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1.
Meat Sci ; 82(2): 284-8, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20416735

RESUMEN

The presence of Escherichia coli, Staphylococcus aureus, Listeria monocytogenes and Salmonella spp. was determined in 75 samples of conventional beef and in 75 samples of organic beef. All samples came from cattle slaughtered and processed in the same slaughterhouse and quartering room. A total of 180 E. coli, 180 S. aureus and 98 L. monocytogenes strains were analyzed by an agar disk diffusion assay for their resistance to 11 antimicrobials, for the case of E. coli and S. aureus, or 9 antimicrobials, for the case of L. monocytogenes. Salmonella spp. were not isolated from any of the beef samples. No significant differences in prevalence were obtained for any of the bacterial species tested between organic and conventional beef. E. coli isolated from organic beef exhibited significant differences in antimicrobial resistance against 5 of the 11 antimicrobials tested as compared to isolates recovered from conventional beef. In the case of S. aureus, these differences were only found for 3 of the 11 antimicrobials tested and for L. monocytogenes, no differences were obtained between isolates obtained from organic or conventional beef. Although no significant differences were obtained in microbiological contamination, E. coli and S. aureus isolates from organically farmed beef samples showed significantly lower rates of antimicrobial resistance in E. coli and S. aureus isolates.

2.
J Food Prot ; 71(12): 2537-42, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19244911

RESUMEN

The presence of Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes was determined in 55 samples of organic poultry meat and in 61 samples of conventional poultry meat. A total of 220 E. coli, 192 S. aureus, and 71 L. monocytogenes strains were analyzed by an agar disk diffusion assay for their resistance to ampicillin, cephalothin, chloramphenicol, ciprofloxacin, doxycycline, fosfomycin, gentamicin, nitrofurantoin, streptomycin, and sulfisoxazole (E. coli); chloramphenicol, ciprofloxacin, clindamycin, doxycycline, erythromycin, gentamicin, nitrofurantoin, oxacillin, and sulfisoxazole (S. aureus); and chloramphenicol, doxycycline, erythromycin, gentamicin, sulfisoxazole, and vancomycin (L. monocytogenes). The results indicated a significantly higher (P < 0.0001) prevalence of E. coli but not of S. aureus and L. monocytogenes in organic poultry meat as compared with conventional poultry meat. E. coli isolated from organic poultry meat exhibited lower levels of antimicrobial resistance against 7 of the 10 antimicrobials tested as compared with isolates recovered from conventional meat. In the case of S. aureus and L. monocytogenes isolated from conventional poultry, antimicrobial resistance was significantly higher only for doxycycline as compared with strains isolated from organic poultry. In the case of E. coli, the presence of multiresistant strains was significantly higher (P < 0.0001) in conventional poultry meat as compared with organic poultry meat. Organically farmed poultry samples showed significantly lower development of antimicrobial resistance in intestinal bacteria such as E. coli.


Asunto(s)
Crianza de Animales Domésticos/métodos , Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Escherichia coli/efectos de los fármacos , Listeria monocytogenes/efectos de los fármacos , Carne/microbiología , Staphylococcus aureus/efectos de los fármacos , Animales , Pollos , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Relación Dosis-Respuesta a Droga , Farmacorresistencia Bacteriana Múltiple , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Humanos , Pruebas de Sensibilidad Microbiana
3.
Poult Sci ; 87(8): 1643-8, 2008 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-18648061

RESUMEN

The resistance rates of intestinal Escherichia coli populations from poultry were determined during treatment and withdrawal period with 3 antimicrobial agents commonly used as therapeutics in poultry medicine. A total of 108 chickens were considered: 18 were treated orally with enrofloxacin, 18 with doxycycline, and 18 with sulfonamides, whereas another 18 chickens were maintained as controls for each antimicrobial group. Fecal samples were taken during the treatment and after the withdrawal period, and E. coli were isolated through Fluorocult media plating. A total of 648 E. coli strains (216 per antimicrobial tested) were isolated and identified though biochemical methods. Minimal inhibitory concentrations to the antimicrobials used were also determined using a broth microdilution method. The resistance rates of intestinal E. coli to all of the antimicrobials tested significantly increased during the course of the therapeutic treatment. In addition, significant differences (P = 0.0136) in resistance rates persisted between the intestinal E. coli of the enrofloxacin-treated and control batches until the end of the withdrawal period, but this difference was not observed for the cases of doxycycline or sulfonamides treatments. Antimicrobial use in poultry medicine seems to select for antimicrobial-resistant strains of pathogenic bacterial species such as E. coli. In some cases, the higher frequencies of resistant strains may persist in the avian intestinal tract until the end of the withdrawal period, when it is legal to use these animals for human consumption.


