bluuebunny/crossref_metadata_2025_split huggingface dataset:
Built-Up-Edge Formation in Micromilling
Authors: Kovvuri V. , Wang Z. , Araujo A. , da Silva M. B. , Bukkapatnam S. , Hung W. N. P. 
Published: March 2016

This paper presents experimental study on conditions for built-up-edge (BUE) formation and its effects in micromilling. Surface finish and BUE area density on a micromilled surface are used to quantify the presence of BUE. A model for surface finish is derived based on the topography of milled surface and tool geometry. Assuming no BUE formation, this empirical model shows the dependence of surface finish on chip load, tool concavity angle, and includes the effect of cutting parameters and milling modes (up-milling or down-milling). Micromilling tools of 100–400 μm diameters are used for milling stainless steel at 10–60 m/min cutting speed, 0.05–1 μm/flute chip load, in minimum quality lubrication condition (MQL). A BUE, embedded onto either a milled surface or tool cutting edge or chip, is identified by scanning electron microscopy and energy dispersive spectroscopy techniques; the severity of BUE formation is quantified as area density when observing a machined surface at high magnification with optical microscopy or interferometry.
Condition for BUE formation is presented by mapping the surface finish and BUE area density against cutting speed and chip load. A microtool would fracture catastrophically at high cutting speeds and/or high chip loads due to excessive dynamic stresses on a microtool; such tool would also fail at the other extreme when low cutting speeds and chip loads promote formation and detachment of BUE on the tool surface, therefore, chipping the fragile microcutting edges of a microtool. There is an optimal zone for effective micromilling without tool failure and BUEs. The measured surface finish approaches the theoretical value when BUE is absent, i.e. micromilling in minimum quantity lubrication at cutting speed between 40–60 m/min and chip load higher than 0.15μm/tooth. The BUE area density for up-milling is lower than that for down-milling at low cutting speed; such difference gradually diminishes when selecting milling parameters in the optimal zone where BUE is practically absent.
A New Strategy of Cavity Cutting Trajectory Generation in High Speed Machining
Authors: Yin Yue , Guo LianShui , Han Ning , Zheng Ji , Zhang Pengpeng 
Published: March 2016

High speed machining is widely used in manufacturing. For its high cutting speed, high feeding rate, and high machining accuracy, its requirements for cutting trajectory in high speed machining are so strict that only continuous and smooth trajectories with even cutting loads can lead to high machining efficiency and accuracy. The traditional row or ring machining trajectory fails to meet these requirements. In order to acquire the continuous and smooth machining trajectories, and to avoid load mutation in the machining process, some researchers developed a curvilinear cutting trajectory generating method based on partial differential equation. This trajectory, however, is still made up from free form curve segment, and unable to completely eliminate the effects on smoothness by line segment interpolation, which has a very adverse effect on the efficiency, tool life and machining accuracy.
A new strategy to generate a continuous and smooth cavity cutting trajectories in high speed machining is introduced in this article. The new trajectory determines the necessity-nodes from outside (the boundary) to inside in the way of spiral cutting. It starts from the cavity center with spiral expanding, and each cutting loop adopts end connection between straight line and the tangent arc, meeting continuous first-order constraint satisfaction. The smooth trajectory reduces the amplitude and directing mutation of cutting force, thus effectively avoids the impact on the machining efficiency and machining accuracy by speeding down in the corner. The strategy also, by controlling the row space, ensures that there is no cutting residual.
A cavity machining programming system based on this strategy is developed on Siemens UG-CAM module. The manufacturing of triangle cavities is studied as a case. It turns out that the new trajectory improves efficiency by 26.23% compared with the traditional one. It ensures a stable operation of the cutting tool in machining, therefore effectively extends the tool life. The main advantages are that the new strategy adopts the geometrical drawing strategy and the trajectories are all made up from the straight lines and the tangent arcs. The trajectory can greatly reduce NC code. It thoroughly removes the effort to mind the smooth, continuity and even cutting load of the tool-path.
Intraspecies Transfer of the Chromosomal Acinetobacter baumannii
bla
NDM-1
Carbapenemase Gene
Authors: Krahn Thomas , Wibberg Daniel , Maus Irena , Winkler Anika , Bontron Séverine , Sczyrba Alexander , Nordmann Patrice , Pühler Alfred , Poirel Laurent , Schlüter Andreas 
Published: March 2016

