bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma hyperosmolality attenuates skin sympathetic nerve activity during passive heat stress in humans
Authors: Gagnon Daniel , Romero Steven A. , Ngo Hai , Poh Paula Y. S. , Crandall Craig G. 
Published: November 2015

Key points
Plasma hyperosmolality delays the onset for sweat production and cutaneous vasodilatation during heat stress in humans; however, the mechanism by which hyperosmolality exerts this effect remains unknown.
This study examined if plasma hyperosmolality exerts a central and/or peripheral modulation of thermoregulatory function in humans.
The main findings are that plasma hyperosmolality delays the increase in skin sympathetic nerve activity during whole‐body passive heat stress in humans. In contrast, local intradermal infusion of hyperosmotic saline did not affect sweating or cutaneous vasodilatation.
These results suggest that plasma hyperosmolality delays the onset threshold for sweating and cutaneous vasodilatation by inhibiting efferent thermoregulatory activity in humans.
AbstractIn humans, plasma hyperosmolality delays the onset of sweating and cutaneous vasodilatation during heat stress. However, it remains unknown if hyperosmolality exerts this effect through a central (i.e. CNS) and/or peripheral (i.e. effector organ) modulation of thermoregulatory activity. We examined if intravenous infusion of hyperosmotic saline affects skin sympathetic nerve activity (SSNA) during whole‐body passive heating in healthy humans. Furthermore, we examined if local intradermal infusion of hyperosmotic saline affects sweating and cutaneous vasodilatation during passive heating. Following intravenous infusion of either 0.9% (ISO) or 3.0% (HYPER) NaCl saline, 12 subjects were passively heated until core temperature increased by ∼0.6°C. During each condition, sweating and cutaneous vascular conductance were measured over two intradermal microdialysis probes, one perfused with ISO saline and the other with HYPER saline. Intravenous infusion of HYPER saline increased plasma osmolality (294 ± 3 to 316 ± 5 mOsm kg–1 H2O, P ≤ 0.01), which remained greater than ISO throughout heating. Plasma hyperosmolality delayed the mean body temperature onset of sweating (+1.24 ± 0.18 vs. +1.60 ± 0.18°C, P ≤ 0.01) and cutaneous vasodilatation (+1.15 ± 0.18 vs. +1.53 ± 0.22°C, P ≤ 0.01), and attenuated the increase in SSNA during heating (+147 ± 178 vs. +427 ± 281%, P ≤ 0.01). Intradermal infusion of HYPER saline increased baseline cutaneous vascular conductance (P ≤ 0.01), which did not increase further during the subsequent heating period (P = 0.11). In contrast, intradermal infusion of HYPER saline did not affect sweating (P = 0.99). These results provide direct evidence that plasma hyperosmolality exerts a central modulatory effect governing efferent thermoregulatory activity in humans.
In Vitro
Activity of β-Lactams in Combination with β-Lactamase Inhibitors against Multidrug-Resistant Mycobacterium tuberculosis Isolates
Authors: Zhang Dan , Wang Yufeng , Lu Jie , Pang Yu 
Published: November 2015

ABSTRACT

The combination of β-lactams and β-lactamase inhibitors has been shown to have potent
in vitro
activity against multidrug-resistant tuberculosis (MDR-TB) isolates. In order to identify the most potent β-lactam–β-lactamase inhibitor combination against MDR-TB, we selected nine β-lactams and three β-lactamase inhibitors, which belong to different subgroups. A total of 121 MDR-TB strains were included in this study. Out of the β-lactams used herein, biapenem was the most effective against MDR-TB and had an MIC
50
value of 8 μg/ml. However, after the addition of clavulanate or sulbactam, meropenem exhibited the most potent anti-MDR-TB activity with an MIC
50
value of 4 μg/ml. For meropenem, 76 (62.8%), 41 (33.9%), and 22 (18.2%) of the 121 MDR-TB strains were subjected to a synergistic effect when the drug was combined with sulbactam, tazobactam, or clavulanate, respectively. Further statistical analysis revealed that significantly more strains experienced a synergistic effect when exposed to the combination of meropenem with sulbactam than when exposed to meropenem in combination with tazobactam or clavulanate, respectively (
P
< 0.01). In addition, a total of 10.7% (13/121) of isolates harbored mutations in the
blaC
gene, with two different nucleotide substitutions: AGT333AGG and ATC786ATT. For the strains with a Ser111Arg substitution in BlaC, a better synergistic effect was observed in the meropenem-clavulanate and in the amoxicillin-clavulanate combinations than that in a synonymous single nucleotide polymorphism (SNP) group. In conclusion, our findings demonstrate that the combination of meropenem and sulbactam shows the most potent activity against MDR-TB isolates. In addition, the Ser111Arg substitution of BlaC may be associated with an increased susceptibility of MDR-TB isolates to meropenem and amoxicillin in the presence of clavulanate.
No Need for Lopinavir Dose Adjustment during Pregnancy: a Population Pharmacokinetic and Exposure-Response Analysis in Pregnant and Nonpregnant HIV-Infected Subjects
Authors: Salem Ahmed Hamed , Jones Aksana Kaefer , Santini-Oliveira Marilia , Taylor Graham P. , Patterson Kristine B. , Nilius Angela M. , Klein Cheri Enders 
Published: November 2015

