bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Activities of a New Lipopeptide Antifungal Agent, FK463, against a Variety of Clinically Important Fungi
Authors: Tawara Shuichi , Ikeda Fumiaki , Maki Katsuyuki , Morishita Yoshihiko , Otomo Kazumi , Teratani Noriko , Goto Toshio , Tomishima Masaki , Ohki Hidenori , Yamada Akira , Kawabata Koji , Takasugi Hisashi , Sakane Kazuo , Tanaka Hirokazu , Matsumoto Fumio , Kuwahara Shogo 
Published: April 2009

ABSTRACT

The in vitro antifungal activity and spectrum of FK463 were compared with those of amphotericin B, fluconazole, and itraconazole by using a broth microdilution method specified by National Committee for Clinical Laboratory Standards document M27-A (National Committee for Clinical Laboratory Standards, Wayne, Pa., 1997). FK463 exhibited broad-spectrum activity against clinically important pathogens including
Candida
species (MIC range, ≦0.0039 to 2 μg/ml) and
Aspergillus
species (MIC range, ≦0.0039 to 0.0313 μg/ml), and its MICs for such fungi were lower than those of the other antifungal agents tested. FK463 was also potently active against azole-resistant
Candida albicans
as well as azole-susceptible strains, and there was no cross-resistance with azoles. FK463 showed fungicidal activity against
C. albicans
, i.e., a 99% reduction in viability after a 24-h exposure at concentrations above 0.0156 μg/ml. The minimum fungicidal concentration (MFC) assays indicated that FK463 was fungicidal against most isolates of
Candida
species. In contrast, the MFCs of FK463 for
A. fumigatus
isolates were much higher than the MICs, indicating that its action is fungistatic against this species. FK463 had no activity against
Cryptococcus neoformans
,
Trichosporon
species, or
Fusarium solani
. Neither the test medium (kind and pH) nor the inoculum size greatly affected the MICs of FK463, while the addition of 4% human serum albumin increased the MICs for
Candida
species and
A. fumigatus
more than 32 times. Results from preclinical in vitro evaluations performed thus far indicate that FK463 should be a potent parenteral antifungal agent.
The R467K Amino Acid Substitution in
Candida albicans
Sterol 14α-Demethylase Causes Drug Resistance through Reduced Affinity
Authors: Lamb David C. , Kelly Diane E. , White Theodore C. , Kelly Steven L. 
Published: April 2009

ABSTRACT

The cytochrome P450 sterol 14α-demethylase (CYP51) of
Candida albicans
is involved in an essential step of ergosterol biosynthesis and is the target for azole antifungal compounds. We have undertaken site-directed mutation of
C. albicans CYP51
to produce a recombinant mutant protein with the amino acid substitution R467K corresponding to a mutation observed clinically. This alteration perturbed the heme environment causing an altered reduced-carbon monoxide difference spectrum with a maximum at 452 nm and reduced the affinity of the enzyme for fluconazole, as shown by ligand binding studies. The specific activity of CYP51(R467K) for the release of formic acid from 3β-[32-
3
H]hydroxylanost-7-en-32-ol was 70 pmol/nmol of P450/min for microsomal protein compared to 240 pmol/nmol of P450/min for microsomal fractions expressing wild-type CYP51. Furthermore, inhibition of activity by fluconazole revealed a 7.5-fold-greater azole resistance of the recombinant protein than that of the wild type. This study demonstrates that resistance observed clinically can result from the altered azole affinity of the fungal CYP51 enzyme.
Zanamivir Susceptibility Monitoring and Characterization of Influenza Virus Clinical Isolates Obtained during Phase II Clinical Efficacy Studies
Authors: Barnett J. M. , Cadman A. , Gor D. , Dempsey M. , Walters M. , Candlin A. , Tisdale M. , Morley P. J. , Owens I. J. , Fenton R. J. , Lewis A. P. , Claas E. C. J. , Rimmelzwaan G. F. , De Groot R. , Osterhaus A. D. M. E. 
Published: April 2009

