bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selection of Heterogeneous Vancomycin-Intermediate
Staphylococcus aureus
by Imipenem
Authors: Katayama Yuki , Murakami-Kuroda Hiroko , Cui Longzhu , Hiramatsu Keiichi 
Published: May 2009

ABSTRACT

Vancomycin (VAN)-intermediate
Staphylococcus aureus
(VISA) and heterogeneous VISA (hVISA) isolates are considered to have emerged from VAN-susceptible
S. aureus
(VSSA) by spontaneous mutation during VAN exposure. We previously reported that laboratory mutant H14, obtained from VSSA strain ΔIP by exposure to imipenem (IPM), showed overexpression of the
vraSR
two-component system and a typical hVISA phenotype. In the present study, to elucidate the mechanism of VSSA conversion to hVISA, we further characterized strain H14 by determining its whole-genome sequence, morphology, cell wall synthetic activity, and gene expression. Genome sequencing revealed that H14 harbored a mutated
vraS
(designated
vraS
H14
) that caused an amino acid substitution (S
329
→L). This mutation is different from the VraS mutation (N
5
→I) identified in representative clinical hVISA strain Mu3. However, H14 exhibited a phenotype similar to that of Mu3, including heterogeneous resistance to VAN, enhanced cell wall synthetic activity, and
vraSR
overexpression. Replacement of the
vraS
gene of ΔIP with the mutated
vraS
H14
gene confirmed that the S
329
→L substitution was responsible for both the upregulation of
vraSR
and conversion to the hVISA phenotype. This conversion was also achieved by using the
vraS
gene of Mu3, which carries a mutation (N
5
→I), but not with the native
vraS
gene of strain N315. Finally, we carried out a study to analyze the appearance of hVISA from VSSA by exposure of ΔIP to selective concentrations of VAN and beta-lactam antibiotics. A total of 8 and 5 hVISA isolates were detected among 50 isolates selected with VAN and IPM, respectively. Among the 13 hVISA mutants, mutation in
vraSR
was detected only in mutant strain H14, suggesting that additional mutational mechanisms can be responsible for evolution to the hVISA phenotype. We conclude that exposure not only to VAN but also to beta-lactams may select for reduced glycopeptide susceptibility in
S. aureus
.
Pharmacokinetic and Pharmacodynamic Evaluation of Liposomal Amikacin for Inhalation in Cystic Fibrosis Patients with Chronic Pseudomonal Infection
Authors: Okusanya Ólanrewaju O. , Bhavnani Sujata M. , Hammel Jeffrey , Minic Predrag , Dupont Lieven J. , Forrest Alan , Mulder Geert-Jan , Mackinson Constance , Ambrose Paul G. , Gupta Renu 
Published: May 2009

ABSTRACTThe pharmacokinetics and pharmacodynamics of a novel liposomal amikacin for inhalation were evaluated in cystic fibrosis patients with chronic pseudomonas infection. Twenty-four patients from two studies received 500 mg of liposomal amikacin by inhalation once daily for 14 days. Serum, sputum, and 24-h urine samples were collected on days 1 and 14 of therapy; pulmonary function tests (PFT) and sputum for quantitative microbiology were assessed at baseline and serially for 14 days. Relationships between amikacin exposure in serum and sputum and absolute change in PFT endpoints and log10CFU ofPseudomonas aeruginosafrom baseline on days 7 and 14 of therapy were assessed. On days 7 and 14, absolute change from baseline in forced expiratory volume in 1 s (FEV1), percent predicted forced expiratory volume in 1 s (FEV1% predicted), and forced expiratory flow between 25 and 75% of forced vital capacity (FEF25-75%) increased by 0.24 (P= 0.002) and 0.13 (P= 0.10) liters, 7.49 (P< 0.001) and 4.38 (P= 0.03), and 0.49 (P< 0.001) and 0.42 (P= 0.02) liters/s, respectively. In addition, relative change from baseline in FEV1% predicted was 10.8% (P< 0.001) and 5.62% (P= 0.073) on days 7 and 14, respectively. While significant relationships between absolute change in PFT endpoints and the ratio of serum or sputum area under the concentration-time curve to the MIC (AUC/MIC) were not observed, relationships between change in log10CFU and serum AUC/MIC ratio and change in log10CFU and absolute changes in all PFT endpoints were significant. Together, these findings likely represent drug effect and warrant the further development of liposomal amikacin for inhalation.
Imcroporin, a New Cationic Antimicrobial Peptide from the Venom of the Scorpion
Isometrus maculates
Authors: Zhao Zhenhuan , Ma Yibao , Dai Chao , Zhao Ruiming , Li SongRyong , Wu Yingliang , Cao Zhijian , Li Wenxin 
Published: May 2009

