bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resistance to Macrolides in
Streptococcus pyogenes
in France in Pediatric Patients
Authors: Bingen Edouard , Fitoussi Frederic , Doit Catherine , Cohen Robert , Tanna Asha , George Robert , Loukil Chawki , Brahimi Naima , Le Thomas Isabelle , Deforche Dominique 
Published: July 2002

ABSTRACT

A total of 1,500 recent throat isolates of
Streptococcus pyogenes
collected between 1996 and 1999 from children throughout France were tested for their susceptibility to erythromycin, azithromycin, josamycin, clindamycin, and streptogramin B. The erythromycin-resistant isolates were further studied for their genetic mechanism of resistance, by means of PCR. The clonality of these strains was also investigated by means of serotyping and ribotyping. In all, 6.2% of the strains were erythromycin resistant, and 3.4 and 2.8% expressed the constitutive MLS
B
and M resistance phenotypes and harbored the
ermB
and
mefA
genes, respectively;
ermTR
was recovered from one isolate which also harbored the
ermB
gene. Ten serotypes and 8 ribotypes were identified, but we identified 17 strains by combining serotyping with ribotyping. Among the eight ribotypes, the
mefA
gene was recovered from six clusters, one being predominant, while the
ermB
gene was recovered from four clusters, of which two were predominant.
Single-Dose AmBisome (Liposomal Amphotericin B) as Prophylaxis for Murine Systemic Candidiasis and Histoplasmosis
Authors: Garcia April , Adler-Moore Jill P. , Proffitt Richard T. 
Published: July 2002

ABSTRACT

AmBisome is a liposomal formulation of amphotericin B that has broad-spectrum antifungal activity and greatly reduced toxicity compared to the parent drug. In this study, amphotericin B deoxycholate (Fungizone) (1 mg/kg) and AmBisome (1 to 20 mg/kg) were tested as single-dose prophylactic agents in both immunocompetent and immunosuppressed C57BL/6 mice challenged with either
Candida albicans
or
Histoplasma capsulatum
. Prophylactic efficacy was based on survival and fungal burden in the target organ (kidneys or spleen). At 9 to 10 days after histoplasma challenge, 80 to 90% of both immunocompetent and immunosuppressed mice in the control and Fungizone groups had died. All AmBisome-treated mice survived, although in the AmBisome groups given 1 mg/kg, the mice became moribund by day 10 to 12. No spleen CFU were detected in the histoplasma-challenged mice given 10 or 20 mg of AmBisome per kg. By 23 to 24 days after histoplasma challenge, fungal growth and/or death had occurred in all immunosuppressed mice except for four mice receiving 20 mg of AmBisome per kg. There were still no detectable fungi in the spleens of immunocompetent mice given 10 or 20 mg of AmBisome per kg. In the
C. albicans
experiment at 7 days postchallenge, all animals in both untreated and treated groups were alive with culture-positive kidneys. The kidney fungal burdens in AmBisome groups given 5 to 20 mg/kg were at least 1 log unit lower than those in the Fungizone group and significantly lower than those in the untreated control group (
P
< 0.05). There was a trend toward decreasing fungal growth in the kidneys as the dose of AmBisome was increased. In conclusion, these results show that a single high dose of AmBisome (5 to 20 mg/kg) had prophylactic efficacy in immunocompetent and immunosuppressed murine
H. capsulatum
and
C. albicans
models.
Postantibiotic Effects of Antituberculosis Agents Alone and in Combination
Authors: Chan Chiu-Yeung , Au-Yeang Carrie , Yew Wing-Wai , Hui Mamie , Cheng Augustine F. B. 
Published: July 2002