ABSTRACT

Zanamivir is a highly selective neuraminidase (NA) inhibitor with demonstrated clinical efficacy against influenza A and B virus infections. In phase II clinical efficacy trials (NAIB2005 and NAIB2008), virological substudies showed mean reductions in virus shedding after 24 h of treatment of 1.5 to 2.0 log
10
50% tissue culture infective doses compared to a placebo, with no reemergence of virus after the completion of therapy. Paired isolates (
n
= 41) obtained before and during therapy with zanamivir demonstrated no shifts in susceptibility to zanamivir when measured by NA assays, although for a few isolates NA activity was too low to evaluate. In plaque reduction assays in MDCK cells, the susceptibility of isolates to zanamivir was extremely variable even at baseline and did not correlate with the speed of resolution of virus shedding. Isolates with apparent limited susceptibility to zanamivir by plaque reduction proved highly susceptible in vivo in the ferret model. Further sequence analysis of paired isolates revealed no changes in the hemagglutinin and NA genes in the majority of isolates. The few changes observed were all natural variants. No amino acid changes that had previously been identified in vitro as being involved with reduced susceptibility to zanamivir were observed. These studies highlighted problems associated with monitoring susceptibility to NA inhibitors in the clinic, in that no reliable cell-based assay is available. At present the NA assay is the best available predictor of susceptibility to NA inhibitors in vivo, as measured in the validated ferret model of infection.
In Vitro Activity of Riboflavin against the Human Malaria Parasite
Plasmodium falciparum
Authors: Akompong Thomas , Ghori Nafisa , Haldar Kasturi 
Published: April 2009

ABSTRACT

The human malaria parasite
Plasmodium falciparum
digests hemoglobin and polymerizes the released free heme into hemozoin. This activity occurs in an acidic organelle called the food vacuole and is essential for survival of the parasite in erythrocytes. Since acidic conditions are known to enhance the auto-oxidation of hemoglobin, we investigated whether hemoglobin ingested by the parasite was oxidized and whether the oxidation process could be a target for chemotherapy against malaria. We released parasites from their host cells and separately analyzed hemoglobin ingested by the parasites from that remaining in the erythrocytes. Isolated parasites contained elevated amounts (38.5% ± 3.5%) of oxidized hemoglobin (methemoglobin) compared to levels (0.8% ± 0.2%) found in normal, uninfected erythrocytes. Further, treatment of infected cells with the reducing agent riboflavin for 24 h decreased the parasite methemoglobin level by 55%. It also inhibited hemozoin production by 50% and decreased the average size of the food vacuole by 47%. Administration of riboflavin for 48 h resulted in a 65% decrease in food vacuole size and inhibited asexual parasite growth in cultures. High doses of riboflavin are used clinically to treat congenital methemoglobinemia without any adverse side effects. This activity, in conjunction with its impressive antimalarial activity, makes riboflavin attractive as a safe and inexpensive drug for treating malaria caused by
P. falciparum
.
Persistence of Infectious Herpes Simplex Virus Type 2 in the Nervous System in Mice after Antiviral Chemotherapy
Authors: Thackray Alana M. , Field Hugh J. 
Published: April 2009

ABSTRACT
Young adult mice were inoculated with herpes simplex virus type 2 (HSV-2) in the ear pinna. A relatively severe infection resulted, and 45% of the mice died by 11 days postinfection. Therapy at 1 mg/ml by means of the drinking water with either famciclovir for periods of 5 or 10 days or valaciclovir for 5, 10, 15, or 20 days decreased clinical signs and reduced mortality to 15% or less. Throughout a period of 27 days, mice were tested daily for the presence of infectious virus in the ear pinna, brain stem, and ipsilateral trigeminal ganglia. Virus was cleared from these tissues in surviving, untreated animals by 12 days postinfection, and no infectious virus was detected subsequently in any tissue. Furthermore, no infectious virus was detected after day 9 in mice that had been treated with famciclovir. In mice that had received valaciclovir therapy, however, infectious virus was repeatedly detected in the trigeminal ganglia and brain stem tissue samples up to 7 days after treatment was discontinued. To date, no specific mechanism to account for these results has been discovered; however, possible mechanisms for the persistence of potentially infectious virus in neural tissue of treated mice are discussed.
Sequestration of Zinc Oxide by Fimbrial Designer Chelators
Authors: Kjærgaard Kristian , Sørensen Jack K. , Schembri Mark A. , Klemm Per 
Published: April 2009

