bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Zidovudine and Stavudine on Mitochondrial DNA of Differentiating 3T3-F442a Cells Are Not Associated with Imbalanced Deoxynucleotide Pools
Authors: Lynx Matthew D. , LaClair Darcy D. , McKee Edward E. 
Published: December 2008

ABSTRACTTo test whether zidovudine (3′-azido-3′-deoxythymidine) (AZT) inhibition of thymidine phosphorylation causes depletion of the TTP pool resulting in mitochondrial DNA depletion, 3T3-F442a cells were differentiated in the presence of AZT and analyzed to determine mitochondrial DNA content and deoxynucleotide levels. These results suggest that AZT toxicity may not be related to deoxynucleotide pool alterations.
Antifungal Therapy of
Aspergillus
Invasive Otitis Externa: Efficacy of Voriconazole and Review
Authors: Parize Perrine , Chandesris Marie-Olivia , Lanternier Fanny , Poirée Sylvain , Viard Jean-Paul , Bienvenu Boris , Mimoun Michaël , Méchai Frédéric , Mamzer Marie-France , Herman Philippe , Bougnoux Marie-Elisabeth , Lecuit Marc , Lortholary Olivier 
Published: December 2008

ABSTRACT

Invasive otitis externa (IOE) due to
Aspergillus
is a rare, potentially life-threatening, invasive fungal infection affecting immunocompromised patients. The invasive process may lead to skull base osteomyelitis with progressive cranial nerve palsies and can result in irreversible hearing and neurological impairment. We report two cases of
Aspergillus
IOE treated with voriconazole alone and a literature review of antifungal therapy of
Aspergillus
IOE. Twenty-five patients, including the two described in the present report, were analyzed. Eighteen patients were treated with amphotericin B, and nine of them received itraconazole as an additional agent. Three patients received initial therapy with itraconazole, and one patient was treated with both voriconazole and caspofungin therapy. The two patients in the present report received voriconazole therapy alone with good clinical and biological tolerance despite prolonged treatment. The last patient did not receive antifungal therapy, as the diagnosis was made postmortem. Eighteen patients underwent an initial extensive surgical debridement. The majority of the patients had a favorable outcome, 17 patients experienced a complete recovery, and 6 showed a partial improvement. Both of the patients reported on here had favorable outcomes, and no aggressive surgical debridement was required. Although voriconazole has been shown to be effective for the treatment of invasive aspergillosis, its precise role in the management of
Aspergillus
IOE had not been documented. These observations demonstrate that voriconazole could be an effective and well-tolerated therapeutic option for the management of
Aspergillus
IOE.
Immobilization Reduces the Activity of Surface-Bound Cationic Antimicrobial Peptides with No Influence upon the Activity Spectrum
Authors: Bagheri Mojtaba , Beyermann Michael , Dathe Margitta 
Published: December 2008

