scholarly journals Modeling the Growth of Listeria monocytogenes in Soft Blue-White Cheese

2012 ◽  
Vol 78 (24) ◽  
pp. 8508-8514 ◽  
Author(s):  
Per Sand Rosshaug ◽  
Ann Detmer ◽  
Hanne Ingmer ◽  
Marianne Halberg Larsen
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Physicochemical Properties ◽  
Predictive Model ◽  
Growth Conditions ◽  
Data Sets ◽  
Growth Data ◽  
Content Type ◽  
White Cheese ◽  
Over Time

ABSTRACTThe aim of this study was to develop a predictive model simulating growth over time of the pathogenic bacteriumListeria monocytogenesin a soft blue-white cheese. The physicochemical properties in a matrix such as cheese are essential controlling factors influencing the growth ofL. monocytogenes. We developed a predictive tertiary model of the bacterial growth ofL. monocytogenesas a function of temperature, pH, NaCl, and lactic acid. We measured the variations over time of the physicochemical properties in the cheese. Our predictive model was developed based on broth data produced in previous studies. New growth data sets were produced to independently calibrate and validate the developed model. A characteristic of this tertiary model is that it handles dynamic growth conditions described in time series of temperature, pH, NaCl, and lactic acid. Supplying the model with realistic production and retail conditions showed that the number ofL. monocytogenescells increases 3 to 3.5 log within the shelf life of the cheese.

scholarly journals Chromosomal Rearrangements in Salmonella enterica Serovar Typhi Strains Isolated from Asymptomatic Human Carriers

mBio ◽  
2011 ◽  
Vol 2 (3) ◽  
Author(s):  
T. David Matthews ◽  
Wolfgang Rabsch ◽  
Stanley Maloy
Keyword(s):  
Salmonella Enterica ◽  
Large Scale ◽  
Chromosomal Rearrangements ◽  
Growth Conditions ◽  
Genetic Changes ◽  
Content Type ◽  
Long Term Storage ◽  
Bacterial Chromosomes ◽  
Over Time

ABSTRACTHost-specific serovars ofSalmonella entericaoften have large-scale chromosomal rearrangements that occur by recombination betweenrrnoperons. Two hypotheses have been proposed to explain these rearrangements: (i) replichore imbalance from horizontal gene transfer drives the rearrangements to restore balance, or (ii) the rearrangements are a consequence of the host-specific lifestyle. Although recent evidence has refuted the replichore balance hypothesis, there has been no direct evidence for the lifestyle hypothesis. To test this hypothesis, we determined therrnarrangement type for 20Salmonella entericaserovar Typhi strains obtained from human carriers at periodic intervals over multiple years. These strains were also phage typed and analyzed for rearrangements that occurred over long-term storage versus routine culturing. Strains isolated from the same carrier at different time points often exhibited different arrangement types. Furthermore, colonies isolated directly from the Dorset egg slants used to store the strains also had different arrangement types. In contrast, colonies that were repeatedly cultured always had the same arrangement type. Estimated replichore balance of isolated strains did not improve over time, and some of the rearrangements resulted in decreased replicore balance. Our results support the hypothesis that the restricted lifestyle of host-specificSalmonellais responsible for the frequent chromosomal rearrangements in these serovars.IMPORTANCEAlthough it was previously thought that bacterial chromosomes were stable, comparative genomics has demonstrated that bacterial chromosomes are dynamic, undergoing rearrangements that change the order and expression of genes. While mostSalmonellastrains have a conserved chromosomal arrangement type, rearrangements are very common in host-specificSalmonellastrains. This study suggests that chromosome rearrangements in the host-specificSalmonella entericaserovar Typhi, the causal agent of typhoid fever, occur within the human host over time. The results also indicate that rearrangements can occur during long-term maintenance on laboratory medium. Although these genetic changes do not limit survival under slow-growth conditions, they may limit the survival ofSalmonellaTyphi in other environments, as predicted for the role of pseudogenes and genome reduction in niche-restricted bacteria.

US academic libraries' staffing and expenditure trends (1996–2016)

2020 ◽  
Vol 41 (4/5) ◽  
pp. 247-268 ◽  
Author(s):  
Starr Hoffman ◽  
Samantha Godbey
Keyword(s):  
Academic Libraries ◽  
The United States ◽  
Data Sets ◽  
Size Category ◽  
Data Set ◽  
Content Type ◽  
Education Statistics ◽  
Trends Over Time ◽  
Doctoral Institutions ◽  
Over Time