ABSTRACT

The postantibiotic effects (PAEs) of seven antimycobacterial agents, tested at their respective peak concentrations in serum alone and in different combinations, against
Mycobacterium tuberculosis
ATCC 27294 were studied with a radiometric culture system in parallel with the viable count method. Rifampin gave the longest PAE (67.8 h) among the drugs used alone, and combinations of first-line drugs generally gave PAEs longer than 120 h. The data obtained might help provide a better understanding of the scientific basis of intermittently administered antituberculosis chemotherapy.
Effect of Prolonged Treatment with Azithromycin, Clarithromycin, or Levofloxacin onChlamydia pneumoniaein a Continuous-Infection Model
Authors: Kutlin Andrei , Roblin Patricia M. , Hammerschlag Margaret R. 
Published: July 2002

ABSTRACTPersistent infections withChlamydia pneumoniaehave been implicated in the development of chronic diseases, such as atherosclerosis and asthma. Although azithromycin, clarithromycin, and levofloxacin are frequently used for the treatment of respiratoryC. pneumoniaeinfections, little is known about the dose and duration of therapy needed to treat a putative chronicC. pneumoniaeinfection. In this study, we investigated the effect of prolonged treatment with azithromycin, clarithromycin, or levofloxacin on the viability ofC. pneumoniaeand cytokine production in an in vitro model of continuous infection. We found that a 30-day treatment with azithromycin, clarithromycin, and levofloxacin at concentrations comparable to those achieved in the pulmonary epithelial lining fluid reduced but did not eliminateC. pneumoniaein continuously infected HEp-2 cells. All three antibiotics decreased levels of interleukin-6 (IL-6) and IL-8 in HEp-2 cells, but this effect appeared to be secondary to the antichlamydial activity, as the cytokine levels correlated with the concentrations of microorganisms. The levels of IL-1β, IL-4, IL-10, tumor necrosis factor alpha, and gamma interferon were too low to assess the effect of antibiotics. These data suggest that the dosage and duration of antibiotic therapy currently being used may not be sufficient to eradicate a putative chronicC. pneumoniaeinfection.
Oral Artesunate Dose-Response Relationship in Acute Falciparum Malaria
Authors: Angus Brian J. , Thaiaporn Itaporn , Chanthapadith Kenechanh , Suputtamongkol Yupin , White Nicholas J. 
Published: July 2002

ABSTRACT

The combination of an oral artemisinin derivative (usually artesunate) and mefloquine has become standard treatment for multidrug-resistant falciparum malaria in several parts of Southeast Asia. The doses of artesunate used in monotherapy and combination treatment have largely been derived empirically. In order to characterize the in vivo dose-response relationship for artesunate and thus rationalize dosing, 47 adult patients with acute uncomplicated falciparum malaria and parasitemia ≥1% were randomized to receive a single oral dose of artesunate varying between 0 and 250 mg together with a curative dose of oral mefloquine. Acceleration of parasite clearance was used as the pharmacodynamic variable. An inhibitory sigmoidal maximum effect (
E
max
) pharmacodynamic model typical of a dose-response curve was fitted to the relationship between dose and shortening of parasite clearance time (PCT). The
E
max
was estimated as 28.6 oral h, and the 50% effective concentration was 1.6 mg/kg of body weight. These results imply that there is no reduction in PCTs with the use of single doses of artesunate higher than 2 mg/kg, and this therefore reflects the average lower limit of the maximally effective dose.
Assessment of Poliovirus Eradication in Japan: Genomic Analysis of Polioviruses Isolated from River Water and Sewage in Toyama Prefecture
Authors: Matsuura Kumiko , Ishikura Mitsuhiro , Yoshida Hiromu , Nakayama Takashi , Hasegawa Sumiyo , Ando Shuji , Horie Hitoshi , Miyamura Tatsuo , Kitamura Takashi 
Published: July 2002

