bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mycobacterium abscessus WhiB7 Regulates a Species-Specific Repertoire of Genes To Confer Extreme Antibiotic Resistance
Authors: Hurst-Hess Kelley , Rudra Paulami , Ghosh Pallavi 
Published: September 2017

ABSTRACT

Mycobacterium abscessus
causes acute and chronic bronchopulmonary infection in patients with chronic lung damage, of which cystic fibrosis (CF) patients are particularly vulnerable. The major threat posed by this organism is its high intrinsic antibiotic resistance. A typical treatment regimen involves a 6- to 12-month-long combination therapy of clarithromycin and amikacin, with cure rates below 50% and multiple side effects, especially due to amikacin. In the present work, we show that
M. abscessus
whiB7
, a homologue of
Mycobacterium tuberculosis
and
Mycobacterium smegmatis whiB7
with previously demonstrated effects on intrinsic antibiotic resistance, is strongly induced when exposed to clinically relevant antibiotics that target the ribosome: erythromycin, clarithromycin, amikacin, tetracycline, and spectinomycin. The deletion of
M. abscessus
whiB7
results in sensitivity to all of the above-mentioned antibiotics. Further, we have defined and compared the
whiB7
regulon of
M. abscessus
with the closely related nontuberculous mycobacterium (NTM)
M. smegmatis
to demonstrate the induction of a species-specific repertoire of genes. Finally, we show that one such gene,
eis2
, is specifically induced in
M. abscessus
by
whiB7
and contributes to its higher levels of intrinsic amikacin resistance. This species-specific pattern of gene induction might account for the differences in drug susceptibilities to other antibiotics and between different mycobacterial species.
Immunodeficiency and Intermittent Dosing Promote Acquired Rifamycin Monoresistance in Murine Tuberculosis
Authors: Park Sang-Won , Tasneen Rokeya , Converse Paul J. , Nuermberger Eric L. 
Published: September 2017

ABSTRACT

More-permissive preclinical models may be useful in evaluating antituberculosis regimens for their propensity to select drug-resistant mutants. To evaluate whether acquired rifamycin monoresistance could be recapitulated in mice and, if so, to evaluate the effects of immunodeficiency, intermittent dosing, and drug exposures, athymic nude and BALB/c mice were infected. Controls received daily rifapentine alone or 2 months of rifampin, isoniazid, pyrazinamide, and ethambutol, followed by 4 months of rifampin/isoniazid, either daily or twice weekly with one of two isoniazid doses. Test groups received the same intensive regimen followed by once-weekly rifapentine or isoniazid/rifapentine with rifapentine doses of 10, 15, or 20 mg/kg of body weight plus one of two isoniazid doses. All combination regimens rendered BALB/c mouse cultures negative but selected mutants resistant to isoniazid (8.5%, 12/140) or rifampin (3.5%, 5/140) in nude mice (
P
< 0.001). Intermittently dosed intensive-phase therapy selected isoniazid and rifampin resistance in 10% (8/80,
P
< 0.001) and 20% (16/80,
P
= 0.009) of nude mice, respectively, compared to 0% treated with a daily regimen. Once-weekly rifapentine-containing continuation-phase regimens selected rifampin-resistant mutants at a rate of 18.0% (18/100,
P
= 0.035 compared to rifampin/isoniazid regimens). Higher isoniazid doses in the intermittent-treatment control regimen and higher rifapentine doses in once-weekly regimens were associated with less selection of isoniazid resistance. Acquired resistance, including rifamycin monoresistance, was more likely to occur in nude mice despite administration of combination therapy. These results recapitulate clinical outcomes and indicate that nude mice may be useful for evaluating the ability of novel regimens to prevent the selection of resistance.
Salmonella Utilizes Zinc To Subvert Antimicrobial Host Defense of Macrophages via Modulation of NF-κB Signaling
Authors: Wu Aimin , Tymoszuk Piotr , Haschka David , Heeke Simon , Dichtl Stefanie , Petzer Verena , Seifert Markus , Hilbe Richard , Sopper Sieghart , Talasz Heribert , Bumann Dirk , Lass-Flörl Cornelia , Theurl Igor , Zhang Keying , Weiss Guenter 
Published: September 2017

