In vitro enzymatic degradation of non-porous films of segmented poly(ether urethane) (Pellethane 2363-80AE) was investigated by incubating the biomaterial in concentrated trypsin solutions for 5 months at room temperature. Chemical degradation of films was monitored by surface analysis techniques such as Fourier transform infrared spectroscopy-attenuated total reflectance and electron spectroscopy for chemical analysis. This latter technique proved to be much superior in detecting chemical changes. Extraction of films with methanol and characterization of the extracts by gel permeation chromatography revealed the presence of low-molecular-weight polymers. Results have shown that trypsin has the ability to induce degradation in PEU, the soft segment being most affected, particularly the CH2-O bond of the ether linkages.
Enterohemorrhagic Escherichia coli O157:H7 is an important pathogen associated with infections caused by consumption of undercooked raw meat. Sensitive and rapid detection methods for E. coli O157:H7 are essential for the meat industry to ensure a safe meat supply. This study was conducted to compare the sensitivity of the VIDAS ultra performance E. coli test (ECPT UP) with a noncommercial real-time (RT) PCR method and the U.S. Department of Agriculture, Food Safety and Inspection Service (USDA-FSIS) reference method for detecting E. coli O157:H7 in raw ground beef. Optimal enrichment times and the efficacy of testing different types of raw meat, either as individual samples (25 g) or as composites (375 g), were examined. For 25-g samples of each type of raw ground beef tested, 6 h of enrichment was sufficient for both the VIDAS ECPT UP and RT-PCR methods, but for 375-g samples, 24 h of enrichment was required. Both the VIDAS ECPT UP and RT-PCR methods produced results similar to those obtained with the USDA-FSIS reference method after 18 to 24 h of enrichment. The primer specificity of the RT-PCR assay and the highly specific phage ligand used in the VIDAS ECPT UP for target recognition enabled the detection of low levels of E. coli O157:H7 in 25 g of various types of raw ground beef. The tests also allowed the detection of E. coli O157:H7 in composite raw ground beef and trimmings in samples of up to 375 g.
Enterohemorrhagic Escherichia coli (EHEC; E. coli) are food-borne agents associated with gastroenteritis, enterocolitis, bloody diarrhea and the hemolytic-uremic syndrome (HUS). Bovine milk glycans have been shown to contain oligosaccharides which are similar to host epithelial cell receptors and can therefore prevent bacterial adhesion. This study aimed to describe interactions between EHEC O157:H7 EDL933 and O26:H11 21765 and milk fat globules (MFGs) in raw milk and raw milk cheese, and the impact of MFGs on EHEC strains adhesion to the intestinal tract in vitro and in vivo. Both EHEC serotypes clearly associated with native bovine MFGs and significantly limited their adhesion to a co-culture of intestinal cells. The presence of MFGs in raw milk cheese had two effects on the adhesion of both EHEC serotypes to the intestinal tracts of streptomycin-treated mice. First, it delayed and reduced EHEC excretion in mouse feces for both strains. Second, the prime implantation site for both EHEC strains was 6 cm more proximal in the intestinal tracts of mice fed with contaminated cheese containing less than 5% of fat than in those fed with contaminated cheese containing 40% of fat. Feeding mice with 40% fat cheese reduced the intestinal surface contaminated with EHEC and may therefore decrease severity of illness.
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