Three Escherichia coli Ol57:H7 (EHEC) strains were inoculated separately into portions of commercially prepared mayonnaise held at 25 or 7°C, then examined periodically for survival of detectable EHEC. Four mayonnaise-based sauces including: a) mayonnaise-mustard sauce, b) blue cheese dressing, c) thousand island dressing and d) seafood sauce, were each inoculated with one EHEC strain. Samples of these sauces were held at 5°C, and assayed periodically for survival of detectable EHEC. Both direct plate count and selective enrichment recovery were employed as assay procedures. Escherichia coli O157:H7 strains, when inoculated and mixed into mayonnaise and stored at 25°C, became undetectable after 72 h storage when assayed by direct plating or by selective enrichment. The same strains inoculated into mayonnaise and stored at 7°C were detectable up to 35 days when assayed by direct plating or by selective enrichment. Escherichia coli O157:H7 inoculated into mayonnaise-based sauces and held at 5°C were detectable past 35 days in three of the four sauces. Loss of EHEC culturability occurred within 3 days in mayonnaise-mustard sauce.
Floating catchment area (FCA) metrics are a family of measures used to quantify spatial accessibility. Spatial accessibility fuses the concepts of accessibility and availability to describe the relationship between the supply and demand of resources. FCA metrics have been applied to measure accessibility of numerous amenities including health services, public transportation, and recreation areas. Macro-level data such as census tracts and census blocks are often used to represent population locations in the calculation of FCA metrics. This approach is susceptible to masking geographic variability that may exist at less aggregated levels, such as at the individual level. This research explores how level of data aggregation can impact the measurement and interpretation of FCA based metrics. Our case study uses the E2SFCA method to measure and compare the spatial accessibility of public parks using micro-and macro-level population representations. Our analysis shows a general agreement in the FCA results among various levels of data aggregation. As expected, error in the FCA measurements generally increased as larger areal units were used; however, our results also show a somewhat nuanced picture, as particularities arising from the Modifiable Areal Unit Problem and the gravity-based calculation of the E2SFCA appear to affect the resulting differences among FCA values. Because obtaining and using individual based data can be challenging for researchers, macro-level data are often the only reliable alternative. Our findings provide insight into the limitations associated with using macro-level data to measure and interpret spatial accessibility.
A newly revised enrichment and agar-plating system was tested for selectivity and sensitivity in recovery of unstressed and cold-stressed Escherichia coli O157:H7 from foods. Various foods inoculated with known levels of enterohemorrhagic E. coli O157:H7 (EHEC) were tested by enrichment for 6 h at 37°C in modified tryptic soy broth (mTSB) base supplemented with vancomycin, cefsulodin and cefixime, referred to as EHEC enrichment broth (EEB). Subsequently, portions were spread-plated on sorbitol–MacConkey agar supplemented with tellurite and cefixime (TCSMAC). Further selective enrichment was also examined using immunomagnetic separation (IMS) from the EEB prior to spread-plating on TCSMAC agar. These methods were compared to a procedure of enrichment in mTSB (supplemented with novobiocin) at 37°C for 24 h followed by spread-plating of decimal dilutions on hemorrhagic colitis 4–methylumbelliferyl–B–D–glucuronide (HC–MUG) agar. The new enrichment isolation technique was found to be sensitive at a level of one EHEC organism per 10 g of food in four food types. This represents an approximate l00-fold to 1,000-fold enhancement in sensitivity over the comparative method for foods with high levels of competitive microflora. These enrichment-isolation protocols also were compared in analysis of naturally contaminated raw or undercooked ground beef samples implicated in foodborne illness. EEB-TCSMAC with and without IMS were combined with rapid biochemical tests, and with O157 latex agglutination and confirmation of toxin genes by polymerase chain reaction (PCR) to provide a completed test within 30 h of initiating testing. The new system was successful in 15 of 17 samples, where only 6 of 17 were found positive by the comparative technique.
This guideline was compiled by members of a standing committee of the American Academy of Otolaryngic Allergy. The intent of this guideline is to provide practitioners, referring physicians, patients, third-party payers, and cognizant government authorities with the fundamental principles involved in the diagnosis and treatment of the patient with allergic rhinitis. Although developed solely through the American Academy of Otolaryngic Allergy, the statements and recommendations are drawn from the entire spectrum of English-speaking literature from the United States and Europe. Articles were independently reviewed by members of the Committee, many of whom sit on editorial review boards for major professional publications. A grading system was used to categorize individual articles to demonstrate the format used to arrive at conclusions. The grade is recorded at the end of each article reference. The grading scale follows: Grade A: A study involving prospective or well-selected retrospective patient populations. The conclusions drawn are well supported by the scientific work. Little controversy relating to these conclusions would be expected. Grade B: A scientific study executed without major flaws. Limitations may exist such that the conclusions drawn remain subject to controversy. Grade C: An anecdotal or case report study.
Food and patient isolates from an Escherichia coli O157:H7 outbreak associated with undercooked ground beef were characterized by pulsed-field gel electrophoresis and Shiga-like toxin genotype. Pulsed-field gel electrophoresis confirmed the epidemiologically implicated source of the two-state outbreak and differentiated between outbreak and sporadic strains. Escherichia coli O157:H7 is an important food-borne pathogen in North America and Europe. Pathogenicity is associated with the production of one or more Shiga-like toxins (SLT-I, SLT-II, or both) (8, 13). Most food-borne outbreaks, as well as sporadic cases of gastrointestinal illness, have been linked epidemiologically to undercooked ground beef (6). Other food and water sources, as well as person-to-person transmission, have also been documented (3, 5, 6, 9, 10). In January 1994, the state health departments of Washington and Oregon began a joint epidemiological investigation of a two-state outbreak of E. coli O157:H7 infections. There were 33 culture-confirmed cases of E. coli O157:H7 infection, with onset from mid-January to mid-March 1994, in the two states. Using a recently improved method (15) for detection of E. coli O157:H7 in food, we analyzed 10 samples of raw or undercooked ground beef collected from the homes of six patients with culture-confirmed E. coli O157:H7 illness. Using SLT gene profiles and pulsed-field gel electrophoresis (PFGE) patterns, we then compared the E. coli O157:H7 strains isolated from the ground beef with isolates obtained from patients by the respective state health laboratories. The purposes of this study were to confirm the epidemiologically implicated source of the two-state E. coli O157:H7 outbreak and to differentiate unrelated sporadic strains from outbreak strains. A total of 39 E. coli O157:H7 strains were analyzed: 26 patient isolates, 12 food-borne isolates from seven positive ground beef samples, and one control strain, EDL 933 (Table 1). The PCR method (15) was used to assess the presence of SLT-I and SLT-II genes in the E. coli O157:H7 isolates. PFGE was performed by modification of the method of Böhm and Karch (4). Briefly, isolates were grown in tryptic soy broth with 0.6% yeast extract at 35ЊC on a rotator to an optical density at 600 nm of 0.8 to 1.0. The cells were washed and resuspended in 1 M NaCl-10 mM Tris-50 mM EDTA, mixed with an equal volume of 1% low-melting-point preparative-grade agarose (Bio-Rad Laboratories, Hercules, Calif.), and dispensed into plug molds (Bio-Rad). After the plugs solidified, they were transferred to tubes that contained 1 mg of lysozyme per ml in 1 M NaCl-6 mM Tris-0.1 M EDTA-0.5% Sarkosyl-0.2% deoxycholate for 1 h at 37ЊC with gentle agitation. The solution was replaced with 1 mg of proteinase K per ml in 0.5 M
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