantification of OTC and the impurities in the drug preparations. The advantage of this method compared to the other separation methods is an empty separation window right after the large peak corresponding to OTC in the chromatogram, which facilitates an accurate determination of ADOTC and the other impurities.

Chromatography, High Pressure Liquid↗
PubMed2004

Evaluation of manometric respiration tests to assess the effects of veterinary antibiotics in soil.

Extensive use of antimicrobials in veterinary medicine results in environmental exposure. Of major concern are microbial effects; including effects on nutrient soil cycles and antibiotic resistance. There is a need to assess the effects of these compounds in the environment. The application of standardized guidelines is relevant in studying many compounds. However there is a lack of special test methods designed for antibiotics. We validate manometric test flasks using glucose and a recalcitrant herbicide. The suitability of these tests for studying antibacterial agents is then investigated using two target functions (aerobic biodegradation and carbon transformation). Compound stability is quantified using HPLC techniques. Effects on total soil respiration in the biodegradation test are immediate and differ significantly from background. We show that compounds do not function as substrates, so effects are due to other soil processes, correlate well to sorption characteristics and are not dose dependent. This test provides details of relative antimicrobial potency towards soil microorganisms and can be used to rank compounds. However the test does not provide details on the nature or extent of specific microbial effects. In contrast, the carbon transformation test is more specific and provides a reproducible indication of dose effect relationships, which is more suitable in assessing the effects of these compounds in the environment. Presently, standard guidelines do not take into account the normal input of antibiotics into soils via contaminated sludge or manure. This should be corrected in future guidelines as these inputs alter microbial composition, organic matter, ionic strength and pH affect sorption and overall impact the test results.

Anti-Bacterial Agents↗
PubMed2004

Chemical stability of chlortetracycline and chlortetracycline degradation products and epimers in soil interstitial water.

Tetracyclines and tetracycline degradation products and epimers end up in the environment. In order to predict the persistence of the potential dominating species of the chlortetracyclines in the environment, the chemical stability of chlortetracycline (CTC) and four major CTC degradation products and epimers (iso-CTC, 4-epi-CTC, anhydro-CTC, and 4-epi-anhydro-CTC) was studied in milliQ water and soil interstitial water (SIW) under environmentally relevant conditions (oxygen, light, pH (3-9), and temperature (6 degrees C and 20 degrees C)). The chemical stability of the compounds was evaluated by following the decrease in amount of parent compound over time. In order to compare the results obtained under the varying conditions, apparent pseudo-first-order rate constants (k(obs)) for the disappearance of the parent compound and corresponding apparent half-lives were calculated. A statistical evaluation of the data showed that the chemical stability of the chlortetracyclines was generally dependent on photolysis, temperature, and matrix. The presence or absence of oxygen did not influence on the chemical stability. The presence of calcium and magnesium ions in SIW is believed to account for the significant differences in half-lives between milliQ water and SIW, although numerous of other factors are believed to influence as well. Generally, the five compounds were more persistent at pH 3-4 than at pH above 5.

Calcium↗
PubMed2003

Fate of estrogens in a municipal sewage treatment plant.

The fate of the highly potent endocrine disrupters estrone (E1), 17beta-estradiol (E2), and 17alpha-ethinylestradiol (EE2) was investigated in mechanical and biological sewage treatment as well as in sewage-sludge treatment at a municipal German sewage treatment plant (STP). The main outcome of the study was that a common municipal STP with an activated sludge system for nitrification and denitrification including sludge recirculation can appreciably eliminate natural and synthetic estrogens. As a consequence, the endocrine effects of biota in the receiving waters should be significantly reduced. All estrogen concentrations decreased gradually along the treatment train. In the STP effluent, the steroid estrogen concentrations were always below the quantification limit of 1 ng/L. The elimination efficiency of the natural estrogens (E1 and E2) exceeded 98%, and EE2 was reduced by more than 90%. The natural estrogens were largely degraded biologically in the denitrifying and aerated nitrifying tanks of the activated sludge system, whereas EE2 was only degraded in the nitrifying tank. Only about 5% of the estrogens are sorbed onto digested sewage sludge. It is very likely that conjugates (glucuronides and sulfates) of the estrogens were cleaved into the parent compounds mainly in the first denitrification tank.

Adsorption↗
PubMed2003

Susceptibility of Escherichia coli and Enterococcus faecium isolated from pigs and broiler chickens to tetracycline degradation products and distribution of tetracycline resistance determinants in E. coli from food animals.

One hundred Escherichia coli isolates from diseased and healthy pigs, cattle and broiler chickens were screened for the presence of tetracycline resistance genes tet(A), (B), (C), (D) or (E). The tet(A) gene was the most abundant (71% of the 100 isolates) followed by tet(B) (25%). The predominance of tet(A) and tet(B) applied to all three animal species, and there was no difference between the distribution of tet(A) and tet(B) genes among non-pathogenic and pathogenic E. coli in any of the animal species. The susceptibility of 20 of these isolates together with 10 tetracycline sensitive E. coli and 18 tetracycline resistant and 10 sensitive Enterococcus faecium to tetracyclines and tetracycline degradation products was determined. The resistant isolates showed reduced resistance to anhydrotetracycline, 4-epi-anhydrotetracycline, anhydrochlortetracycline and 4-epi-anhydrochlortetracycline. In general both the tetracycline resistant and susceptible E. faecium were more susceptible to the compounds tested than E. coli.

Animals↗