ABSTRACT

The species
Acinetobacter baumannii
is one of the most important multidrug-resistant human pathogens. To determine its virulence and antibiotic resistance determinants, the genome of the nosocomial
bla
NDM-1
-positive
A. baumannii
strain R2090 originating from Egypt was completely sequenced. Genome analysis revealed that strain R2090 is highly related to the community-acquired Australian
A. baumannii
strain D1279779. The two strains belong to sequence type 267 (ST267). Isolate R2090 harbored the chromosomally integrated transposon Tn
125
carrying the carbapenemase gene
bla
NDM-1
that is not present in the D1279779 genome. To test the transferability of the metallo-β-lactamase (MBL) gene region, the clinical isolate R2090 was mated with the susceptible
A. baumannii
recipient CIP 70.10, and the carbapenem-resistant derivative R2091 was obtained. Genome sequencing of the R2091 derivative revealed that it had received an approximately 66-kb region comprising the transposon Tn
125
embedding the
bla
NDM-1
gene. This region had integrated into the chromosome of the recipient strain CIP 70.10. From the four known mechanisms for horizontal gene transfer (conjugation, outer membrane vesicle-mediated transfer, transformation, and transduction), conjugation could be ruled out, since strain R2090 lacks any plasmid, and a type IV secretion system is not encoded in its chromosome. However, strain R2090 possesses three putative prophages, two of which were predicted to be complete and therefore functional. Accordingly, it was supposed that the transfer of the resistance gene region from the clinical isolate R2090 to the recipient occurred by general transduction facilitated by one of the prophages present in the R2090 genome. Hence, phage-mediated transduction has to be taken into account for the dissemination of antibiotic resistance genes within the species
A. baumannii
.
Ureolytic Biomineralization Reduces Proteus mirabilis Biofilm Susceptibility to Ciprofloxacin
Authors: Li Xiaobao , Lu Nanxi , Brady Hannah R. , Packman Aaron I. 
Published: March 2016

ABSTRACT

Ureolytic biomineralization induced by urease-producing bacteria, particularly
Proteus mirabilis
, is responsible for the formation of urinary tract calculi and the encrustation of indwelling urinary catheters. Such microbial biofilms are challenging to eradicate and contribute to the persistence of catheter-associated urinary tract infections, but the mechanisms responsible for this recalcitrance remain obscure. In this study, we characterized the susceptibility of wild-type (ure+) and urease-negative (ure−)
P. mirabilis
biofilms to killing by ciprofloxacin. Ure+ biofilms produced fine biomineral precipitates that were homogeneously distributed within the biofilm biomass in artificial urine, while ure− biofilms did not produce biomineral deposits under identical growth conditions. Following exposure to ciprofloxacin, ure+ biofilms showed greater survival (less killing) than ure− biofilms, indicating that biomineralization protected biofilm-resident cells against the antimicrobial. To evaluate the mechanism responsible for this recalcitrance, we observed and quantified the transport of Cy5-conjugated ciprofloxacin into the biofilm by video confocal microscopy. These observations revealed that the reduced susceptibility of ure+ biofilms resulted from hindered delivery of ciprofloxacin into biomineralized regions of the biofilm. Further, biomineralization enhanced retention of viable cells on the surface following antimicrobial exposure. These findings together show that ureolytic biomineralization induced by
P. mirabilis
metabolism strongly regulates antimicrobial susceptibility by reducing internal solute transport and increasing biofilm stability.
Acquisition of Broad-Spectrum Cephalosporin Resistance Leading to Colistin Resistance in Klebsiella pneumoniae
Authors: Jayol Aurélie , Nordmann Patrice , Desroches Marine , Decousser Jean-Winoc , Poirel Laurent 
Published: March 2016

ABSTRACT

An extended-spectrum β-lactamase (ESBL)-producing and colistin-resistant
Klebsiella pneumoniae
clinical isolate was recovered from a patient who was treated with cefotaxime. This isolate harbored a
bla
CTX-M-15
ESBL gene that was associated with an IS
Ecp1
insertion sequence. Transposition of that tandem occurred within the chromosomal
mgrB
gene, leading to inactivation of the
mgrB
gene and consequently to acquired resistance to colistin. We showed here a coselection of colistin resistance as a result of a broad-spectrum cephalosporin selective pressure.
Inhibition of Glutathione Biosynthesis Sensitizes Plasmodium berghei to Antifolates
Authors: Songsungthong Warangkhana , Koonyosying Pongpisid , Uthaipibull Chairat , Kamchonwongpaisan Sumalee 
Published: March 2016