Asunto(s)
Antibacterianos/farmacología , Pollos/microbiología , Escherichia coli/efectos de los fármacos , Intestinos/microbiología , Animales , Farmacorresistencia Bacteriana , Escherichia coli/genética , Escherichia coli/crecimiento & desarrollo , Masculino , Pruebas de Sensibilidad Microbiana/veterinaria
4.
Artículo en Inglés | MEDLINE | ID: mdl-30103921

RESUMEN

Based on the premise that the fatty acid composition of human milk can be substantially altered by diet, the current study investigated the fatty acid profile (fattyacidome) of breast milk in Galicia, a small region located in the north-west of Spain and characterized by the Southern European Atlantic Diet (SEAD). A cross-country comparison was also performed to assess worldwide variety and diet impact, reviewing the profiles reported various European, North and South American, Asian and African countries and Australia. Galician human milk appeared similar to the rest of Europe, with some particular features related to the SEAD (dairy, pork, beef and sunflower and olive oils), such as relatively high levels of linoleic acid and lower α-linolenic acid. The results also showed the existence of woman-specific profiles and significant changes over lactation in some fatty acids. Worldwide, the fatty acid profiles were similar, with the clear exception of Asiatic breast milk. The impact of fatty acids on infant health warrants further investigation.


Asunto(s)
Ácidos Grasos/análisis , Conducta Alimentaria/clasificación , Leche Humana/química , Adulto , Femenino , Humanos , Ácido Linoleico/análisis , Factores Sexuales , España , Ácido alfa-Linolénico/análisis
5.
Int J Food Microbiol ; 115(2): 149-58, 2007 Apr 10.
Artículo en Inglés | MEDLINE | ID: mdl-17175053

RESUMEN

A novel screening method based on room temperature phosphorescence (RTP) for the visual detection of aflatoxigenic strains from Aspergillus genus is described. Strains were cultured on media widely used in food mycology to which methyl-beta-cyclodextrin plus bile salts (0.6% sodium deoxycholate) were added. Aflatoxin production was readily detectable after 3 days of incubation at 28 degrees C by RTP emission from the mycelium of aflatoxigenic strains observed after exposure to UV light. The method was tested on thirty-two Aspergillus sp. strains. The phosphorescence phenomenon was reproduced in vitro by immobilizing aflatoxin B1 on ion exchange resin beads.


Asunto(s)
Aflatoxinas/biosíntesis , Aspergillus/aislamiento & purificación , Aspergillus/metabolismo , Técnicas de Tipificación Micológica/métodos , Aflatoxinas/aislamiento & purificación , Aspergillus/clasificación , Aspergillus/crecimiento & desarrollo , Recuento de Colonia Microbiana , Medios de Cultivo/química , Ciclodextrinas/metabolismo , Fluorescencia , Especificidad de la Especie , Temperatura , Factores de Tiempo , Rayos Ultravioleta
6.
J Food Prot ; 70(4): 1021-4, 2007 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-17477278

