bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of a
Mycobacterium smegmatis
Mutant That Is Simultaneously Resistant to
d
-Cycloserine and Vancomycin
Authors: Peteroy Marcy , Severin Anatoly , Zhao Frances , Rosner Dalya , Lopatin Uri , Scherman Hataichanouk , Belanger Aimee , Harvey Bohdan , Hatfull Graham F. , Brennan Patrick J. , Connell Nancy D. 
Published: July 2002

ABSTRACT

A mutant of
Mycobacterium smegmatis
has been isolated that is simultaneously resistant to both
d
-cycloserine (
d
-CS) and vancomycin. Genetic complementation with a PBP4 homolog restores sensitivity to both drugs. Resistance to
d
-CS and vancomycin in this mutant is most likely due to a novel mechanism involving peptidoglycan assembly at the cell surface.
Effect of Zidovudine on the Primary Cytolytic T-Lymphocyte Response and T-Cell Effector Function
Authors: Francke Sabine , Orosz Charles G. , Hayes Kathleen A. , Mathes Lawrence E. 
Published: July 2002

ABSTRACTAzidothymidine (AZT) and other nucleoside analogues, used to treat AIDS, can cause severe clinical side effects and are suspected of suppressing immune cell proliferation and effector immune cell function. The purpose of the present study was to quantitatively measure the effects of AZT on cytotoxic T-lymphocyte (CTL) priming and to determine if the major histocompatibility complex-restricted CTL killing was affected by AZT exposure. For this purpose, we employed a murine alloantigen model and limiting-dilution analysis (LDA) to estimate cytotoxic effector cell frequencies of alloreactive splenocytes treated with drug during antigen sensitization. This noninfectious model was chosen to avoid analysis of a virus-compromised immune system. Exposure of splenocytes to therapeutic concentrations of AZT (2 to 10 μM) caused a two- to threefold dose-dependent reduction in CLT precursor frequency. This reduction was caused by decreased proliferation of alloantigen-specific CTLs rather than loss of function, because full cytolytic function could be restored by adjusting the AZT-treated effector/target cell ratios to that of untreated cells. In addition, when AZT was added to the assay system at various times during antigen sensitization there was a time-related loss of the suppressive effect on the generation of cytolytic effector function, suggesting that functional CTLs are not affected by even high doses of AZT. Taken together, the data indicate that the reduction of CTL function associated with AZT treatment is due to a quantitative decrease of effector cell precursor frequency rather than to direct drug cytotoxicity or interference with mediation of cytolysis. Furthermore, antigen-naive immune cells were most sensitive to this effect during the first few days following antigen encounter.
Effects of Azithromycin and Rifampin onChlamydia trachomatisInfection In Vitro
Authors: Dreses-Werringloer Ute , Padubrin Ingrid , Zeidler Henning , Köhler Lars 
Published: July 2002

ABSTRACTAn in vitro cell culture model was used to investigate the long-term effects of azithromycin, rifampin, and the combination of azithromycin and rifampin onChlamydia trachomatisinfection. Although standard in vitro susceptibility testing indicated efficient inhibition by azithromycin, prolonged treatment did not reveal a clear elimination of chlamydia from host cells. Chlamydia were temporarily arrested in a persistent state, characterized by culture-negative, but viable, metabolically active chlamydia, as demonstrated by the presence of short-lived rRNA transcripts. Additionally, azithromycin induced generation of aberrant inclusions and an altered steady-state level of chlamydial antigens, with the predominance of Hsp60 protein compared to the level of the major outer membrane protein. Treatment with azithromycin finally resulted in suppression of rRNA synthesis. Chlamydial lipopolysaccharide and processed, functional rRNA were detectable throughout the entire incubation period. These in vitro data show a good correlation to those from some recent clinical investigations that have reported on the persistence of chlamydia, despite appropriate antibiotic treatment with azithromycin. Rifampin was highly active by in vitro susceptibility testing, but prolonged exposure to rifampin alone for up to 20 days resulted in the emergence of resistance. No development of resistance to rifampin was observed when chlamydia-infected cells were incubated with a combination of azithromycin and rifampin. This combination was shown to be more efficient than azithromycin alone, in that suppression of rRNA synthesis occurred earlier. Thus, such a combination may prove more useful than azithromycin alone.
Ritonavir-Saquinavir Dual Protease Inhibitor Compared to Ritonavir Alone in Human Immunodeficiency Virus-Infected Patients
Authors: Michelet Christian , Ruffault Annick , Sébille Véronique , Arvieux Cedric , Jaccard Philippe , Raffi François , Bazin Claude , Chapplain Jean-Marc , Chauvin Jean-Pierre , Dohin Elisabeth , Cartier François , Bellissant Eric 
Published: July 2002