ABSTRACTLopinavir-ritonavir is frequently prescribed to HIV-1-infected women during pregnancy. Decreased lopinavir exposure has been reported during pregnancy, but the clinical significance of this reduction is uncertain. This analysis aimed to evaluate the need for lopinavir dose adjustment during pregnancy. We conducted a population pharmacokinetic analysis of lopinavir and ritonavir concentrations collected from 84 pregnant and 595 nonpregnant treatment-naive and -experienced HIV-1-infected subjects enrolled in six clinical studies. Lopinavir-ritonavir doses in the studies ranged between 400/100 and 600/150 mg twice daily. In addition, linear mixed-effect analysis was used to compare the area under the concentration-time curve from 0 to 12 h (AUC0–12) and concentration prior to dosing (Cpredose) in pregnant women and nonpregnant subjects. The relationship between lopinavir exposure and virologic suppression in pregnant women and nonpregnant subjects was evaluated. Population pharmacokinetic analysis estimated 17% higher lopinavir clearance in pregnant women than in nonpregnant subjects. Lopinavir clearance values postpartum were 26.4% and 37.1% lower than in nonpregnant subjects and pregnant women, respectively. As the tablet formulation was estimated to be 20% more bioavailable than the capsule formulation, no statistically significant differences between lopinavir exposure in pregnant women receiving the tablet formulation and nonpregnant subjects receiving the capsule formulation were identified. In the range of lopinavir AUC0–12orCpredosevalues observed in the third trimester, there was no correlation between lopinavir exposure and viral load or proportion of subjects with virologic suppression. Similar efficacy was observed between pregnant women and nonpregnant subjects receiving lopinavir-ritonavir at 400/100 mg twice daily. The pharmacokinetic and pharmacodynamic results support the use of a lopinavir-ritonavir 400/100-mg twice-daily dose during pregnancy.
Pharmacodynamics of Ceftazidime and Avibactam in Neutropenic Mice with Thigh or Lung Infection
Authors: Berkhout Johanna , Melchers Maria J. , van Mil Anita C. , Seyedmousavi Seyedmojtaba , Lagarde Claudia M. , Schuck Virna J. , Nichols Wright W. , Mouton Johan W. 
Published: November 2015

ABSTRACT

Avibactam is a new non-β-lactam β-lactamase inhibitor that shows promising restoration of ceftazidime activity against microorganisms producing Ambler class A extended-spectrum β-lactamases (ESBLs) and carbapenemases such as KPCs, class C β-lactamases (AmpC), and some class D enzymes. To determine optimal dosing combinations of ceftazidime-avibactam for treating infections with ceftazidime-resistant
Pseudomonas aeruginosa
, pharmacodynamic responses were explored in murine neutropenic thigh and lung infection models. Exposure-response relationships for ceftazidime monotherapy were determined first. Subsequently, the efficacy of adding avibactam every 2 h (q2h) or q8h to a fixed q2h dose of ceftazidime was determined in lung infection for two strains. Dosing avibactam q2h was significantly more efficacious, reducing the avibactam daily dose for static effect by factors of 2.7 and 10.1, whereas the mean percentage of the dosing interval that free drug concentrations remain above the threshold concentration of 1 mg/liter (%
f
T>C
T
1 mg/liter) yielding bacteriostasis was similar for both regimens, with mean values of 21.6 (q2h) and 18.5 (q8h). Dose fractionation studies of avibactam in both the thigh and lung models indicated that the effect of avibactam correlated well with %
f
T>C
T
1 mg/liter. This parameter of avibactam was further explored for four
P. aeruginosa
strains in the lung model and six in the thigh model. Parameter estimates of %
f
T>C
T
1 mg/liter for avibactam ranged from 0 to 21.4% in the lung model and from 14.1 to 62.5% in the thigh model to achieve stasis. In conclusion, addition of avibactam enhanced the effect of ceftazidime, which was more pronounced at frequent dosing and well related with %
f
T>C
T
1 mg/liter. The thigh model appeared more stringent, with higher values, ranging up to 62.5%
f
T>C
T
1 mg/liter, required for a static effect.
Cefotaxime and Amoxicillin-Clavulanate Synergism against Extended-Spectrum-β-Lactamase-Producing
Escherichia coli
in a Murine Model of Urinary Tract Infection
Authors: Rossi B. , Soubirou J. F. , Chau F. , Massias L. , Dion S. , Lepeule R. , Fantin B. , Lefort A. 
Published: November 2015