ABSTRACT

The pace of resistance against antibiotics almost exceeds that of the development of new drugs. As many bacteria have become resistant to conventional antibiotics, new drugs or drug resources are badly needed to combat antibiotic-resistant pathogens, like methicillin-resistant
Staphylococcus aureus
(MRSA). Antimicrobial peptides, rich sources existing in nature, are able to effectively kill multidrug-resistant pathogens. Here, imcroporin, a new antimicrobial peptide, was screened and isolated from the cDNA library of the venomous gland of
Isometrus maculates
. The MIC of imcroporin against MRSA was 50 μg/ml, 8-fold lower than that of cefotaxime and 40-fold lower than that of penicillin. Imcroporin killed bacteria rapidly in vitro, inhibited bacterial growth, and cured infected mice. These results revealed that imcroporin could be considered a potential anti-infective drug or lead compound, especially for treating antibiotic-resistant pathogens.
Effects of Azithromycin in Combination with Vancomycin, Daptomycin, Fosfomycin, Tigecycline, and Ceftriaxone on
Staphylococcus epidermidis
Biofilms
Authors: Presterl Elisabeth , Hajdu Stefan , Lassnigg Andrea M. , Hirschl Alexander M. , Holinka Johannes , Graninger Wolfgang 
Published: May 2009

ABSTRACT

Staphylococcal biofilms on surgical implants are the underlying cause of a lack of response to antimicrobial treatment. We investigated the effects of vancomycin (VAN), daptomycin (DAP), fosfomycin (FOS), tigecycline (TGC), and ceftriaxone (CRX), alone and in combination with azithromycin (AZI), on established biofilms of
Staphylococcus epidermidis
. Biofilms were studied using the static microtiter plate model with established
S. epidermidis
biofilms, with an initial inoculum of 10
6
/ml in 96-well polystyrene flat-bottom microtiter plates. Biofilms were inoculated with VAN, DAP, FOS, TGC, or CRX at two concentrations, alone or in combination with AZI (2, 512, or 1,024 mg/liter). To assess the reduction in biomass, the optical density ratio (ODr), calculated as (optical density [OD] of the treated biofilm)/(OD of the untreated biofilm, taken as 1), was used. For antibacterial efficacy, the viable bacterial count was used. Reductions in the biofilm ODr were observed for VAN (15 and 40 mg/liter) and FOS (200 mg/liter) only (ODr [mean ± standard deviation] for VAN at 15 and 40 mg/liter, 0.77 ± 0.32 and 0.8 ± 0.35, respectively; ODr for FOS at 200 mg/liter, 0.78 ± 0.26;
P
< 0.05), but not for DAP (2 and 5 mg/liter), TGC (0.2 and 2 mg/liter), or CRX (600 and 2,400 mg/liter). The addition of AZI had no further effect on the ODr, but a significant reduction of bacterial growth was achieved with high doses of AZI plus TGC or AZI plus CRX (a 3-log count reduction for AZI at 1,024 mg/liter plus CRX at 600 mg/liter and for AZI at 512 or 1,024 mg/liter plus CRX at 2,400 mg/liter; a 2-log count reduction for AZI at 512 or 1,024 mg/liter plus TGC at 2 mg/liter [
P
< 0.05]). No significant reduction in bacterial growth was observed for FOS (50 and 200 mg/liter), DAP (2 and 5 mg/liter), or TGC (0.2 mg/liter) in combination with AZI. None of the antibiotics at either concentration reduced the bacterial count of the biofilms when used alone. Thus, the use of a combination of AZI plus TGC, FOS, or CRX at high concentrations has little effect on biofilm density but significantly reduces bacterial growth.
Protease Inhibitor Resistance Analysis in the MONARK Trial Comparing First-Line Lopinavir-Ritonavir Monotherapy to Lopinavir-Ritonavir plus Zidovudine and Lamivudine Triple Therapy
Authors: Delaugerre Constance , Flandre Philippe , Chaix Marie Laure , Ghosn Jade , Raffi François , Dellamonica Pierre , Jaeger H. , Shürmann D. , Cohen-Codar Isabelle , Ngo Van Philippe , Norton Michael , Taburet Anne-Marie , Delfraissy Jean-François , Rouzioux Christine 
Published: May 2009