ABSTRACTThe objective of this study was to evaluate the antiretroviral efficacy and safety of ritonavir (600 mg twice a day [b.i.d.])-saquinavir (400 mg b.i.d.) compared to ritonavir (600 mg b.i.d.) in patients pretreated and receiving continued treatment with two nucleoside analogs. The study was placebo controlled, randomized, and double blind. Inclusion criteria included protease inhibitor naive status and a viral load of >10,000 copies/ml. The main end point was viral load at week 24. Forty-seven patients were included (25 given ritonavir and 22 given ritonavir-saquinavir) and monitored until week 48. At inclusion, 23% had had at least one AIDS-defining event. Previous treatment durations (mean and standard deviation) were 42 ± 25 and 37 ± 23 months, viral loads were 4.75 ± 0.62 and 4.76 ± 0.50 log10copies/ml, and CD4 cell counts were 236 ± 126 and 234 ± 125/mm3in the ritonavir and ritonavir-saquinavir groups, respectively. At week 24, viral loads were 2.81 ± 1.48 and 2.08 ± 1.14 log10copies/ml (P= 0.04) and CD4 cell counts were 330 ± 151 and 364 ± 185/mm3(P= 0.49) in the ritonavir and ritonavir-saquinavir groups, respectively. Similar results were observed at week 48. Moreover, at week 48, 40 and 68% (P= 0.05) and 28 and 59% (P= 0.03) of patients achieved viral suppression at below 200 and 50 copies/ml in the ritonavir and ritonavir-saquinavir groups, respectively. At week 24, six patients in the ritonavir group but only one in the ritonavir-saquinavir group had key mutations conferring resistance to protease inhibitors. Clinical and biological tolerances were similar in both groups. In nucleoside analog-pretreated patients, ritonavir-saquinavir has higher antiretroviral efficacy than and is as well tolerated as ritonavir alone.
Efficacy of Recombinant Gamma Interferon for Treatment of Systemic Cryptococcosis in SCID Mice
Authors: Clemons Karl V. , Lutz Jon E. , Stevens David A. 
Published: July 2002

ABSTRACTWe have previously shown that gamma interferon (IFN-γ) is a useful adjunct to therapy of experimental systemic cryptococcosis in normal mice. To better emulate AIDS patients, SCID mice were infected intravenously withCryptococcus neoformans. Mice received no therapy, 3 mg of amphotericin B (AmB) per kg of body weight, or 105U of IFN-γ alone (prophylactically and therapeutically or only therapeutically) or with AmB. In the first experiment, >75% of the mice survived. Therapy with AmB alone was efficacious compared to no therapy in all organs. Both regimens of IFN-γ alone were efficacious in the brain and lungs, and the combination of AmB and IFN-γ showed significant synergy in the kidneys. AmB alone cured 40% of mice of infection, whereas the combination regimens cured >50% of the mice and 90% of the brain infections. In a second study, IFN-γ again proved efficacious alone, and when given with AmB its efficacy was improved. Therapeutic IFN-γ alone was effective only in the liver compared to no therapy, and the combination regimen, although highly effective, showed no significant synergy. In a third experiment, AmB alone or in combination with IFN-γ prolonged survival compared to no therapy or IFN-γ alone. The combination regimen showed significant synergy over AmB alone in the brain, liver, kidneys, and lungs. AmB alone cured no mice of infections in more than two organs, whereas AmB in combination with IFN-γ cured 55% of infections in three or more organs. These results indicate that IFN-γ has therapeutic efficacy in severely immunodeficient animals, especially in combination with AmB. Significant synergistic activity was noted in all organs except the spleen. Overall, IFN-γ has utility as an adjunctive therapy against systemic cryptococcosis in the severely immunocompromised host.
Antimicrobial Susceptibility of
Ehrlichia phagocytophila
Authors: Horowitz Harold W. , Hsieh T.-C. , Aguero-Rosenfeld Maria E. , Kalantarpour Fatemeh , Chowdhury Ishraq , Wormser Gary P. , Wu Joseph M. 
Published: July 2002

