The purpose of this study was to develop data on the risk of listeriosis to support a science-based strategy for addressing Listeria monocytogenes in foods in the United States. Eight categories of ...ready-to-eat foods were collected over 14 to 23 months from retail markets at Maryland and northern California FoodNet sites. The product categories included luncheon meats, deli salads, fresh soft "Hispanic-style" cheeses, bagged salads, blue-veined and soft mold-ripened cheeses, smoked seafood, and seafood salads. The presence and levels of L. monocytogenes in the samples were determined by rapid DNA-based assays in combination with culture methods. Of 31,705 samples tested, 577 were positive. The overall prevalence was 1.82%. with prevalences ranging from 0.17 to 4.7% among the product categories. L. monocytogenes levels in the positive samples varied from <0.3 MPN (most probable number) per g to 1.5 x 10(5) CFU/g, with 402 samples having levels of <0.3 MPN/g, 21 samples having levels of >10(2) CFU/g, and the rest of the samples having intermediate levels. No obvious trends with respect to seasonality were observed. Significant differences (P < 0.05) between the sampling sites were found, with higher prevalences for threes categories in northern California and for two categories in Maryland. Significantly (P < 0.001) higher prevalences were found for in-store-packaged samples than for manufacturer-packaged samples of luncheon meats, deli salads, and seafood salads, while 16 of the 21 samples with higher counts were manufacturer packaged. The data collected in this study help to fill gaps in the knowledge about the occurrence of L. monocytogenes in foods, and this new information should be useful in the assessment of the risk posed by L. monocytogenes to consumers.
Washing whole and cut produce by dipping or submerging in chlorinated water has a sanitizing effect, although reduction in microbial populations is minimal and is usually less than 100-fold. A study ...was undertaken to evaluate the efficacy of a spray application of chlorine in killing Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, yeasts and molds, and total aerobic mesophilic microorganisms on whole apples, tomatoes, and lettuce leaves. Inoculated produce was treated (sprayed and then soaked) with water (control) or solutions containing 200 or 2,000 ppm of chlorine for 0, 1, 3, 5, or 10 min, rinsed with sterile water, and analyzed for populations (CFU/cm2) of target microorganisms. Compared to the control treatment, further reductions in numbers of pathogens of 0.35 to 2.30 log CFU/cm2 were achieved by treatment with chlorine. Chlorine was generally more effective at 2,000 ppm than at 200 ppm. Inactivation of microorganisms occurred essentially within 1 min after application of chlorine. These reductions are significant relative to populations of pathogenic microorganisms that may be present on produce. Spray application of chlorine to raw produce at food service or household levels may be a suitable, and more convenient, alternative to treatment by dipping or submersion.
Historical ecology draws on a broad range of information sources and methods to provide insight into ecological and social change, especially over the past ∼12000 yr. While its results are often ...relevant to conservation and restoration, insights from its diverse disciplines, environments, and geographies have frequently remained siloed or underrepresented, restricting their full potential. Here, scholars and practitioners working in marine, freshwater, and terrestrial environments on 6 continents and various archipelagoes synthesize knowledge from the fields of history, anthropology, paleontology, and ecology with the goal of describing global research priorities for historical ecology to influence conservation. We used a structured decision-making process to identify and address questions in 4 key priority areas: (1) methods and concepts, (2) knowledge co-production and community engagement, (3) policy and management, and (4) climate change impacts. This work highlights the ways that historical ecology has developed and matured in its use of novel information sources, efforts to move beyond extractive research practices and toward knowledge co-production, and application to management challenges including climate change. We demonstrate the ways that this field has brought together researchers across disciplines, connected academics to practitioners, and engaged communities to create and apply knowledge of the past to address the challenges of our shared future.