ABSTRACTThe MONARK study was a pilot randomized trial comparing the safety and efficacy of lopinavir-ritonavir (LPV/r) monotherapy to those of LPV/r-zidovudine-lamivudine triple therapy for antiretroviral-naïve human immunodeficiency virus type 1 (HIV-1)-infected patients. Resistance testing was performed at the time of initial screening and at the time of virological failure (defined to include low-level viremia with >50 and <400 HIV-1 virus RNA copies/ml of plasma). Changes from the baseline sequences, including mutations noted on the 2008 International AIDS Society—USA list of resistance-associated protease mutations, were considered. Drug resistance testing was performed for 38 patients (5 of 53 on triple therapy and 33 of 83 on monotherapy). By week 96 (W96), virus samples from 18 of 33 patients in the monotherapy arm showed changes from baseline sequences, and 5 of these patients had viruses with major protease inhibitor (PI) resistance-associated mutations (M46I at W40, L76V at W48, M46I and L76V at W48, L10F and V82A at W72, and L76V at W84). Data on virus phenotypes detected at the time of initial screening and the time of virological failure were available for four patients in whom major PI resistance mutations developed, and these data revealed a mean increase of 2.2-fold (range, 0.75- to 4.6-fold) in the LPV 50% inhibitory concentration. All three patients in whom the L76V PI resistance mutation developed were infected with HIV-1 subtype CRF02_AG. In the triple-therapy group, no major PI resistance mutation was selected among the three patients with protease changes by W48. No association between the baseline CD4 cell count and the viral load, the W4 and final viral loads, or the final LPV trough concentration and the emergence of a major PI resistance mutation was found. Major PI resistance-associated mutations were detected in 5 (6%) of 83 patients treated with LPV/r monotherapy, suggesting that LPV/r monotherapy is an inappropriate first option. The mutation L76V may be considered in further studies of lopinavir resistance.
Pharmacokinetics-Pharmacodynamics of Pyrazinamide in a Novel In Vitro Model of Tuberculosis for Sterilizing Effect: a Paradigm for Faster Assessment of New Antituberculosis Drugs
Authors: Gumbo Tawanda , Siyambalapitiyage Dona Chandima S. W. , Meek Claudia , Leff Richard 
Published: May 2009