ABSTRACT

Human granulocytic ehrlichiosis is a recently described disease caused by an obligate intracellular gram-negative organism recently named
Ehrlichia phagocytophila
. To expand our knowledge of the susceptibility of
E. phagocytophila
, we tested six New York State isolates for susceptibility to 12 antimicrobials using an HL-60 cell culture system. All of the isolates were susceptible to doxycycline (MIC, ≤0.125 μg/ml; minimum bactericidal concentration [MBC], 0.125 to 0.5 μg/ml), rifampin (MIC, ≤0.125 μg/ml; MBC, ≤0.125 μg/ml), ofloxacin (MIC, ≤2 μg/ml; MBC, ≤2 μg/ml), levofloxacin (MIC, ≤1 μg/ml; MBC, ≤1 μg/ml), and trovafloxacin (MIC, ≤0.032 μg/ml; MBC, ≤0.032 μg/ml). Isolates were uniformly resistant to amoxicillin, ceftriaxone, erythromycin, azithromycin, clarithromycin, and amikacin. For one strain, the MBC of chloramphenicol was ≤8 μg/ml. These data suggest that quinolone antibiotics and rifampin may be alternative agents for patients with intolerance to tetracyclines.
Teicoplanin Stress-Selected Mutations Increasing ς
B
Activity in
Staphylococcus aureus
Authors: Bischoff Markus , Berger-Bächi Brigitte 
Published: July 2002

ABSTRACT

A natural
rsbU
mutant of
Staphylococcus aureus,
unable to activate the alternative transcription factor ς
B
via the RsbU pathway and therefore forming unpigmented colonies, produced first-step teicoplanin-resistant mutants upon selection for growth in the presence of teicoplanin, of which the majority were of an intense orange color. By using an
asp23
promoter-luciferase fusion as an indicator, the pigmented mutants were shown to express increased ς
B
activity. Increased ς
B
activity was associated with point mutations in
rsbW,
releasing ς
B
from sequestration by the anti-sigma factor RsbW, or to promoter mutations increasing the ς
B
/RsbW ratio. Genetic manipulations involving the
sigB
operon suggested that the mutations within the operon were associated with the increase in teicoplanin resistance. The upregulation of ς
B
suggests that a ς
B
-controlled gene(s) is directly or indirectly involved in the development of teicoplanin resistance in
S. aureus
. Carotenoids do not contribute to teicoplanin resistance, since inactivation of the dehydrosqualene synthase gene
crtM
abolished pigment formation without affecting teicoplanin resistance. The relevant ς
B
-controlled target genes involved in teicoplanin resistance remain to be identified.
Activities of Faropenem, an Oral β-Lactam, against Recent U.S. Isolates of
Streptococcus pneumoniae
,
Haemophilus influenzae
, and
Moraxella catarrhalis
Authors: Critchley Ian A. , Karlowsky James A. , Draghi Deborah C. , Jones Mark E. , Thornsberry Clyde , Murfitt Kate , Sahm Daniel F. 
Published: July 2002

