bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Antibiotic Treatment Delay on Therapeutic Outcome of Experimental Acute Otitis Media Caused by
Streptococcus pneumoniae
Strains with Different Susceptibilities to Amoxicillin
Authors: Parra Araceli , Ponte Carmen , Cenjor Carlos , Martínez-Marín Carmen , Soriano Francisco 
Published: February 2004

ABSTRACT

The effect of delayed administration of amoxicillin on the course of acute otitis media (AOM) caused by two
Streptococcus pneumoniae
strains with different susceptibilities to amoxicillin (MICs of 0.016 and 1 μg/ml for strains A and B, respectively) was evaluated in the gerbil model. The organisms were inoculated by transbullar challenge into the middle ear, and antibiotic treatment was administered at various times thereafter. The bacteriological and clinical efficacies of treatment diminished significantly with the delay of antibiotic administration. The bacterial eradication rates when antibiotic treatment was started at 2, 5, 8, 18, and 21 h post-bacterial inoculation were different for both strains (95, 95, 90, 55, and 55% for strain A and 95, 95, 65, 10, and 0% for strain B). Results of further experiments using strain B with higher antibiotic doses and numbers of administrations and different follow-up times indicate that the failures observed with the delayed administration were not related to the bacterial burden, selection of antibiotic-resistant mutants, or inadequate pharmacodynamic parameters. Such failures may be related to the metabolic bacterial status. The delayed amoxicillin treatment of AOM caused by
S. pneumoniae
may lead to therapeutic failures, mainly when organisms with diminished antibiotic susceptibility are involved.
Plasmodium falciparum
Isolates in India Exhibit a Progressive Increase in Mutations Associated with Sulfadoxine-Pyrimethamine Resistance
Authors: Ahmed Anwar , Bararia Deepak , Vinayak Sumiti , Yameen Mohammed , Biswas Sukla , Dev Vas , Kumar Ashwani , Ansari Musharraf A. , Sharma Yagya D. 
Published: February 2004

ABSTRACT

The combination of sulfadoxine-pyrimethamine (SP) is used as a second line of therapy for the treatment of uncomplicated chloroquine-resistant
Plasmodium falciparum
malaria. Resistance to SP arises due to certain point mutations in the genes for the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) enzymes of the parasite. We have analyzed these mutations in 312 field isolates of
P. falciparum
collected from different parts of India to assess the effects of drug pressure. The rate of mutation in the gene for DHFR was found to be higher than that in the gene for DHPS, although the latter had mutations in more alleles. There was a temporal rise in the number of isolates with double
dhfr
mutations and single
dhps
mutations, resulting in an increased total number of mutations in the loci for DHFR and DHPS combined over a 5-year period. During these 5 years, the number of isolates with drug-sensitive genotypes decreased and the number of isolates with drug-resistant genotypes (double DHFR mutations and a single DHPS mutation) increased significantly. The number of isolates with the triple mutations in each of the genes for the two enzymes (for a total of six mutations), however, remained very low, coinciding with the very low rate of SP treatment failure in the country. There was a regional bias in the mutation rate, as isolates from the northeastern region (the state of Assam) showed higher rates of mutation and more complex genotypes than isolates from the other regions. It was concluded that even though SP is prescribed as a second line of treatment in India, the mutations associated with SP resistance continue to be progressively increasing.
Killing by Ampicillin and Ofloxacin Induces Overlapping Changes in
Escherichia coli
Transcription Profile
Authors: Kaldalu Niilo , Mei Rui , Lewis Kim 
Published: February 2004

ABSTRACT

The basis of bactericidal versus bacteriostatic action of antibiotics and the mechanism of bacterial cell death are largely unknown. Related to this important issue is the essential invulnerability to killing of persisters: cells forming a small subpopulation largely responsible for the recalcitrance of biofilms to chemotherapy. To learn whether death is accompanied by changes in expression of particular genes, we compared transcription profiles of log-phase
Escherichia coli
treated with bactericidal concentrations of two unrelated antibiotics: ampicillin and ofloxacin. Massive changes in transcription profile were observed in response to either agent, and there was a significant overlap in genes whose transcription was affected. A small group of mostly uncharacterized genes was induced and a much larger set was transcriptionally repressed by both antibiotics. Among the repressed genes were those required for flagellar synthesis, energy metabolism, transport of small molecules, and protein synthesis.
Tetracycline and Streptomycin Resistance Genes, Transposons, and Plasmids in
Salmonella enterica
Isolates from Animals in Italy
Authors: Pezzella Cristina , Ricci Antonia , DiGiannatale Elisabetta , Luzzi Ida , Carattoli Alessandra 
Published: February 2004

