bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of Antibiotics with Various Target Sites on the Metabolome of Staphylococcus aureus
Authors: Dörries Kirsten , Schlueter Rabea , Lalk Michael 
Published: September 2014

ABSTRACT

In this study, global intra- and extracellular metabolic profiles were exploited to investigate the impact of antibiotic compounds with different cellular targets on the metabolome of
Staphylococcus aureus
HG001. Primary metabolism was largely covered, yet uncommon staphylococcal metabolites were detected in the cytosol of
S. aureus
, including sedoheptulose-1,7-bisphosphate and the UDP-MurNAc-pentapeptide with an alanine-seryl residue. By comparing the metabolic profiles of unstressed and stressed staphylococcal cells in a time-dependent manner, we found far-ranging effects within the metabolome. For each antibiotic compound, accumulation as well as depletion of metabolites was detected, often comprising whole biosynthetic pathways, such as central carbon and amino acid metabolism and peptidoglycan, purine, and pyrimidine synthesis. Ciprofloxacin altered the pool of (deoxy)nucleotides as well as peptidoglycan precursors, thus linking stalled DNA and cell wall synthesis. Erythromycin tended to increase the amounts of intermediates of the pentose phosphate pathway and lysine. Fosfomycin inhibited the first enzymatic step of peptidoglycan synthesis, which was followed by decreased levels of peptidoglycan precursors but enhanced levels of substrates such as UDP-GlcNAc and alanine-alanine. In contrast, vancomycin and ampicillin inhibited the last stage of peptidoglycan construction on the outer cell surface. As a result, the amounts of UDP-MurNAc-peptides drastically increased, resulting in morphological alterations in the septal region and in an overall decrease in central metabolite levels. Moreover, each antibiotic affected intracellular levels of tricarboxylic acid cycle intermediates.
In Vivo
Efficacy of Humanized Exposures of Ceftazidime-Avibactam in Comparison with Ceftazidime against Contemporary Enterobacteriaceae Isolates
Authors: MacVane Shawn H. , Crandon Jared L. , Nichols Wright W. , Nicolau David P. 
Published: September 2014

ABSTRACT

Ceftazidime-avibactam is a β-lactam β-lactamase inhibitor combination under investigation for the treatment of serious Gram-negative infections. When combined with avibactam, a novel non-β-lactam β-lactamase inhibitor, ceftazidime has activity against isolates that produce Ambler class A, class C, and some class D β-lactamases. However, little is known of the
in vivo
efficacy of the combination against these targeted ceftazidime- and carbapenem-resistant
Enterobacteriaceae
. Using humanized exposures in the murine thigh model, we evaluated the efficacy of ceftazidime-avibactam against
Enterobacteriaceae
exhibiting MICs of ≥8 μg/ml to aid in the assignment of interpretive susceptibility criteria. Eighteen clinical
Enterobacteriaceae
isolates, including nine carbapenem-resistant strains, were evaluated against ceftazidime-avibactam (2,000 mg/500 mg) as a 2-h infusion every 8 h. To highlight the impact of avibactam, 13 select isolates were tested in the neutropenic model against a humanized regimen of 2,000 mg ceftazidime every 8 h (2-h infusion). Additionally, nine isolates were evaluated in immunocompetent animals. The efficacy was evaluated as the change in log
10
CFU compared with that of 0-h controls after 24 h. The vast majority (17/18, 94%) of the isolates were resistant to ceftazidime alone. The ceftazidime monotherapy failed to have activity against 10 of 13 isolates, while ceftazidime-avibactam produced reductions in bacterial density against 16 of 18 isolates. Ceftazidime-avibactam (2,000 mg/500 mg) every 8 h (2-h infusion) displayed dependable activity against the
Enterobacteriaceae
isolates, exhibiting MICs of ≤16 μg/ml (free drug concentration above the MIC [
f
T
>MIC
] of ≥62%) and variable activity was noted at an MIC of 32 μg/ml (
f
T
>MIC
of 34%). The presence of a functioning immune system enhanced the efficacy for both regimens against all tested isolates. These data support further examination of the use of ceftazidime-avibactam as an effective therapy against infections due to Gram-negative infections, including carbapenem-resistant
Enterobacteriaceae
.
HIV-1 Group O Integrase Displays Lower Enzymatic Efficiency and Higher Susceptibility to Raltegravir than HIV-1 Group M Subtype B Integrase
Authors: Depatureaux Agnès , Quashie Peter K. , Mesplède Thibault , Han Yingshan , Koubi Hannah , Plantier Jean-Christophe , Oliveira Maureen , Moisi Daniela , Brenner Bluma , Wainberg Mark A. 
Published: September 2014