RESUMEN

The mean counts of Enterococcus spp. were determined for 30 samples each of organic chicken meat, conventional chicken meat, and turkey meat, and differences for Enterococcus contamination in meat were determined. Two enterococci strains from each sample were isolated to obtain a total of 180 strains, and resistance to ampicillin, chloramphenicol, doxycycline, ciprofloxacin, erythromycin, gentamicin, nitrofurantoin, and vancomycin was determined by a disk diffusion method. Average counts obtained showed that Enterococcus mean counts from organic chicken meat (3.18 log CFU/g) were significantly higher than those obtained from conventional chicken meat (2.06 log CFU/g) or conventional turkey meat (1.23 log CFU/g). However, the resistance data obtained showed that isolates from organic chicken meat were less resistant than enterococci isolates from conventional chicken meat to ampicillin (P = 0.0067), chloramphenicol (P = 0.0154), doxycycline (P = 0.0277), ciprofloxacin (P = 0.0024), erythromycin (P = 0.0028), and vancomycin (P = 0.0241). In addition, isolates from organic chicken were less resistant than conventional turkey meat isolates to ciprofloxacin (P = 0.001) and erythromycin (P = 0.0137). Multidrug-resistant isolates were found in every group tested, but rates of multidrug-resistant strains were significantly higher in conventional chicken and turkey than those obtained from organic chicken meat. Enterococcus faecalis was the most common species isolated from organic chicken (36.67%), whereas Enterococcus durans was the most common species isolated from conventional chicken (58.33%) and turkey (56.67%). The rates obtained for antimicrobial resistance suggest that although organic chicken meat may have higher numbers of Enterococcus, these bacteria present a lower level of antimicrobial resistance.


Asunto(s)
Agricultura/métodos , Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Enterococcus/efectos de los fármacos , Carne/microbiología , Animales , Pollos , Recuento de Colonia Microbiana , Relación Dosis-Respuesta a Droga , Microbiología de Alimentos , Humanos , Pruebas de Sensibilidad Microbiana , Pavos
7.
J Chromatogr A ; 723(1): 69-75, 1996 Feb 02.
Artículo en Inglés | MEDLINE | ID: mdl-8819823

RESUMEN

A new and highly sensitive method for the detection of the important mycotoxin, citrinin, has been developed. Spectroscopic studies demonstrate that the fluorescence of this metabolite is influenced by the pH of the environment. This fact was exploited in the chromatographic determination of citrinin with fluorescence detection. The proposed method, based on the addition of 1 M hydrochloric acid as an acidic post-column reagent, has a limit of detection of 0.9 center dot 10(-7) M. Analytical validation shows that linearity can be assumed from 2 center dot 10(-7) to 10(-4) M citrinin. The repeatability and reproducibility are satisfactory, with R.S.D. = 5.1% (n = 9, c = 10(-5) M) and R.S.D. = 7.2% (n = 9, c = 10(-5) M). The method was also applied to the determination of this mycotoxin produced by mould cultures isolated from soft cheese and also from soft cheese and also from cheese extracts spiked with citrinin. The specificity of the method is demonstrated and the necessity for post-column acidification is illustrated on real samples.


Asunto(s)
Queso/análisis , Cromatografía Líquida de Alta Presión/métodos , Citrinina/análisis , Cromatografía Líquida de Alta Presión/estadística & datos numéricos , Medios de Cultivo Condicionados/análisis , Concentración de Iones de Hidrógeno , Penicillium/metabolismo , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Espectrometría de Fluorescencia
8.
J Chromatogr A ; 815(1): 21-9, 1998 Jul 31.
Artículo en Inglés | MEDLINE | ID: mdl-9718703

RESUMEN

The fluorescence properties of the aflatoxins M1, Q1, P1 in solution and the effect of various cyclodextrins (alpha-, beta-, gamma-, hydroxypropyl-beta- and alpha-beta-heptakis-di-O-methyl-beta-) on their fluorescence emission were studied. Among the aflatoxins, a substantial enhancement of the fluorescence emission of aflatoxin Q1 in the presence of aqueous solutions of alpha-, beta-, hydroxypropyl-beta, and alpha-beta-heptakis-di-O-methyl-beta-cyclodextrin, was observed. On the contrary, gamma-cyclodextrin proved to be inefficient to enhance the fluorescence properties of this compound. No important fluorescence enhancement was found for aflatoxins P1 or M1 for any of the cyclodextrin derivatives tested. The complex formation constant (Kf) of these compounds with beta-cyclodextrin was chromatographically determined, and from the results obtained, we can conclude that Kf cannot be used alone to explain the fluorescence increase. Thermodynamic studies showed that delta-H and delta-S parameters, associated with the partition of aflatoxins in RP-HPLC, increased when beta-cyclodextrin was added to the eluent.