ABSTRACT
Seventy-eight poliovirus strains isolated from river water and sewage in Toyama Prefecture, Japan, during 1993 to 1995 were characterized by the PCR-restriction fragment length polymorphism (RFLP) method and by partially sequencing the VP3 and VP1 regions of the viral genome. Of these isolates, 36 were identified as Sabin vaccine strains, and 42 were identified as vaccine variant strains that had less than 1.4% nucleotide divergence from the Sabin strains, including 7 isolates with patterns different from those of Sabin strains as determined by PCR-RFLP analysis. These findings suggest that wild-type poliovirus was not circulating in Toyama Prefecture.
Medium-Chain Fatty Acids Affect Citrinin Production in the Filamentous Fungus
Monascus ruber
Authors: Hajjaj Hassan , Klaébé Alain , Goma Gérard , Blanc Philippe J. , Barbier Estelle , François Jean 
Published: July 2002

ABSTRACT

During submerged culture in the presence of glucose and glutamate, the filamentous fungus
Monascus ruber
produces water-soluble red pigments together with citrinin, a mycotoxin with nephrotoxic and hepatoxic effects on animals. Analysis of the
13
C-pigment molecules from mycelia cultivated with [1-
13
C]-, [2-
13
C]-, or [1,2-
13
C]acetate by
13
C nuclear magnetic resonance indicated that the biosynthesis of the red pigments used both the polyketide pathway, to generate the chromophore structure, and the fatty acid synthesis pathway, to produce a medium-chain fatty acid (octanoic acid) which was then bound to the chromophore by a
trans
-esterification reaction. Hence, to enhance pigment production, we tried to short-circuit the de novo synthesis of medium-chain fatty acids by adding them to the culture broth. Of fatty acids with carbon chains ranging from 6 to 18 carbon atoms, only octanoic acid showed a 30 to 50% stimulation of red pigment production, by a mechanism which, in contrast to expectation, did not involve its direct
trans
-esterification on the chromophore backbone. However, the medium- and long-chain fatty acids tested were readily assimilated by the fungus, and in the case of fatty acids ranging from 8 to 12 carbon atoms, 30 to 40% of their initial amount transiently accumulated in the growth medium in the form of the corresponding methylketone 1 carbon unit shorter. Very interestingly, these fatty acids or their corresponding methylketones caused a strong reduction in, or even a complete inhibition of, citrinin production by
M. ruber
when they were added to the medium. Several data indicated that this effect could be due to the degradation of the newly synthesized citrinin (or an intermediate in the citrinin pathway) by hydrogen peroxide resulting from peroxisome proliferation induced by medium-chain fatty acids or methylketones.
Purification to Homogeneity and Characterization of a Novel
Pseudomonas putida
Chromate Reductase
Authors: Park C. H. , Keyhan M. , Wielinga B. , Fendorf S. , Matin A. 
Published: July 2002

ABSTRACT

Cr(VI) (chromate) is a widespread environmental contaminant. Bacterial chromate reductases can convert soluble and toxic chromate to the insoluble and less toxic Cr(III). Bioremediation can therefore be effective in removing chromate from the environment, especially if the bacterial propensity for such removal is enhanced by genetic and biochemical engineering. To clone the chromate reductase-encoding gene, we purified to homogeneity (>600-fold purification) and characterized a novel soluble chromate reductase from
Pseudomonas putida
, using ammonium sulfate precipitation (55 to 70%), anion-exchange chromatography (DEAE Sepharose CL-6B), chromatofocusing (Polybuffer exchanger 94), and gel filtration (Superose 12 HR 10/30). The enzyme activity was dependent on NADH or NADPH; the temperature and pH optima for chromate reduction were 80°C and 5, respectively; and the

K
m

was 374 μM, with a
V
max
of 1.72 μmol/min/mg of protein. Sulfate inhibited the enzyme activity noncompetitively. The reductase activity remained virtually unaltered after 30 min of exposure to 50°C; even exposure to higher temperatures did not immediately inactivate the enzyme. X-ray absorption near-edge-structure spectra showed quantitative conversion of chromate to Cr(III) during the enzyme reaction.
Microbial Manganese and Sulfate Reduction in Black Sea Shelf Sediments
Authors: Thamdrup Bo , Rosselló-Mora Ramón , Amann Rudolf 
Published: July 2002