PurposeThis paper explores trends over time in library staffing and staffing expenditures among two- and four-year colleges and universities in the United States.Design/methodology/approachResearchers merged and analyzed data from 1996 to 2016 from the National Center for Education Statistics for over 3,500 libraries at postsecondary institutions. This study is primarily descriptive in nature and addresses the research questions: How do staffing trends in academic libraries over this period of time relate to Carnegie classification and institution size? How do trends in library staffing expenditures over this period of time correspond to these same variables?FindingsAcross all institutions, on average, total library staff decreased from 1998 to 2012. Numbers of librarians declined at master’s and doctoral institutions between 1998 and 2016. Numbers of students per librarian increased over time in each Carnegie and size category. Average inflation-adjusted staffing expenditures have remained steady for master's, baccalaureate and associate's institutions. Salaries as a percent of library budget decreased only among doctoral institutions and institutions with 20,000 or more students.Originality/valueThis is a valuable study of trends over time, which has been difficult without downloading and merging separate data sets from multiple government sources. As a result, few studies have taken such an approach to this data. Consequently, institutions and libraries are making decisions about resource allocation based on only a fraction of the available data. Academic libraries can use this study and the resulting data set to benchmark key staffing characteristics.

Positive crossover loyalty shifts or negative temporal changes? The evolution of shopping mechanism in the O2O era

2020 ◽  
Vol 54 (6) ◽  
pp. 1383-1405
Author(s):  
Hong-Youl Ha ◽  
Philip J. Kitchen
Keyword(s):  
Service Quality ◽  
Positive Impact ◽  
Data Sets ◽  
Crossover Effect ◽  
Provider Satisfaction ◽  
Content Type ◽  
Crossover Effects ◽  
Research Findings ◽  
Practical Implications ◽  
Over Time

Purpose This paper aims to examine how customers encounter consumption-based evolution between mobile and offline platforms together with temporal and crossover effects. Counter to research on customer satisfaction theory, which shows that satisfaction directly affects loyalty, the authors show that when shopping between mobile and offline platforms, customers differently evaluate loyalty compared to the traditional satisfaction and loyalty approach. Also, customers differently evaluate three types of service quality from online to offline (O2O) platforms and response dynamically to firm satisfaction and loyalty. Design/methodology/approach This study tests temporal, carryover and crossover effects using longitudinal data sets. Findings From crossover loyalty shifts, the findings show that the relationship between offline provider satisfaction (OS) and mobile provider loyalty (ML) during consumption periods is consistently significant with similar impact. However, mobile provider satisfaction (MS) during the same periods does not impact offline provider loyalty (OL) in the same manner, but differs considerably in terms of pattern of influence. Specifically, the findings show that this crossover effect increases over time even though statistical impact is insignificant. Thus, the carryover loyalty shift has a positive impact when it originally occurs in the offline platform but differs significantly when it originates via the mobile platform. Practical implications – this study offers valuable guidance to managers on how O2O platform-centric firms try to enhance satisfaction with consumption system that links to three types of service quality and loyalty. Research limitations/implications This study offers valuable insights into offline and ML. This is seen, however, as an experimental study and further research using the same method would enable cross-cultural comparators. Practical implications Insights can be drawn from the findings, enabling comparisons relative to service quality-satisfaction-loyalty linkage across dual platforms. The idea of evolution and progression over time is particular pertinent to business practice assuming data sets are gathered, maintained and analyzed. Originality/value Insights can be used from the research findings, including but not limited to comparing the service quality-satisfaction-loyalty linkage across dual platforms and providing firms with an explanation of temporal evolution.

scholarly journals Listeria monocytogenes inhibition by lactic acid bacteria and coliforms in Brazilian fresh white cheese

2021 ◽  
Author(s):  
Lina Casale Aragon-Alegro ◽  
Emília Maria França Lima ◽  
Gabriela Palcich ◽  
Tatiana Pacheco Nunes ◽  
Kátia Leani Oliveira de Souza ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
White Cheese

scholarly journals Stability of the Virome in Lab- and Field-Collected Aedes albopictus Mosquitoes across Different Developmental Stages and Possible Core Viruses in the Publicly Available Virome Data of Aedes Mosquitoes

mSystems ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Chenyan Shi ◽  
Lu Zhao ◽  
Evans Atoni ◽  
Weifeng Zeng ◽  
Xiaomin Hu ◽  
...  
Keyword(s):  
Aedes Albopictus ◽  
Developmental Stages ◽  
Metagenomic Data ◽  
Data Sets ◽  
Transmission Route ◽  
Content Type ◽  
The Core ◽  
Aedes Mosquitoes ◽  
Arbovirus Infection ◽  
Over Time

