bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo
Characterization of the Activation and Interaction of the VanR-VanS Two-Component Regulatory System Controlling Glycopeptide Antibiotic Resistance in Two Related Streptomyces Species
Authors: Novotna Gabriela Balikova , Kwun Min Jung , Hong Hee-Jeon 
Published: December 2015

ABSTRACT

The VanR-VanS two-component system is responsible for inducing resistance to glycopeptide antibiotics in various bacteria. We have performed a comparative study of the VanR-VanS systems from two streptomyces strains,
Streptomyces coelicolor
and
Streptomyces toyocaensis
, to characterize how the two proteins cooperate to signal the presence of antibiotics and to define the functional nature of each protein in each strain background. The results indicate that the glycopeptide antibiotic inducer specificity is determined solely by the differences between the amino acid sequences of the VanR-VanS two-component systems present in each strain rather than by any inherent differences in general cell properties, including cell wall structure and biosynthesis. VanR of
S. coelicolor
(VanRsc) functioned with either sensor kinase partner, while VanR of
S. toyocaensis
(VanRst) functioned only with its cognate partner,
S. toyocaensis
VanS (VanSst). In contrast to VanRsc, which is known to be capable of phosphorylation by acetylphosphate, VanRst could not be activated
in vivo
independently of a VanS sensor kinase. A series of amino acid sequence modifications changing residues in the N-terminal receiver (REC) domain of VanRst to the corresponding residues present in VanRsc failed to create a protein capable of being activated by VanS of
S. coelicolor
(VanSsc), which suggests that interaction of the response regulator with its cognate sensor kinase may require a region more extended than the REC domain. A T69S amino acid substitution in the REC domain of VanRst produced a strain exhibiting weak constitutive resistance, indicating that this particular amino acid may play a key role for VanS-independent phosphorylation in the response regulator protein.
Doripenem Treatment during Continuous Renal Replacement Therapy
Authors: Vossen M. G. , Wenisch J. M. , Maier-Salamon A. , Fritsch A. , Saria K. , Zuba C. , Jilch S. , Lemmerer R. , Unger M. , Jaehde U. , Jäger W. , Thalhammer F. 
Published: December 2015

ABSTRACT

Doripenem is a broad-spectrum parenteral carbapenem with enhanced activity against
Pseudomonas aeruginosa
. While the initial dosing recommendation for renally competent patients and patients undergoing continuous renal replacement therapy (cRRT) was 500 mg every 8 h (q8h), the dose for renally competent patients was updated to 1 g q8h in June 2012. There are no updated data for the dosing of patients on continuous renal replacement therapy. The original dosing regimen for cRRT patients was based on nonseptic patients, while newer publications chose comparatively low target concentrations for a carbapenem. Thus, there is an urgent need for updated recommendations for dosing during cRRT. In the trial presented here, we included 13 oliguric septic patients undergoing cRRT in an intensive care setting. Five patients each were treated with hemodiafiltration or hemodialysis, while three patients received hemofiltration treatment. All patients received 1 g doripenem every 8 h. Doripenem concentrations in the plasma and ultrafiltrate were measured over 48 h. The mean hemofilter clearance was 36.53 ml/min, and the mean volume of distribution was 59.26 liters. The steady-state trough levels were found at 8.5 mg/liter, with no considerable accumulation. Based on pharmacokinetic and pharmacodynamic considerations, we propose a regimen of 1 g q8h, which may be combined with a loading dose of 1.5 to 2 g for critically ill patients. (This study has been registered with EudraCT under registration no. 2009-018010-18 and at ClinicalTrials.gov under registration no. NCT02018939.)
Randomized Trial of Clarithromycin for Mediterranean Spotted Fever
Authors: Anton Esperança , Muñoz Tomas , Travería Francisco Javier , Navarro Gemma , Font Bernat , Sanfeliu Isabel , Segura Ferran 
Published: December 2015