ABSTRACT

Zinc sequestration by macrophages is considered a crucial host defense strategy against infection by the intracellular bacterium
Salmonella enterica
serovar Typhimurium. However, the underlying mechanisms remain elusive. In this study, we found that zinc favors pathogen survival within macrophages.
Salmonella
-hosting macrophages contained higher free zinc levels than did uninfected macrophages and cells that successfully eliminated bacteria, which was paralleled by the impaired production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in bacterium-harboring cells. A profound, zinc-mediated inhibition of NF-κB p65 transcriptional activity affecting the expression of the ROS- and RNS-forming enzymes phos47 and inducible nitric oxide synthase (iNOS) provided a mechanistic explanation for this phenomenon. Macrophages responded to infection by enhancing the expression of zinc-scavenging metallothioneins 1 and 2, whose genetic deletion caused increased free zinc levels, reduced ROS and RNS production, and increased the survival of
Salmonella
. Our data suggest that
Salmonella
invasion of macrophages results in a bacterium-driven increase in the intracellular zinc level, which weakens antimicrobial defense and the ability of macrophages to eradicate the pathogen. Thus, limitation of cytoplasmic zinc levels may help to control infection by intracellular bacteria.
Modulation of CD4
+
and CD8
+
T Cell Function and Cytokine Responses in Strongyloides stercoralis Infection by Interleukin-27 (IL-27) and IL-37
Authors: Anuradha Rajamanickam , Munisankar Saravanan , Bhootra Yukthi , Dolla Chandrakumar , Kumaran Paul , Nutman Thomas B. , Babu Subash 
Published: September 2017

ABSTRACT

Strongyloides stercoralis
infection is associated with diminished antigen-specific Th1- and Th17-associated responses and enhanced Th2-associated responses. Interleukin-27 (IL-27) and IL-37 are two known anti-inflammatory cytokines that are highly expressed in
S. stercoralis
infection. We therefore wanted to examine the role of IL-27 and IL-37 in regulating CD4
+
and CD8
+
T cell responses in
S. stercoralis
infection. To this end, we examined the frequency of Th1/Tc1, Th2/Tc2, Th9/Tc9, Th17/Tc17, and Th22/Tc22 cells in 15
S. stercoralis
-infected individuals and 10 uninfected individuals stimulated with parasite antigen following IL-27 or IL-37 neutralization. We also examined the production of prototypical type 1, type 2, type 9, type 17, and type 22 cytokines in the whole-blood supernatants. Our data reveal that IL-27 or IL-37 neutralization resulted in significantly enhanced frequencies of Th1/Tc1, Th2/Tc2, Th17/Tc17, Th9, and Th22 cells with parasite antigen stimulation. There was no induction of any T cell response in uninfected individuals following parasite antigen stimulation and IL-27 or IL-37 neutralization. Moreover, we also observed increased production of gamma interferon (IFN-γ), IL-5, IL-9, IL-17, and IL-22 and decreased production of IL-10 following IL-27 and IL-37 neutralization and parasite antigen stimulation in whole-blood cultures. Thus, we demonstrate that IL-27 and IL-37 limit the induction of particular T cell subsets along with cytokine responses in
S. stercoralis
infections, which suggest the importance of IL-27 and IL-37 in immune modulation in a chronic helminth infection.
Defining the Mechanical Determinants of Kingella kingae Adherence to Host Cells
Authors: Kern Brad K. , Porsch Eric A. , St. Geme Joseph W. 
Published: September 2017

ABSTRACT

Kingella kingae
is an important pathogen in young children and initiates infection by colonizing the posterior pharynx. Adherence to pharyngeal epithelial cells is an important first step in the process of colonization. In the present study, we sought to elucidate the interplay of type IV pili (T4P), a trimeric autotransporter adhesin called Knh, and the polysaccharide capsule in
K. kingae
adherence to host cells. Using adherence assays performed under shear stress, we observed that a strain expressing only Knh was capable of higher levels of adherence than a strain expressing only T4P. Using atomic force microscopy and transmission electron microscopy (TEM), we established that the capsule had a mean depth of 700 nm and that Knh was approximately 110 nm long. Using cationic ferritin capsule staining and thin-section transmission electron microscopy, we found that when bacteria expressing retractile T4P were in close contact with host cells, the capsule was absent at the point of contact between the bacterium and the host cell membrane. In a T4P retraction-deficient mutant, the capsule depth remained intact and adherence levels were markedly reduced. These results support the following model: T4P make initial contact with the host cell and mediate low-strength adherence. T4P retract, pulling the organism closer to the host cell and displacing the capsule, allowing Knh to be exposed and mediate high-strength, tight adherence to the host cell surface. This report provides the first description of the mechanical displacement of capsule enabling intimate bacterial adherence to host cells.