Asunto(s)
Aflatoxina M1/química , Aflatoxinas/química , Ciclodextrinas/química , Micotoxinas/química , Indicadores y Reactivos , Soluciones , Espectrometría de Fluorescencia , Espectrofotometría Ultravioleta , Temperatura
9.
J Chromatogr A ; 871(1-2): 31-6, 2000 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-10735283

RESUMEN

A rapid, specific reversed-phase HPLC method is described, with solid-phase extraction, for assaying five quinolones (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin and marbofloxacin) with confirmative diode-array detection in samples of bovine kidney, muscle and eggs. The least efficient extraction was marbofloxacin from kidney tissue (64%). The lower detection limit for each quinolone was: enrofloxacin and ciprofloxacin, 1 ng; norfloxacin and difloxacin, 2 ng; marbofloxacin, 4 ng injected. The intra-day relative standard deviations were lower than 7.9% and lower than 8.6% for inter-day assays. These results indicate that the developed method had an acceptable precision.


Asunto(s)
Antiinfecciosos/análisis , Cromatografía Líquida de Alta Presión/métodos , Huevos/análisis , Carne/análisis , 4-Quinolonas , Animales , Calibración , Bovinos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Espectrofotometría Ultravioleta
10.
J Chromatogr A ; 882(1-2): 1-10, 2000 Jun 16.
Artículo en Inglés | MEDLINE | ID: mdl-10895926

RESUMEN

HPLC using fluorescence detection has already become the most accepted method for the determination of aflatoxins due to its several advantages over other analytical methods. Both normal- and reversed-phase HPLC can be used. However the reversed-phase HPLC methods are more popular. Liquid chromatographic determination of aflatoxins using fluorescence detection and its application in food analysis is reviewed in this article.


Asunto(s)
Aflatoxinas/análisis , Cromatografía Líquida de Alta Presión/métodos , Análisis de los Alimentos/métodos , Espectrometría de Fluorescencia
11.
J Chromatogr A ; 721(1): 69-74, 1996 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-8653196

RESUMEN

Measurement of fluorescence increase was used for the comparative quantification of the effect that several cyclodextrins (alpha-, beta-, heptakis-2,6-beta-omicron-dimethyl- and gamma-) produce on the fluorescent response of aflatoxins B1 and G1. This constitutes a new chromatographic method with stability of the mobile phase, and shows general improvements in the chromatographic conditions with respect to other methods (especially those using an iodine reservoir as a postcolumn reactor). A C18-type column was used, with methanol-water (60:40, v/v) as the mobile phase. The excitation phase of the natural fluorescence of aflatoxins, a 10(-2) M solution of each cyclodextrin, was introduced postcolumn. The determination of the elution order aflatoxin G2 > G1 > B2 > B1 was performed for each phase in less than 15 min. As expected using an aqueous-alcoholic medium, an increase in the fluorescence response of aflatoxins with an unsaturated furanic ring was found to occur with all the cyclodextrins studied, except gamma-cyclodextrin. The observed increase was larger for heptakis-2,6-beta-omicron-dimethyl- than for beta-cyclodextrin (to our knowledge, the only cyclodextrin previously described in the literature to serve for the determination of aflatoxins). The difference is of the order of 70.1-fold in the case of aflatoxin G1 and 45.2-fold in the case of aflatoxin B1. The detection limit in the mobile phase used was determined (for aflatoxin B1) for beta-cyclodextrin and 2,6-beta-omicron-dimethylcyclodextrin (signal-to-noise ratio 1:3) to be 4 and 9 mg 1(-1), respectively.


Asunto(s)
Aflatoxinas/análisis , Cromatografía Líquida de Alta Presión/métodos , Ciclodextrinas , Análisis de los Alimentos/métodos , beta-Ciclodextrinas , Aflatoxina B1/análisis , Cromatografía Líquida de Alta Presión/estadística & datos numéricos , Fluorescencia , Contaminación de Alimentos
12.
Artículo en Inglés | MEDLINE | ID: mdl-11824813

RESUMEN

A confirmatory method for the analysis of ethinylestradiol extracted from cattle hair was developed. After the extraction of the xenobiotic from the hair, by using alkaline digestion, the purification of the extract was carried out by employing diphasic dialysis. For the optimization of the technique several parameters was evaluated such as pH, extraction solvents, temperatures, times and agitation speeds. The detection and confirmation of the steroid was accomplished by using a GC-MS2 ion trap system after trimethylsilylation. The calibration curve was linear over the range of 4-20 ng/g. The detection and quantification limit were 0.52 and 0.80 ng/g respectively; with recoveries up to 94%.


