Development and evaluation of a novel decellularized vascular xenograft.

Although autogenous saphenous vein remains the standard for coronary and infrapopliteal bypass, many patients do not have a suitable vein. Attempts at developing a small-caliber vascular graft have failed largely due to occlusion, neointimal hyperplasia, or aneurismal degradation. We have designed and characterized a novel small-caliber vascular xenograft that may overcome these failure modes. To reduce immune reactions, porcine common carotid arteries were decellularized by enzymatic and detergent treatments. Histology and electron microscopic examination showed complete removal of cellular components while the extracellular matrix structure remained intact. To reduce thrombogeneity, decellularized vascular grafts were covalently linked with heparin. The efficiency of heparin linkage was demonstrated with toluidine blue staining and the antithrombogeneity of the heparin-treated grafts was demonstrated with a clot time test. Mechanical testing of the graft was performed. Decellularized-heparin-treated grafts were similar in compliance to fresh vessels and burst testing showed grafts to withstand pressures exceeding 10 times physiologic blood pressure. There was no difference in suture retention strength between fresh vessels and decellularized-heparin-treated grafts. Decellularized, heparinized grafts were implanted in dogs as carotid artery bypass grafts and showed smooth muscle cells densely populating the wall, and endothelial cells lining the lumen by two months. This study provides a new strategy to develop a small-caliber vascular graft with excellent mechanical properties, antithrombogeneity, and tissue compatibility.

Delayed nephrectomy in grade V renal injury with two interesting anatomic variations.

The decision to perform early nephrectomy in hemodynamically stable grade V injury rather than to provide supportive nonoperative care is not universally accepted. The management of isolated grade V renal injury, as well as the management of coexisting abdominal trauma that requires operative intervention, is an area of controversy. We present the case of a grade V renal injury that was initially managed expectantly at a level I trauma center. After transfer to our facility, nephrectomy was performed. The case illustrates the merit of prompt definitive surgical treatment.

Determination of the sensitivity of a rapid Escherichia coli O157:H7 assay for testing 375-gram composite samples.

Both 25-g single-size ground beef samples and 375-g composite ground beef samples were tested by a method combining an immunomagnetic separation (IMS) technique with a sandwich enzyme-linked immunosorbent assay (ELISA) system (IMS-ELISA). The results demonstrated that IMS-ELISA could detect the target, Escherichia coli O157:H7, at the level of 10(-1) CFU/g of sample in either the 25- or 375-g sample size.

Inactivation of Escherichia coli O157:H7 and Escherichia coli 8739 in apple juice by pulsed electric fields.

The effect of high voltage pulsed electric field (PEF) treatment on Escherichia coli O157:H7 and generic E. coli 8739 in apple juice was investigated. Fresh apple juice samples inoculated with E. coli O157:H7 and E. coli 8739 were treated by PEF with selected parameters including electric field strength, treatment time, and treatment temperature. Samples were exposed to bipolar pulses with electric field strengths of 30, 26, 22, and 18 kV/cm and total treatment times of 172, 144, 115, and 86 micros. A 5-log reduction in both cultures was determined by a standard nonselective medium spread plate laboratory procedure. Treatment temperature was kept below 35 degrees C. Results showed no difference in the sensitivities of E. coli O157:H7 and E. coli 8739 against PEF treatment. PEF is a promising technology for the inactivation of E. coli O157:H7 and E. coli 8739 in apple juice.

Biosensors: applications for dairy food industry.

Biosensors are defined as indicators of biological compounds that can be as simple as temperature-sensitive paint or as complex as DNA-RNA probes. Food microbiologists are constantly seeking rapid and reliable automated systems for the detection of biological activity. Biosensors provide sensitive, miniaturized systems that can be used to detect unwanted microbial activity or the presence of a biologically active compound, such as glucose or a pesticide. Immunodiagnostics and enzyme biosensors are two of the leading technologies that have had the greatest impact on the food industry. The use of these two systems has reduced the time for detection of pathogens such as Salmonella to 24 h and has provided detection of biological compounds such as cholesterol or chymotrypsin. The continued development of biosensor technology will soon make available "on-line quality control" of food production, which will not only reduce cost of food production but will also provide greater safety and increased food quality.

Effects of electroconductive heat treatment and electrical pretreatment on thermal death kinetics of selected microorganisms.

Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subjected to conventional (hot water) and ohmic (electric current) heating under identical temperature histories. Experiments were also conducted with cells of Escherichia coli to compare the lethal effect of combination of sublethal electrical preteatment and conventional heating with conventional heating. The kinetic parameters (D,Z,K and E(a)) were determined for both organisms during different treatments. There was no significant difference in the death rate of yeast cells during conventional and ohmic heating at the voltage range used in this study. Results of electrical pretreatment and conventional heating on E. coli indicated differences under certain conditions when compared with pure conventional heating. Thus it is concluded that microbial death during ohmic heating was due primarily to thermal effects with no significant effect of electric current per se. Sublethal electrical pretreatment appears to offer potential for increased bacterial inactivation in certain cases.

Microbiological quality and safety of zoo food.

Two types of commercial products for feeding zoo animals (a frozen meat product, referred to as zoo food, and a dry product, referred to as dry food) were microbiologically examined for spoilage organisms (aerobic, psychrotrophic, coliform, Escherichia coli, mold, and yeasts) and pathogens (Salmonella spp., Listeria monocytogenes, and Campylobacter jejuni). Levels of microorganisms in frozen ground zoo food were compared with those in frozen ground beef and frozen ground turkey meat. The level of microbial contaminants in frozen ground zoo meat was found to be similar to that in frozen ground beef and higher than that in frozen ground turkey meat. Sixty percent of the frozen zoo meat samples were Salmonella positive, and all of the samples were L. monocytogenes positive. Dry zoo food was documented to have microbial levels lower than those in frozen zoo meat; the pathogen levels were less than 1/25 g of food. Defrosting zoo meat at 10, 25, and 37 degrees C for 24 h showed that 10 degrees C is the best temperature for defrosting frozen ground zoo meat loaves (length, 9 in. [22.8 cm]; radius, 2 in. [5.1 cm]) without affecting the microbiological quality or safety of the product.