ABSTRACT

We investigated the efficacies of cefotaxime (CTX) and amoxicillin (AMX)-clavulanate (CLA) (AMC) against extended-spectrum-β-lactamase (ESBL)-producing
Escherichia coli
in vitro
and in a murine model of urinary tract infection (UTI). MICs, the checkerboard dilution method, and time-kill curves were used to explore the
in vitro
synergism between cefotaxime and amoxicillin-clavulanate against two isogenic
E. coli
strains—CFT073-RR and its transconjugant, CFT073-RR Tc
bla
CTX-M-15
—harboring a
bla
CTX-M-15
plasmid and a
bla
OXA-1
plasmid. For
in vivo
experiments, mice were separately infected with each strain and treated with cefotaxime, amoxicillin, and clavulanate, alone or in combination, or imipenem, using therapeutic regimens reproducing time of free-drug concentrations above the MIC (
fT
≥MIC) values close to that obtained in humans. MICs of amoxicillin, cefotaxime, and imipenem were 4/>1,024, 0.125/1,024, and 0.5/0.5 mg/liter, for CFT073-RR and CFT073-RR Tc
bla
CTX-M-15
, respectively. The addition of 2 mg/liter of clavulanate (CLA) restored the susceptibility of CFT073-RR Tc
bla
CTX-M-15
to CTX (MICs of the CTX-CLA combination, 0.125 mg/liter). The checkerboard dilution method and time-kill curves confirmed an
in vitro
synergy between amoxicillin-clavulanate and cefotaxime against CFT073-RR Tc
bla
CTX-M-15
.
In vivo
, this antibiotic combination was similarly active against both strains and as effective as imipenem. In conclusion, the cefotaxime and amoxicillin-clavulanate combination appear to be an effective, easy, and already available alternative to carbapenems for the treatment of UTI due to CTX-M-producing
E. coli
strains.
Type III Secretion-Dependent Sensitivity of Escherichia coli O157 to Specific Ketolides
Authors: Fernandez-Brando Romina J. , Yamaguchi Nao , Tahoun Amin , McAteer Sean P. , Gillespie Trudi , Wang Dai , Argyle Sally A. , Palermo Marina S. , Gally David L. 
Published: November 2015

ABSTRACT

A subset of Gram-negative bacterial pathogens uses a type III secretion system (T3SS) to open up a conduit into eukaryotic cells in order to inject effector proteins. These modulate pathways to enhance bacterial colonization. In this study, we screened established bioactive compounds for any that could repress T3SS expression in enterohemorrhagic
Escherichia coli
(EHEC) O157. The ketolides telithromycin and, subsequently, solithromycin both demonstrated repressive effects on expression of the bacterial T3SS at sub-MICs, leading to significant reductions in bacterial binding and actin-rich pedestal formation on epithelial cells. Preincubation of epithelial cells with solithromycin resulted in significantly less attachment of
E. coli
O157. Moreover, bacteria expressing the T3SS were more susceptible to solithromycin, and there was significant preferential killing of
E. coli
O157 bacteria when they were added to epithelial cells that had been preexposed to the ketolide. This killing was dependent on expression of the T3SS. Taken together, this research indicates that the ketolide that has accumulated in epithelial cells may traffic back into the bacteria via the T3SS. Considering that neither ketolide induces the SOS response, nontoxic members of this class of antibiotics, such as solithromycin, should be considered for future testing and trials evaluating their use for treatment of EHEC infections. These antibiotics may also have broader significance for treating infections caused by other pathogenic bacteria, including intracellular bacteria, that express a T3SS.
Effect of High-Dose Antimicrobials on Biofilm Growth of Achromobacter Species Isolated from Cystic Fibrosis Patients
Authors: Tom Sean K. , Yau Yvonne C. W. , Beaudoin Trevor , LiPuma John J. , Waters Valerie 
Published: November 2015