ABSTRACTHIV-1 group O (HIV-O) is a rare HIV-1 variant characterized by a high number of polymorphisms, especially in the integrase coding region. As HIV-O integrase enzymes have not previously been studied, our aim was to assess the impact of HIV-O integrase polymorphisms on enzyme function and susceptibility to integrase inhibitors. Accordingly, we cloned and purified integrase proteins from each of HIV-1 group O clades A and B, an HIV-O divergent strain, and HIV-1 group M (HIV-M, subtype B), used as a reference. To assess enzymatic function of HIV-O integrase, we carried out strand transfer and 3′ processing assays with various concentrations of substrate (DNA target and long terminal repeats [LTR], respectively) and characterized these enzymes for susceptibility to integrase strand transfer inhibitors (INSTIs) in cell-free assays and in tissue culture, in the absence or presence of various concentrations of several INSTIs. The inhibition constant (Ki) and 50% effective concentration (EC50) values were calculated for HIV-O integrases and HIV-O viruses, respectively, and compared with those of HIV-M. The results showed that HIV-O integrase displayed lower activity in strand transfer assays than did HIV-M enzyme, whereas 3′ processing activities were similar to those of HIV-M. HIV-O integrases were more susceptible to raltegravir (RAL) in competitive inhibition assays and in tissue culture than were HIV-M enzymes and viruses, respectively. Molecular modeling suggests that two key polymorphic residues that are close to the integrase catalytic site, 74I and 153A, may play a role in these differences.
Inflammation Is Associated with Voriconazole Trough Concentrations
Authors: van Wanrooy Marjolijn J. P. , Span Lambert F. R. , Rodgers Michael G. G. , van den Heuvel Edwin R. , Uges Donald R. A. , van der Werf Tjip S. , Kosterink Jos G. W. , Alffenaar Jan-Willem C. 
Published: September 2014

ABSTRACT

Voriconazole concentrations display a large variability, which cannot completely be explained by known factors. Inflammation may be a contributing factor, as inflammatory stimuli can change the activities and expression levels of cytochrome P450 isoenzymes. We explored the correlation between inflammation, reflected by C-reactive protein (CRP) concentrations, and voriconazole trough concentrations. A retrospective chart review of patients with at least one steady-state voriconazole trough concentration and a CRP concentration measured on the same day was performed. A total of 128 patients were included. A significantly (
P
< 0.001) higher voriconazole trough concentration was observed in patients with severe inflammation (6.2 mg/liter; interquartile range [IQR], 3.4 to 8.7 mg/liter;
n
= 20) than in patients with moderate inflammation (3.4 mg/liter; IQR, 1.6 to 5.4 mg/liter;
n
= 60) and in patients with no to mild inflammation (1.6 mg/liter; IQR, 0.8 to 3.0 mg/liter;
n
= 48). The patients in all three groups received similar voriconazole doses based on mg/kg body weight (
P
= 0.368). Linear regression analyses, both unadjusted and adjusted for covariates of gender, age, dose, route of administration, liver enzymes, and interacting coadministered medications, showed a significant association between voriconazole and CRP concentration (
P
< 0.001). For every 1-mg/liter increase in the CRP concentration, the voriconazole trough concentration increased by 0.015 mg/liter (unadjusted 95% confidence interval [CI], 0.011 to 0.020 mg/liter; adjusted 95% CI, 0.011 to 0.019 mg/liter). Inflammation, reflected by the C-reactive protein concentration, is associated with voriconazole trough concentrations. Further research is necessary to assess if taking the inflammatory status of a patient into account is helpful in therapeutic drug monitoring of voriconazole to maintain concentrations in the therapeutic window, thereby possibly preventing suboptimal treatment or adverse events.
Effect of Ceftriaxone on the Outcome of Murine Pyelonephritis Caused by Extended-Spectrum-β-Lactamase-Producing Escherichia coli
Authors: Tratselas A. , Simitsopoulou M. , Giannakopoulou A. , Dori I. , Saoulidis S. , Kollios K. , Papaioannidou P. , Pournaras S. , Roilides E. 
Published: September 2014