ABSTRACT

Glutathione plays a central role in maintaining cellular redox homeostasis, and modulations to this status may affect malaria parasite sensitivity to certain types of antimalarials. In this study, we demonstrate that inhibition of glutathione biosynthesis in the
Plasmodium berghei
ANKA strain through disruption of the γ-glutamylcysteine synthetase (γ-GCS) gene, which encodes the first and rate-limiting enzyme in the glutathione biosynthetic pathway, significantly sensitizes parasites
in vivo
to pyrimethamine and sulfadoxine, but not to chloroquine, artesunate, or primaquine, compared with control parasites containing the same pyrimethamine-resistant marker cassette. Treatment of mice infected with an antifolate-resistant
P. berghei
control line with a γ-GCS inhibitor, buthionine sulfoximine, could partially abrogate pyrimethamine and sulfadoxine resistance. The role of glutathione in modulating the malaria parasite's response to antifolates suggests that development of specific inhibitors against
Plasmodium
γ-GCS may offer a new approach to counter
Plasmodium
antifolate resistance.
Vancomycin 24-Hour Area under the Curve/Minimum Bactericidal Concentration Ratio as a Novel Predictor of Mortality in Methicillin-Resistant Staphylococcus aureus Bacteremia
Authors: Britt Nicholas S. , Patel Nimish , Horvat Rebecca T. , Steed Molly E. 
Published: March 2016

ABSTRACT

While previous studies have examined the association between vancomycin (VAN) exposure and MIC with regard to outcomes in methicillin-resistant
Staphylococcus aureus
bacteremia (MRSA-B), none have explored if a relationship exists with the VAN minimum bactericidal concentration (MBC). The objective of this study was to evaluate the VAN 24-h area under the curve (AUC
24
)/MBC ratio as a pharmacodynamic predictor of mortality. This retrospective cohort study included patients treated with VAN for MRSA-B with the primary outcome of 30-day all-cause mortality. Data collected included patient demographics, comorbidities, antimicrobial treatment data, therapeutic drug levels, and laboratory and microbiological data. Vancomycin MICs and MBCs were determined by Etest (MIC only) and broth microdilution (BMD). The vancomycin AUC
24
was determined by pharmacokinetic maximum
a posteriori
probability Bayesian (MAP-Bayesian) analysis. The most significant breakpoint for 30-day mortality was determined by classification and regression tree (CART) analysis. The association between pharmacodynamic parameters (VAN AUC
24
/MIC
BMD
, VAN AUC
24
/MIC
Etest
, and AUC
24
/MBC
BMD
) and mortality were determined by χ
2
and multivariable Poisson regression. Overall mortality in this cohort (
n
= 53) was 20.8% (
n
= 11/53), and all corresponding MRSA blood isolates were VAN susceptible (MIC range, 0.5 to 2 μg/ml; MIC
50
, 1 μg/ml; MIC
90
, 1 μg/ml). The CART-derived breakpoints for mortality were 176 (VAN AUC
24
/MBC) and 334 (VAN AUC
24
/MIC
BMD
). In multivariable analysis, the association between a VAN AUC
24
/MBC of ≥176 and survival persisted, but VAN AUC
24
/MIC
BMD
values (≥334 or ≥400) were not associated with improved mortality. In conclusion, VAN AUC
24
/MBC was a more important predictor of 30-day mortality than VAN AUC
24
/MIC for MRSA-B.
First Report of
cfr
-Carrying Plasmids in the Pandemic Sequence Type 22 Methicillin-Resistant Staphylococcus aureus Staphylococcal Cassette Chromosome
mec
Type IV Clone
Authors: Shore Anna C. , Lazaris Alexandros , Kinnevey Peter M. , Brennan Orla M. , Brennan Gráinne I. , O'Connell Brian , Feßler Andrea T. , Schwarz Stefan , Coleman David C. 
Published: March 2016