ABSTRACT

Fifty-eight multidrug-resistant
Salmonella enterica
strains of 20 serotypes, isolated from animal sources in Italy, were analyzed for
tet
(A) and
strA
-
strB
, conferring tetracycline and streptomycin resistance, respectively. The
strA
and
strB
genes were highly prevalent in
Salmonella
strains of our collection, being detected in 84% of the streptomycin-resistant strains. In many strains, the
strA
and
strB
genes were linked to a particular Tn
5393-
derivative transposon characterized by the presence of the insertion sequence IS
1133
, previously identified only in the plant pathogen
Erwinia amylovora.
Sixty-eight percent of the tetracycline-resistant strains were
tet
(A) positive, indicating that this gene is widely diffused in
Salmonella
strains circulating in animals in Italy. Most of the
tet
(A) genes were localized within a deleted Tn
1721
transposon variant. Two prevalent repN and repI1 resistance plasmids were identified in
Salmonella
isolates of our collection.
Novel Chromosomally Encoded Multidrug Efflux Transporter MdeA in
Staphylococcus aureus
Authors: Huang Jianzhong , O'Toole Paul W. , Shen Wei , Amrine-Madsen Heather , Jiang Xinhe , Lobo Neethan , Palmer Leslie M. , Voelker LeRoy , Fan Frank , Gwynn Michael N. , McDevitt Damien 
Published: February 2004

ABSTRACT

Antibiotic efflux is an important mechanism of resistance in pathogenic bacteria. Here we describe the identification and characterization of a novel chromosomally encoded multidrug resistance efflux protein in
Staphylococcus aureus
, MdeA (multidrug efflux A). MdeA was identified from screening an
S. aureus
open reading frame expression library for resistance to antibiotic compounds. When overexpressed, MdeA confers resistance on
S. aureus
to a range of quaternary ammonium compounds and antibiotics, but not fluoroquinolones. MdeA is a 52-kDa protein with 14 predicted transmembrane segments. It belongs to the major facilitator superfamily and is most closely related, among known efflux proteins, to LmrB of
Bacillus subtilis
and EmrB of
Escherichia coli
. Overexpression of
mdeA
in
S. aureus
reduced ethidium bromide uptake and enhanced its efflux, which could be inhibited by reserpine and abolished by an uncoupler. The
mdeA
promoter was identified by primer extension. Spontaneous mutants selected for increased resistance to an MdeA substrate had undergone mutations in the promoter for
mdeA
, and their
mdeA
transcription levels were increased by as much as 15-fold. The
mdeA
gene was present in the genomes of all six strains of
S. aureus
examined. Uncharacterized homologs of MdeA were present elsewhere in the
S. aureus
genome, but their overexpression did not mediate resistance to the antibacterials tested. However, MdeA homologs were identified in other bacteria, including
Bacillus anthracis
, some of which were shown to be functional orthologs of MdeA.
Quercetin Induces Apoptosis of
Trypanosoma brucei gambiense
and Decreases the Proinflammatory Response of Human Macrophages
Authors: Mamani-Matsuda Maria , Rambert Jérôme , Malvy Denis , Lejoly-Boisseau Hélène , Daulouède Sylvie , Thiolat Denis , Coves Sara , Courtois Pierrette , Vincendeau Philippe , Mossalayi M. Djavad 
Published: February 2004

ABSTRACT

In addition to parasite spread, the severity of disease observed in cases of human African trypanosomiasis (HAT), or sleeping sickness, is associated with increased levels of inflammatory mediators, including tumor necrosis factor (TNF)-α and nitric oxide derivatives. In the present study, quercetin (3,3′,4′,5,7-pentahydroxyflavone), a potent immunomodulating flavonoid, was shown to directly induce the death of
Trypanosoma brucei gambiense
, the causative agent of HAT, without affecting normal human cell viability. Quercetin directly promoted
T. b. gambiense
death by apoptosis as shown by Annexin V binding. In addition to microbicidal activity, quercetin induced dose-dependent decreases in the levels of TNF-α and nitric oxide produced by activated human macrophages. These results highlight the potential use of quercetin as an antimicrobial and anti-inflammatory agent for the treatment of African trypanomiasis.
Two Sets of Paralogous Genes Encode the Enzymes Involved in the Early Stages of Clavulanic Acid and Clavam Metabolite Biosynthesis in
Streptomyces clavuligerus
Authors: Tahlan Kapil , Park Hyeon Ung , Wong Annie , Beatty Perrin H. , Jensen Susan E. 
Published: February 2004