Raw ground beef patties inoculated with stationary-phase cells of Escherichia coli O157:H7, salmonellae, or Campylobacter jejuni were subjected to gamma irradiation (60Co) treatment, with doses ...ranging from 0 to 2.52 kGy. The influence of two levels of fat (8 to 14% low fat and 27 to 28% high fat) and temperature (frozen -17 to -15 degrees C and refrigerated 3 to 5 degrees C) on the inactivation of each pathogen by irradiation was investigated. In ascending order of irradiation resistance, the D10 values ranged from 0.175 to 0.235 kGy (C. jejuni), from 0.241 to 0.307 kGy (E. coli O157:H7), and from 0.618 to 0.800 kGy (salmonellae). Statistical analysis revealed that E. coli O157:H7 had a significantly (P 0.05) higher D10 value when irradiated at -17 to -15 degrees C than when irradiated at 3 to 5 degrees C. Regardless of the temperature during irradiation, the level of fat did not have a significant effect on the D10 value. Salmonellae behaved like E. coli O157:H7 in low-fat beef, but temperature did not have a significant effect when the pathogen was irradiated in high-fat ground beef. Significantly higher D10 values were calculated for C. jejuni irradiated in frozen than in refrigerated low-fat beef. C. jejuni was more resistant to irradiation in low-fat beef than in high-fat beef when treatment was at -17 to -15 degrees C. Regardless of the fat level and temperature during inactivation, these pathogens were highly sensitive to gamma irradiation. An applied dose of 2.5 kGy would be sufficient to kill 10(8.1) E. coli O157:H7, 10(3.1) salmonellae, and 10(10.6) C. jejuni, resulting in a high probability of complete inactivation of populations much higher than those occasionally present in ground beef patties
Rates of thermal inactivation of five strains of Escherichia coli O157:H7 isolated from ground beef implicated in outbreaks of hemorrhagic colitis and five strains isolated from bovine feces were ...determined. Ground beef (22% fat, 10 g), inoculated with individual test strains at populations ranging from 6.85 to 7.40 log10 CFU g-1 of beef, was formed into patties (0.3 cm thick and 8.0 cm in diameter) and sealed in polyethylene bags. For each strain and treatment temperature (54.4, 58.9, 62.8, 65.6, or 68.3 degrees C), 6 bags were simultaneously immersed into a recirculating water bath. Viable cells in patties heated for various lengths of time were enumerated by plating diluted samples on sorbitol MacConkey agar supplemented with 4-methylumbelliferyl-beta-D-glucuronide (MSMA) and modified eosin methylene blue (MEMB) agar. Regardless of strain or treatment temperature, higher numbers of E. coli O157:H7 cells were generally recovered on MEMB agar than on MSMA, indicating the inferiority of MSMA as a recovery medium for quantitative determination of E. coli O157:H7 cells in heat-processed ground beef. Significantly (P less than or equal to 0.05) higher D values when enumeration was done using MEMB agar compared with MSMA. Mean D values for combined strain data at 54.4, 58.9, 62.8, and 65.6 degrees C from cultures on MEMB agar were 123.90, 6.47, 0.62, and 0.20 min, respectively, whereas D values of 25.5, 5.21, 0.57, and 0.18 min were obtained at the same temperatures from cultures on MSMA. Results suggest that cooking ground beef patties to an internal temperature of 68.3 degrees C for 40 s will inactivate at least 99.99% of E. coli O157:H7 cells; z values of 4.0 and 5.1 degrees C were calculated from mean D values obtained from MEMB agar and MSMA, respectively, as recovery media. Differences in D values and z values existed among strains but rates of thermal inactivation do not appear to be correlated with the sources of the isolates
The presence of psychrotrophic enterotoxigenic Bacillus cereus in ready-to-serve meats and meat products that have not been subjected to sterilization treatment is a public health concern. A study ...was undertaken to determine the survival, growth, and diarrheal enterotoxin production characteristics of four strains of psychrotrophic B. cereus in brain heart infusion (BHI) broth and beef gravy as affected by temperature and supplementation with nisin. A portion of unheated vegetative cells from 24-h BHI broth cultures was sensitive to nisin as evidenced by an inability to form colonies on BHI agar containing 10 micrograms of nisin/ml. Heat-stressed cells exhibited increased sensitivity to nisin. At concentrations as low as 1 microgram/ml, nisin was lethal to B. cereus, the effect being more pronounced in BHI broth than in beef gravy. The inhibitory effect of nisin (1 microgram/ml) was greater on vegetative cells than on spores inoculated into beef gravy and was more pronounced at 8 degrees C than at 15 degrees C. Nisin, at a concentration of 5 or 50 micrograms/ml, inhibited growth in gravy inoculated with vegetative cells and stored at 8 or 15 degrees C, respectively, for 14 days. Growth of vegetative cells and spores of B. cereus after an initial period of inhibition is attributed to loss of activity of nisin. One of two test strains produced diarrheal enterotoxin in gravy stored at 8 or 15 degrees C within 9 or 3 days, respectively. Enterotoxin production was inhibited in gravy supplemented with 1 microgram of nisin/ml and stored at 8 degrees C for 14 days; 5 micrograms of nisin/ml was required for inhibition at 15 degrees C. Enterotoxin was not detected in gravy in which less than 5.85 log10 CFU of B. cereus/ml had grown