ABSTRACT

Linezolid is often the drug of last resort for serious methicillin-resistant
Staphylococcus aureus
(MRSA) infections. Linezolid resistance is mediated by mutations in 23S rRNA and genes for ribosomal proteins;
cfr
, encoding phenicol, lincosamide, oxazolidinone, pleuromutilin, and streptogramin A (PhLOPS
A
) resistance; its homologue
cfr
(B); or
optrA
, conferring oxazolidinone and phenicol resistance. Linezolid resistance is rare in
S. aureus
, and
cfr
is even rarer. This study investigated the clonality and linezolid resistance mechanisms of two MRSA isolates from patients in separate Irish hospitals. Isolates were subjected to
cfr
PCR, PhLOPS
A
susceptibility testing, 23S rRNA PCR and sequencing, DNA microarray profiling,
spa
typing, pulsed-field gel electrophoresis (PFGE), plasmid curing, and conjugative transfer. Whole-genome sequencing was used for single-nucleotide variant (SNV) analysis, multilocus sequence typing, L protein mutation identification,
cfr
plasmid sequence analysis, and
optrA
and
cfr
(B) detection. Isolates M12/0145 and M13/0401 exhibited linezolid MICs of 64 and 16 mg/liter, respectively, and harbored identical 23S rRNA and L22 mutations, but M12/0145 exhibited the mutation in 2/6 23S rRNA alleles, compared to 1/5 in M13/0401. Both isolates were sequence type 22 MRSA staphylococcal cassette chromosome
mec
type IV (ST22-MRSA-IV)/
spa
type t032 isolates, harbored
cfr
, exhibited the PhLOPS
A
phenotype, and lacked
optrA
and
cfr
(B). They differed by five PFGE bands and 603 SNVs. Isolate M12/0145 harbored
cfr
and
fexA
on a 41-kb conjugative pSCFS3-type plasmid, whereas M13/0401 harbored
cfr
and
lsa
(B) on a novel 27-kb plasmid. This is the first report of
cfr
in the pandemic ST22-MRSA-IV clone. Different
cfr
plasmids and mutations associated with linezolid resistance in genotypically distinct ST22-MRSA-IV isolates highlight that prudent management of linezolid use is essential.
Identification and Characterization of the Rhoptry Neck Protein 2 in Babesia divergens and B. microti
Authors: Ord Rosalynn L. , Rodriguez Marilis , Cursino-Santos Jeny R. , Hong Hyunryung , Singh Manpreet , Gray Jeremy , Lobo Cheryl A. 
Published: March 2016

ABSTRACT

Apicomplexan parasites include those of the genera
Plasmodium
,
Cryptosporidium
, and
Toxoplasma
and those of the relatively understudied zoonotic genus
Babesia
. In humans, babesiosis, particularly transfusion-transmitted babesiosis, has been emerging as a major threat to public health. Like malaria, the disease pathology is a consequence of the parasitemia which develops through cyclical replication of
Babesia
parasites in host erythrocytes. However, there are no exoerythrocytic stages in
Babesia
, so targeting of the blood stage and associated proteins to directly prevent parasite invasion is the most desirable option for effective disease control. Especially promising among such molecules are the rhoptry neck proteins (RONs), whose homologs have been identified in many apicomplexan parasites. RONs are involved in the formation of the moving junction, along with AMA1, but no RON has been identified and characterized in any
Babesia
spp. Here we identify the RON2 proteins of
Babesia divergens
(BdRON2) and
B. microti
(BmRON2) and show that they are localized apically and that anti-BdRON2 antibodies are significant inhibitors of parasite invasion
in vitro
. Neither protein is immunodominant, as both proteins react only marginally with sera from infected animals. Further characterization of the direct role of both BdRON2 and BmRON2 in parasite invasion is required, but knowledge of the level of conformity of RON2 proteins within the apicomplexan phylum, particularly that of the AMA1-RON2 complex at the moving junction, along with the availability of an animal model for
B. microti
studies, provides a key to target this complex with a goal of preventing the erythrocytic invasion of these parasites and to further our understanding of the role of these conserved ligands in invasion.
STAT6 Signaling Attenuates Interleukin-17-Producing γδ T Cells during Acute Klebsiella pneumoniae Infection
Authors: Bloodworth Melissa H. , Newcomb Dawn C. , Dulek Daniel E. , Stier Matthew T. , Cephus Jacqueline Y. , Zhang Jian , Goleniewska Kasia , Kolls Jay K. , Peebles R. Stokes 
Published: March 2016