ABSTRACT

The in vitro activities of faropenem and other antimicrobial agents were determined against 4,725
Streptococcus pneumoniae
isolates, 2,614
Haemophilus influenzae
isolates, and 1,193
Moraxella catarrhalis
isolates collected from 273 U.S. laboratories during 1999. Faropenem MICs at which 90% of isolates are inhibited were 0.008, 0.25, and 1 μg/ml for penicillin-susceptible, -intermediate, and -resistant
S. pneumoniae
strains, respectively; 0.5 and 1 μg/ml for β-lactamase-positive and -negative
H. influenzae
strains, respectively; and 0.12 and 0.5 μg/ml for β-lactamase-negative and -positive
M. catarrhalis
strains, respectively. Faropenem holds promise as an oral therapy for community-acquired respiratory tract infections.
A Missense Mutation in the
fabB
(β-Ketoacyl-Acyl Carrier Protein Synthase I) Gene Confers Thiolactomycin Resistance to
Escherichia coli
Authors: Jackowski Suzanne , Zhang Yong-Mei , Price Allen C. , White Stephen W. , Rock Charles O. 
Published: July 2002

ABSTRACT

Thiolactomycin (TLM) is an antibiotic that inhibits bacterial type II fatty acid synthesis at the condensing enzyme step, and β-ketoacyl-acyl carrier protein synthase I (FabB) is the relevant target in
Escherichia coli
. TLM resistance is associated with the upregulation of efflux pumps. Therefore, a
tolC
knockout mutant (strain ANS1) was constructed to eliminate the contribution of type I secretion systems to TLM resistance. Six independent TLM-resistant clones of strain ANS1 were isolated, and all possessed the same missense mutation in the
fabB
gene (T1168G) that directed the expression of a mutant protein, FabB(F390V). FabB(F390V) was resistant to TLM in vitro. Leucine is the only other amino acid found at position 390 in nature, and the
Staphylococcus aureus
FabF protein, which contains this substitution, was sensitive to TLM. Structural modeling predicted that the CG2 methyl group of the valine side chain interfered with the positioning of the C11 methyl on the isoprenoid side chain of TLM in the binary complex, whereas the absence of a bulky methyl group on the leucine side chain permitted TLM binding. These data illustrate that missense mutations that introduce valine at position 390 confer TLM resistance while maintaining the vital catalytic properties of FabB.
In Vitro and In Vivo Antifungal Activities of TAK-456, a Novel Oral Triazole with a Broad Antifungal Spectrum
Authors: Tsuchimori Noboru , Hayashi Ryogo , Kitamoto Naomi , Asai Kentaro , Kitazaki Tomoyuki , Iizawa Yuji , Itoh Katsumi , Okonogi Kenji 
Published: July 2002

ABSTRACT

TAK-456 is a novel oral triazole compound with potent and broad-spectrum in vitro antifungal activity and strong in vivo efficacy against
Candida albicans
and
Aspergillus fumigatus
. TAK-456 inhibited sterol synthesis of
C. albicans
and
A. fumigatus
by 50% at 3 to 11 ng/ml. TAK-456 showed strong in vitro activity against clinical isolates of
Candida
spp.,
Aspergillus
spp., and
Cryptococcus neoformans
, except for
Candida glabrata
. The MICs at which 90% of the isolates tested were inhibited byTAK-456, fluconazole, itraconazole, voriconazole, and amphotericin B were 0.25, 4, 0.5, 0.13, and 0.5 μg/ml, respectively, for clinical isolates of
C. albicans
and 1, >64, 0.5, 0.5, and 0.5 μg/ml, respectively, for clinical isolates of
A. fumigatus
. Therapeutic activities of TAK-456 and reference triazoles against systemic lethal infections caused by
C. albicans
and
A. fumigatus
in mice were investigated by orally administering drugs once daily for 5 days, and efficacies of the compounds were evaluated by the prolongation of survival. In normal mice, TAK-456 and fluconazole were effective against infection caused by fluconazole-susceptible
C. albicans
at a dose of 1 mg/kg. In transiently neutropenic mice, therapeutic activity of TAK-456 at 1 mg/kg of body weight against infection with the same strain was stronger than those at 1 mg/kg of fluconazole. TAK-456 was effective against infections with two strains of fluconazole-resistant
C. albicans
at a dose of 10 mg/kg. TAK-456 also expressed activities similar to or higher than those of itraconazole against the infections caused by two strains of
A. fumigatus
in neutropenic mice at a dose of 10 mg/kg. These results suggest that TAK-456 is a promising candidate for development for the treatment of candidiasis and aspergillosis in humans.
Enhancement of Secretion and Extracellular Stability of Staphylokinase in
Bacillus subtilis
by
wprA
Gene Disruption
Authors: Lee Sang Jun , Kim Dong Min , Bae Kwang Hee , Byun Si Myung , Chung Jae Hoon 
Published: July 2002