ABSTRACT

Urinary tract infections (UTIs) due to extended-spectrum-β-lactamase (ESBL)-producing
Enterobacteriaceae
in children are becoming more frequent, and they are commonly treated initially with a second- or third-generation cephalosporin. We developed a murine model of ascending UTI caused by ESBL-producing
Escherichia coli
. Using this model, we investigated the renal bacterial burden, interleukin-6 (IL-6) expression, and histopathological alterations caused by ESBL- and non-ESBL-producing bacteria after 1, 2, or 6 days with or without ceftriaxone therapy. The renal bacterial burden, IL-6 concentration, and histological inflammatory lesions were not significantly different between mice infected with ESBL- and non-ESBL-producing bacteria without treatment at any of the time points examined. Following ceftriaxone administration, the bacterial burden was eliminated in the kidneys of mice infected with ESBL- and non-ESBL-producing bacteria on the 6th postinfection day. The histological analysis demonstrated that among mice treated with ceftriaxone, those infected with ESBL-producing bacteria had more profound renal alterations than those infected with non-ESBL-producing bacteria on the 6th day (
P
< 0.001). In comparison, microbiological outcomes did not differ significantly between mice infected with ESBL- and non-ESBL-producing bacteria at any of the time points examined. The effectiveness of ceftriaxone in mice with UTIs due to ESBL-producing
E. coli
may have therapeutic implications; it is, however, hampered by limited activity on the histopathological lesions, a finding that needs further investigation.
Cellular Requirements for Systemic Control of Salmonella enterica Serovar Typhimurium Infections in Mice
Authors: Kupz Andreas , Bedoui Sammy , Strugnell Richard A. 
Published: September 2014

ABSTRACTThe rational design of vaccines requires an understanding of the contributions of individual immune cell subsets to immunity. With this understanding, targeted vaccine delivery approaches and adjuvants can be developed to maximize vaccine efficiency and to minimize side effects (S. H. E. Kaufmann et al., Immunity 33:555–577, 2010; T. Ben-Yedidia and R. Arnon, Hum. Vaccines 1:95–101, 2005). We have addressed the contributions of different immune cell subsets and their ability to contribute to the control and clearance of the facultative intracellular pathogenSalmonella entericaserovar Typhimurium (S. Typhimurium) in a murine model. Using a systematic and reproducible model of experimental attenuatedS. Typhimurium infection, we show that distinct lymphocyte deficiencies lead to one of four different infection outcomes: clearance, chronic infection, early death, or late death. Our study demonstrates a high level of functional redundancy in the ability of different lymphocyte subsets to provide interferon gamma (IFN-γ), a critical cytokine inSalmonellaimmunity. Whereas early control of the infection was entirely dependent on IFN-γ but not on any particular lymphocyte subset, clearance of the infection critically required CD4+T cells but appeared to be independent of IFN-γ. These data reinforce the idea of a bimodal immune response againstSalmonella: an early T cell-independent but IFN-γ-dependent phase and a late T cell-dependent phase that may be IFN-γ independent.
Antigenic Variation of TprK Facilitates Development of Secondary Syphilis
Authors: Reid Tara B. , Molini Barbara J. , Fernandez Mark C. , Lukehart Sheila A. 
Published: September 2014

ABSTRACTAlthough primary syphilis lesions heal spontaneously, the infection is chronic, with subsequent clinical stages. Healing of the primary chancre occurs as antibodies against outer membrane antigens facilitate opsonophagocytosis of the bacteria by activated macrophages. TprK is an outer membrane protein that undergoes antigenic variation at 7 variable regions, and variants are selected by immune pressure. We hypothesized that individual TprK variants escape immune clearance and seed new disseminated lesions to cause secondary syphilis. As in human syphilis, infected rabbits may develop disseminated secondary skin lesions. This study explores the nature of secondary syphilis, specifically, the contribution of antigenic variation to the development of secondary lesions. Our data from the rabbit model show that the odds of secondary lesions containing predominately TprK variant treponemes is 3.3 times higher than the odds of finding TprK variants in disseminated primary lesions (odds ratio [OR] = 3.3 [95% confidence interval {CI}, 0.98 to 11.0];P= 0.055) and that 96% of TprK variant secondary lesions are likely seeded by single treponemes. Analysis of antibody responses demonstrates significantly higher antibody titers totprKvariable region sequences found in the inoculum compared to reactivity totprKvariant sequences found in newly arising secondary lesions. This suggests thattprKvariants escape the initial immune response raised against the V regions expressed in the inoculum. These data further support a role for TprK in immune evasion and suggest that the ability of TprK variants to persist despite a robust immune response is instrumental in the development of later stages of syphilis.
Enhanced Virulence of the Escherichia coli O157:H7 Spinach-Associated Outbreak Strain in Two Animal Models Is Associated with Higher Levels of Stx2 Production after Induction with Ciprofloxacin
Authors: Zangari T. , Melton-Celsa A. R. , Panda A. , Smith M. A. , Tatarov I. , De Tolla L. , O'Brien A. D. 
Published: September 2014