ABSTRACT

The microbial ecology of anaerobic carbon oxidation processes was investigated in Black Sea shelf sediments from mid-shelf with well-oxygenated bottom water to the oxic-anoxic chemocline at the shelf-break. At all stations, organic carbon (C
org
) oxidation rates were rapidly attenuated with depth in anoxically incubated sediment. Dissimilatory Mn reduction was the most important terminal electron-accepting process in the active surface layer to a depth of ∼1 cm, while SO
4
2−
reduction accounted for the entire C
org
oxidation below. Manganese reduction was supported by moderately high Mn oxide concentrations. A contribution from microbial Fe reduction could not be discerned, and the process was not stimulated by addition of ferrihydrite. Manganese reduction resulted in carbonate precipitation, which complicated the quantification of C
org
oxidation rates. The relative contribution of Mn reduction to C
org
oxidation in the anaerobic incubations was 25 to 73% at the stations with oxic bottom water. In situ, where Mn reduction must compete with oxygen respiration, the contribution of the process will vary in response to fluctuations in bottom water oxygen concentrations. Total bacterial numbers as well as the detection frequency of bacteria with fluorescent in situ hybridization scaled to the mineralization rates. Most-probable-number enumerations yielded up to 10
5
cells of acetate-oxidizing Mn-reducing bacteria (MnRB) cm
−3
, while counts of Fe reducers were <10
2
cm
−3
. At two stations, organisms affiliated with
Arcobacter
were the only types identified from 16S rRNA clone libraries from the highest positive MPN dilutions for MnRB. At the third station, a clone type affiliated with
Pelobacter
was also observed. Our results delineate a niche for dissimilatory Mn-reducing bacteria in sediments with Mn oxide concentrations greater than ∼10 μmol cm
−3
and indicate that bacteria that are specialized in Mn reduction, rather than known Mn and Fe reducers, are important in this niche.
Lactococcus lactis
as a Cell Factory for High-Level Diacetyl Production
Authors: Hugenholtz Jeroen , Kleerebezem Michiel , Starrenburg Marjo , Delcour Jean , de Vos Willem , Hols Pascal 
Published: July 2002

ABSTRACT

We report the engineering of
Lactococcus lactis
for the efficient conversion of sugar into diacetyl by combining NADH-oxidase overproduction and α-acetolactate decarboxylase inactivation. Eighty percent of the carbon flux was found to be rerouted via α-acetolactate to the production of diacetyl by preloading the cells with NADH-oxidase before their use as a cell factory.
An
rpsL
Cassette, Janus, for Gene Replacement through Negative Selection in
Streptococcus pneumoniae
Authors: Sung C. K. , Li H. , Claverys J. P. , Morrison D. A. 
Published: July 2002

ABSTRACT

Natural genetic transformation offers a direct route by which synthetic gene constructs can be placed into the single circular chromosome of
Streptococcus pneumoniae
. However, the lack of a general negative-selection marker has hampered the introduction of constructs that do not confer a selectable phenotype. A 1.3-kb cassette was constructed comprising a kanamycin (Kn) resistance marker (
kan
) and a counterselectable
rpsL
+
marker. The cassette conferred dominant streptomycin (Sm) sensitivity in an Sm-resistant background in
S. pneumoniae
. It was demonstrated that it could be used in a two-step transformation procedure to place DNA of arbitrary sequence at a chosen target site. The first transformation into an Sm-resistant strain used the cassette to tag a target gene on the chromosome by homologous recombination while conferring Kn resistance but Sm sensitivity on the recombinant. Replacement of the cassette by an arbitrary segment of DNA during a second transformation restored Sm resistance (and Kn sensitivity), allowing construction of silent mutations and deletions or other gene replacements which lack a selectable phenotype. It was also shown that gene conversion occurred between the two
rpsL
alleles in a process that depended on
recA
and that was susceptible to correction by mismatch repair.
Endophytic Colonization and In Planta Nitrogen Fixation by a
Herbaspirillum
sp. Isolated from Wild Rice Species
Authors: Elbeltagy Adel , Nishioka Kiyo , Sato Tadashi , Suzuki Hisa , Ye Bin , Hamada Toru , Isawa Tsuyoshi , Mitsui Hisayuki , Minamisawa Kiwamu 
Published: July 2002