ABSTRACT

Staphylokinase (SAK), a polypeptide secreted by
Staphylococcus aureus
, is a plasminogen activator with a therapeutic potential in thrombosis diseases. A
Bacillus subtilis
strain which is multiply deficient in exoproteases was transformed by an expression plasmid carrying a promoter and a signal sequence of subtilisin fused in frame with the
sak
open reading frame. However, the amount of SAK secretion was marginal (45 mg/liter). In contrast, disruption of the
wprA
gene, which encodes a subtilisin-type protease, strongly promoted the production of SAK in the stationary phase (181 mg/liter). In addition, the extracellular stability of mature SAK was dramatically enhanced. These data indicate a significant role of the
wprA
gene product in degrading foreign proteins, both during secretion and in the extracellular milieu.
Pathogenic Role of SEF14, SEF17, and SEF21 Fimbriae in
Salmonella enterica
Serovar Enteritidis Infection of Chickens
Authors: Rajashekara Gireesh , Munir Shirin , Alexeyev Mikhail F. , Halvorson David A. , Wells Carol L. , Nagaraja Kakambi V. 
Published: July 2002

ABSTRACT

Very little is known about the contribution of surface appendages of
Salmonella enterica
serovar Enteritidis to pathogenesis in chickens. This study was designed to clarify the role of SEF14, SEF17, and SEF21 fimbriae in serovar Enteritidis pathogenesis. Stable, single, defined
sefA
(SEF14),
agfA
(SEF17), and
fimA
(SEF21) insertionally inactivated fimbrial gene mutants of serovar Enteritidis were constructed. All mutant strains invaded Caco-2 and HT-29 enterocytes at levels similar to that of the wild type. Both mutant and wild-type strains were ingested equally well by chicken macrophage cell lines HD11 and MQ-NCSU. There were no significant differences in the abilities of these strains to colonize chicken ceca. The SEF14
−
strain was isolated in lower numbers from the livers of infected chickens and was cleared from the spleens faster than other strains. No significant differences in fecal shedding of these strains were observed.
Mycotoxins in Crude Building Materials from Water-Damaged Buildings
Authors: Tuomi Tapani , Reijula Kari , Johnsson Tom , Hemminki Kaisa , Hintikka Eeva-Liisa , Lindroos Outi , Kalso Seija , Koukila-Kähkölä Pirkko , Mussalo-Rauhamaa Helena , Haahtela Tari 
Published: July 2002