ABSTRACT

There are currently renewed efforts to develop drugs that could shorten the duration of antituberculosis therapy. This is best achieved by optimizing the sterilizing effect. However, the current pathway for the development of new molecules with the potential to have a sterilizing effect is inefficient. We designed an in vitro pharmacokinetic-pharmacodynamic model in which
Mycobacterium tuberculosis
replicating slowly at pH 5.8 was exposed to pyrazinamide by use of the concentration-time profiles encountered in patients. The sterilizing effect rates and the time to the emergence of drug resistance were examined. Daily pyrazinamide dosing for 28 days accurately achieved (i) the pyrazinamide pharmacokinetic parameters, (ii) the lack of early bactericidal activity, (iii) a sterilizing effect rate of 0.10 log
10
CFU/ml per day starting on day 6 of therapy, and (iv) a time to the emergence of resistance of the from 2 to 3 weeks of monotherapy encountered in patients with tuberculosis. Next, dose-scheduling studies were performed. The sterilizing effect was linked to the pyrazinamide ratio of the area under the concentration-time curve from 0 to 24 h (AUC
0-24
) to the MIC (
r
2
= 0.80 to 0.90), with 90% of the maximal effect being achieved by an AUC
0-24
/MIC of 209.08. Resistance suppression was associated with the percentage of time that the concentration persisted above the MIC (
r
2
= 0.73 to 0.91). Monte Carlo simulations of 10,000 patients demonstrated that the currently recommended pyrazinamide doses (15 to 30 mg/kg of body weight/day) achieved the AUC
0-24
/MIC of 209.08 in the epithelial lining fluid of only 15.1 to 53.3% of patients. Doses of >60 mg/kg per day performed better. Our vitro model for the sterilizing effect, together with Monte Carlo simulations, can be used for the faster identification of the clinical doses that are needed to achieve a sterilizing effect and that can then be studied in clinical trials.
Daptomycin Rapidly Penetrates a
Staphylococcus epidermidis
Biofilm
Authors: Stewart Philip S. , Davison William M. , Steenbergen Judith N. 
Published: May 2009

ABSTRACT

Fluorescently tagged daptomycin accessed the interior of
Staphylococcus epidermidis
biofilm cell clusters within minutes. The diffusion coefficient of daptomycin in the biofilm was 28% of its value in pure water. Daptomycin activity against staphylococci embedded in biofilms is unlikely to be limited by penetration of the antibiotic into the biofilm.
An Immunogenic, Surface-Exposed Domain of
Haemophilus ducreyi
Outer Membrane Protein HgbA Is Involved in Hemoglobin Binding
Authors: Nepluev Igor , Afonina Galyna , Fusco William G. , Leduc Isabelle , Olsen Bonnie , Temple Brenda , Elkins Christopher 
Published: May 2009

ABSTRACT

HgbA is the sole TonB-dependent receptor for hemoglobin (Hb) acquisition of
Haemophilus ducreyi
. Binding of Hb to HgbA is the initial step in heme acquisition from Hb. To better understand this step, we mutagenized
hgbA
by deletion of each of the 11 putative surface-exposed loops and expressed each of the mutant proteins in
trans
in host strain
H
.
ducreyi
FX547
hgbA
. All mutant proteins were expressed, exported, and detected on the surface by anti-HgbA immunoglobulin G (IgG). Deletion of sequences in loops 5 and 7 of HgbA abolished Hb binding in two different formats. In contrast, HgbA proteins containing deletions in the other nine loops retained the ability to bind Hb. None of the clones expressing mutant proteins were able to grow on plates containing low concentrations of Hb. Previously we demonstrated in a swine model of chancroid infection that an HgbA vaccine conferred complete protection from a challenge infection. Using anti-HgbA IgG from this study and the above deletion mutants, we show that loops 4, 5, and 7 of HgbA were immunogenic and surface exposed and that IgG directed against loops 4 and 5 blocked Hb binding. Furthermore, loop 6 was cleaved by protease on intact
H
.
ducreyi
, suggesting surface exposure. These data implicate a central domain of HgbA (in respect to the primary amino acid sequence) as important in Hb binding and suggest that this region of the molecule might have potential as a subunit vaccine.
Surfactant Protein D Increases Phagocytosis of HypocapsularCryptococcus neoformansby Murine Macrophages and Enhances Fungal Survival
Authors: Geunes-Boyer Scarlett , Oliver Timothy N. , Janbon Guilhem , Lodge Jennifer K. , Heitman Joseph , Perfect John R. , Wright Jo Rae 
Published: May 2009

