38 research outputs found
Controlling the Density of Plasma Species in Ar/CF4 Radiofrequency Capacitively Coupled Plasma Discharges
In this manuscript, a fluid model is utilized to calculate the density of
plasma species assuming geometrically symmetric Ar/CF4 Radiofrequency
Capacitively Coupled Plasmas. The electrodes are driven by a sinusoidal
waefront with an amplitude of 200 V and a frequency of 13.56 MHz. The gap
between the electrodes is 5cm. The plasma species density is calculated as a
function of the gas pressure, electron temperature, and the gas composition. In
a good agreement with recent experimental results, and F are dominant
for all considered simulation parameters. The results explain the pathways to
perform atomic layer etching and nanolayer deposition processes. In order to
reveal the effect of electron heating on the discharge dynamics, The
spatiotemporal electron energy equation is coupled to the fluid model.
Tailoring the driven potential has been found to control the concentration of
some plasma species. When the plasma is driven with the fundamental frequency,
Ohmic and stochastic heating allows electrons to be heated symmetrically.
Higher harmonics give rise to an electrical asymmetry and electron heating
asymmetry between the powered and grounded sheaths. The electron temperature
depends on the driven harmonics; it adjusts gain and loss rates and some plasma
species densities
Molecular profiling and antimicrobial resistance of Shiga toxin-producing Escherichia coli O26, O45, O103, O121, O145 and O157 isolates from cattle on cow-calf operations in South Africa
In this study, 140 cattle STEC isolates belonging to serogroups O157, O26, O145, O121, O103 and O45
were characterized for 38 virulence-associated genes, antimicrobial resistance profiles and genotyped
by PFGE. The majority of isolates carried both stx1 and stx2 concurrently, stx2c, and stx2d; plasmidencoded
genes ehxA, espP, subA and saa but lacked katP and etpD and eaeA. Possession of eaeA was
significantly associated with the presence of nle genes, katP, etpD, ureC and terC. However, saa and
subA, stx1c and stx1d were only detected in eaeA negative isolates. A complete OI-122 and most non-
LEE effector genes were detected in only two eaeA positive serotypes, including STEC O157:H7 and
O103:H2. The eaeA gene was detected in STEC serotypes that are commonly implicated in severe
humans disease and outbreaks including STEC O157:H7, STEC O145:H28 and O103:H2. PFGE revealed
that the isolates were highly diverse with very low rates of antimicrobial resistance. In conclusion, only
a small number of cattle STEC serotypes that possessed eaeA, had the highest number of virulenceassociated
genes, indicative of their high virulence. Further characterization of STEC O157:H7, STEC
O145:H28 and O103:H2 using whole genome sequencing will be needed to fully understand their
virulence potential for humans.This manuscript is part a
dissertation submitted in the Veterinary Public Health section, Department of Paraclinical Sciences, University
of Pretoria, in partial fulfilment of the requirements for the degree of Master of Science (Veterinary Science). (http://hdl.handle.net/2263/65499)The Gauteng Department of Agriculture and Rural Development (GDARD) (Grant
No. FY 2013/14âA0W907), the Global Disease Detection (GDD) Program of the Centers for Disease Control
and Prevention (CDC) (Grant No. 1U2GGH001874â01) and the National Research Foundation (NRF) of South
Africa Thuthuka (TTK13062619943), Research Technology (RTF14012762427) Funds.https://www.nature.com/srepam2019Paraclinical Science
Two screening assays to detect vancomycin-resistant Enterococcus spp.