The efficacy of tryptic soy agar (TSA), modified sorbitol MacConkey agar (MSMA), modified eosin methylene blue (MEMB) agar, and modified SD-39 (MSD) agar in recovering a five-strain mixture of ...enterohemorrhagic Escherichia coli O157:H7 and five non-O157 strains of E. coli heated in tryptic soy broth at 52, 54, or 56 degrees C for 10, 20, and 30 min was determined. Nonselective TSA supported the highest recovery of heated cells. Significantly (P less than or equal to 0.05) lower recovery of heat-stressed cells was observed on MSMA than on TSA, MEMB agar, or MSD agar. The suitability of MEMB agar or MSD agar for recovery of E. coli O157:H7 from heated or frozen (-20 degrees C) low- or high-fat ground beef was determined. Recovery of E. coli O157:H7 from heated ground beef was significantly (P less than or equal to 0.05) higher on TSA than on MEMB agar, which in turn supported higher recovery than MSD agar did; MSMA was inferior. Recovery from frozen ground beef was also higher on MEMB and MSD agars than on MSMA. Higher populations were generally recovered from high-fat beef than from low-fat beef, but the relative performance of the recovery media was the same. The inability of MSMA to recover stressed cells of E. coli O157:H7 underscores the need to develop a better selective medium for enumerating E. coli O157:H7
Over the last century, psychological discourse ranks among the main cultural forces in Western societies. As such, it undoubtedly exerts considerable influence on how we express, demand, struggle ...for, and conceive of recognition. However, since psychology is far from being a monolithic discipline, said influence is exerted in non-univocal, sometimes contradictory ways. In this paper, I explore this heterogeneous impact by contrasting the idea of recognition underlying two popular psychological schools. On the one hand, psychoanalysis’ emphasis on trauma stresses our dependence on being recognized by others, vindicates the importance of communication, and contributes to redefining the status of victim. On the other hand, positive psychology’s advocacy for autonomous self-fulfillment seems to downsize the importance of recognition, and of the struggle for it, based on a statistical, morally-neutral approach.
Bacteria of the genera Pseudomonas and Bacillus can promote plant growth and protect plants from pathogens. However, the interactions between these plant-beneficial bacteria are understudied. Here, ...we explore the interaction between Bacillus subtilis 3610 and Pseudomonas chlororaphis PCL1606. We show that the extracellular matrix protects B. subtilis colonies from infiltration by P. chlororaphis. The absence of extracellular matrix results in increased fluidity and loss of structure of the B. subtilis colony. The P. chlororaphis type VI secretion system (T6SS) is activated upon contact with B. subtilis cells, and stimulates B. subtilis sporulation. Furthermore, we find that B. subtilis sporulation observed prior to direct contact with P. chlororaphis is mediated by histidine kinases KinA and KinB. Finally, we demonstrate the importance of the extracellular matrix and the T6SS in modulating the coexistence of the two species on melon plant leaves and seeds.
In late 1995, fecal coliforms were detected in iced tea obtained from several restaurants in the U.S. On the basis of fecal coliform results, the news media inaccurately and sensationally accused the ...tea industry of marketing tea containing feces. We analyzed 11 iced-tea samples obtained from fast-food restaurants and 25 dry leaf-tea samples purchased from retail grocers for the presence of coliforms and fecal coliforms. All samples of iced tea contained coliforms and fecal coliforms; most probable numbers of coliforms in iced tea ranged from 210 to 1,100/ml, whereas those of fecal coliforms were 15 to 1,100/ml. Twenty-three of twenty-five leaf-tea samples contained coliforms and fecal coliforms; ranges for positive samples were 3 to 1,100(g and 3 to 460/g), respectively. Two Klebsiella species and three Enterobacter species were isolated from iced tea. Only Klebsiella pneumoniae (93.8% of isolates) and Enterobacter cloacae (62%) were isolated from leaf tea. Escherichia coli was not isolated from any of the iced-tea or leaf-tea samples analyzed. The D55 degrees C values of two isolates of K. pneumoniae and three isolates of E. cloacae from leaf tea, when heated in steeped tea, ranged from 3.75 to 5.08 min. Initial populations of up to 5.70 log CFU/ml were reduced to 10 CFU/ml within 5 min at 65 degrees C. While 23 of 25 (92%) of the leaf-tea samples analyzed contained fecal coliforms, as defined by standard methodology, there is no evidence that leaf tea represents a health hazard. The expected presence in leaf tea of Klebsiella and Enterobacter species, which test positive for the fecal coliform group, should not automatically be construed as indicators of fecal contamination nor as an imminent threat to human health. The presence of coliforms and fecal coliforms in iced tea indicates post-steeping contamination caused by poor sanitation practices in restaurants at which the iced tea was purchased