ABSTRACTCryptococcus neoformansis a facultative intracellular opportunistic pathogen and the leading cause of fungal meningitis in humans. In the absence of a protective cellular immune response, the inhalation ofC. neoformanscells or spores results in pulmonary infection.C. neoformanscells produce a polysaccharide capsule composed predominantly of glucuronoxylomannan, which constitutes approximately 90% of the capsular material. In the lungs, surfactant protein A (SP-A) and SP-D contribute to immune defense by facilitating the aggregation, uptake, and killing of many microorganisms by phagocytic cells. We hypothesized that SP-D plays a role inC. neoformanspathogenesis by binding to and enhancing the phagocytosis of the yeast. Here, the abilities of SP-D to bind to and facilitate the phagocytosis and survival of the wild-type encapsulated strain H99 and thecap59Δ mutant hypocapsular strain are assessed. SP-D binding tocap59Δ mutant cells was approximately sixfold greater than binding to wild-type cells. SP-D enhanced the phagocytosis ofcap59Δ cells by approximately fourfold in vitro. To investigate SP-D binding in vivo, SP-D−/−mice were intranasally inoculated with Alexa Fluor 488-labeledcap59Δ or H99 cells. By confocal microscopy, a greater number of phagocytosedC. neoformanscells in wild-type mice than in SP-D−/−mice was observed, consistent with in vitro data. Interestingly, SP-D protectedC. neoformanscells against macrophage-mediated defense mechanisms in vitro, as demonstrated by an analysis of fungal viability using a CFU assay. These findings provide evidence thatC. neoformanssubverts host defense mechanisms involving surfactant, establishing a novel virulence paradigm that may be targeted for therapy.
Evidence for Capsule Switching between Carried and Disease-CausingNeisseria meningitidisStrains
Authors: Beddek Amanda J. , Li Ming-Shi , Kroll J. Simon , Jordan T. William , Martin Diana R. 
Published: May 2009

ABSTRACTChanging antigenic structure such as with capsule polysaccharide is a common strategy for bacterial pathogens to evade a host immune system. The recent emergence of an invasive W:2a:P1.7-2,4 sequence type 11 (ST-11) strain ofNeisseria meningitidisin New Zealand, an uncommon serogroup/serotype in New Zealand disease cases, was investigated for its genetic origins. Molecular typing of 107 meningococcal isolates with similar serotyping characteristics was undertaken to determine genetic relationships. Results indicated that the W:2a:P1.7-2,4 strain had emerged via capsule switching from a group C strain (C:2a:P1.7-2,4). Neither the upstream nor downstream sites of recombination could be elucidated, but sequence analysis demonstrated that at least 45 kb of DNA was involved in the recombination, including the entire capsule gene cluster. TheoatWYgene carried by the W:2a:P1.7-2,4 strain contained the insertion sequence element IS1301, one of five variants ofoatWYfound in group W135 strains belonging to the carriage-associated ST-22 clonal complex. This suggested that the origin of the capsule genes carried by the invasive W:2a:P1.7-2,4 strain is carriage associated. These results provide novel evidence for the long-standing dogma that disease-associated strains acquire antigenic structure from carriage-associated strains. Moreover, the capsule switch described here has arisen from the exchange of the entire capsule locus.
The Posttranslocation Chaperone PrsA2 Contributes to Multiple Facets ofListeria monocytogenesPathogenesis
Authors: Alonzo Francis , Port Gary C. , Cao Min , Freitag Nancy E. 
Published: May 2009