ABSTRACT

MICs and biofilm inhibitory concentrations (BICs) were measured for 68 cystic fibrosis (CF)
Achromobacter
isolates for amikacin, aztreonam, colistin, levofloxacin, and tobramycin. With the exception of colistin and levofloxacin, the remaining antibiotics had MIC
90
s, BICs at which 50% of the isolates were susceptible (BIC
50
s), and BICs at which 90% of the isolates were susceptible (BIC
90
s) equal to or above the highest concentrations tested. In a biofilm model, tobramycin was able to significantly increase killing of bacterial cells compared to controls, for intermediate-resistant strains only, at concentrations of 1,000 and 2,000 μg/ml.
Pneumococcal 6-Phospho-β-Glucosidase (BglA3) Is Involved in Virulence and Nutrient Metabolism
Authors: Terra Vanessa Sofia , Zhi Xiangyun , Kahya Hasan F. , Andrew Peter W. , Yesilkaya Hasan 
Published: November 2015

ABSTRACT

For the generation of energy, the important human pathogen
Streptococcus pneumoniae
relies on host-derived sugars, including β-glucoside analogs. The catabolism of these nutrients involves the action of 6-phospho-β-glucosidase to convert them into usable monosaccharaides. In this study, we characterized a 6-phospho-β-glucosidase (BglA3) encoded by SPD_0247. We found that this enzyme has a cell membrane localization and is active only against a phosphorylated substrate. A mutated pneumococcal ΔSPD0247 strain had reduced 6-phospho-glucosidase activity and was attenuated in growth on cellobiose and hyaluronic acid compared to the growth of wild-type D39. ΔSPD0247-infected mice survived significantly longer than the wild-type-infected cohort, and the colony counts of the mutant were lower than those of the wild type in the lungs. The expression of SPD_0247 in
S. pneumoniae
harvested from infected tissues was significantly increased relative to its expression
in vitro
on glucose. Additionally, ΔSPD0247 is severely impaired in its attachment to an abiotic surface. These results indicate the importance of β-glucoside metabolism in pneumococcal survival and virulence.
Global Regulator of Virulence A (GrvA) Coordinates Expression of Discrete Pathogenic Mechanisms in Enterohemorrhagic Escherichia coli through Interactions with GadW-GadE
Authors: Morgan Jason K. , Carroll Ronan K. , Harro Carly M. , Vendura Khoury W. , Shaw Lindsey N. , Riordan James T. 
Published: November 2015

ABSTRACT

Global regulator of virulence A (GrvA) is a ToxR-family transcriptional regulator that activates locus of enterocyte effacement (LEE)-dependent adherence in enterohemorrhagic
Escherichia coli
(EHEC). LEE activation by GrvA requires the Rcs phosphorelay response regulator RcsB and is sensitive to physiologically relevant concentrations of bicarbonate, a known stimulant of virulence systems in intestinal pathogens. This study determines the genomic scale of GrvA-dependent regulation and uncovers details of the molecular mechanism underlying GrvA-dependent regulation of pathogenic mechanisms in EHEC. In a
grvA
-null background of EHEC strain TW14359, RNA sequencing analysis revealed the altered expression of over 700 genes, including the downregulation of LEE- and non-LEE-encoded effectors and the upregulation of genes for glutamate-dependent acid resistance (GDAR). Upregulation of GDAR genes corresponded with a marked increase in acid resistance. GrvA-dependent regulation of GDAR and the LEE required
gadE
, the central activator of GDAR genes and a direct repressor of the LEE. Control of
gadE
by GrvA was further determined to occur through downregulation of the
gadE
activator GadW. This interaction of GrvA with GadW-GadE represses the acid resistance phenotype, while it concomitantly activates the LEE-dependent adherence and secretion of immune subversion effectors. The results of this study significantly broaden the scope of GrvA-dependent regulation and its role in EHEC pathogenesis.