Our study revealed that the virome was very stable across all developmental stages of both lab-derived and field-collected Aedes albopictus. The data representing the core virome in lab A. albopictus proved the vertical transmission route of these viruses, forming a “vertically transmitted core virome.” Field mosquitoes also contained this stable vertically transmitted core virome as well as additional viruses, which probably represented “environment-derived core virome” and which therefore were less stable over time and geography. By further screening publicly available SRA viral metagenomic data sets from mosquitoes belonging to the genus Aedes, some of the identified core ISVs were shown to be present in the majority of SRAs, such as Phasi Charoen-like phasivirus and Guadeloupe mosquito virus. How these core ISVs influence the biology of the mosquito host and arbovirus infection and evolution deserves to be further explored.

scholarly journals Establishing Equivalence for Microbial-Growth-Inhibitory Effects (“Iso-Hurdle Rules”) by Analyzing Disparate Listeria monocytogenes Data with a Gamma-Type Predictive Model

2011 ◽  
Vol 78 (4) ◽  
pp. 1069-1080 ◽  
Author(s):  
Laure Pujol ◽  
Denis Kan-King-Yu ◽  
Yvan Le Marc ◽  
Moira D. Johnston ◽  
Florence Rama-Heuzard ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Predictive Model ◽  
Growth Rates ◽  
Sorbic Acid ◽  
Inhibitory Effect ◽  
Control Measures ◽  
Type Model ◽  
Data Generation ◽  
Inhibitory Effects ◽  
Content Type

ABSTRACTPreservative factors act as hurdles against microorganisms by inhibiting their growth; these are essential control measures for particular food-borne pathogens. Different combinations of hurdles can be quantified and compared to each other in terms of their inhibitory effect (“iso-hurdle”). We present here a methodology for establishing microbial iso-hurdle rules in three steps: (i) developing a predictive model based on existing but disparate data sets, (ii) building an experimental design focused on the iso-hurdles using the model output, and (iii) validating the model and the iso-hurdle rules with new data. The methodology is illustrated withListeria monocytogenes. Existing data from industry, a public database, and the literature were collected and analyzed, after which a total of 650 growth rates were retained. A gamma-type model was developed for the factors temperature, pH, aw, and acetic, lactic, and sorbic acids. Three iso-hurdle rules were assessed (40 logcount curves generated): salt replacement by addition of organic acids, sorbic acid replacement by addition of acetic and lactic acid, and sorbic acid replacement by addition of lactic/acetic acid and salt. For the three rules, the growth rates were equivalent in the whole experimental domain (γ from 0.1 to 0.5). The lag times were also equivalent in the case of mild inhibitory conditions (γ ≥ 0.2), while they were longer in the presence of salt than acids under stress conditions (γ < 0.2). This methodology allows an assessment of the equivalence of inhibitory effects without intensive data generation; it could be applied to develop milder formulations which guarantee microbial safety and stability.

scholarly journals Genome Sequence and Transcriptome Analysis of Meat-Spoilage-Associated Lactic Acid Bacterium Lactococcus piscium MKFS47

2015 ◽  
Vol 81 (11) ◽  
pp. 3800-3811 ◽  
Author(s):  
Margarita Andreevskaya ◽  
Per Johansson ◽  
Pia Laine ◽  
Olli-Pekka Smolander ◽  
Matti Sonck ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacterium ◽  
Time Course ◽  
Genomic Sequence ◽  
Meat Products ◽  
Growth Conditions ◽  
Content Type ◽  
Meat Spoilage ◽  
Wide Range ◽  
Odor Compounds

ABSTRACTLactococcus pisciumis a psychrotrophic lactic acid bacterium and is known to be one of the predominant species within spoilage microbial communities in cold-stored packaged foods, particularly in meat products. Its presence in such products has been associated with the formation of buttery and sour off-odors. Nevertheless, the spoilage potential ofL. pisciumvaries dramatically depending on the strain and growth conditions. Additional knowledge about the genome is required to explain such variation, understand its phylogeny, and study gene functions. Here, we present the complete and annotated genomic sequence ofL. pisciumMKFS47, combined with a time course analysis of the glucose catabolism-based transcriptome. In addition, a comparative analysis of gene contents was done forL. pisciumMKFS47 and 29 other lactococci, revealing three distinct clades within the genus. The genome ofL. pisciumMKFS47 consists of one chromosome, carrying 2,289 genes, and two plasmids. A wide range of carbohydrates was predicted to be fermented, and growth on glycerol was observed. Both carbohydrate and glycerol catabolic pathways were significantly upregulated in the course of time as a result of glucose exhaustion. At the same time, differential expression of the pyruvate utilization pathways, implicated in the formation of spoilage substances, switched the metabolism toward a heterofermentative mode. In agreement with data from previous inoculation studies,L. pisciumMKFS47 was identified as an efficient producer of buttery-odor compounds under aerobic conditions. Finally, genes and pathways that may contribute to increased survival in meat environments were considered.

