Pulsed field gel electrophoresis (PFGE) analysis for multidrug resistant Salmonella enterica serovar Schwarzengrund isolates collected in six years (2000-2005) from retail chicken meat in Taiwan.

Salmonella Schwarzengrund is one of the causative agents of human salmonellosis and animal infections. High prevalence of multidrug resistant strains of S. Schwarzengrund from chicken meat has been recently reported in Taiwan. With an attempt to see if such prevalence in chicken meat was due to the recirculation of S. Schwarzengrund strains in traditional marketplaces, a total of 173 S. Schwarzengrund strains isolated between 2000 and 2005 from 417 retail chicken meat samples purchased from Taipei, Taiwan were analyzed using pulsed field gel electrophoresis (PFGE) method. For XbaI and AvrII digested DNA, a total of 23 and 16 PFGE patterns, respectively, were obtained. When these patterns were combined, a total of 47 subtypes were obtained and the major subtypes were X3A2, X1A2 and X2A1. Since it was found that these major subtypes were repeatedly found for multidrug resistant strains collected from 2000 to 2005, we then collected the chicken meat isolates from central and southern Taiwan in 2006. These strains did not show similar major subtypes as those found in Taipei. Such results might also suggest that the repeated appearance of some major subtypes for S. Schwarzengrund strains isolated each year in Taipei was due to the recirculation of these strains in retail marketplace during these years.

Simultaneous determination of residual thiamphenicol and florfenicol in foods of animal origin by HPLC/electrospray ionization-MS/MS.

A simple and reliable method using HPLC/MS/MS has been developed for determination of thiamphenicol and florfenicol in foods of animal origin, such as pork, porcine liver, porcine kidney, beef, bovine liver, fish, and chicken. The HPLC separation was performed on a Waters XTerra phenyl column (100 x 2.1 mm, 3.5 microm) with a gradient mobile phase system of 0.1% formic acid-methanol at a flow rate 0.35 ml/min. Negative ionization produced the molecular ions at m/z 354 and 356 for thiamphenicol and florfenicol, respectively. Two characteristic transition reactions (m/z 354-->185, 290 and m/z 356-->336, 185) in the selected reaction monitoring mode were tested for detection and confirmation of thiamphenicol and florfenicol simultaneously. The analytes were extracted with ethyl acetate and defatted with n-hexane by liquid-liquid extraction. The recoveries of thiamphenicol and florfenicol by the developed method were 72.5-97.6%. The limits of determination were 1.0 ng/g (ppb) for both compounds.

Exposure Estimation for Risk Assessment of the Phthalate Incident in Taiwan.

BACKGROUND: In May 2011, di(2-ethylhexyl) phthalates (DEHP) and, to a lesser extent, di-iso-nonyl phthalate (DiNP) were found to have been illegally used for many years in Taiwan as clouding agents in foods including sports drinks, juice beverages, tea drinks, fruit jam/nectar/jelly, and health or nutrient supplements. OBJECTIVE: To estimate the DEHP exposure for the study participants for the follow-up epidemiological study and health risk assessment. METHODS: A total of 347 individuals possibly highly exposed to phthalate-tainted foods participated in the study. Exposure assessment was performed based on the participants' responses to a structured questionnaire, self-report of exposure history, urinary metabolite concentrations, and DEHP concentration information in 2449 food records. A Bayesian statistical approach using Markov chain Monte Carlo simulation was employed to deal with the uncertainties in the DEHP concentrations of the contaminated foods and the participants' likelihood of being exposed. RESULTS: An estimated 37% and 15% of children younger than 12 years old were exposed to DEHP at medium (20-50 µg / kg_bw / day) and high AvDIs (50-100 µg / kg_bw / day), respectively, prior to the episode (9% and 3% in adults, respectively). Moreover, 11% of children and 1% of adults were highly exposed (> 100 µg / kg_bw / day), with a maximum of 414.1 µg / kg_bw / day and 126.4 µg / kg_bw / day, respectively. CONCLUSIONS: The phthalate exposure-associated adverse health effects for these participants warrant further investigation. The estimation procedure may be applied to other exposure assessment with various sources of uncertainties.

Trace elements and heavy metals in poultry and livestock meat in Taiwan.

Trace elements and heavy metals were determined in poultry and livestock meat by inductively coupled plasma mass spectrometry after graphite block digestion. Samples were collected from markets in Taiwan and included beef (20), mutton (20), pork (30), chicken (30), duck (10) and goose (10). Mean concentrations of Mn, Co, As, Se, Mo, Cd, Sb and Pb in meat samples were 0.106-0.365 µg/g, 0.002-0.033 µg/g, 0.005-0.035 µg/g, 0.108-0.349 µg/g, 0.029-0.140 µg/g, <0.002-0.003 µg/g, <0.002-0.004 µg/g and 0.009-0.046 µg/g, respectively. Arsenic concentrations in both pork and chicken were higher than in other meat. Lead concentrations were higher in duck. Risk assessment from these data did not indicate harm for public health.

Multiclass analysis of 23 veterinary drugs in milk by ultraperformance liquid chromatography-electrospray tandem mass spectrometry.

An ultraperformance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous detection and confirmation of 23 veterinary (multiclass) drugs in milk was developed and validated. The analytes were extracted by acetonitrile, evaporated and injected into the UPLC-MS/MS system on a Waters UPLC HSS T3 column in gradient mode. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring (MRM) of two ion transitions per compound to provide a high degree of specificity. Results showed good repeatability, and recoveries for the 12 macrolide, 7 ß-lactam and 2 lincosamide antibiotics and 2 other veterinary drugs (morantel, orbifloxacin) used in milk averaged 51.8-139.0%, 51.5-100.6%, 82.4-102.5% and 87.5-99.4%, respectively. The coefficients of variation (C.V.) of the recoveries were less than 15% for intraday and interday precisions. The limits of quantification (LOQs) were all lower than 5 ng/ml. This method was applied to 17 fresh milk samples and only lincomycin was found in milk samples under allowable levels. Overall, this method is a suitable and rapid tool to confirm the presence of 23 veterinary drug residues in milk.