ABSTRACT

Recently, a second copy of a gene encoding proclavaminate amidinohydrolase (
pah1
), an enzyme involved in the early stages of clavulanic acid and clavam metabolite biosynthesis in
Streptomyces clavuligerus
, was identified and isolated. Using Southern analysis, we have now isolated second copies of the genes encoding the carboxyethylarginine synthase (
ceaS
) and β-lactam synthetase (
bls
) enzymes. These new paralogues are given the gene designations
ceaS1
and
bls1
and are located immediately upstream of
pah1
on the chromosome. Furthermore, sequence analysis of the region downstream of
pah1
revealed a second copy of a gene encoding ornithine acetyltransferase (
oat1
), thus indicating the presence of a cluster of paralogue genes.
ceaS1
,
bls1
, and
oat1
display 73, 60, and 63% identities, respectively, at the nucleotide level to the original
ceaS2
,
bls2
, and
oat2
genes from the clavulanic acid gene cluster. Single mutants defective in
ceaS1
,
bls1
, or
oat1
were prepared and characterized and were found to be affected to variable degrees in their ability to produce clavulanic acid and clavam metabolites. Double mutants defective in both copies of the genes were also prepared and tested. The
ceaS1
/
ceaS2
and the
bls1
/
bls2
mutant strains were completely blocked in clavulanic acid and clavam metabolite biosynthesis. On the other hand,
oat1
/
oat2
double mutants still produced some clavulanic acid and clavam metabolites. This may be attributed to the presence of the
argJ
gene in
S. clavuligerus
, which encodes yet another ornithine acetyltransferase enzyme that may be able to compensate for the lack of OAT1 and -2 in the double mutants.
Activities of Ciprofloxacin and Moxifloxacin against
Stenotrophomonas maltophilia
and Emergence of Resistant Mutants in an In Vitro Pharmacokinetic-Pharmacodynamic Model
Authors: Ba Boubakar B. , Feghali Hala , Arpin Corinne , Saux Marie-Claude , Quentin Claudine 
Published: February 2004

ABSTRACT

A two-compartment in vitro pharmacokinetic-pharmacodynamic model, with full computer-controlled devices, was used to accurately simulate human plasma pharmacokinetic profiles after multidose oral regimens of ciprofloxacin (750 mg every 12 h) and moxifloxacin (400 mg every 24 h) during 48 h. Pharmacodynamics of these drugs was investigated against three quinolone-susceptible strains of
Stenotrophomonas maltophilia
(MICs of ciprofloxacin and moxifloxacin of 0.5 to 2 and 0.0625 to 0.5 μg/ml, respectively). The first dose of ciprofloxacin and moxifloxacin reduced the bacterial count by 1 and 2 log CFU/ml, respectively, prior to a bacterial regrowth that reached the plateau value of the growth control curve at 13 to 24 h versus 24 to 36 h and persisted despite repeated administration of both drugs. The surviving bacterial cells were quinolone-resistant mutants (2 to 128 times the MIC) that exhibited cross-resistance to unrelated antibiotics. Their antibiotic resistance probably resulted from the overproduction of different multidrug resistance efflux system(s).
C
max
/MIC and area under the concentration-time curve from 0 to 24 h (AUC
0-24
)/MIC values were at least threefold higher for moxifloxacin than for ciprofloxacin. Moreover, integral parameters of ciprofloxacin and moxifloxacin, in particular the area under the killing and regrowth curve from 0 to 48 h (AUBC
0-48
, 342.3 to 401.3 versus 295.2 to 378.7 h × log CFU/ml, respectively) and the area between the control growth curve and the killing and regrowth curve from 0 to 48 h (ABBC
0-48
, 40.4 to 101.1 versus 72.9 to 144.7 h × log CFU/ml, respectively), demonstrated a better antibacterial effect of moxifloxacin than ciprofloxacin on
S. maltophilia
. However, selection of resistant mutants by both fluoroquinolones, although delayed with moxifloxacin, emphasizes the need to use maximal dosages and combined therapy in the treatment of systemic
S. maltophilia
infections.
In Vitro Evaluation of Double and Triple Combinations of Antifungal Drugs against
Aspergillus fumigatus
and
Aspergillus terreus
Authors: Dannaoui Eric , Lortholary Olivier , Dromer Françoise 
Published: February 2004