ABSTRACT

Shiga toxin (Stx)-producing
Escherichia coli
(STEC) causes hemorrhagic colitis and the hemolytic-uremic syndrome (HUS). STEC strains may produce Stx1a and/or Stx2a or variants of either toxin. A 2006 spinach-associated outbreak of STEC O157:H7 resulted in higher hospitalization and HUS rates than previous STEC outbreaks. The spinach isolate, strain K3995, contains both
stx
2a
and
stx
2c
. We hypothesized that the enhanced virulence of K3995 reflects the combination of
stx
2
alleles (carried on lysogenic phages) and/or the amount of Stx2 made by that strain. We compared the virulence of K3995 to those of other O157:H7 isolates and an isogenic Stx2 mutant in rabbits and mice. We also measured the relative levels of Stx2 produced from those strains with or without induction of the
stx
-carrying phage. Some rabbits infected with K3995 exhibited intestinal pathology and succumbed to infection, while none of those infected with O157:H7 strain 2812 (Stx1a
+
Stx2a
+
) died or showed pathological signs. Rabbits infected with the isogenic Stx2a mutant K3995
stx
2a
::
cat
were not colonized as well as those infected with K3995 and exhibited no signs of disease. In the streptomycin-treated mouse model, more animals infected with K3995 died than did those infected with O157:H7 strain 86-24 (Stx2a
+
). Additionally, K3995 produced higher levels of total Stx2 and toxin phage DNA in cultures after phage induction than did 86-24. Our results demonstrate the greater virulence of K3995 compared to other O157:H7 strains in rabbits and mice. We conclude that this enhanced virulence is linked to higher levels of Stx2 expression as a consequence of increased phage induction.
Fasciola hepatica Fatty Acid Binding Protein Induces the Alternative Activation of Human Macrophages
Authors: Figueroa-Santiago Olgary , Espino Ana M. 
Published: September 2014

ABSTRACT

The liver fluke
Fasciola hepatica
is a highly evolved parasite that uses sophisticated mechanisms to evade the host immune response. The immunosuppressive capabilities of the parasite have been associated with antigens secreted through the parasite's tegument, called excretory-secretory products (ESPs). Proteomic studies have identified the fatty acid binding protein (FABP) as one of molecules present in the parasite ESPs. Although FABP has been investigated for potential use in the development of vaccines against fascioliasis, its direct interaction with cells of immune system has not been studied. In this study, FABP was purified in native form from soluble extracts of
F. hepatica
adult flukes using a combination of molecular sieving chromatography and preparative isoelectric focusing. The immunological effect of the purified protein, termed Fh12, was assayed
in vitro
using monocyte-derived macrophages (MDM) obtained from healthy human donors. Results from the assay indicate that Fh12 produced a significantly increased arginase expression and activity and induced the expression of chitinase-3-like protein (CHI3L1). The assay also showed that Fh12 downregulated the production of nitric oxide (NO) and the expression of nitric oxide synthase (NOS2). This indicates that Fh12 induced the production of alternatively activated macrophages (AAMϕ). The results also demonstrated the ability of Fh12 to downregulate the secretion of the proinflammatory and inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and IL-1βB, even after stimulation with lipopolysaccharide (LPS), as well as its ability to stimulate the overexpression of IL-10. These results suggest a potent anti-inflammatory role for Fh12, which could occur via targeting of Toll-like receptor 4 (TLR4).
Sporulation during Growth in a Gut Isolate of Bacillus subtilis
Authors: Serra Cláudia R. , Earl Ashlee M. , Barbosa Teresa M. , Kolter Roberto , Henriques Adriano O. 
Published: September 2014