ABSTRACTEarly studies of immobilized peptides mainly focused upon the relationship between structural properties and the activity of soluble and surface-tethered sequences. The intention of this study was to analyze the influence of immobilization parameters upon the activity profile of peptides. Resin beads (TentaGel S NH2, HypoGel 400 NH2, and HypoGel 200 NH2) with polyethylene glycol spacers of different lengths were rendered antimicrobial by linkage of an amphipathic model KLAL peptide and magainin-derived MK5E. Standard solid-phase peptide synthesis, thioalkylation, and ligation strategies were used to immobilize the peptides at the C and N termini and via different side-chain positions. Depending upon the resin capacity and the coupling strategies, peptide loading ranged between 0.1 and 0.25 μmol/mg for C-terminally and around 0.03 μmol/mg for N-terminally and side-chain-immobilized peptides. Tethering conserved the activity spectra of the soluble peptides at reduced concentrations. The resin-bound peptides were antimicrobial towardEscherichia coliandBacillus subtilisin the millimolar range compared to the results seen with micromolar concentrations of the free peptides.B. subtiliswas more susceptible thanE. coli. The antimicrobial activity distinctly decreased with reduction of the spacer length. Slight differences in the antimicrobial effect of KLAL and MK5E bound at different chain positions on TentaGel S NH2suggest that the activity is less dependent upon the position of immobilization. Soluble KLAL was active toward red blood cells, whereas MK5E was nonhemolytic at up to about 400 μM. Resin-induced hemolysis hampered the determination of the hemolytic effect of the immobilized peptides. TentaGel S NH2-bound peptides enhanced the permeability of the POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-choline) and mixed POPC/1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (POPC/POPG) bilayers used to model the charge properties of the biological targets. The results suggest that surface immobilization of the cationic amphipathic antimicrobial peptides does not influence the membrane-permeabilizing mode of action. Peptide insertion into the target membrane and likely the exchange of membrane-stabilizing bivalent cations contribute to the antimicrobial effect. In conclusion, reasonable antimicrobial activity of surface-bound peptides requires the optimization of the coupling parameters, with the length of the spacer and the amount of target-accessible peptide being the most important factors.
CMY-31 and CMY-36 Cephalosporinases Encoded by ColE1-Like Plasmids
Authors: Zioga A. , Whichard J. M. , Kotsakis S. D. , Tzouvelekis L. S. , Tzelepi E. , Miriagou V. 
Published: December 2008

ABSTRACT

Two CMY-2 derivatives, CMY-31 (Gln
215
→Arg) from
Salmonella enterica
serotype Newport and CMY-36 (Ala
77
→Cys and Gln
193
→Glu) from
Klebsiella pneumoniae
, were characterized. Both cephalosporinases functionally resembled CMY-2.
bla
CMY
alleles occurred as parts of a putative transposon comprising IS
Ecp1B
and a
Citrobacter freundii
-derived sequence carried by ColE1-like plasmids similar to CMY-5-encoding pTKH11 from
Klebsiella oxytoca
.
Identification by Genomic and Genetic Analysis of Two New Genes Playing a Key Role in Intermediate Glycopeptide Resistance in
Staphylococcus aureus
Authors: Renzoni Adriana , Kelley William L. , Barras Christine , Monod Antoinette , Huggler Elzbieta , François Patrice , Schrenzel Jacques , Studer René , Vaudaux Pierre , Lew Daniel P. 
Published: December 2008

ABSTRACT

Endogenous, low-level glycopeptide resistance in
Staphylococcus aureus
results from multifactorial genetic changes. Comparative genomic hybridization analysis revealed the specific deletion of a 1.8-kb segment encompassing two adjacent open reading frames (ORFs) of unknown function in a teicoplanin-susceptible revertant (strain 14-4rev) compared to the sequence of its isogenic, teicoplanin-resistant parental strain, strain 14-4. This provocative finding prompted us to perform a detailed genetic analysis of the contribution of this genomic segment to glycopeptide resistance. Despite repeated efforts in our laboratory, 14-4 and 14-4rev have proven refractory to most genetic manipulations. To circumvent this difficulty, we evaluated the contribution of both putative ORFs (designated teicoplanin resistance factors
trfA
and
trfB
) on teicoplanin resistance in a different, genetically tractable background. Genetic analysis showed that single or double
trfA
and/or
trfB
mutations abolished teicoplanin resistance in two independent teicoplanin-resistant derivatives of NCTC8325 strain ISP794 generated by two-step passages with the drug. The frequency of teicoplanin-resistant mutants was markedly decreased by the absence of
trfAB
in the teicoplanin-susceptible ISP794 background. Nevertheless, a low rate of teicoplanin-resistant mutants was selected from ISP794
trfAB
, thus indicating an additional contribution of
trfAB
-independent pathways in the emergence of low-level glycopeptide resistance. Further experiments performed with clinical glycopeptide-intermediate
S. aureus
isolate NRS3 indicated that the
trfAB
mutation could affect not only teicoplanin resistance but also vancomycin and oxacillin resistance. In conclusion, our study demonstrates the key role of two novel loci in endogenous, low-level glycopeptide resistance in
S. aureus
whose precise molecular functions warrant further investigation.
Breakthrough
Aspergillus fumigatus
and
Candida albicans
Double Infection during Caspofungin Treatment: Laboratory Characteristics and Implication for Susceptibility Testing
Authors: Arendrup Maiken Cavling , Garcia-Effron Guillermo , Buzina Walter , Mortensen Klaus Leth , Reiter Nanna , Lundin Christian , Jensen Henrik Elvang , Lass-Flörl Cornelia , Perlin David S. , Bruun Brita 
Published: December 2008

