Four strains of Escherichia coli O157:H7 isolated from patients during an outbreak of disease associated with ground beef: importance of evaluating multiple colonies from an outbreak-associated product.
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This report describes the investigation of a ground-beef-associated outbreak that involved five genetically distinct patient strains of Escherichia coli O157:H7. Human and product isolates were evaluated by pulsed-field gel electrophoresis (PFGE) with two endonucleases. The multiple-strain etiology of this outbreak underscores the importance of isolating and evaluating multiple colonies from outbreak-related products and comparing two endonuclease PFGE patterns of all product and human isolates identified during outbreak periods. This investigation emphasizes the importance of interviewing all confirmed and suspected case patients during the outbreak period, regardless of the PFGE pattern of their isolate, to confirm or rule out an epidemiologic link to the outbreak. (+info)
Simultaneous determination of nitrate and nitrite in saliva and foodstuffs by non-suppressed ion chromatography with bulk acoustic wave detector.
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In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination. (+info)
Pork quality, processing, and sensory characteristics of dry-cured hams as influenced by Duroc crossing and sex.
(51/467)
This study was designed to evaluate Duroc (DU) crossing for Carso dry-cured ham production. One hundred fifty-four pigs (81 females and 73 castrates) of four different genotypes, pure Landrace pigs (LAN), offspring of LAN females crossed with Large White (LW) males (LWxLAN), offspring of LAN females crossed with DU males (DUxLAN), and offspring of LWxLAN females crossed with DU males (DUx[LWxLAN]), were chosen in the weight range of 105 to 120 kg (112.7 +/- 0.4 kg). Raw material quality was evaluated for ham fatness (intra- and intermuscular and subcutaneous) and meat quality (pH, color, water-holding capacity) of longissimus dorsi, biceps femoris, and semimembranosus muscles. Ham weight losses were recorded at different stages of processing. The biceps femoris and semimembranosus muscles were analyzed for chemical composition before (lipid, moisture, total nitrogen, nonprotein nitrogen) and after (moisture, salt, total nitrogen, nonprotein nitrogen) processing. Chemical and sensory analyses were performed on 96 dry hams (12 castrates and 12 females per genotype). Biceps femoris and semimembranosus muscles were evaluated for color, saltiness, aroma, and texture. Pigs of the four genotypes had similar ham fatness as estimated by subcutaneous fat thickness. Duroc crosses exhibited higher intramuscular fat content, marbling, and intermuscular fat. Crossing with DU resulted in lower weight losses during ham processing. Castrates were fatter and had more intra- and intermuscular fat and lower ham processing weight losses than females. A strong negative relationship between ham fatness and ham processing losses was observed. Chemical and sensory traits of dry ham muscles were little affected by DU crossing. Lower salt content of biceps femoris was found in DU crosses. Dry hams from female pigs had higher total and nonprotein nitrogen, but drier, firmer texture and higher resistance to cutting force compared to dry hams from castrated pigs. Crossing with DU demonstrated some disadvantages (more intermuscular fat, more slice visible fat) and advantages (lower weight loss and salt intake) for the quality of dry-cured ham. (+info)
Novel prevention program for trichinellosis in inuit communities.
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Repeated outbreaks of trichinellosis caused by the consumption of Trichinella-infected walrus (Odobenus rosmarus) meat, which have sometimes led to serious morbidity, have stimulated Inuit communities in Nunavik (northern Quebec), Canada, to develop an innovative trichinellosis prevention program. The program involves preconsumption testing of meat samples from harvested walrus at a regional laboratory and the rapid dissemination of the results of such testing to communities. Local health authorities in Inukjuak conducted an epidemiological investigation after testing identified Trichinella-positive walrus meat in September 1997. This report describes the events that occurred before, during, and after the trichinellosis outbreak and also documents how the prevention program contributed to successful resolution of the outbreak. (+info)
A single daily dose of soybean phytosterols in ground beef decreases serum total cholesterol and LDL cholesterol in young, mildly hypercholesterolemic men.
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BACKGROUND: Consumption of phytosterol-supplemented margarine lowers total plasma cholesterol (TC) and LDL-cholesterol concentrations in older middle-aged hypercholesterolemic individuals. The effects of incorporating phytosterols into lower-fat foods on the plasma lipids of young men at increased risk of developing cardiovascular disease have not been studied. OBJECTIVE: We tested the hypothesis that a single daily dose of soybean phytosterols added to ground beef will lower plasma TC and LDL-cholesterol concentrations in mildly hypercholesterolemic young men. DESIGN: In a triple-blind, 4-wk study, 34 male college students with elevated plasma TC (5.85 +/- 0.70 mmol/L), LDL cholesterol (4.02 +/- 0.60 mmol/L), and TC:HDL cholesterol (5.5 +/- 1.2) were randomly assigned to the control (ground beef alone) or treatment (ground beef with 2.7 g of phytosterols) group. The phytosterol mixture was two-thirds esterified and one-third nonesterified and consisted of beta-sitosterol (48%), campesterol (27%), and stigmasterol (21%). RESULTS: Consumption of phytosterol-supplemented ground beef lowered plasma TC and LDL-cholesterol concentrations and TC:HDL cholesterol from baseline by 9.3%, 14.6%, and 9.1%, respectively (P < 0.001). The LDL particle size did not change, suggesting that the decrease was primarily of particle number. The decreases were similar in subjects with (n = 8) and without (n = 9) a family history of premature cardiovascular disease. No significant changes were found in the control group. CONCLUSION: Phytosterol-supplemented ground beef effectively lowers plasma TC and LDL cholesterol and has the potential to become a functional food to help reduce the risk of cardiovascular disease. (+info)
Purification and characterization of an extracellular protease from Penicillium chrysogenum Pg222 active against meat proteins.
