食品微生物外文文獻(xiàn)201719

1、脈沖強(qiáng)光對諾如病毒和沙門及0157的滅活作用Pulsed light (PL) inactivation of two human norovirus (HuNoV) surrogates, murine norovirus (MNV-1) and Tulane virus (TV), and two bacterial pathogens, Escherichia coli O157:H7 and Salmonella, were evaluated. The viruses and bacteria were suspended in phosphate buffered saline (

2、PBS) to final populations of -6 log PFU/mL and -6 log CFU/mL, respectively. Both viral and bacterial suspensions were then irradiated by PL for different durations and the reductions of each microorganisms were determined. MNV-1 and TV were significantly (P Brucella Bolton broth. Under microaerobic

3、conditions levels in MH = Brucella Bolton broth. Levels of DO in MH and Brucella broth were lower under microaerobic conditions but those of Bolton did not differ under the 2 atm. Experimental conditions and especially the DO of broth media confound previous conclusions drawn about aerobic biofilm f

4、ormation by C. jejuni. 熱-紫外處理對液體食品的滅菌效果優(yōu)化The combination of ultraviolet radiation and heat (UV-H treatment) has been demonstrated as a promising strategy to overcome the limited UV germicidal effect in fruit juices. Nonetheless, there are so far no data regarding the efficacy of the combined process

5、 for the inactivation of bacterial foodborne pathogens in other liquid foods with different pH and composition. In this investigation, the optimum UV-H processing conditions for the inactivation of Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, and S. aureus in chicken and vegetab

6、le broth, in addition to juices, were determined. From these data models that accurately predict the most advantageous UV-H treatment temperature and the expected synergistic lethal effect from UV and heat resistance data separately were constructed. Equations demonstrated that the optimumUV-H treat

7、ment temperature mostly depended on heat resistance, whereas the maximum synergistic lethal effect also was affected by the UV resistance of the microorganism of concern in a particular food.腸炎沙門鞭毛對侵襲的作用Nontyphoidal Salmonella strains are the main source of pathogenic bacterial contamination in the

8、poultry industry. Recently, Salmonella entericaserovar Kentucky has been recognized as the most prominent serovar on carcasses in poultry-processing plants. Previous studies showed that flagella are one of the main factors that contribute to bacterial attachment to broiler skin. However, the precise

9、 role of flagella and the mechanism of attachment are unknown. There are two different flagellar subunits (fliC and fljB) expressed alternatively in Salmonella entericaserovars using phase variation. Here, by making deletions in genes encoding flagellar structural subunits (flgK, fliC, and fljB), an

10、d flagellar motor (motA), we were able to differentiate the role of flagella and their rotary motion in the colonization of broiler skin and cellular attachment. Utilizing a broiler skin assay, we demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the a

11、lternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate tight attachment. Deletion of the flgK gene prevents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S. Kentucky with deletions in all thr

12、ee structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while an fljB mutant was as adherent and invasive as the wild-type strain.IMPORTANCE In this work, we answered clearly the role of flagella in S. Kentucky atta

13、chment to the chicken skin and Caco-2 cells. We demonstrated that the presence of FliC is necessary for attachment to broiler skin. Expression of the alternative flagellar subunit FljB enables Salmonella motility, but this subunit is unable to mediate strong attachment. Deletion of the flgK gene pre

14、vents proper flagellar assembly, making Salmonella significantly less adherent to broiler skin than the wild type. S. Kentucky with deletions in all three structural genes, fliC, fljB, and flgK, as well as a flagellar motor mutant (motA), exhibited less adhesion and invasion of Caco-2 cells, while a

15、n fljB mutant was as adherent and invasive as the wild-type strain. We expect these results will contribute to the understanding of the mechanisms of Salmonella attachment to food products.單增李斯特菌可能是通過胃液和體外細(xì)胞侵染的主要細(xì)菌Various Listeria monocytogenes strains may contaminate a single food product, potentia

16、lly resulting in simultaneous exposure of consumers to multiple strains. However, due to bias in strain recovery, L. monocytogenes strains isolated from foods by selective enrichment (SE) might not always represent those that can better survive the immune system of a patient. We investigated the eff

17、ect of cocultivation in tryptic soy broth with 0.6% yeast extract (TSB-Y) at 10 C for 8 days on (i) the detection of L. monocytogenes strains during SE with the ISO 11290-1:1996/Amd 1:2004 protocol and (ii) the in vitro virulence of strains toward the Caco-2 human colon epithelial cancer cell line f

18、ollowing exposure to simulated gastric fluid (SGF; pH 2.0)-HCl (37 C). We determined whether the strains which were favored by SE would be effective competitors under the conditions of challenges related to gastrointestinal passage of the pathogen. Interstrain competition of L. monocytogenes in TSB-

19、Y determined the relative population of each strain at the beginning of SE. This in turn impacted the outcome of SE (i.e., favoring survival of competitors with better fitness) and the levels exposed subsequently to SGF.However, strong growth competitors could be outcompeted after SGF exposure and i

20、nfection of Caco-2 cells by strains outgrown in TSB-Y and underdetected (or even missed) during enrichment. Our data demonstrate a preferential selection of certain L. monocytogenes strains during enrichments, often not reflecting a selective advantage of strains during infection. These findings hig