IMPORTANCE
Adherence to host cells is an important first step in bacterial colonization and pathogenicity.
Kingella kingae
has three surface factors that are involved in adherence: type IV pili (T4P), a trimeric autotransporter adhesin called Knh, and a polysaccharide capsule. Our results suggest that T4P mediate initial contact and low-strength adherence to host cells. T4P retraction draws the bacterium closer to the host cell and causes the displacement of capsule. This displacement exposes Knh and allows Knh to mediate high-strength adherence to the host cell. This work provides new insight into the interplay of T4P, a nonpilus adhesin, and a capsule and their effects on bacterial adherence to host cells.
Extracellular SalB Contributes to Intrinsic Cephalosporin Resistance and Cell Envelope Integrity in Enterococcus faecalis
Authors: Djorić Dušanka , Kristich Christopher J. 
Published: September 2017

ABSTRACT

Enterococci are major causes of hospital-acquired infections. Intrinsic resistance to cephalosporins is a universal trait among clinically relevant enterococci. Cephalosporin resistance enables enterococci to proliferate to high densities in the intestines of patients undergoing cephalosporin treatment, a precursor to the emergence of infection. However, the genetic and biochemical mechanisms of intrinsic cephalosporin resistance in enterococci are not well understood. A two-component signal transduction system, CroR/S, is required for cephalosporin resistance in enterococci. Although the CroR/S regulon is not well defined, one gene reported to be CroR dependent in
Enterococcus faecalis
JH2-2 encodes an extracellular putative peptidoglycan hydrolase, SalB. To test the hypothesis that SalB is responsible for CroR-dependent cephalosporin resistance, we examined Δ
salB
mutants in multiple genetic lineages of
E. faecalis
, revealing that SalB is required not only for intrinsic cephalosporin resistance but also for maintenance of cell envelope integrity in the absence of antibiotic stress. The N-terminal signal sequence is necessary for SalB secretion, and secretion is required for SalB to promote cephalosporin resistance. Functional dissection revealed that the C-terminal SCP domain of SalB is essential for biological activity and identified three residues within the SCP domain that are required for the stability and function of SalB. Additionally, we found that in contrast to what is seen in
E. faecalis
JH2-2, SalB is not regulated by the CroR/S two-component system in
E. faecalis
OG1, suggesting diversity in the CroR/S regulon among distinct lineages of
E. faecalis
.

IMPORTANCE
Resistance to cephalosporins is universal among clinically relevant enterococci, enabling enterococcal proliferation to high densities in the intestines of patients undergoing cephalosporin treatment, a precursor to the emergence of infection. Disabling cephalosporin resistance could therefore reduce the incidence of enterococcal infections. However, the genetic and biochemical mechanisms of cephalosporin resistance are not well understood. The significance of this work is the identification of a novel extracellular factor (SalB) that promotes cephalosporin resistance in
E. faecalis
, which could potentially serve as a target for therapeutics that impair enterococcal cephalosporin resistance. Additionally, our work highlights the importance of the C-terminal SCP domain of SalB, including several conserved residues within the SCP domain, for the ability of SalB to promote cephalosporin resistance.
Inhibition of the ATP Synthase Eliminates the Intrinsic Resistance of
Staphylococcus aureus
towards Polymyxins
Authors: Vestergaard Martin , Nøhr-Meldgaard Katrine , Bojer Martin Saxtorph , Krogsgård Nielsen Christina , Meyer Rikke Louise , Slavetinsky Christoph , Peschel Andreas , Ingmer Hanne 
Published: September 2017

ABSTRACT

Staphylococcus aureus
is intrinsically resistant to polymyxins (polymyxin B and colistin), an important class of cationic antimicrobial peptides used in treatment of Gram-negative bacterial infections. To understand the mechanisms underlying intrinsic polymyxin resistance in
S. aureus
, we screened the Nebraska Transposon Mutant Library established in
S. aureus
strain JE2 for increased susceptibility to polymyxin B. Nineteen mutants displayed at least 2-fold reductions in MIC, while the greatest reductions (8-fold) were observed for mutants with inactivation of either
graS
,
graR
,
vraF
, or
vraG
or the subunits of the ATP synthase (
atpA
,
atpB
,
atpG
, or
atpH
), which during respiration is the main source of energy. Inactivation of
atpA
also conferred hypersusceptibility to colistin and the aminoglycoside gentamicin, whereas susceptibilities to nisin, gallidermin, bacitracin, vancomycin, ciprofloxacin, linezolid, daptomycin, and oxacillin were unchanged. ATP synthase activity is known to be inhibited by oligomycin A, and the presence of this compound increased polymyxin B-mediated killing of
S. aureus
. Our results demonstrate that the ATP synthase contributes to intrinsic resistance of
S. aureus
towards polymyxins and that inhibition of the ATP synthase sensitizes
S. aureus
to this group of compounds. These findings show that by modulation of bacterial metabolism, new classes of antibiotics may show efficacy against pathogens towards which they were previously considered inapplicable. In light of the need for new treatment options for infections with serious pathogens like
S. aureus
, this approach may pave the way for novel applications of existing antibiotics.