Asunto(s)
Diálisis/métodos , Residuos de Medicamentos/aislamiento & purificación , Etinilestradiol/aislamiento & purificación , Cromatografía de Gases y Espectrometría de Masas/métodos , Cabello/química , Animales , Calibración , Bovinos , Residuos de Medicamentos/análisis , Etinilestradiol/análisis , Sensibilidad y Especificidad
13.
Int J Food Microbiol ; 83(2): 219-25, 2003 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-12706042

RESUMEN

This report describes a simple, rapid and reliable method for screening the aflatoxin production by moulds of the Aspergillus flavus group. Strains were cultivated on yeast extract agar to which methylated beta-cyclodextrin derivative plus sodium desoxycholate was added. Production of aflatoxins was readily detectable by direct visualisation of a beige ring surrounding colonies after an incubation time of 3 days at 28 degrees C. When this ring was examined under UV light, it exhibited blue fluorescence. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by HPLC with fluorescence detection.


Asunto(s)
Aflatoxinas/biosíntesis , Aspergillus flavus/aislamiento & purificación , Aspergillus flavus/metabolismo , Cromatografía Líquida de Alta Presión/métodos , Medios de Cultivo/química , Ciclodextrinas/metabolismo , Fluorescencia , Técnicas de Tipificación Micológica
14.
J Agric Food Chem ; 50(3): 436-40, 2002 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-11804509

RESUMEN

A gas chromatography-tandem mass spectrometry (GC-MS(2)) method for the detection and quantification of 17alpha-ethinylestradiol in the hair of cattle has been developed, and uses an ion trap analyzer. After the digestion of 500 mg of hair by alkaline digestion using 1 M NaOH, extraction and purification of the steroid were performed in the same step by means of diphasic dialysis. This technique is a semipermeable-membrane technology developed for the direct extraction of relatively low-molecular-mass analytes. The process was performed by employing acetate buffer to homogenize the digested hair, dichloromethane as the extraction solvent at 37 degrees C, and stirring at 150 rpm for 4 h. The recovery was between 74 and 94%. The detection limit was 0.52 ng/g in hair. To evaluate the validity of the methodology, five animals, approximately 3 months old, received an intramuscular anabolic dose of the drug. The xenobiotic could be detected 7 or 14 days after the treatment (between 2.01 and 23.61 ng/g), and until the end of the study (day 98). No statistical difference between hair color and hair assay outcomes was found.


Asunto(s)
Congéneres del Estradiol/análisis , Etinilestradiol/análisis , Cromatografía de Gases y Espectrometría de Masas/métodos , Cabello/química , Animales , Bovinos , Residuos de Medicamentos/análisis , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
15.
J Agric Food Chem ; 47(10): 4275-9, 1999 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-10552801

RESUMEN

A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).


Asunto(s)
Antiinflamatorios/análisis , Cromatografía Líquida de Alta Presión , Dexametasona/análisis , Residuos de Medicamentos/análisis , Hígado/química , Animales , Antiinflamatorios/aislamiento & purificación , Bovinos , Cromatografía Líquida de Alta Presión/métodos , Dexametasona/aislamiento & purificación , Residuos de Medicamentos/aislamiento & purificación , Inspección de Alimentos/métodos , Humanos , Mediciones Luminiscentes
16.
J Food Prot ; 66(2): 311-8, 2003 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-12597494