ABSTRACT

Nitrogen-fixing bacteria were isolated from the stems of wild and cultivated rice on a modified Rennie medium. Based on 16S ribosomal DNA (rDNA) sequences, the diazotrophic isolates were phylogenetically close to four genera:
Herbaspirillum
,
Ideonella
,
Enterobacter
, and
Azospirillum
. Phenotypic properties and signature sequences of 16S rDNA indicated that three isolates (B65, B501, and B512) belong to the
Herbaspirillum
genus. To examine whether
Herbaspirillum
sp. strain B501 isolated from wild rice,
Oryza officinalis
, endophytically colonizes rice plants, the
gfp
gene encoding green fluorescent protein (GFP) was introduced into the bacteria. Observations by fluorescence stereomicroscopy showed that the GFP-tagged bacteria colonized shoots and seeds of aseptically grown seedlings of the original wild rice after inoculation of the seeds. Conversely, for cultivated rice
Oryza sativa
, no GFP fluorescence was observed for shoots and only weak signals were observed for seeds. Observations by fluorescence and electron microscopy revealed that
Herbaspirillum
sp. strain B501 colonized mainly intercellular spaces in the leaves of wild rice. Colony counts of surface-sterilized rice seedlings inoculated with the GFP-tagged bacteria indicated significantly more bacterial populations inside the original wild rice than in cultivated rice varieties. Moreover, after bacterial inoculation, in planta nitrogen fixation in young seedlings of wild rice,
O. officinalis
, was detected by the acetylene reduction and
15
N
2
gas incorporation assays. Therefore, we conclude that
Herbaspirillum
sp. strain B501 is a diazotrophic endophyte compatible with wild rice, particularly
O. officinalis
.
Development of a Gene Cloning and Inactivation System for Halorespiring
Desulfitobacterium dehalogenans
Authors: Smidt Hauke , van der Oost John , de Vos Willem M. 
Published: July 2002

ABSTRACT

Efficient host-vector systems have been developed for the versatile, strictly anaerobic, halo- and fumarate-respiring gram-positive bacterium
Desulfitobacterium dehalogenans
. An electroporation-based transformation procedure resulting in approximately 10
3
to 10
4
transformants per μg of the cloning vector pIL253 was developed and validated. The broad-host-range vector pG
+
host9 was shown to replicate at a permissive temperature of 30°C, whereas the replicon was not functional at 40°C. The
D. dehalogenans frdCAB
operon, predicted to encode a fumarate reductase, was cloned, characterized, and targeted for insertional inactivation by pG
+
host9 carrying a 0.6-kb internal
frdA
fragment. Single-crossover integration at the
frdA
locus occurred at a frequency of 3.3 × 10
−4
per cell and resulted in partially impaired fumarate reductase activity. The gene cloning and inactivation systems described here provide a solid basis for the further elucidation of the halorespiratory network in
D. dehalogenans
and allow for its further exploitation as a dedicated degrader.
Characterization of Neutralizing Antibodies and Identification of Neutralizing Epitope Mimics on theClostridium botulinumNeurotoxin Type A
Authors: Wu Han-Chung , Yeh Chia-Tsui , Huang Yue-Ling , Tarn Lih-Jeng , Lung Chien-Cheng 
Published: July 2002