IMPORTANCE
Enterohemorrhagic
Escherichia coli
(EHEC) is an intestinal human pathogen causing acute hemorrhagic colitis and life-threatening hemolytic-uremic syndrome. For successful transmission and gut colonization, EHEC relies on the glutamate-dependent acid resistance (GDAR) system and a type III secretion apparatus, encoded on the LEE pathogenicity island. This study investigates the mechanism whereby the DNA-binding regulator GrvA coordinates activation of the LEE with repression of GDAR. Investigating how these systems are regulated leads to an understanding of pathogenic behavior and novel strategies aimed at disease prevention and control.
AcrB-AcrA Fusion Proteins That Act as Multidrug Efflux Transporters
Authors: Hayashi Katsuhiko , Nakashima Ryosuke , Sakurai Keisuke , Kitagawa Kimie , Yamasaki Seiji , Nishino Kunihiko , Yamaguchi Akihito 
Published: November 2015

ABSTRACT

The AcrAB-TolC system in
Escherichia coli
is an intrinsic RND-type multidrug efflux transporter that functions as a tripartite complex of the inner membrane transporter AcrB, the outer membrane channel TolC, and the adaptor protein AcrA. Although the crystal structures of each component of this system have been elucidated, the crystal structure of the whole complex has not been solved. The available crystal structures have shown that AcrB and TolC function as trimers, but the number of AcrA molecules in the complex is now under debate. Disulfide chemical cross-linking experiments have indicated that the stoichiometry of AcrB-AcrA-TolC is 1:1:1; on the other hand, recent cryo-electron microscopy images of AcrAB-TolC suggested a 1:2:1 stoichiometry. In this study, we constructed 1:1-fixed AcrB-AcrA fusion proteins using various linkers. Surprisingly, all the 1:1-fixed linker proteins showed drug export activity under both
acrAB
-deficient conditions and
acrAB acrEF
double-pump-knockout conditions regardless of the lengths of the linkers. Finally, we optimized a shorter linker lacking the conformational freedom imparted by the AcrB C terminus. These results suggest that a complex with equal amounts of AcrA and AcrB is sufficient for drug export function.

IMPORTANCE
The structure and stoichiometry of the RND-type multidrug exporter AcrB-AcrA-TolC complex are still under debate. Recently, electron microscopic images of the AcrB-AcrA-TolC complex have been reported, suggesting a 1:2:1 stoichiometry. However, we report here that the AcrB-AcrA 1:1 fusion protein is active for drug export under
acrAB
-deficient conditions and also under
acrAB
acrEF
double-deficient conditions, which eliminate the aid of free AcrA and its close homolog AcrE, indicating that the AcrB-AcrA 1:1 stoichiometry is enough for drug export function. In addition, the AcrB-AcrA fusion protein can function without the aid of free AcrA. We believe that these results are very important for considering the structure and mechanism of AcrAB-TolC-mediated multidrug export.
Glutamate Limitation, BvgAS Activation, and (p)ppGpp Regulate the Expression of the Bordetella pertussis Type 3 Secretion System
Authors: Hanawa Tomoko , Kamachi Kazunari , Yonezawa Hideo , Fukutomi Toshiyuki , Kawakami Hayato , Kamiya Shigeru 
Published: November 2015

ABSTRACT

Bordetella pertussis
is a bacterium that is considered to be highly adapted to humans, and it has not been isolated from the environment. As this bacterium does not utilize sugars, the abundant supply of glutamate in Stainer Scholte (SS) medium enables
B. pertussis
to grow efficiently in liquid culture
in vitro
, and as such, SS medium is a popular choice for laboratory experiments. However, the concentration of glutamate in the
in vivo
niche of
B. pertussis
is quite low. We investigated the bacterial response to low concentrations of glutamate to elucidate bacterial physiology via the expression of the type 3 secretion system (T3SS), and we discuss its relationship to the Bvg mode in which the two-component regulator of pathogenesis (BvgAS) is activated. Glutamate limitation induced the expression of both the T3SS apparatus and effector genes at the transcriptional level. (p)ppGpp, a modulator of the stringent response, was necessary for maximum expression of the T3SS genes. These observations indicate that the expression of the T3SS is managed by nutrient starvation. In addition, the autoaggregation ability was high in the absence of glutamate and no autoaggregation was observed in glutamate-replete medium. Taken together, glutamate-limited conditions in Bvg
+
mode elicit the high expression of T3SS genes in
B. pertussis
and promotes its sessile form.

IMPORTANCE
Bordetella pertussis
is a highly contagious pathogen that causes respiratory infectious disease. In spite of the increasing use of vaccination, the number of patients with pertussis is increasing. The proteins produced
in vivo
often are different from the protein profile under laboratory conditions; therefore, the development of conditions reflecting the host environment is important to understand native bacterial behavior. In the present study, we examined the effect of glutamate limitation, as its concentration
in vivo
is much lower than that in the culture medium currently used for
B. pertussis
experiments. As predicted, the T3SS was induced by glutamate limitation. These results are suggestive of the importance of regulation by nutrient conditions and in the pathogenicity of
B. pertussis
.