RESUMEN

Molds and yeasts from 91 samples of feed and raw materials used in feed formulation were enumerated on a new culture medium to which a beta cyclodextrin (beta-W7M 1.8-cyclodextrin) had been added. This medium was compared with other media normally used in laboratories for the routine analysis of fungi, such as Sabouraud agar, malt agar supplemented with 2% dextrose, and potato dextrose agar. When a t test for paired data (0.05 significance level, 95% confidence interval) was applied, no statistically significant differences between the results obtained with the new culture medium and those obtained with the other media used to enumerate molds and yeasts were found. For the evaluation of contamination due to aflatoxin for all of the samples, Sabouraud agar and yeast extract agar, both supplemented with 0.3% beta-W7M 1.8-cyclodextrin, and APA (aflatoxin-producing ability) medium were used. Aflatoxin was detected in 21% of the feed samples and in 23% of the raw-material samples analyzed, with maximal amounts of 2.8 and 6.0 microg of aflatoxin B1 per kg, respectively, being detected. In any case, the aflatoxin contents found exceeded the legally stipulated limits. The t test for paired data (0.05 significance level, 95% confidence interval) did not show statistically significant differences between the results obtained with the different culture media used for the detection of aflatoxins. The advantage of the new medium developed (Sabouraud agar with 0.3% beta-W7M 1.8-cyclodextrin) is that it allows simultaneous fungal enumeration and determination (under UV light) of the presence of aflatoxin-producing strains without prior isolation and culture procedures involving expensive and/or complex specific media and thus saves work, time, and money.


Asunto(s)
Aflatoxinas/aislamiento & purificación , Alimentación Animal/microbiología , Ciclodextrinas/metabolismo , Hongos/crecimiento & desarrollo , Aflatoxinas/biosíntesis , Agar , Alimentación Animal/análisis , Animales , Aspergillus/crecimiento & desarrollo , Aspergillus/aislamiento & purificación , Aspergillus/metabolismo , Aspergillus flavus/crecimiento & desarrollo , Aspergillus flavus/aislamiento & purificación , Aspergillus flavus/metabolismo , Recuento de Colonia Microbiana , Medios de Cultivo , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Hongos/aislamiento & purificación , Hongos/metabolismo , Levaduras/crecimiento & desarrollo , Levaduras/aislamiento & purificación , Levaduras/metabolismo
17.
Meat Sci ; 84(1): 196-201, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-20374774

RESUMEN

This paper describes the development, validation and application of a confirmatory method to detect 17alpha-methyltestosterone (MT) in bovine hair, to aid in controlling the administration of this growth promoter in meat-producing animals. After cryogenic grinding, MT was removed from the hair matrix using a single step extraction procedure with acetonitrile. Hydroxylamine derivatisation was used to enhance analyte determination with an electrospray ionisation (ESI) source. Determination was carried out using a triple quadrupole liquid chromatography tandem mass spectrometer (LC-MS/MS) in multiple reaction monitoring mode (MRM). The method was validated in accordance with the criteria defined in Commission Decision 2002/657/EC and using deuterated testosterone (T-d(3)) as the internal standard. The decision limit (CCalpha) was 0.07 ng g(-1) and the detection capability (CCbeta) was 0.12 ng g(-1). Repeatability was CV% (7%), within-laboratory reproducibility was CV% (11.0%), and trueness was (87%). Applicability of the method was demonstrated in an animal study. Samples obtained from animal experiments were analyzed and the presence of MT was confirmed.


Asunto(s)
Anabolizantes/análisis , Bovinos , Cabello/química , Metiltestosterona/análisis , Espectrometría de Masa por Ionización de Electrospray/métodos , Anabolizantes/química , Anabolizantes/aislamiento & purificación , Anabolizantes/farmacocinética , Métodos Analíticos de la Preparación de la Muestra , Andrógenos/análisis , Andrógenos/química , Andrógenos/aislamiento & purificación , Andrógenos/farmacocinética , Animales , Calibración , Cromatografía Líquida de Alta Presión/métodos , Residuos de Medicamentos/análisis , Residuos de Medicamentos/química , Residuos de Medicamentos/aislamiento & purificación , Residuos de Medicamentos/farmacocinética , Contaminación de Alimentos/prevención & control , Hidroxilamina/química , Límite de Detección , Metiltestosterona/química , Metiltestosterona/aislamiento & purificación , Metiltestosterona/farmacocinética , Pigmentación , Reproducibilidad de los Resultados , Espectrometría de Masas en Tándem
18.
Luminescence ; 20(3): 197-204, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-15924320