ABSTRACT

The classic antibiotic treatment for Mediterranean spotted fever (MSF) is based on tetracyclines or chloramphenicol, but chloramphenicol's bone marrow toxicity makes tetracyclines the treatment of choice. However, it is convenient to have alternatives available for patients who are allergic to tetracyclines, pregnant women, and children <8 years old. We conducted a randomized clinical trial to compare clarithromycin with doxycycline or josamycin in the treatment of MSF. Forty patients were evaluated (23 male; mean age, 39.87 years); 13 patients were aged <14 years. Seventeen patients received clarithromycin, and 23 received doxycycline or josamycin. The interval between the onset of symptoms and the start of treatment was 4.04 ± 1.70 days in the clarithromycin group versus 4.11 ± 1.60 days in the doxycycline/josamycin group (
P
= not significant [NS]). Time to the disappearance of fever after treatment was 2.67 ± 1.55 days in the clarithromycin group versus 2.22 ± 1.35 days in the doxycycline/josamycin (
P
= NS). The symptoms had disappeared at 4.70 ± 2.25 days in the clarithromycin group versus at 4.75 ± 3.08 days in the doxycycline/josamycin (
P
= NS). There were no adverse reactions to treatment or relapses in either group. In conclusion, clarithromycin is a good alternative to doxycycline or josamycin in the treatment of MSF.
Atovaquone-Proguanil Remains a Potential Stopgap Therapy for Multidrug-Resistant Plasmodium falciparum in Areas along the Thai-Cambodian Border
Authors: Saunders David L. , Chaorattanakawee Suwanna , Gosi Panita , Lanteri Charlotte , Somethy Sok , Kuntawunginn Worachet , Ittiverakul Mali , Chann Soklyda , Gregory Carrie , Chuor Char Meng , Prom Satharath , Spring Michele D. , Lon Chanthap 
Published: December 2015

ABSTRACT

Our recent report of dihydroartemisinin-piperaquine failure to treat
Plasmodium falciparum
infections in Cambodia adds new urgency to the search for alternative treatments. Despite dihydroartemisinin-piperaquine failure, and higher piperaquine 50% inhibitory concentrations (IC
50
s) following reanalysis than those previously reported,
P. falciparum
remained sensitive to atovaquone (ATQ)
in vitro
. There were no point mutations in the
P. falciparum
cytochrome
b
ATQ resistance gene. Mefloquine, artemisinin, chloroquine, and quinine IC
50
s remained comparable to those from other recent reports. Atovaquone-proguanil may be a useful stopgap but remains susceptible to developing resistance when used as blood-stage therapy.
What Is the Appropriate Meropenem MIC for Screening of Carbapenemase-Producing Enterobacteriaceae in Low-Prevalence Settings?
Authors: Fattouh Ramzi , Tijet Nathalie , McGeer Allison , Poutanen Susan M. , Melano Roberto G. , Patel Samir N. 
Published: December 2015

ABSTRACT

Infection with carbapenemase-producing
Enterobacteriaceae
(CPE) has been shown to cause significant illness among hospitalized patients. Given the paucity of treatment options, there is a critical need to stop the spread of CPE. However, screening for the presence of CPE in laboratory settings has been challenging. In order to assess the effectiveness of current CPE detection guidelines, we analyzed the meropenem MIC distribution for a large set of clinical
Enterobacteriaceae
isolates. A total of 1,022 isolates submitted to the Public Health Ontario Laboratories (PHOL) from January 2011 to March 2014 were examined. Only isolates displaying a meropenem or ertapenem MIC of ≥0.25 or ≥1 μg/ml, respectively, were included. Carbapenemase-positive isolates were identified by multiplex PCR. We identified 189 isolates positive for carbapenemases, which primarily comprised NDM, KPC, and OXA-48-like carbapenemases, and these isolates were largely
Klebsiella
spp.,
Escherichia coli
, and
Enterobacter
spp. Interestingly, 14 to 20% of these isolates displayed meropenem MICs within the susceptible range on the basis of CLSI and EUCAST breakpoint interpretive criteria. While the majority of meropenem-susceptible CPE isolates were observed to be
E. coli
, meropenem susceptibility was not exclusive to any one species/genus or carbapenemase type. Application of CLSI screening recommendations captured only 86% of carbapenemase-producing isolates, whereas application of EUCAST recommendations detected 98.4% of CPE isolates. In a region with a low carbapenemase prevalence, meropenem-based screening approaches require a cutoff MIC near the epidemiological wild-type threshold in order to achieve nearly optimal CPE identification.
Ceftolozane-Tazobactam Pharmacokinetics in a Critically Ill Patient on Continuous Venovenous Hemofiltration
Authors: Oliver Wesley D. , Heil Emily L. , Gonzales Jeffrey P. , Mehrotra Shailly , Robinett Kathryn , Saleeb Paul , Nicolau David P. 
Published: December 2015