ABSTRACT

Caspofungin is used for the treatment of acute invasive candidiasis and as salvage treatment for invasive aspergillosis. We report characteristics of isolates of
Candida albicans
and
Aspergillus fumigatus
detected in a patient with breakthrough infection complicating severe gastrointestinal surgery and evaluate the capability of susceptibility methods to identify candin resistance. The susceptibility of
C. albicans
to caspofungin and anidulafungin was investigated by Etest, microdilution (European Committee on Antibiotic Susceptibility Testing [EUCAST] and CLSI), disk diffusion, agar dilution, and
FKS1
sequencing and in a mouse model. Tissue was examined by immunohistochemistry, PCR, and sequencing for the presence of
A. fumigatus
and resistance mutations. The MICs for the
C. albicans
isolate were as follows: >32 μg/ml caspofungin and 0.5 μg/ml anidulafungin by Etest, 2 μg/ml caspofungin and 0.125 μg/ml anidulafungin by EUCAST methods, and 1 μg/ml caspofungin and 0.5 μg/ml anidulafungin by CLSI methods. Sequencing of the
FKS1
gene revealed a mutation leading to an S645P substitution. Caspofungin and anidulafungin failed to reduce kidney CFU counts in animals inoculated with this isolate (
P
> 0.05 compared to untreated control animals), while both candins completely sterilized the kidneys in animals infected with a control isolate. Disk diffusion and agar dilution methods clearly separated the two isolates. Immunohistochemistry and sequencing confirmed the presence of
A. fumigatus
without
FSK1
resistance mutations in liver and lung tissues. Breakthrough disseminated aspergillosis and candidiasis developed despite an absence of characteristic
FKS1
resistance mutations in the
Aspergillus
isolates. EUCAST and CLSI methodology did not separate the candin-resistant clinical isolate from the sensitive control isolate as well as did the Etest and agar methods.
Changes in
aac(6
′
)-Ib-cr
Prevalence and Fluoroquinolone Resistance in Nosocomial Isolates of
Escherichia coli
Collected from 1991 through 2005
Authors: Warburg Gabriela , Korem Maya , Robicsek Ari , Engelstein Dalia , Moses Allon E. , Block Colin , Strahilevitz Jacob 
Published: December 2008

ABSTRACT

Clinical isolates of
Escherichia coli
collected from 1991 through 2005 at a tertiary-care center were studied for
qnr
and
aac(6
′
)-Ib-cr
genes. Isolates bearing
aac(6
′
)-Ib-cr
emerged in 1998, coinciding with an increase in ciprofloxacin resistance. The presence of
aac(6
′
)-Ib-cr
was multiclonal and was associated with the presence of extended-spectrum β-lactamases.
Mutations at
embB
Codon 306 Are an Important Molecular Indicator of Ethambutol Resistance in
Mycobacterium tuberculosis
Authors: Starks Angela M. , Gumusboga Aysel , Plikaytis Bonnie B. , Shinnick Thomas M. , Posey James E. 
Published: December 2008