21、hlight a noteworthy scenario associated with the difficulty of matching the source of infection (food) with the L. monocytogenes isolate appearing to be the causative agent during listeriosis outbreak investigations.系統(tǒng)模型的建立來描述動物糞便是果蔬感染致病菌的主要途徑The majority of foodborne outbreaks in the United States

22、associated with the consumption of leafy greens contaminated with Escherichia coli O157:H7 have been reported during the period of July to November. A dynamic system model consisting of subsystems and inputs to the system (soil, irrigation, cattle, wild pig, and rainfall) simulating a hypothetical f

23、arm was developed. The model assumed two crops of lettuce in a year and simulated planting, irrigation, harvesting, ground preparation for the new crop, contamination of soil and plants, and survival of E. coli O157:H7. As predicted by the baseline model for crops harvested in different months from

24、conventional fields, an estimated 13 out of 257 (5.05%) first crops harvested in July would have at least one plant with at least 1 CFU of E. coli O157:H7. Predictions indicate that no first crops would be contaminated with at least 1 CFU of E. coli O157:H7 for other months (April to June).The maxim

25、um E. coli O157:H7 concentration in a plant was higher in the second crop (27.10 CFU) than in the first crop (9.82 CFU). For the second crop, the probabilities of having at least one plant with at least 1 CFU of E. coli O157:H7 in a crop were predicted as 15/228 (6.6%), 5/333 (1.5%), 14/324 (4.3%),

26、and 6/115 (5.2%) in August, September, October, and November, respectively. For organic fields, the probabilities of having at least one plant with 1 CFU of E. coli O157:H7 in a crop (3.45%) were predicted to be higher than those for the conventional fields (2.15%).O157迫于環(huán)境壓力的嗜熱和蘇醒加速進(jìn)化The developmen

27、t of resistance in foodborne pathogens to food preservation techniques is an issue of increasing concern, especially in minimally processed foods where safety relies on hurdle technology. In this context, mild heat can be used in combination with so-called nonthermal processes, such as high hydrosta

28、tic pressure (HHP), at lower individual intensities to better retain the quality of the food. However, mild stresses may increase the risk of (cross-)resistance development in the surviving population, which in turn might compromise food safety. In this investigation, we examined the evolution of Es

29、cherichia coli O157:H7 strain ATCC43888 after recurrent exposure to progressively intensifying mild heat shocks (from 54.0 C to 60.0 C in 0.5 C increments) with intermittent resuscitation and growth of survivors. As such, mutant strains were obtained after 10 cycles of selection with ca. 106-fold hi

30、gher heat resistance than that for the parental strain at 58.0 C, although this resistance did not extend to temperatures exceeding 60.0 C. Moreover, these mutant strains typically displayed cross-resistance against HHP shock and displayed signs of enhanced RpoS and RpoH activity. Interestingly, add

31、itional cycles of selection maintaining the intensity of the heat shock constant (58.5 C) selected for mutant strains in which resuscitation speed, rather than resistance, appeared to be increased. Therefore, it seems that resistance and resuscitation speed are rapidly evolvable traits in E. coli AT

32、CC 43888 that can compromise food safety.肉桂油抑制大腸0157噬菌體的入侵和增殖This study evaluated the inhibitory effect of cinnamon oil against Escherichia coli O157:H7 Shiga toxin (Stx) production and further explored the underlying mechanisms. The MIC and minimum bactericidal concentration (MBC) of cinnamon oil a

33、gainst E. coli O157:H7 were 0.025% and 0.05% (vol/vol), respectively. Cinnamon oil significantly reduced Stx2 production and the stx2 mRNA expression that is associated with diminished Vero cell cytotoxicity. Consistently, induction of the Stx-converting phage where the stx2 gene is located, along w

34、ith the total number of phages, decreased proportionally to cinnamon oil concentration. In line with decreased Stx2 phage induction, cinnamon oil at 0.75x and 1.0 x MIC eliminated RecA, a key mediator of SOS response,polynucleotide phosphorylase (PNPase), and poly(A) polymerase (PAP I), which positi

35、vely regulate Stx-converting phages, contributing to reduced Stx-converting phage induction and Stx production. Furthermore, cinnamon oil at 0.75x and 1.0 x MIC strongly inhibited the qseBC andluxS expression associated with decreased AI-2 production, a universal quorum sensing signaling molecule. H

36、owever, the expression of oxidative stress response genes oxyR, soxR, and rpoS was increased in response to cinnamon oil at 0.25 or 0.5 MIC, which may contribute to stunted bacterial growth and reduced Stx2 phage induction and Stx2 production due to the inhibitory effect of OxyR on prophage activati

37、on. Collectively, cinnamon oil inhibits Stx2 production and Stx2 phage induction in E. coli O157:H7 in multiple ways. 長時間接觸導(dǎo)致增加了產(chǎn)氣腸桿菌的食品感染 Bacterial cross-contamination from surfaces to food can contribute to foodborne disease. The cross-contamination rate of Enterobacteraerogenes on household surfaces was evaluated by using scenarios that differed by surface type, food type, contact time (1,5, 30, and 300 s), and inoculum matrix (tryptic soy broth or peptone buffer). The surfaces used were stainless steel,