Effect of Curing Method and Freeze-Thawing on Subsequent Growth of Listeria monocytogenes on Cold-Smoked Salmon

2012 ◽  
Vol 75 (9) ◽  
pp. 1619-1626 ◽  
Author(s):  
JIHUN KANG ◽  
SILIN TANG ◽  
RUI HAI LIU ◽  
MARTIN WIEDMANN ◽  
KATHRYN J. BOOR ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Lactic Acid Bacteria ◽  
Physicochemical Properties ◽  
Effective Control ◽  
Subsequent Growth ◽  
Smoked Salmon ◽  
Curing Method ◽  
Unbiased Risk ◽  
The Impact

The presence of the foodborne pathogen Listeria monocytogenes on cold-smoked salmon is a major concern for the seafood industry. Understanding processing and postprocessing handling factors that affect the ability of this pathogen to grow on cold-smoked salmon is critical for developing effective control strategies. In this study, we investigated the effect of curing method and freeze-thawing of cold-smoked salmon on (i) physicochemical properties and (ii) subsequent growth of genetically diverse strains of L. monocytogenes (inoculated after freeze-thawing) and endogenous lactic acid bacteria. The majority of the measured physicochemical properties were unaffected by freezing and thawing. Overall, wet-cured cold-smoked salmon had higher pH, water activity, and moisture, as well as lower fat, water-phase salt, and phenolic content compared with dry-cured cold-smoked salmon. The curing method and freeze-thawing did not affect growth of endogenous lactic acid bacteria. Freeze-thawing cold-smoked salmon prior to inoculation led to pronounced growth of L. monocytogenes at 7°C. The increase in cell density between days 0 and 30 was significantly (P = 0.0078) greater for cold-smoked salmon that was frozen and thawed prior to inoculation compared with nonfrozen cold-smoked salmon. On dry-cured, freeze-thawed cold-smoked salmon, L. monocytogenes had a lag phase ranging from 3.7 ± 0.1 to 11.2 ± 1.4 days compared with salmon that was wet cured and freeze-thawed, on which L. monocytogenes began to grow within 24 h. Variation in growth among L. monocytogenes strains was also observed, indicating the significance of assessing multiple strains. Further efforts to understand the impact of processing and postprocessing handling steps of cold-smoked salmon on the growth of genetically diverse L. monocytogenes will contribute to improved challenge study designs and data. This, in turn, will likely lead to more reliable and unbiased risk assessments and control measures.

scholarly journals Genomic Differences between Listeria monocytogenes EGDe Isolates Reveal Crucial Roles for SigB and Wall Rhamnosylation in Biofilm Formation

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Chih-Yu Hsu ◽  
Lynne Cairns ◽  
Laura Hobley ◽  
James Abbott ◽  
Conor O’Byrne ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Biofilm Formation ◽  
Teichoic Acid ◽  
Growth Conditions ◽  
Nucleotide Polymorphisms ◽  
Wall Teichoic Acid ◽  
Content Type ◽  
Upstream Regulator ◽  
Fundamental Information ◽  
New Treatments

ABSTRACT Listeria monocytogenes is a Gram-positive firmicute that causes foodborne infections, in part due to its ability to use multiple strategies, including biofilm formation, to survive adverse growth conditions. As a potential way to screen for genes required for biofilm formation, we harnessed the ability of bacteria to accumulate mutations in the genome over time, diverging the properties of seemingly identical strains. By sequencing the genomes of four laboratory reference strains of the commonly used L. monocytogenes EGDe, we showed that each isolate contains single nucleotide polymorphisms (SNPs) compared with the reference genome. We discovered that two SNPs, contained in two independent genes within one of the isolates, impacted biofilm formation. Using bacterial genetics and phenotypic assays, we confirmed that rsbU and rmlA influence biofilm formation. RsbU is the upstream regulator of the alternative sigma factor SigB, and mutation of either rsbU or sigB increased biofilm formation. In contrast, deletion of rmlA, which encodes the first enzyme for TDP-l-rhamnose biosynthesis, resulted in a reduction in the amount of biofilm formed. Further analysis of biofilm formation in a strain that still produces TDP-l-rhamnose but which cannot decorate the wall teichoic acid with rhamnose (rmlT mutant) showed that it is the decorated wall teichoic acid that is required for adhesion of the cells to surfaces. Together, these data uncover novel routes by which biofilm formation by L. monocytogenes can be impacted. IMPORTANCE Biofilms are an important mode of growth in many settings. Here, we looked at small differences in the genomes of the bacterium Listeria monocytogenes isolate EGDe and used them to find out how biofilms form. This important fundamental information may help new treatments to be developed and also highlights the fact that isolates of the same identity often diverge.

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