IMPORTANCE
Bacterial pathogens that cause disease in humans remain a serious threat to public health, and antibiotics are still our primary weapon in treating bacterial diseases. The ability to eradicate bacterial infections is critically challenged by development of resistance to all clinically available antibiotics. Polymyxins constitute an important class of antibiotics for treatment of infections caused by Gram-negative pathogens, whereas Gram-positive bacteria remain largely insusceptible towards class of antibiotics. Here we performed a whole-genome screen among nonessential genes for polymyxin intrinsic resistance determinants in
Staphylococcus aureus
. We found that the ATP synthase is important for polymyxin susceptibility and that inhibition of the ATP synthase sensitizes
S. aureus
towards polymyxins. Our study provides novel insights into the mechanisms that limit polymyxin activity against
S. aureus
and provides valuable targets for inhibitors to potentially enable the use of polymyxins against
S. aureus
and other Gram-positive pathogens.
Pyruvate Accumulation Is the First Line of Cell Defense against Heat Stress in a Fungus
Authors: Zhang Xing , St. Leger Raymond J. , Fang Weiguo 
Published: September 2017

ABSTRACT

Heat tolerance is well known to be key to fungal survival in many habitats, but our mechanistic understanding of how organisms adapt to heat stress is still incomplete. Using
Metarhizium robertsii
, an emerging model organism for assessing evolutionary processes, we report that pyruvate is in the vanguard of molecules that scavenge heat-induced reactive oxygen species (ROS). We show that, as well as inducing a rapid burst of ROS production, heat stress also downregulates genes for pyruvate consumption. The accumulating pyruvate is the fastest acting of several
M. robertsii
ROS scavengers, efficiently reducing protein carbonylation, stabilizing mitochondrial membrane potential, and promoting fungal growth. The acetate produced from pyruvate-ROS reactions itself causes acid stress, tolerance to which is regulated by Hog1 mitogen-activated protein kinase. Heat stress also induces pyruvate accumulation in several other fungi, suggesting that scavenging of heat-induced ROS by pyruvate is widespread.

IMPORTANCE
Heat is a dangerous challenge for most organisms, as it denatures proteins and induces the production of ROS that inactivate proteins, lipid membranes, and DNA. How organisms respond to this stress is not fully understood. Using the experimentally tractable insect pathogen
Metarhizium robertsii
as a model organism, we show for the first time that heat stress induces pyruvate production and that this functions as the first line of defense against heat-induced ROS. Heat stress also induces rapid pyruvate accumulation in other fungi, suggesting that pyruvate is a common but unappreciated defense against stress.
A novel prognostic model for transplant-free survival in primary sclerosing cholangitis
Authors: de Vries Elisabeth M , Wang Junfeng , Williamson Kate D , Leeflang Mariska M , Boonstra Kirsten , Weersma Rinse K , Beuers Ulrich , Chapman Roger W , Geskus Ronald B , Ponsioen Cyriel Y 
Published: September 2017

Objective
Most prognostic models for primary sclerosing cholangitis (PSC) are based on patients referred to tertiary care and may not be applicable for the majority of patients with PSC. The aim of this study was to construct and externally validate a novel, broadly applicable prognostic model for transplant-free survival in PSC, based on a large, predominantly population-based cohort using readily available variables.

Design
The derivation cohort consisted of 692 patients with PSC from the Netherlands, the validation cohort of 264 patients with PSC from the UK. Retrospectively, clinical and biochemical variables were collected. We derived the prognostic index from a multivariable Cox regression model in which predictors were selected and parameters were estimated using the least absolute shrinkage and selection operator. The composite end point of PSC-related death and liver transplantation was used. To quantify the models’ predictive value, we calculated the C-statistic as discrimination index and established its calibration accuracy by comparing predicted curves with Kaplan-Meier estimates.