ABSTRACT

Extended-infusion ceftolozane-tazobactam treatment at 1.5 g every 8 h was used to treat multidrug-resistant
Pseudomonas aeruginosa
in a critically ill patient on continuous venovenous hemofiltration. Serum drug concentrations were measured at 1, 4, 5, 6, and 8 h after the start of infusion. Prefilter levels of ceftolozane produced a maximum concentration of drug (
C
max
) of 38.57 μg/ml, concentration at the end of the dosing interval (
C
min
) of 31.63 μg/ml, time to
C
max
(
T
max
) of 4 h, area under the concentration-time curve from 0 to 8 h (AUC
0–8
) of 284.38 μg · h/ml, and a half-life (
t
1/2
) of 30.7 h. The concentrations were eight times the susceptibility breakpoint for the entire dosing interval.
Elevated Plasma Viral Loads in Romidepsin-Treated Simian Immunodeficiency Virus-Infected Rhesus Macaques on Suppressive Combination Antiretroviral Therapy
Authors: Del Prete Gregory Q. , Oswald Kelli , Lara Abigail , Shoemaker Rebecca , Smedley Jeremy , Macallister Rhonda , Coalter Vicky , Wiles Adam , Wiles Rodney , Li Yuan , Fast Randy , Kiser Rebecca , Lu Bing , Zheng Jim , Alvord W. Gregory , Trubey Charles M. , Piatak Michael , Deleage Claire , Keele Brandon F. , Estes Jacob D. , Hesselgesser Joseph , Geleziunas Romas , Lifson Jeffrey D. 
Published: December 2015

ABSTRACT

Replication-competent human immunodeficiency virus (HIV) persists in infected people despite suppressive combination antiretroviral therapy (cART), and it represents a major obstacle to HIV functional cure or eradication. We have developed a model of cART-mediated viral suppression in simian human immunodeficiency virus (SIV) mac239-infected Indian rhesus macaques and evaluated the impact of the histone deacetylase inhibitor (HDACi) romidepsin (RMD) on viremia
in vivo
. Eight macaques virologically suppressed to clinically relevant levels (<30 viral RNA copies/ml of plasma), using a three-class five-drug cART regimen, received multiple intravenous infusions of either RMD (
n
= 5) or saline (
n
= 3) starting 31 to 54 weeks after cART initiation.
In vivo
RMD treatment resulted in significant transient increases in acetylated histone levels in CD4
+
T cells. RMD-treated animals demonstrated plasma viral load measurements for each 2-week treatment cycle that were significantly higher than those in saline control-treated animals during periods of treatment, suggestive of RMD-induced viral reactivation. However, plasma virus rebound was indistinguishable between RMD-treated and control-treated animals for a subset of animals released from cART. These findings suggest that HDACi drugs, such as RMD, can reactivate residual virus in the presence of suppressive antiviral therapy and may be a valuable component of a comprehensive HIV functional cure/eradication strategy.
Synergistic Activity of Combined NS5A Inhibitors
Authors: O'Boyle Donald R. , Nower Peter T. , Gao Min , Fridell Robert , Wang Chunfu , Hewawasam Piyasena , Lopez Omar , Tu Yong , Meanwell Nicholas A. , Belema Makonen , Roberts Susan B. , Cockett Mark , Sun Jin-Hua 
Published: December 2015