ABSTRACTγδ T cells are prevalent at mucosal and epithelial surfaces and are a critical first line of defense against bacterial and fungal pathogens. γδ17 cells are a subset of γδ T cells which, in the presence of IL-23 and IL-1β, produce large quantities of interleukin-17A (IL-17A), a cytokine crucial to these cells' antibacterial and antifungal function. STAT6, an important transcription factor in Th2 differentiation and inhibition of Th1 differentiation, is expressed at high levels in the T cells of people with parasitic infections and asthma. Our group and others have shown that STAT6 attenuates IL-17A protein expression by CD4+T cells. By extension, we hypothesized that STAT6 activation also inhibits innate γδ17 cell cytokine secretion. We show here that γδ17 cells expressed the type I IL-4 receptor (IL-4R), and IL-4 increased STAT6 phosphorylation in γδ T cells. IL-4 inhibited γδ17 cell production of IL-17A. IL-4 also decreased γδ17 cell expression of IL-23R as well as Sgk1. To determine whether STAT6 signaling regulates γδ17 cell numbersin vivo, we used a model ofKlebsiella pneumoniaein mice deficient in STAT6. We choseK. pneumoniaefor ourin vivomodel, sinceK. pneumoniaeincreases IL-17A expression and γδ17 numbers.K. pneumoniaeinfection of STAT6 knockout mice resulted in a statistically significant increase in the number of γδ17 cells compared to that of wild-type mice. These studies are the first to demonstrate that γδ17 cells express the type I IL-4R and that STAT6 signaling negatively regulates γδ17 cells, a cell population that plays a front-line role in mucosal immunity.
Distinct Roles of Myosins in Aspergillus fumigatus Hyphal Growth and Pathogenesis
Authors: Renshaw Hilary , Vargas-Muñiz José M. , Richards Amber D. , Asfaw Yohannes G. , Juvvadi Praveen R. , Steinbach William J. 
Published: March 2016

ABSTRACT

Myosins are a family of actin-based motor proteins found in many organisms and are categorized into classes based on their structures. Class II and V myosins are known to be important for critical cellular processes, including cytokinesis, endocytosis, exocytosis, and organelle trafficking, in the model fungi
Saccharomyces cerevisiae
and
Aspergillus nidulans
. However, the roles of myosins in the growth and virulence of the pathogen
Aspergillus fumigatus
are unknown. We constructed single- and double-deletion strains of the class II and class V myosins in
A. fumigatus
and found that while the class II myosin (
myoB
) is dispensable for growth, the class V myosin (
myoE
) is required for proper hyphal extension; deletion of
myoE
resulted in hyperbranching and loss of hyphal polarity. Both
myoB
and
myoE
are necessary for proper septation, conidiation, and conidial germination, but only
myoB
is required for conidial viability. Infection with the Δ
myoE
strain in the invertebrate
Galleria mellonella
model and also in a persistently immunosuppressed murine model of invasive aspergillosis resulted in hypovirulence, while analysis of bronchoalveolar lavage fluid revealed that tumor necrosis factor alpha (TNF-α) release and cellular infiltration were similar compared to those of the wild-type strain. The Δ
myoE
strain showed fungal growth in the murine lung, while the Δ
myoB
strain exhibited little fungal burden, most likely due to the reduced conidial viability. These results show, for the first time, the important role these cytoskeletal components play in the growth of and disease caused by a known pathogen, prompting future studies to understand their regulation and potential targeting for novel antifungal therapies.
CotG-Like Modular Proteins Are Common among Spore-Forming Bacilli
Authors: Saggese Anella , Isticato Rachele , Cangiano Giuseppina , Ricca Ezio , Baccigalupi Loredana 
Published: March 2016

ABSTRACT

CotG is an abundant protein initially identified as an outer component of the
Bacillus subtilis
spore coat. It has an unusual structure characterized by several repeats of positively charged amino acids that are probably the outcome of multiple rounds of gene elongation events in an ancestral minigene. CotG is not highly conserved, and its orthologues are present in only two
Bacillus
and two
Geobacillus
species. In
B. subtilis
, CotG is the target of extensive phosphorylation by a still unidentified enzyme and has a role in the assembly of some outer coat proteins. We report now that most spore-forming bacilli contain a protein not homologous to CotG of
B. subtilis
but sharing a central “modular” region defined by a pronounced positive charge and randomly coiled tandem repeats. Conservation of the structural features in most spore-forming bacilli suggests a relevant role for the CotG-like protein family in the structure and function of the bacterial endospore. To expand our knowledge on the role of CotG, we dissected the
B. subtilis
protein by constructing deletion mutants that express specific regions of the protein and observed that they have different roles in the assembly of other coat proteins and in spore germination.

IMPORTANCE
CotG of
B. subtilis
is not highly conserved in the
Bacillus
genus; however, a CotG-like protein with a modular structure and chemical features similar to those of CotG is common in spore-forming bacilli, at least when CotH is also present. The conservation of CotG-like features when CotH is present suggests that the two proteins act together and may have a relevant role in the structure and function of the bacterial endospore. Dissection of the modular composition of CotG of
B. subtilis
by constructing mutants that express only some of the modules has allowed a first characterization of CotG modules and will be the basis for a more detailed functional analysis.