Results
The final model included the variables: PSC subtype, age at PSC diagnosis, albumin, platelets, aspartate aminotransferase, alkaline phosphatase and bilirubin. The C-statistic was 0.68 (95% CI 0.51 to 0.85). Calibration was satisfactory. The model was robust in the sense that the C-statistic did not change when prediction was based on biochemical variables collected at follow-up.

Conclusion
The Amsterdam-Oxford model for PSC showed adequate performance in estimating PSC-related death and/or liver transplant in a predominantly population-based setting. The transplant-free survival probability can be recalculated when updated biochemical values are available.
Plate-type metamaterials for extremely broadband low-frequency sound insulation
Authors: Wang Xiaopeng , Guo Xinwei , Chen Tianning , Yao Ge 
Published: September 2017

A novel plate-type acoustic metamaterial with a high sound transmission loss (STL) in the low-frequency range ([Formula: see text]1000 Hz) is designed, theoretically proven and then experimentally verified. The thin plates with large modulus used in this paper mean that we do not need to apply tension to the plates, which is more applicable to practical engineering, the achievement of noise reduction is better and the installation of plates is more user-friendly than that of the membranes. The effects of different structural parameters of the plates on the sound-proofed performance at low-frequencies were also investigated by experiment and finite element method (FEM). The results showed that the STL can be modulated effectively and predictably using vibration theory by changing the structural parameters, such as the radius and thickness of the plate. Furthermore, using unit cells of different geometric sizes which are responsible for different frequency regions, the stacked panels with thickness [Formula: see text]16 mm and weight [Formula: see text]5 kg/m2 showed high STL below 2000 Hz. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation.
A Phase II Trial of Neoadjuvant MK-2206, an AKT Inhibitor, with Anastrozole in Clinical Stage II or IIIPIK3CA-Mutant ER-Positive and HER2-Negative Breast Cancer
Authors: Ma Cynthia X. , Suman Vera , Goetz Matthew P. , Northfelt Donald , Burkard Mark E. , Ademuyiwa Foluso , Naughton Michael , Margenthaler Julie , Aft Rebecca , Gray Richard , Tevaarwerk Amye , Wilke Lee , Haddad Tufia , Moynihan Timothy , Loprinzi Charles , Hieken Tina , Barnell Erica K. , Skidmore Zachary L. , Feng Yan-Yang , Krysiak Kilannin , Hoog Jeremy , Guo Zhanfang , Nehring Leslie , Wisinski Kari B. , Mardis Elaine , Hagemann Ian S. , Vij Kiran , Sanati Souzan , Al-Kateb Hussam , Griffith Obi L. , Griffith Malachi , Doyle Laurence , Erlichman Charles , Ellis Matthew J. 
Published: September 2017

AbstractPurpose: Hyperactivation of AKT is common and associated with endocrine resistance in estrogen receptor–positive (ER+) breast cancer. The allosteric pan-AKT inhibitor MK-2206 induced apoptosis in PIK3CA-mutant ER+ breast cancer under estrogen-deprived condition in preclinical studies. This neoadjuvant phase II trial was therefore conducted to test the hypothesis that adding MK-2206 to anastrozole induces pathologic complete response (pCR) in PIK3CA mutant ER+ breast cancer.Experimental Design: Potential eligible patients with clinical stage II/III ER+/HER2− breast cancer were preregistered and received anastrozole (goserelin if premenopausal) for 28 days in cycle 0 pending tumor PIK3CA sequencing. Patients positive for PIK3CA mutation in the tumor were eligible to start MK-2206 (150 mg orally weekly, with prophylactic prednisone) on cycle 1 day 2 (C1D2) and to receive a maximum of four 28-day cycles of combination therapy before surgery. Serial biopsies were collected at preregistration, C1D1 and C1D17.Results: Fifty-one patients preregistered and 16 of 22 with PIK3CA-mutant tumors received study drug. Three patients went off study due to C1D17 Ki67 &gt;10% (n = 2) and toxicity (n = 1). Thirteen patients completed neoadjuvant therapy followed by surgery. No pCRs were observed. Rash was common. MK-2206 did not further suppress cell proliferation and did not induce apoptosis on C1D17 biopsies. Although AKT phosphorylation was reduced, PRAS40 phosphorylation at C1D17 after MK-2206 persisted. One patient acquired an ESR1 mutation at surgery.Conclusions: MK-2206 is unlikely to add to the efficacy of anastrozole alone in PIK3CA-mutant ER+ breast cancer and should not be studied further in the target patient population. Clin Cancer Res; 23(22); 6823–32. ©2017 AACR.