ABSTRACT

Microdilution broth checkerboard techniques based on the National Committee for Clinical Laboratory Standards methodology were used to study double and triple antifungal combinations against clinical isolates of
Aspergillus fumigatus
and
A. terreus
. The influences of the end-point definition (partial or complete inhibition) and the mode of reading (visually or spectrophotometrically) were determined. Interactions between antifungal drugs were also evaluated by agar diffusion tests. Combinations of caspofungin with either amphotericin B or voriconazole were additive for all the isolates, and antagonism was not observed. The interaction between caspofungin and flucytosine was synergistic for 62% of the isolates. In contrast, the interaction between voriconazole and flucytosine was never synergistic and antagonism was noted for 93% of the isolates. The triple combination of caspofungin with flucytosine and amphotericin B was synergistic for all the isolates tested. The triple combination of caspofungin with flucytosine and voriconazole was also mostly synergistic; but complex interactions were obtained for some isolates, with synergy or antagonism depending on the concentrations of caspofungin and voriconazole. Analysis of the influence of the reading technique on the results showed that spectrophotometric reading was a good alternative to the recommended visual reading. The results of these in vitro tests suggest that the activity of flucytosine as part of a double combination with caspofungin and as part of a triple combination with caspofungin and amphotericin B against
Aspergillus
spp. warrants further investigations. Animal studies are needed to evaluate the in vivo efficacies of these combinations.
Amphotericin B and Fluconazole, a Potent Combination Therapy for Cryptococcal Meningitis
Authors: Larsen Robert A. , Bauer Madeline , Thomas Ann M. , Graybill J. Richard 
Published: February 2004

ABSTRACT

We evaluated the antifungal activities of amphotericin B, fluconazole, and flucytosine, alone and in combination, in a murine model of cryptococcal meningitis. The objectives were to determine the greatest antifungal effects achievable with these drugs alone or in combination. Meningitis was established in male BALB/c mice weighing 23 to 25 g by intracerebral injection of
Cryptococcus neoformans
. Treatment was started on day 2. Amphotericin B was tested at 0.3 to 1.3 mg/kg of body weight/day by slow intravenous injection. Fluconazole at 10 to 40 mg/kg/day and flucytosine at 20 to 105 mg/kg/day were administered in the sole source of drinking water. The mice were killed at 16 days, and the numbers of fungal colonies in the brain were quantified. The association between the response and the dose combination was evaluated by local nonparametric response surface methods; 99% confidence intervals were used to evaluate the antifungal effects. Ninety-five percent of the mice treated with amphotericin B at 0.5 mg/kg survived to the end of the experiment, regardless of the fluconazole or flucytosine dose used. The greatest activity was seen with amphotericin B plus fluconazole with or without flucytosine. However, the addition of flucytosine did not increase the antifungal activity. Given the widespread availability of amphotericin B and fluconazole and the relative safety profile of fluconazole compared to that of flucytosine, the full potential of this two-drug combination deserves further evaluation.
CD154/CD40-Mediated Expression of CD154 in Endothelial Cells: Consequences for Endothelial Cell–Monocyte Interaction
Authors: Wagner Andreas H. , Güldenzoph Björn , Lienenlüke Bianca , Hecker Markus 
Published: February 2004

Objective—CD40 ligand (CD154) expressed on activated T helper cells is a key costimulatory molecule for antigen-presenting cells expressing the corresponding receptor CD40. Moreover, CD40 stimulation in nonimmune cells, such as endothelial cells, may play an important role in atherogenesis. One gene product that is induced in endothelial cells on exposure to CD154 is CD154 itself.Methods and Results—In human primary cultured endothelial cells, constitutive CD154 expression was virtually absent and insensitive to proinflammatory cytokines such as tumor necrosis factor α and/or interferon-γ. However, CD154 expression was markedly induced, both on the mRNA and protein level, after CD40 stimulation. Moreover, CD40-positive human monocytes (THP-1 cell line) transmigrating through CD154-expressing endothelial cells responded with an increased expression of interleukin-1β (IL-1β) mRNA, indicative of their activation. This increase in IL-1β expression was confirmed on the protein level and could be abrogated by prior treatment of the endothelial cells with a neutralizing anti-CD154 antibody.Conclusions—By way of CD154-induced CD154 expression, human endothelial cells thus seem capable of influencing the progression of proinflammatory reactions, including atherogenesis through activation of extravasating monocytes.
Hemangiopoietin, a novel human growth factor for the primitive cells of both hematopoietic and endothelial cell lineages
Authors: Liu Yong Jun , Lu Shi Hong , Xu Bin , Yang Ren Chi , Ren Qian , Liu Bin , Li Bin , Lu Min , Yan Feng Ying , Han Zhi Bo , Han Zhong Chao 
Published: February 2004