Conventional tube and microplate Limulus amoebocyte lysate procedures for determination of gram-negative bacteria in milk.

A comparison was made of the conventional tube and microplate Limulus amoebocyte lysate assay for detection of gram-negative bacterial lipopolysaccharide in milk. Raw whole milk samples were maintained frozen and portions were examined periodically on alternate days during 13-d storage to evaluate the reproducibility of both Limulus amoebocyte lysate procedures and to determine optimum reaction conditions for the microplate method. One-day-old, raw and locally purchased pasteurized milk samples, held at 7 degrees C, were analyzed during storage to establish the correlation of both procedures with aerobic and modified psychrotrophic plate counts. Vitamin- and mineral-fortified dairy-based products were examined using the microplate Limulus amoebocyte lysate test as a potential indicator of raw material or finished product bacterial quality and possible postprocessing contamination. Statistical analysis of the data collected comparing the conventional tube and the microplate Limulus amoebocyte lysate assay demonstrated no significant difference exists between the methods when either the modified psychrotrophic bacterial count or the aerobic plate count was used to determine gram-negative bacteria in pasteurized or raw milk (P less than .91). The microplate method, which uses half the lysate reagent, was a good indicator of the bacterial quality of milk and fortified dairy products, consistently detecting bacterial levels greater than 10(3) to 10(4)/ml.

Monitoring microbial numbers in food by density centrifugation.

Some foods contain low numbers of microbes that may be difficult to enumerate by the plate count method due to small food particles that interfere with the counting of colonies. Ludox colloidal silicon was coated with reducing agents to produce a nontoxic density material. Food homogenates were applied to a layered 10 and 80% mixture of modified Ludox and centrifuged at low speed. The top and bottom of the tube contained the food material, and the Ludox-containing portion was evaluated by conventional pour plate techniques. Plate counts of the Ludox mixture agreed with plate counts of the food homogenate alone. The absence of small food particles from pour plates resulted in a plate that was more easily read than pour plates of the homogenate alone. Modified Ludox was evaluated for its effect on bacteria at 4 degrees C during a 24-h incubation period. No inhibition was observed. This method is applicable to food products, such as doughnuts, spices, tomato products, and meat, in which small food particles often interfere with routine plate counts or low dilution may inhibit colony formation. Inhibitory substances can be removed from spices, resulting in higher counts. Ludox is more economical than similar products, such as Percoll. Modified Ludox is easily rendered nontoxic by the addition of common laboratory reagents. In addition, the mixture is compatible with microbiological media.

Microbiological and Sensory Evaluation of Fresh Fish Packaged in Carbon Dioxide for Retail Outlets in the Midwest.

Fresh fish obtained from a commercial packaging plant were evaluated for microbial content and sensory changes during 3 weeks of storage. Fish were packaged in (a) nylon-Surlyn bags and backflushed with approximately 80% CO2, (b) in nylon-Surlyn bags with no alternation of gaseous environment, or (c) over-wrapped with polyvinyl chloride film. After packaging, fish were stored at 1°C. Two types of fish (ocean perch and sea trout) were analyzed. The data indicate that fish packaged in the nylon-Surlyn bag with CO2 had the smallest increase in microbial numbers followed by the fish packaged without CO2. An increase in the bacterial lag phase was observed for the fish packaged in CO2 when compared with fish packaged without CO2 or over-wrapped. The fish packaged in CO2 maintained a lower pH during storage compared with fish packaged without CO2. The highest microbial load was found in fish packaged with the polyvinyl chloride over-wrap.

Evaluation of an X-ray microprobe technique as a possible aid to detect salmonellae.

The X-ray microprobe was examined as a possible aid in the detection of salmonellae. Results obtained indicate that specific bacterial antigen (Salmonella) increased in phosphorus and sulfur after reaction with the fluorescein isothiocyanate tagged specific antibody. Nonspecific antigen (Escherichia coli) did not increase in phosphorus and sulfur after reaction with fluorescein isothiocyanate tagged anti-Salmonella antibody. The technique developed supports the hypothesis that X-ray microprobe analysis may be useful in detecting salmonellae, or other bacteria, by determining increases in the elemental constituents of bacterial cells when reacted with elemental-tagged antibodies.

Gas-Liquid Chromatographic Differentiation Between Salmonella gallinarum and Salmonella pullorum.

Salmonella gallinarom and Salmonella pullorom have been considered as one serovar, S. gallinarom-pullorom or S. gallinarom . This serovar possesses group D somatic antigens with no flagellar antigen. Reportedly S. gallinarom differs from S. pullorom in dulcitol fermentation. This reaction is positive, but delayed up to 5 d for S. gallinarom and negative for S. pullorom . Gas-liquid chromatography of organic acid by-products from a dulcitol medium was performed on 10 isolates of each biovar. Viable plate counts confirmed approximately the same number of organisms per ml of culture. Results of pH determinations supported gas-liquid chromatographic analysis of more acid formation in all S. gallinarom cultures as compared with the S. pullorom cultures after incubation for 24 h. A quantitative measurement of succinic acid resulted in confirmation of the differences in metabolic function of both biovars. The additional test procedure of gas-liquid chromatography of organic acid by-products aids the clinician or researcher in rapidly and accurately distinguishing these two similar biovars.