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An extracellular protease from Penicillium chrysogenum (Pg222) isolated from dry-cured ham has been purified. The purification procedure involved several steps: ammonium sulfate precipitation, ion-exchange chromatography, filtration, and separation by high-performance liquid chromatography. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and gel filtration, the purified fraction showed a molecular mass of about 35 kDa. The hydrolytic properties of the purified enzyme (EPg222) on extracted pork myofibrillar proteins under several conditions were evaluated by SDS-PAGE. EPg222 showed activity in the range of 10 to 60 degrees C in temperature, 0 to 3 M NaCl, and pH 5 to 7, with maximum activity at pH 6, 45 degrees C, and 0.25 M NaCl. Under these conditions the enzyme was most active against tropomyosin, actin, and myosin. EPg222 showed collagenolytic activity but did not hydrolyze myoglobin. EPg222 showed higher activity than other proteolytic enzymes like papain, trypsin, and Aspergillus oryzae protease. The N-terminal amino acid sequence was determined and was found to be Glu-Asn-Pro-Leu-Gln-Pro-Asn-Ala-Pro-Ser-Trp. This partial amino acid sequence revealed a 55% homology with serine proteases from Penicillium citrinum. The activity of this novel protease may be of interest in ripening and generating the flavor of dry-cured meat products. (+info)
Molecular epidemiology of Clostridium perfringens related to food-borne outbreaks of disease in Finland from 1984 to 1999.
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From 1975 to 1999, Clostridium perfringens caused 238 food-borne disease outbreaks in Finland, which is 20% of all such reported outbreaks during these years. The fact that C. perfringens is commonly found in human and animal stools and that it is also widespread in the environment is a disadvantage when one is searching for the specific cause of a food-borne infection by traditional methods. In order to strengthen the evidence-based diagnostics of food poisonings suspected to be caused by C. perfringens, we retrospectively investigated 47 C. perfringens isolates by PCR for the cpe gene, which encodes enterotoxin; by reversed passive latex agglutination to detect the enterotoxin production; and by pulsed-field gel electrophoresis (PFGE) to compare their genotypes after restriction of DNA by the enzymes SmaI and ApaI. The strains were isolated during 1984 to 1999 from nine food-borne outbreaks of disease originally reported as having been caused by C. perfringens. In seven of the nine outbreaks our results supported the fact that the cause was C. perfringens. Our findings emphasize the importance of a more detailed characterization of C. perfringens isolates than mere identification to the species level in order to verify the cause of an outbreak. Also, to increase the probability of finding the significant cpe-positive C. perfringens strains, it is very important to isolate and investigate more than one colony from the fecal culture of a patient and screen all these isolates for the presence of the cpe gene before further laboratory work is done. (+info)
Cloning and inactivation of a branched-chain-amino-acid aminotransferase gene from Staphylococcus carnosus and characterization of the enzyme.
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Staphylococcus carnosus and Staphylococcus xylosus are widely used as aroma producers in the manufacture of dried fermented sausages. Catabolism of branched-chain amino acids (BCAAs) by these strains contributes to aroma formation by production of methyl-branched aldehydes and carboxy acids. The first step in the catabolism is most likely a transamination reaction catalyzed by BCAA aminotransferases (IlvE proteins). In this study, we cloned the ilvE gene from S. carnosus by using degenerate oligonucleotides and PCR. We found that the deduced amino acid sequence was 80% identical to that of the corresponding enzyme in Staphylococcus aureus and that the ilvE gene was constitutively expressed as a monocistronic transcript. To study the influence of ilvE on BCAA catabolism, we constructed an ilvE deletion mutant by gene replacement. The IlvE protein from S. carnosus was shown mainly to catalyze the transamination of isoleucine, valine, leucine, and, to some extent, methionine using pyridoxal 5'-phosphate as a coenzyme. The ilvE mutant degraded less than 5% of the BCAAs, while the wild-type strain degraded 75 to 95%. Furthermore, the mutant strain produced approximately 100-fold less of the methyl-branched carboxy acids, 2-methylpropanoic acid, 2-methylbutanoic acid, and 3-methylbutanoic acid, which derived from the BCAA catabolism, clearly emphasizing the role of IlvE in aroma formation. In contrast to previous reports, we found that IlvE was the only enzyme that catalyzed the deamination of BCAAs in S. carnosus. The ilvE mutant strain showed remarkably lower growth rate and biomass yield compared to those of the wild-type strain when grown in rich medium. Normal growth rate and biomass yield were restored by addition of the three BCAA-derived alpha-keto acids, showing that degradation products of BCAAs were essential for optimal cell growth. (+info)