Enterococci have become major nosocomial pathogens. An increasing number of these
infections are as a result of vancomycin-resistant enterococci. Accurate detection of vancomycinresistant
enterococci (VRE) is important, so that appropriate therapy and infection control measures
may be instituted, including veterinary surveillance. Two screening assays to detect vancomycin
resistance in enterococci are proposed. Barnes Basal Medium agar (Ba) and Brain Heart Infusion (BHI)
broth (plus 1% TTC-2,3,5-triphenyltetrazolium chloride) with several concentrations of vancomycin
were used in this work. Five Enterococcus casseliflavus strains with low-level resistance to vancomycin
(4 g/mL) were used. Both media were able to quickly detect the breakpoint of the vancomycinresistant
strains used in this work, and also provided insight into the dynamics of the antibiotic effect
at a low concentration on the tested bacterial suspensions.European Food Safety Authority (EFSA).https://www.mdpi.com/journal/microbiolresam2023Paraclinical Science
Evolution and antimicrobial resistance of enterococci isolated from Pecorino and goat cheese manufactured on-farm in an area facing constraints as per EU Regulation 1305/2013 in Umbria, Italy
The latest EU regulation on geographical indications (EU Regulation No. 1151/2012) has introduced a set of new tools for the protection and enhancement of food products in rural areas, under the group name of optional quality term (OQT). The Commission Delegated EU Regulation, No. 665/2014, regulated the conditions for the use of the optional quality term mountain product (MP), to support the implementation of a mountain value chain. This new tool is aimed at promoting local development, maintaining the economic activities in mountain areas, and redistributing wealth, whilst, at the same time, promoting the territory. Pecorino and goat cheeses are typical Italian cheeses made usually with whole raw eweâs or raw goatâs milk, without starter culture addition. In an attempt to characterize these productions, the aim of this study was to investigate the evolution of enterococci during the production and ripening of Pecorino cheese made in three different farms, located in Umbria, Italy in areas facing natural or other specific constraints as stipulated by Regulation 1305/2013 on support for rural development by the European Agricultural Fund for Rural Development (EAFRD). Enterococci are enteric organisms which are commonly isolated from ewe and goatâs milk production in Umbria, Italy. Counts of enterococci in raw milk ranged from 1.75 for ovine milk to 3.62 for ewe milk and a marked reduction was observed after thermization especially in ovine milk. Out of 100 isolates, 69 were E. faecium, 23 E. durans, 8 E. faecalis and 2 E. casseliflavus and the distribution of species between farms and between samples showed a prevalence of E. faecium in ovine farms and E. durans in ewes farms, with an equal distribution between samples. High percentages of susceptible isolates were found for amoxicillin/clavulanic acid, ampicillin, chloramphenicol, sulphamethoxazole, sulphamethoxazole/trimethoprim, ticarcillin, vancomycin. A high prevalence of resistant strains (>30%) was observed for amikacin, ciprofloxacin, ceftriaxone, kanamycin, tetracycline. A comparison of this results with those of previous works on similar dairy products revealed high levels of resistance to antimicrobials which needs to be addressed.European Food Safety Authority (EFSA).https://www.pagepressjournals.org/index.php/ijfsam2023Paraclinical Science
A study on the application of natural extracts as alternatives to sodium nitrite in processed meat
Hygienic characteristics and detection of antibiotic resistance genes in crickets (Acheta domesticus) breed for flour production
During the last ten years, the worldwide interest in using insects as food and feed has
surged. Edible insects fall within the category of novel foods, i.e., the category of food not consumed
in significant amounts in the European Union before 15 May 1997 (the date of entry into force of
Regulation (EC) No. 258/1997, later repealed by Regulation (EU) No. 2283/2015). One of the most
promising insect species to be raised for food is the house cricket (Acheta domesticus). In this study,
the rearing of a stock of house crickets was studied over a period of four months. The microbiological
quality of the farm was studied using swabs on the surface of the rearing boxes to analyze the
trend over time of different populations of microorganisms (total aerobic mesophilic microbiota,
Lactobacillus spp., enterococci, Staphylococcus spp., Enterobacteriaceae, total coliforms, Pseudomonas
spp. and molds). The presence of four antimicrobial resistance genes (aph, blaZ, sul1, and tetM) was
investigated by polymerase chain reaction. A production scheme was also developed in order to
obtain a cricket-based flour, which was analyzed for its microbiological and chemical-centesimal
profile. The results obtained in this study demonstrate that the contamination increases with time
and that a proper management of the farming system for insects is of the utmost importance, as it is
for conventional farm animals such as ungulates, poultry, and rabbits. The old-fashioned adage âall
full, all emptyâ for the farming system summarizes the need for proper cleaning and disinfection of
the structures at the end of each production cycle.European Food Safety Authority (EFSA)https://www.mdpi.com/journal/microbiolresam2022Paraclinical Science
Virulence characteristics and antimicrobial resistance profiles of Shiga toxin-producing escherichia coli isolates from humans in South Africa : 2006â2013
Shiga toxin-producing Escherichia coli (STEC) isolates (N = 38) that were incriminated in
human disease from 2006 to 2013 in South Africa were characterized by serotype, virulence-associated
genes, antimicrobial resistance and pulsed-field gel electrophoresis (PFGE). The isolates belonged
to 11 O:H serotypes. STEC O26:H11 (24%) was the most frequent serotype associated with human
disease, followed by O111:H8 (16%), O157:H7 (13%) and O117:H7 (13%). The majority of isolates were
positive for key virulence-associated genes including stx1 (84%), eaeA (61%), ehxA (68.4%) and espP
(55%), but lacked stx2 (29%), katP (42%), etpD (16%), saa (16%) and subA (3%). stx2 positive isolates
carried stx2c (26%) and/or stx2d (26%) subtypes. All pathogenicity island encoded virulence marker
genes were detected in all (100%) isolates except nleA (47%), nleC (84%) and nleD (76%). Multidrug
resistance was observed in 89% of isolates. PFGE revealed 34 profiles with eight distinct clusters that
shared 80% intra-serotype similarity, regardless of the year of isolation. In conclusion, STEC isolates
that were implicated in human disease between 2006 and 2013 in South Africa were mainly non-O157
strains which possessed virulence genes and markers commonly associated with STEC strains that
have been incriminated in mild to severe human disease worldwide. Improved STEC monitoring and
surveillance programs are needed in South Africa to control and prevent STEC disease in humans.The National Research Foundation (NRF) of South Africa: Thuthuka (TTK13062619943),
Research Technology Fund (RTF14012762427), the Gauteng Department of Agriculture and Rural Development
(GDARD Grants-2013-2015) and the South African Medical Research Council (Self-Initiated Research 2017-2019).https://www.mdpi.com/journal/toxinsam2019Paraclinical Science
Effect of packaging and storage conditions on some quality traits of bovine meat
Packaging is considered one of the most
interesting technological aspects of food
production and is a constantly evolving subject
in food production. The type of packaging
is important for the quality and safety of
the product and for the visual appearance of
the product to be immediately evaluated by
consumers. The purpose of this study was to
investigate the effect of four different types
of modified atmosphere packaging (ATM)
and vacuum packaging (VP) currently used
by a company in central Italy, on the main
qualitative characteristics of beef. For these
two traditional and two new solutions with
reduced environmental impact and compostable
were evaluated. For each type of
packaging, two different products were analyzed:
steaks and hamburgers. The samples,
immediately after production, were transported
to the laboratory in refrigerated containers.