ABSTRACT

Ethambutol resistance in clinical
Mycobacterium tuberculosis
isolates is associated primarily with missense mutations in the
embB
gene. However, recent reports have described the presence of
embB
mutations, especially those at
embB
codon 306, in isolates susceptible to ethambutol. To clarify the role of
embB
mutations in ethambutol resistance, we sequenced the ethambutol resistance-determining region in spontaneous ethambutol-resistant mutants. In our study, 66% of spontaneous mutants contained a single point mutation in
embB
, with 55% of these occurring at
embB
306. The MIC of ethambutol for spontaneous mutants was increased two- to eightfold relative to the pansusceptible
M. tuberculosis
strains from which the mutants were generated. To further characterize the role of
embB
306 mutations, we directly introduced mutant alleles,
embB
(
M306V
) or
embB
(
M306I
), into pansusceptible
M. tuberculosis
strains and conversely reverted mutant alleles in spontaneous ethambutol-resistant mutants back to those of the wild type via allelic exchange using specialized linkage transduction. We determined that the MIC of ethambutol was reduced fourfold for three of the four spontaneous ethambutol-resistant
embB
306 mutants when the mutant allele was replaced with the wild-type
embB
allele. The MIC for one of the spontaneous mutants genetically reverted to wild-type
embB
was reduced by only twofold. When the wild-type
embB
allele was converted to the mutant allele
embB
(
M306V
), the ethambutol MIC was increased fourfold, and when the allele was changed to M306I, the ethambutol MIC increased twofold. Our data indicate that
embB
306 mutations are sufficient to confer ethambutol resistance, and detection of these mutations should be considered in the development of rapid molecular tests.
Affinity of Tomopenem (CS-023) for Penicillin-Binding Proteins in
Staphylococcus aureus
,
Escherichia coli
, and
Pseudomonas aeruginosa
Authors: Koga Tetsufumi , Sugihara Chika , Kakuta Masayo , Masuda Nobuhisa , Namba Eiko , Fukuoka Takashi 
Published: December 2008

ABSTRACT

Tomopenem (formerly CS-023), a novel 1β-methylcarbapenem, exhibited high affinity for penicillin-binding protein (PBP) 2 in
Staphylococcus aureus
, PBP 2 in
Escherichia coli
, and PBPs 2 and 3 in
Pseudomonas aeruginosa
, which are considered major lethal targets. Morphologically, tomopenem induced spherical forms in
E. coli
and short filamentation with bulges in
P. aeruginosa
, which correlated with the drug's PBP profiles. The potential of resistance of these bacteria to tomopenem was comparable to that to imipenem.
In Vivo and In Vitro Efficacy of Amodiaquine Monotherapy for Treatment of Infection by Chloroquine-Resistant
Plasmodium vivax
Authors: Hasugian A. R. , Tjitra E. , Ratcliff A. , Siswantoro H. , Kenangalem E. , Wuwung R. M. , Purba H. L. E. , Piera K. A. , Chalfien F. , Marfurt J. , Penttinen P. M. , Russell B. , Anstey N. M. , Price R. N. 
Published: December 2008