ABSTRACTClostridium botulinumneurotoxin type A (BTx-A) is known to inhibit the release of acetylcholine at the neuromuscular junctions and synapses and to cause neuroparalysis and death. In this study, we have identified two monoclonal antibodies, BT57-1 and BT150-3, which protect ICR mice against lethal doses of BTx-A challenge. The neutralizing activities for BT57-1 and BT150-3 were 103and 104times the 50% lethal dose, respectively. Using immunoblotting analysis, BT57-1 was recognized as a light chain and BT150-3 was recognized as a heavy chain of BTx-A. Also, applying the phage display method, we investigated the antibodies' neutralizing B-cell epitopes. These immunopositive phage clones displayed consensus motifs, Asp-Pro-Leu for BT57-1 and Cys-X-Asp-Cys for BT150. The synthetic peptide P4M (KGTFDPLQEPRT) corresponded to the phage-displayed peptide selected by BT57-1 and was able to bind the antibodies specifically. This peptide was also shown by competitive inhibition assay to be able to inhibit phage clone binding to BT57-1. Aspartic acid (D5) in P4M was crucial to the binding of P4M to BT57-1, since its binding activity dramatically decreased when it was changed to lysine (K5). Finally, immunizing mice with the selected phage clones elicited a specific humoral response against BTx-A. These results suggest that phage-displayed random-peptide libraries are useful in identifying the neutralizing epitopes of monoclonal antibodies. In the future, the identification of the neutralizing epitopes of BTx-A may provide important information for the identification of the BTx-A receptor and the design of a BTx-A vaccine.
Isolation and In Vivo and In Vitro Antifungal Activity of Phenylacetic Acid and Sodium Phenylacetate from
Streptomyces humidus
Authors: Hwang Byung Kook , Lim Song Won , Kim Beom Seok , Lee Jung Yeop , Moon Surk Sik 
Published: July 2002

ABSTRACT

The antifungal substances SH-1 and SH-2 were isolated from
Streptomyces humidus
strain S5-55 cultures by various purification procedures and identified as phenylacetic acid and sodium phenylacetate, respectively, based on the nuclear magnetic resonance, electron ionization mass spectral, and inductively coupled plasma mass spectral data. SH-1 and SH-2 completely inhibited the growth of
Pythium ultimum, Phytophthora capsici, Rhizoctonia solani, Saccharomyces cerevisiae
, and
Pseudomonas syringae
pv. syringae at concentrations from 10 to 50 μg/ml. The two compounds were as effective as the commercial fungicide metalaxyl in inhibiting spore germination and hyphal growth of
P. capsici
. However, the in vivo control efficacies of the two antifungal compounds against
P. capsici
infection on pepper plants were similar to those of H
3
PO
3
and fosetyl-AI but less than that of metalaxyl.
Photoreactivation in Airborne
Mycobacterium parafortuitum
Authors: Peccia Jordan , Hernandez Mark 
Published: July 2002

ABSTRACT

Photoreactivation was observed in airborne
Mycobacterium parafortuitum
exposed concurrently to UV radiation (254 nm) and visible light. Photoreactivation rates of airborne cells increased with increasing relative humidity (RH) and decreased with increasing UV dose. Under a constant UV dose with visible light absent, the UV inactivation rate of airborne
M. parafortuitum
cells decreased by a factor of 4 as RH increased from 40 to 95%; however, under identical conditions with visible light present, the UV inactivation rate of airborne cells decreased only by a factor of 2. When irradiated in the absence of visible light, cellular cyclobutane thymine dimer content of UV-irradiated airborne
M. parafortuitum
and
Serratia marcescens
increased in response to RH increases. Results suggest that, unlike in waterborne bacteria, cyclobutane thymine dimers are not the most significant form of UV-induced DNA damage incurred by airborne bacteria and that the distribution of DNA photoproducts incorporated into UV-irradiated airborne cells is a function of RH.