RESUMEN

The development of a black market of chemical cocktails for illegal growth promotion in food-producing animals includes substances that are potentially dangerous for human health, such as synthetic corticosteroids. The potential presence of these residues in food makes it necessary to develop rapid and sensitive analytical methodologies to detect such substances, preferably in live animals before they arrive at the market. A chemiluminescence (CL) detection method for the determination of four synthetic corticosteroids (prednisolone, betamethasone, dexamethasone and flumethasone) in bovine urine has been developed. The proposed system, which does not need any derivatization procedure, offers an easy method well suited for routine research. Urine samples were homogenized with methanol:water (50:50, v/v) and centrifuged. The upper layer was collected and Strata X cartridges were used for cleaning up. The purified residues were evaporated to dryness and then redissolved in the mobile phase. Analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection, employing luminol as the CL reagent. The recovery curves, obtained at four spiking levels (different for each corticosteroid), showed that recoveries of at least 70% could be obtained for urine. The chemiluminescence detection procedure afforded satisfactory results with respect to sensitivity and the LOD and LOQ, taken as the first point of the regression curve, ranged from 4 ppb to 65 ppb. The maximum mean RSD was below 13% and below 15% for intra- and inter-day assay, respectively, in all cases.


Asunto(s)
Corticoesteroides/orina , Cromatografía Líquida de Alta Presión/métodos , Animales , Betametasona/orina , Bovinos , Dexametasona/orina , Flumetasona/orina , Contaminación de Alimentos/análisis , Mediciones Luminiscentes/métodos , Mediciones Luminiscentes/normas , Luminol , Prednisolona/orina
19.
Lett Appl Microbiol ; 41(2): 153-6, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-16033513

RESUMEN

AIMS: To investigate the productivity and specificity of a new chromogenic enterococci selective medium (Chromocult enterococci agar) recently developed by Merck. METHODS AND RESULTS: The study was carried out comparing Chromocult enterococci agar with MRS agar (Merck), a basal lactic acid bacteria medium in current use. A total of 216 faecal samples from poultry were collected and enterococci populations were counted. Likewise, 100 randomly selected strains were identified for each medium. The differences found between the two media were analysed and discussed. CONCLUSIONS: A good sensitivity of 98% was obtained for Chromocult agar and all false-positive isolates obtained were identified as Leuconostoc spp. However significant differences (P<0.01) were obtained between the enterococci species isolation rates identified from these two media, suggesting the poor growth of some species in Chromocult enterococci agar. Viable counts of Enterococcus spp. obtained with MRS agar were significantly higher than those obtained with Chromocult enterococci agar. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of chromogenic media for microbiological analysis is increasing. Independent studies are important to evaluate newly developed chromogenic media.


Asunto(s)
Pollos/microbiología , Medios de Cultivo , Enterococcus/aislamiento & purificación , Agar , Animales , Recuento de Colonia Microbiana , Enterococcus/crecimiento & desarrollo , Heces/microbiología , Sensibilidad y Especificidad
20.
Appl Environ Microbiol ; 67(10): 4858-62, 2001 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-11571194

RESUMEN

A new reliable, fast, and simple method for the detection of aflatoxigenic Aspergillus strains, consisting of the addition of a cyclodextrin (a methylated beta-cyclodextrin derivative) to common media used for testing mycotoxin production ability, was developed. We propose the use of this compound as an additive for fungal culture media to enhance the natural fluorescence of aflatoxins. The production of aflatoxins coincided with the presence of a bright blue or blue-green fluorescent area surrounding colonies when observed under long-wavelength (365-nm) UV light after 3 days of incubation at 28 degrees C. The presence of aflatoxins was confirmed by extracting the medium with chloroform and examining the extracts by high-pressure liquid chromatography with fluorescence detection.


Asunto(s)
Aflatoxinas/biosíntesis , Aspergillus/clasificación , Aspergillus/crecimiento & desarrollo , Ciclodextrinas/metabolismo , Aspergillus/metabolismo , Medios de Cultivo/química , Técnicas de Tipificación Micológica
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