ABSTRACT

We analyzed 79 bulk samples of moldy interior finishes from Finnish buildings with moisture problems for 17 mycotoxins, as well as for fungi that could be isolated using one medium and one set of growth conditions. We found the aflatoxin precursor, sterigmatocystin, in 24% of the samples and trichothecenes in 19% of the samples. Trichothecenes found included satratoxin G or H in five samples; diacetoxyscirpenol in five samples; and 3-acetyl-deoxynivalenol, deoxynivalenol, verrucarol, or T-2-tetraol in an additional five samples. Citrinine was found in three samples.
Aspergillus versicolor
was present in most sterigmatocystin-containing samples, and
Stachybotrys
spp. were present in the samples where satratoxins were found. In many cases, however, the presence of fungi thought to produce the mycotoxins was not correlated with the presence of the expected compounds. However, when mycotoxins were found, some toxigenic fungi usually were present, even if the species originally responsible for producing the mycotoxin was not isolated. We conclude that the identification and enumeration of fungal species present in bulk materials are important to verify the severity of mold damage but that chemical analyses are necessary if the goal is to establish the presence of mycotoxins in moldy materials.
A Comparison of Methods for Counting Viruses in Aquatic Systems
Authors: Bettarel Yvan , Sime-Ngando Telesphore , Amblard Christian , Laveran Henri 
Published: July 2002

ABSTRACT

In this study, we compared different methods—including transmission electron microscopy—and various nucleic acid labeling methods in which we used the fluorochromes 4′,6′-diamidino-2-phenylindole (DAPI), 4-[3-methyl-2,3-dihydro-(benzo-1,3-oxazole)-2-methylmethyledene]-1-(3′-trimethyl ammoniumpropyl)-quinilinium diioide (YOPRO-1), and SYBR Green I, which can be detected by epifluorescence microscopy (EM), for counting viruses in samples obtained from freshwater ecosystems whose trophic status varied and from a culture of T7 phages. From a quantitative and qualitative viewpoint, our results showed that the greatest efficiency for all ecosystems was obtained when we used the EM counting protocol in which YOPRO-1 was the label, as this fluorochrome exhibited strong and very stable fluorescence. A modification of the original protocol in which YOPRO-1 was used is recommended, because this modification makes the protocol faster and allows it to be used for routine analysis of fixed samples. Because SYBR Green I fades very quickly, the use of this fluorochrome is not recommended for systems in which the viral content is very high (>10
8
particles/ml), such as treated domestic sewage effluents. Experiments in which we used DNase and RNase revealed that the number of viruses determined by EM was slightly overestimated (by approximately 15%) because of interference caused by the presence of free nucleic acids.
Alterations in the Proteome of the
Euprymna scolopes
Light Organ in Response to Symbiotic
Vibrio fischeri
Authors: Doino Lemus Judith , McFall-Ngai Margaret J. 
Published: July 2002

ABSTRACT

During the onset of the cooperative association between the Hawaiian sepiolid squid
Euprymna scolopes
and the marine luminous bacterium
Vibrio fischeri
, the anatomy and morphology of the host's symbiotic organ undergo dramatic changes that require interaction with the bacteria. This morphogenetic process involves an array of tissues, including those in direct contact with, as well as those remote from, the symbiotic bacteria. The bacteria induce the developmental program soon after colonization of the organ, although complete morphogenesis requires 96 h. In this study, to determine critical time points, we examined the biochemistry underlying bacterium-induced host development using two-dimensional polyacrylamide gel electrophoresis. Specifically,
V. fischeri
-induced changes in the soluble proteome of the symbiotic organ during the first 96 h of symbiosis were identified by comparing the protein profiles of symbiont-colonized and uncolonized organs. Both symbiosis-related changes and age-related changes were analyzed to determine what proportion of the differences in the proteomes was the result of specific responses to interaction with bacteria. Although no differences were detected over the first 24 h, numerous symbiosis-related changes became apparent at 48 and 96 h and were more abundant than age-related changes. In addition, many age-related protein changes occurred 48 h sooner in symbiotic animals, suggesting that the interaction of squid tissue with
V. fischeri
cells accelerates certain developmental processes of the symbiotic organ. These data suggest that
V. fischeri
-induced modifications in host tissues that occur in the first 24 h of the symbiosis are independent of marked alterations in the patterns of abundant proteins but that the full 4-day morphogenetic program requires significant alteration of the host soluble proteome.