ABSTRACT

Daclatasvir (DCV) is a first-in-class hepatitis C virus (HCV) nonstructural 5A replication complex inhibitor (NS5A RCI) that is clinically effective in interferon-free combinations with direct-acting antivirals (DAAs) targeting alternate HCV proteins. Recently, we reported NS5A RCI combinations that enhance HCV inhibitory potential
in vitro
, defining a new class of HCV inhibitors termed NS5A synergists (J. Sun, D. R. O’Boyle II, R. A. Fridell, D. R. Langley, C. Wang, S. Roberts, P. Nower, B. M. Johnson F. Moulin, M. J. Nophsker, Y. Wang, M. Liu, K. Rigat, Y. Tu, P. Hewawasam, J. Kadow, N. A. Meanwell, M. Cockett, J. A. Lemm, M. Kramer, M. Belema, and M. Gao, Nature 527:245–248, 2015, doi:
10.1038/nature15711
). To extend the characterization of NS5A synergists, we tested new combinations of DCV and NS5A synergists against genotype (gt) 1 to 6 replicons and gt 1a, 2a, and 3a viruses. The kinetics of inhibition in HCV-infected cells treated with DCV, an NS5A synergist (NS5A-Syn), or a combination of DCV and NS5A-Syn were distinctive. Similar to activity observed clinically, DCV caused a multilog drop in HCV, followed by rebound due to the emergence of resistance. DCV–NS5A-Syn combinations were highly efficient at clearing cells of viruses, in line with the trend seen in replicon studies. The retreatment of resistant viruses that emerged using DCV monotherapy with DCV–NS5A-Syn resulted in a multilog drop and rebound in HCV similar to the initial decline and rebound observed with DCV alone on wild-type (WT) virus. A triple combination of DCV, NS5A-Syn, and a DAA targeting the NS3 or NS5B protein cleared the cells of viruses that are highly resistant to DCV. Our data support the observation that the cooperative interaction of DCV and NS5A-Syn potentiates both the genotype coverage and resistance barrier of DCV, offering an additional DAA option for combination therapy and tools for explorations of NS5A function.
Sequential Evolution of Vancomycin-Intermediate Resistance Alters Virulence in Staphylococcus aureus: Pharmacokinetic/Pharmacodynamic Targets for Vancomycin Exposure
Authors: Lenhard Justin R. , Brown Tanya , Rybak Michael J. , Meaney Calvin J. , Norgard Nicholas B. , Bulman Zackery P. , Brazeau Daniel A. , Gill Steven R. , Tsuji Brian T. 
Published: December 2015

ABSTRACT

Staphylococcus aureus
possesses exceptional virulence and a remarkable ability to adapt in the face of antibiotic therapy. We examined the
in vitro
evolution of
S. aureus
in response to escalating vancomycin exposure by evaluating bacterial killing and the progression of resistance. A hollow-fiber infection model was utilized to simulate human doses of vancomycin increasing from 0.5 to 4 g every 12 h (q12h) versus a high inoculum (10
8
CFU/ml) of methicillin-resistant
S. aureus
(MRSA) USA300 and USA400. Host-pathogen interactions using
Galleria mellonella
and accessory gene regulator (
agr
) expression were studied in serially obtained isolates. In both USA300 and USA400 MRSA isolates, vancomycin exposure up to 2 g q12h resulted in persistence and regrowth, whereas 4 g administered q12h achieved sustained killing against both strains. As vancomycin exposure increased from 0.5 to 2 g q12h, the bacterial population shifted toward vancomycin-intermediate resistance, and collateral increases in the MICs of daptomycin and televancin were observed over 10 days. Guideline-recommended exposure of a ratio of the area under the concentration-time curve for the free, unbound fraction of the drug to the MIC (
f
AUC/MIC ratio) of 200 displayed a 0.344-log bacterial reduction in area, whereas
f
AUC/MICs of 371 and 554 were needed to achieve 1.00- and 2.00-log reductions in area, respectively. The stepwise increase in resistance paralleled a decrease in
G. mellonella
mortality (
P
= 0.021) and a gradual decline of RNAIII expression over 10 days. Currently recommended doses of vancomycin resulted in amplification of resistance and collateral damage to other antibiotics. Decreases in
agr
expression and virulence during therapy may be an adaptive mechanism of
S. aureus
persistence.
Comparison of UV-Induced Inactivation and RNA Damage in MS2 Phage across the Germicidal UV Spectrum
Authors: Beck Sara E. , Rodriguez Roberto A. , Hawkins Michael A. , Hargy Thomas M. , Larason Thomas C. , Linden Karl G. 
Published: December 2015

ABSTRACT
Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength. The bacteriophage was exposed to monochromatic UV irradiation from a tunable laser at wavelengths of between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (reverse transcription-quantitative PCR) was performed to measure genomic damage for comparison with genomic damage at 253.7 nm. The results indicate that the rates of RNA damage closely mirror the loss of viral infectivity across the germicidal UV spectrum. This demonstrates that genomic damage is the dominant cause of MS2 inactivation from exposure to germicidal UV irradiation. These findings contrast those for adenovirus, for which MS2 is used as a viral surrogate for validating polychromatic UV reactors.
Assessment of Chlamydia psittaci Shedding and Environmental Contamination as Potential Sources of Worker Exposure throughout the Mule Duck Breeding Process
Authors: Hulin V. , Bernard P. , Vorimore F. , Aaziz R. , Cléva D. , Robineau J. , Durand B. , Angelis L. , Siarkou V. I. , Laroucau K. 
Published: December 2015