ABSTRACT

Sporulation by
Bacillus subtilis
is a cell density-dependent response to nutrient deprivation. Central to the decision of entering sporulation is a phosphorelay, through which sensor kinases promote phosphorylation of Spo0A. The phosphorelay integrates both positive and negative signals, ensuring that sporulation, a time- and energy-consuming process that may bring an ecological cost, is only triggered should other adaptations fail. Here we report that a gastrointestinal isolate of
B. subtilis
sporulates with high efficiency during growth, bypassing the cell density, nutritional, and other signals that normally make sporulation a post-exponential-phase response. Sporulation during growth occurs because Spo0A is more active per cell and in a higher fraction of the population than in a laboratory strain. This in turn, is primarily caused by the absence from the gut strain of the genes
rapE
and
rapK
, coding for two aspartyl phosphatases that negatively modulate the flow of phosphoryl groups to Spo0A. We show, in line with recent results, that activation of Spo0A through the phosphorelay is the limiting step for sporulation initiation in the gut strain. Our results further suggest that the phosphorelay is tuned to favor sporulation during growth in gastrointestinal
B. subtilis
isolates, presumably as a form of survival and/or propagation in the gut environment.
Role of Lipase from Community-Associated Methicillin-Resistant Staphylococcus aureus Strain USA300 in Hydrolyzing Triglycerides into Growth-Inhibitory Free Fatty Acids
Authors: Cadieux Brigitte , Vijayakumaran Vithooshan , Bernards Mark A. , McGavin Martin J. , Heinrichs David E. 
Published: September 2014

ABSTRACT

Part of the human host innate immune response involves the secretion of bactericidal lipids on the skin and delivery of triglycerides into abscesses to control invading pathogens. Two

S
taphylococcus
a
ureus

l
ipases, named SAL1 and SAL2, were identified in the community-associated methicillin-resistant
S. aureus
strain USA300, which, presumably, are produced and function to degrade triglycerides to release free fatty acids. We show that the SAL2 lipase is one of the most abundant proteins secreted by USA300 and is proteolytically processed from the 72-kDa proSAL2 to the 44-kDa mature SAL2 by the metalloprotease aureolysin. We show that spent culture supernatants had lipase activity on both short- and long-chain fatty acid substrates and that deletion of
gehB
, encoding SAL2, resulted in the complete loss of these activities. With the use of gas chromatography-mass spectrometry, we show that SAL2 hydrolyzed trilinolein to linoleic acid, a fatty acid with known antistaphylococcal properties. When added to cultures of USA300, trilinolein and, to a lesser extent, triolein inhibited growth in a SAL2-dependent manner. This effect was shown to be due to the enzymatic activity of SAL2 on these triglycerides, since the catalytically inactive SAL2 Ser412Ala mutant was incapable of hydrolyzing the triglycerides or yielding delayed growth in their presence. Overall, these results reveal that SAL2 hydrolyzes triglycerides of both short- and long-chain fatty acids and that the released free fatty acids have the potential to cause significant delays in growth, depending on the chemical nature of the free fatty acid.
New criteria for a ring to have a semisimple left quotient ring
Authors: Bavula V. V. 
Published: September 2014

Goldie's Theorem (1960), which is one of the most important results in Ring Theory, is a criterion for a ring to have a semisimple left quotient ring. The aim of the paper is to give four new criteria (using a completely different approach and new ideas). The first one is based on the recent fact that for an arbitrary ring R the set ℳ of maximal left denominator sets of R is a non-empty set [V. V. Bavula, The largest left quotient ring of a ring, preprint (2011), arXiv:math.RA:1101.5107]: Theorem (The First Criterion). A ring R has a semisimple left quotient ring Q iff ℳ is a finite set, ⋂S∈ℳ ass (S) = 0 and, for each S ∈ ℳ, the ring S-1R is a simple left Artinian ring. In this case, Q ≃ ∏S∈ℳ S-1R. The Second Criterion is given via the minimal primes of R and goes further than the First one in the sense that it describes explicitly the maximal left denominator sets S via the minimal primes of R. The Third Criterion is close to Goldie's Criterion but it is easier to check in applications (basically, it reduces Goldie's Theorem to the prime case). The Fourth Criterion is given via certain left denominator sets.