AbstractThe cells of hematopoietic and vascular endothelial cell lineages are believed to share a common precursor, termed hemangioblast. However, the existence of a growth factor acting relatively specifically on hemangioblasts remains unclear. Here we report the identification of hemangiopoietin (HAPO), a novel growth factor acting on both hematopoietic and endothelial cell lineages. In vitro in the human system, recombinant human HAPO (rhHAPO) significantly stimulated the proliferation and hematopoietic and/or endothelial differentiation of human bone marrow mononuclear cells and of purified CD34+, CD133+, kinase domain receptor-positive (KDR+), or CD34+/KDR+ cell populations. In the murine system, rhHAPO stimulated the proliferation of long-term culture-initiating cells (LTC-ICs) as well as CD34+ and stem cell antigen-1 (Sca-1+) cell subsets. In vivo, subcutaneous injection of rhHAPO into normal mice resulted in a significant increase in bone marrow hematopoietic cells. Furthermore, irradiated mice injected with rhHAPO had an enhanced survival rate and accelerated hematopoiesis. Our data suggest that HAPO is a novel growth factor acting on the primitive cells of both hematopoietic and endothelial cell lineages and that HAPO may have a clinical potential in the treatment of various cytopenias and radiation injury and in the expansion of hematopoietic and endothelial stem/progenitor cells. (Blood. 2004;103:4449-4456)
SOCS1 and SHP1 hypermethylation in multiple myeloma: implications for epigenetic activation of the Jak/STAT pathway
Authors: Chim Chor-Sang , Fung Tsz-Kin , Cheung Wai-Chung , Liang Raymond , Kwong Yok-Lam 
Published: February 2004

Abstract
SOCS1 and SHP1 negatively regulate the Janus kinase/signal transducer and activator of transcription (Jak/STAT) signaling pathway. The role of promoter hypermethylation leading to epigenetic inactivation of SOCS1 and SHP1 in myeloma was investigated. The methylation-specific polymerase chain reaction (MSP) was used to define SOCS1 and SHP1 methylation in 34 diagnostic myeloma samples. For SOCS1, MSP primers 3′ to the translation start site were unreliable and gave positive results in normal controls. However, primers in the 5′ promoter region were specific, although no myeloma samples showed methylation. For SHP1, 27 of 34 (79.4%) myeloma samples showed SHP1 hypermethylation. The biologic significance of SHP1 methylation was investigated in the U266 human myeloma line. U266 contained completely methylated SHP1. Furthermore, there was constitutive STAT3 phosphorylation. Treatment with 5-azacytidine led to progressive demethylation of SHP1 on days 2 to 5, with consequent increasing reexpression of SHP1 as shown by reverse transcription-polymerase chain reaction (RT-PCR). Concomitant with increasing SHP1, a parallel down-regulation of phosphorylated STAT3 occurred, so that by day 5 phosphorylated STAT3 was barely detectable. The overall survivals of patients with and without SHP1 methylation were similar. SHP1 methylation leading to epigenetic activation of the Jak/STAT pathway might have a tentative role in the pathogenesis of myeloma, which should be further confirmed by functional studies in primary myeloma samples. (Blood. 2004;103:4630-4635)
Modification of hematopoietic stem cell fate by 5aza 2′deoxycytidine and trichostatin A
Authors: Milhem Mohammed , Mahmud Nadim , Lavelle Donald , Araki Hiroto , DeSimone Joseph , Saunthararajah Yogen , Hoffman Ronald 
Published: February 2004

Abstract
Efforts to change the fate of human hematopoietic stem cells (HSCs) and progenitor cells (HPCs) in vitro have met with limited success. We hypothesized that previously utilized in vitro conditions might result in silencing of genes required for the maintenance of primitive HSCs/HPCs. DNA methylation and histone deacetylation are components of an epigenetic program that regulates gene expression. Using pharmacologic agents in vitro that might possibly interfere with DNA methylation and histone deacetylation, we attempted to maintain and expand cells with phenotypic and functional characteristics of primitive HSCs/HPCs. Human marrow CD34+ cells were exposed to a cytokine cocktail favoring differentiation in combination with 5aza 2′deoxycytidine (5azaD) and trichostatin A (TSA), resulting in a significant expansion of a subset of CD34+ cells that possessed phenotypic properties as well as the proliferative potential characteristic of primitive HSCs/HPCs. In addition, 5azaD- and TSA-pretreated cells but not the CD34+ cells exposed to cytokines alone retained the ability to repopulate immunodeficient mice. Our findings demonstrate that 5azaD and TSA can be used to alter the fate of primitive HSCs/HPCs during in vitro culture.