ABSTRACT

Chlamydia psittaci
is an obligate intracellular bacterium responsible for avian chlamydiosis, otherwise known as psittacosis, a zoonotic disease that may lead to severe atypical pneumonia. This study was conducted on seven mule duck flocks harboring asymptomatic birds to explore the circulation and persistence of
C. psittaci
during the entire breeding process and assess the potential sources of worker exposure. Cloacal swabs and air samples were taken on each occasion requiring humans to handle the birds. In parallel, environmental samples, including dust, water, and soil, were collected. Specific real-time PCR analyses revealed the presence of
C. psittaci
in all flocks but with three different shedding patterns involving ducks about the age of 4, 8, and 12 weeks with heavy, moderate, and low excretion levels, respectively. Air samples were only positive in flocks harboring heavy shedders. Dust in flocks with heavy or moderate shedders carried chlamydial loads strongly associated with the loads detected in avian and soil samples. Environmental contamination, significantly correlated with shedding dynamics, was considered to be the most probable source of exposure. The high prevalence of bacteriophage Chp1 in all flocks, mostly jointly present with chlamydia, suggests an important factor in
C. psittaci
persistence, thus creating a greater risk for humans. A survey conducted in these flocks regarding farming practices and activities showed that disinfection seems to be the most promising practice for reducing
C. psittaci
prevalence in ducks and that the place and the duration of action during operations seem to be potential risk factors. Strict adherence to good practices is strongly recommended.
Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph
Authors: Harrold Zoë R. , Skidmore Mark L. , Hamilton Trinity L. , Desch Libby , Amada Kirina , van Gelder Will , Glover Kevin , Roden Eric E. , Boyd Eric S. 
Published: December 2015

ABSTRACTGeochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O32−), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O32−that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2oxidation product sulfate (SO42−) several orders of magnitude higher than those of S2O32−. Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobeThiobacillussp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O32−, CO2fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O32−as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts ofsoxB, which encodes a component of the S2O32−-oxidizing complex, were closely affiliated withsoxBfrom RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O32−by RG5-like populations may accelerate abiotic FeS2oxidation, thereby enhancing mineral weathering in the subglacial environment.
Characterization of New Virulence Factors Involved in the Intracellular Growth and Survival of Burkholderia pseudomallei
Authors: Moule Madeleine G. , Spink Natasha , Willcocks Sam , Lim Jiali , Guerra-Assunção José Afonso , Cia Felipe , Champion Olivia L. , Senior Nicola J. , Atkins Helen S. , Clark Taane , Bancroft Gregory J. , Cuccui Jon , Wren Brendan W. 
Published: December 2015

ABSTRACT

Burkholderia pseudomallei
, the causative agent of melioidosis, has complex and poorly understood extracellular and intracellular lifestyles. We used transposon-directed insertion site sequencing (TraDIS) to retrospectively analyze a transposon library that had previously been screened through a BALB/c mouse model to identify genes important for growth and survival
in vivo
. This allowed us to identify the insertion sites and phenotypes of negatively selected mutants that were previously overlooked due to technical constraints. All 23 unique genes identified in the original screen were confirmed by TraDIS, and an additional 105 mutants with various degrees of attenuation
in vivo
were identified. Five of the newly identified genes were chosen for further characterization, and clean, unmarked
bpsl2248
,
tex
,
rpiR
,
bpsl1728
, and
bpss1528
deletion mutants were constructed from the wild-type strain K96243. Each of these mutants was tested
in vitro
and
in vivo
to confirm their attenuated phenotypes and investigate the nature of the attenuation. Our results confirm that we have identified new genes important to
in vivo
virulence with roles in different stages of
B. pseudomallei
pathogenesis, including extracellular and intracellular survival. Of particular interest, deletion of the transcription accessory protein Tex was shown to be highly attenuating, and the
tex
mutant was capable of providing protective immunity against challenge with wild-type
B. pseudomallei
, suggesting that the genes identified in our TraDIS screen have the potential to be investigated as live vaccine candidates.