ABSTRACT

Amodiaquine retains efficacy against infection by chloroquine-resistant
Plasmodium falciparum
; however, little information is available on its efficacy against infection by chloroquine-resistant
Plasmodium vivax
. Patients presenting to a rural clinic with a pure
P. vivax
infection that recurred after recent antimalarial treatment were retreated, this time with amodiaquine monotherapy, and the risk of further recurrence within 4 weeks was assessed. Of the 87 patients with pure
P. vivax
infection, 15 patients did not complete a full course of treatment, 4 of whom were intolerant to treatment. In the 72 patients completing treatment, 91% (63 of 69) had cleared their parasitemia within 48 h with no early treatment failure. Follow-up to day 28 or recurrent parasitemia was achieved for 56 patients (78%). The cumulative incidence of treatment failure by day 28 was 22.8% (95% confidence interval, 7.3 to 38%). The in vitro sensitivity profile was determined for a separate set of isolates from outpatients with pure
P. vivax
infection. The median 50% inhibitory concentration of amodiaquine was 11.3 nM (range, 0.37 to 95.8) and was correlated significantly with that of chloroquine (Spearman rank correlation coefficient, 0.602;
P
< 0.001) Although amodiaquine results in a rapid clinical response, the risk of recurrence by day 28 is unacceptably high, reducing its suitability as an alternative treatment of infection by chloroquine-resistant
P. vivax
in this region.
Salmonella entericaSerovar Typhimurium Strains with Regulated Delayed Attenuation In Vivo
Authors: Curtiss Roy , Wanda Soo-Young , Gunn Bronwyn M. , Zhang Xin , Tinge Steven A. , Ananthnarayan Vidya , Mo Hua , Wang Shifeng , Kong Wei 
Published: December 2008

ABSTRACTRecombinant bacterial vaccines must be fully attenuated for animal or human hosts to avoid inducing disease symptoms while exhibiting a high degree of immunogenicity. Unfortunately, many well-studied means for attenuatingSalmonellarender strains more susceptible to host defense stresses encountered following oral vaccination than wild-type virulent strains and/or impair their ability to effectively colonize the gut-associated and internal lymphoid tissues. This thus impairs the ability of recombinant vaccines to serve as factories to produce recombinant antigens to induce the desired protective immunity. To address these problems, we designed strains that display features of wild-type virulent strains ofSalmonellaat the time of immunization to enable strains first to effectively colonize lymphoid tissues and then to exhibit a regulated delayed attenuation in vivo to preclude inducing disease symptoms. We recently described one means to achieve this based on a reversible smooth-rough synthesis of lipopolysaccharide O antigen. We report here a second means to achieve regulated delayed attenuation in vivo that is based on the substitution of a tightly regulatedaraCPBADcassette for the promoters of thefur,crp,phoPQ, andrpoSgenes such that expression of these genes is dependent on arabinose provided during growth. Thus, following colonization of lymphoid tissues, the Fur, Crp, PhoPQ, and/or RpoS proteins cease to be synthesized due to the absence of arabinose such that attenuation is gradually manifest in vivo to preclude induction of diseases symptoms. Means for achieving regulated delayed attenuation can be combined with other mutations, which together may yield safe efficacious recombinant attenuatedSalmonellavaccines.
Mycoplasma genitalium-Encoded MG309 Activates NF-κB via Toll-Like Receptors 2 and 6 To Elicit Proinflammatory Cytokine Secretion from Human Genital Epithelial Cells
Authors: McGowin Chris L. , Ma Liang , Martin David H. , Pyles Richard B. 
Published: December 2008

ABSTRACTMycoplasma genitaliumhas been implicated in several important reproductive tract syndromes in women, including pelvic inflammatory disease, cervicitis, and tubal factor infertility. The mechanisms of immune activation are unclear, and we sought to determine whetherM. genitaliumwas capable of activating innate immune responses through ligation of highly expressed Toll-like receptors (TLR) of the genital tract. Using HEK293 cells expressing specific human TLR, viableM. genitaliumand the recombinant C-terminal portion of the immunogenic protein MG309 (rMG309c) were shown to activate NF-κB via TLR2/6. These data provided a putative mechanism for activation of the innate response in genital tissues. Genital epithelial cells (EC) are the first responders to sexually transmitted pathogens and express high levels of TLR2 and -6. Following exposure to purified rMG309c, vaginal and ecto- and endocervical EC secreted proinflammatory cytokines, including interleukin-6 (IL-6) and IL-8. Vaginal EC were less responsive than cervical EC. The capacity of rMG309c to bind TLR2/6 and elicit inflammation was sensitive to proteinase K digestion and independent of traditional N-terminal lipoylation. Furthermore, the immunostimulatory capacity of rMG309c was localized specifically to a 91-amino-acid subfragment of the recombinant protein, suggesting that TLR activation is likely amino acid based. Together, these data indicated that human vaginal and cervical EC are immunologically responsive toM. genitaliumand to purified rMG309c via highly expressed TLR of the genital tract. These findings provide valuable insights into the mechanisms for activation of acute-phase inflammatory responses and suggest thatM. genitaliumcolonization of reproductive tract tissues may result in inflammatory sequelae.
The H35A Mutated Alpha-Toxin Interferes with Cytotoxicity of Staphylococcal Alpha-Toxin
Authors: Liang Xudong , Yan Meiying , Ji Yinduo 
Published: December 2008