ABSTRACTListeria monocytogenesis an intracellular bacterial pathogen whose virulence depends on the regulated expression of numerous secreted bacterial factors. As for other gram-positive bacteria, many proteins secreted byL. monocytogenesare translocated across the bacterial membrane in an unfolded state to the compartment existing between the membrane and the cell wall. This compartment presents a challenging environment for protein folding due to its high density of negative charge, high concentrations of cations, and low pH. We recently identified PrsA2 as a gene product required forL. monocytogenesvirulence. PrsA2 was identified based on its increased secretion by strains containing a mutationally activated form ofprfA, the key regulator ofL. monocytogenesvirulence gene expression. TheprsA2gene product is one of at least two predicted peptidyl-prolylcis/trans-isomerases encoded byL. monocytogenes; these proteins function as posttranslocation protein chaperones and/or foldases. In this study, we demonstrate that PrsA2 plays a unique and important role inL. monocytogenespathogenesis by promoting the activity and stability of at least two critical secreted virulence factors: listeriolysin O (LLO) and a broad-specificity phospholipase. Loss of PrsA2 activity severely attenuated virulence in mice and impaired bacterial cell-to-cell spread in host cells. In contrast, mutants lackingprsA1resembled wild-type bacteria with respect to intracellular growth and cell-to-cell spread as well as virulence in mice. PrsA2 is thus distinct from PrsA1 in its unique requirement for the stability and full activity ofL. monocytogenes-secreted factors that contribute to host infection.
Elucidating the Pathogenesis of Spores from the Human Fungal PathogenCryptococcus neoformans
Authors: Giles Steven S. , Dagenais Taylor R. T. , Botts Michael R. , Keller Nancy P. , Hull Christina M. 
Published: May 2009

ABSTRACTCryptococcus neoformanswas first described as a human fungal pathogen more than a century ago. One aspect of theC. neoformansinfectious life cycle that has been the subject of earnest debate is whether the spores are pathogenic. Despite much speculation, no direct evidence has been presented to resolve this outstanding question. We present evidence thatC. neoformansspores are pathogenic in a mouse intranasal inhalation model of infection. In addition, we provide mechanistic insights into spore-host interactions. We found thatC. neoformansspores were phagocytosed by alveolar macrophages via interactions between fungal β-(1,3)-glucan and the host receptors Dectin-1 and CD11b. Moreover, we discovered an important link between spore survival and macrophage activation state: intracellular spores were susceptible to reactive oxygen-nitrogen species. We anticipate these results will serve as the basis for a model to further investigate the pathogenic implications of infections caused by fungal spores.
Pseudomonas aeruginosa
Inhibition of Flagellin-Activated NF-κB and Interleukin-8 by Human Airway Epithelial Cells
Authors: Pena Jose , Fu Zhu , Schwarzer Christian , Machen Terry E. 
Published: May 2009

ABSTRACT

Pseudomonas aeruginosa
-induced activation of NF-κB and secretion of proinflammatory cytokines by airway epithelial cells require that the bacteria express flagellin. We tested whether
P. aeruginosa
and human airway epithelial cells secrete factors that modulated this response. Experiments were performed with both the Calu-3 cell line and primary cultures of tracheal epithelial cells.
P. aeruginosa
strain PAK Δ
fliC
(flagellin knockout) did not activate NF-κB or interleukin-8 (IL-8) but inhibited flagellin-activated NF-κB by 40 to 50% and IL-8 secretion by 20 to 25%. PAK Δ
fliC
also inhibited NF-κB induced by IL-1β and Toll-like receptor 2 agonist Pam3CSK4. Similar inhibitions were observed with strains PAK, PAO1, and PA14. The inhibitory factor was present in conditioned medium isolated from PAK Δ
fliC
or Calu-3 plus PAK Δ
fliC
, but it was not present in conditioned medium isolated from Calu-3 cells alone or from PAK Δ
fliC
that had been heat treated. Inhibition by PAK Δ
fliC
-conditioned medium was exerted from either the apical or the basolateral side of the epithelium, was enhanced in simple Ringer's solution over that in tissue culture medium, and did not result from altered pH or depletion of glucose. The inhibitory effect of conditioned medium was abolished by boiling and appeared from filtration studies to result from effects of a factor with a molecular mass of <3 kDa. These and further studies with isogenic mutants led to the conclusion that the NF-κB and IL-8 response of airway epithelial cells to
P. aeruginosa
results from a balance of proinflammatory effects of flagellin and antiinflammatory effects of a small (<3-kDa), heat-sensitive factor(s) that is not lipopolysaccharide, C12 homoserine lactone, alginate, CIF, or exotoxin A, S, T, U, or Y.