Several parameters (color, pH, water
holding capacity, drip loss, and microbiological
characteristics) were evaluated at time 0
and after 7 (T7), 14 (T14) and 21 days (T21) of storage in the dark and at refrigeration
temperature (+4°C ± 2°C). The results
showed that the two types of packaging have
very similar effects on the water-retaining
capacity of the steaks. More noticeable differences
were recorded by the colorimetric
analysis: for both steaks and hamburgers,
the products packaged in the traditional
packaging appeared brighter and redder than
those packaged in the new alternatives. The
microbiological analysis of the steaks
showed higher values in the ânewâ packaging.
The formation of abundant ropy slime
was observed in one of the samples in the
ânewâ modified atmosphere package at T21.
The results of this study showed that the
technological characteristics (in particular,
the color) and the microbiological characteristics
of the steaks and hamburgers were better
in âoldâ packaging, with a better appearance
and a longer shelf life. The results
obtained show how the research for eco-sustainable
products for packaging must be
addressed, taking into account the effect of
the materials on the qualitative and hygienic-
sanitary characteristics of the meat.https://www.pagepressjournals.org/index.php/ijfsam2023Paraclinical Science
Neurocysticercosis: An Overview of Pathology and Pathogenesis
Neurocysticercosis (NCC), a subtle parasite infection of the central nervous system, is a powerful example of the complex interaction between human behavior, zoonotic transmission, and neurological illness development. Given the diseaseâs worldwide prevalence and potentially fatal neurological consequences, research into NCC is critical for advancing knowledge, creating effective diagnostic tools and treatment options, and adopting preventative measures to lessen the diseaseâs impact. Cysticerci causes an immunological response in the CNS, resulting in inflammation and immune cell recruitment. The existence of intraventricular cysts, cysts in the cerebral aqueduct or fourth ventricle, and the degree of inflammation and scarring induced by the infection are all risk factors for the development of hydrocephalus. This book chapter provides an in-depth exploration of the pathology and pathogenesis of NCC, discussing the life cycle of the Taenia solium parasite, its invasion of the central nervous system, and the formation of cysticerci, as well as the diagnostic challenges and imaging findings, clinical manifestations, and potential neurological complications associated with NCC, serving as a valuable resource for medical professionals, researchers, and policymakers
A rapid and simple single-step method for the purification of Toxoplasma gondii tachyzoites and bradyzoites
This study describes a simple method for the large-scale isolation of pure Toxoplasma
gondii tachyzoites and bradyzoites. T. gondii tachyzoites were obtained from infected
human foreskin fibroblasts (HFFs) and peritoneal exudates of mice, while tissue cysts
containing bradyzoites were collected from chronically infected mice. Harvested cells
and brain tissues were incubated in Hanks balanced salt solution (HBSS), containing
0.25% trypsin and 0.5% taurodeoxycholic acid (TDC) for 5 min. Subsequent washes
in phosphate buffered saline (PBS) were conducted, and the cell viability of the preparations
was good, as determined by flow cytometry and ability to reinfect HFF cells
and propagate in mice. The purification procedure allowed for a rapid preparation of pure T. gondii tachyzoites and bradyzoites in sufficient quantity that can be used for
downstream procedures. The advantage of the new method is that it is convenient
and inexpensive.The National Natural Science Foundation of China (No. 31502071), Youth Innovative Talents Project of Guangdong province Education Department (No. 2017KQNCX212), Guangdong province (2017GDK07), Start-up Research Grant Program provided by Foshan University, Foshan city, Guangdong province for distinguished researchers, Guangdong Science and Technology Plan Project (Grant No: 1244060045607389XC), and School of Life Science and Engineering fund (Grant No: KLPREAD201801-02).http://www.wileyonlinelibrary.com/journal/vms3am2021Paraclinical Science