ABSTRACT

Staphylococcal alpha-toxin is an important virulence factor for
Staphylococcus aureus
to cause severe infections. In this study, we explored whether the toxoid of alpha-toxin may be utilized to block the toxicity of wild-type alpha-toxin. We created a series of H35A mutated alpha-toxin expression strains and revealed that the H35A mutation eliminates the activity of alpha-toxin using a human lung epithelial cell line (A549). More importantly, we found that either the pretreatment or simultaneous treatment of the epithelial cells with alpha-toxin-H35A completely disrupted the cytotoxicity of alpha-toxin. Specifically, we demonstrated that alpha-toxin-H35A can effectively interfere with the pore formation and the internalization of alpha-toxin using cytotoxicity and immunofluorescence assays. In addition, we found that the removal of either the 30-amino-acid (aa) or 99-aa C-terminal region of alpha-toxin-H35A reactivated its cytotoxicity, indicating that interactions between the alanine residue at position 35 and these C-terminal regions may be associated with interrupting the toxic activity of alpha-toxin-H35A. Taken together, these results suggest that the alpha-toxin-H35A protein may be developed as a potential alternative therapeutic agent for treating early stages of
S. aureus
infections.
Role of Melanin Pigment in Expression of
Vibrio cholerae
Virulence Factors
Authors: Valeru Soni Priya , Rompikuntal Pramod Kumar , Ishikawa Takahiko , Vaitkevicius Karolis , Sjöling Åsa , Dolganov Nadia , Zhu Jun , Schoolnik Gary , Wai Sun Nyunt 
Published: December 2008

ABSTRACT

We identified the mutated gene locus in a pigment-overproducing
Vibrio cholerae
mutant of strain A1552. The deduced gene product is suggested to be an oxidoreductase based on partial homology to putative homogentisate 1,2-dioxygenase in
Pseudomonas aeruginosa
and
Mesorhizobium loti
, and we propose that the gene VC1345 in the
V. cholerae
genome be denoted
hmgA
in accordance with the nomenclature for other species. The
hmgA
::mini-Tn
5
mutant showed a nonpigmented phenotype after complementation with a plasmid clone carrying the WT
hmgA
+
locus. Microarray transcription analysis revealed that expression of
hmgA
and the neighboring genes encoding a postulated two-component sensor system was growth phase dependent. Results from quantitative reverse transcription-PCR analysis showed that
hmgA
operon expression was reduced in the
rpoS
mutant, but pigment production by the WT
V. cholerae
or the
hmgA
mutant was not detectably influenced by the stationary-phase regulator RpoS. The pigmented mutant showed increased UV resistance in comparison with the WT strain. Interestingly, the pigment-producing mutant expressed more toxin-coregulated pilus and cholera toxin than WT
V. cholerae
. Moreover, the
hmgA
mutant showed a fivefold increase in the ability to colonize the intestines of infant mice. A possible mechanism by which pigment production might cause induction of the ToxR regulon due to generation of hydrogen peroxide was supported by results from tests showing that externally supplied H
2
O
2
led to higher TcpA levels. Taken together, our findings suggest that melanin pigment formation may play a role in
V. cholerae
virulence factor expression.