ABSTRACT

Type 1 fimbriae are surface organelles of
Escherichia coli
. By engineering a structural component of the fimbriae, FimH, to display a random peptide library, we were able to isolate metal-chelating bacteria. A library consisting of 4 × 10
7
independent clones was screened for binding to ZnO. Sequences responsible for ZnO adherence were identified, and distinct binding motifs were characterized. The sequences selected exhibited various degrees of affinity and specificity towards ZnO. Competitive binding experiments revealed that the sequences recognized only the oxide form of Zn. Interestingly, one of the inserts exhibited significant homology to a specific sequence in a putative zinc-containing helicase, which suggests that searches such as this one may aid in identifying binding motifs in nature. The zinc-binding bacteria might have a use in detoxification of metal-polluted water.
The
ntrB
and
ntrC
Genes Are Involved in the Regulation of Poly-3-Hydroxybutyrate Biosynthesis by Ammonia in
Azospirillum brasilense
Sp7
Authors: Sun Jun , Peng Xuan , Van Impe Jan , Vanderleyden Jos 
Published: April 2009

ABSTRACT

Azospirillum brasilense
Sp7 and its
ntrA
(
rpoN
),
ntrBC
, and
ntrC
mutants have been evaluated for their capabilities of poly-3-hydroxybutyrate (PHB) accumulation in media with high and low ammonia concentrations. It was observed that the
ntrBC
and
ntrC
mutants can produce PHB in both low- and high-C/N-ratio media, while no significant PHB production was observed for the wild type or the
ntrA
mutant in low-C/N-ratio media. Further investigation by fermentation analysis indicated that the
ntrBC
and
ntrC
mutants were able to grow and accumulate PHB simultaneously in the presence of a high concentration of ammonia in the medium, while little PHB was produced in the wild type and
ntrA
(
rpoN
) mutant during active growth phase. These results provide the first genetic evidence that the
ntrB
and
ntrC
genes are involved in the regulation of PHB synthesis by ammonia in
A. brasilense
Sp7.
Plasmid Transfer between the
Bacillus thuringiensis
Subspecies
kurstaki
and
tenebrionis
in Laboratory Culture and Soil and in Lepidopteran and Coleopteran Larvae
Authors: Thomas D. John I. , Morgan J. Alun W. , Whipps John M. , Saunders Jon R. 
Published: April 2009

ABSTRACT

Plasmid transfer between
Bacillus thuringiensis
subsp.
kurstaki
HD1 and
B. thuringiensis
subsp.
tenebrionis
donor strains and a streptomycin-resistant
B. thuringiensis
subsp.
kurstaki
recipient was studied under environmentally relevant laboratory conditions in vitro, in soil, and in insects. Plasmid transfer was detected in vitro at temperatures of 5 to 37°C, at pH 5.9 to 9.0, and at water activities of 0.965 to 0.995, and the highest transfer ratios (up to 10
−1
transconjugant/donor) were detected within 4 h. In contrast, no plasmid transfer was detected in nonsterile soil, and rapid formation of spores by the introduced strains probably contributed most to the lack of plasmid transfer observed. When a
B. thuringiensis
subsp.
kurstaki
strain was used as the donor strain, plasmid transfer was detected in killed susceptible lepidopteran insect (
Lacanobia oleracea
) larvae but not in the nonsusceptible coleopteran insect
Phaedon chocleriae
. When a
B. thuringiensis
subsp.
tenerbrionis
strain was used as the donor strain, no plasmid transfer was detected in either of these insects even when they were killed. These results show that in larger susceptible lepidopteran insects there is a greater opportunity for growth of
B. thuringiensis
strains, and this finding, combined with decreased competition due to a low initial background bacterial population, can provide suitable conditions for efficient plasmid transfer in the environment.
Impact of an Urban Effluent on Antibiotic Resistance of Riverine
Enterobacteriaceae
and
Aeromonas
spp
Authors: Goñi-Urriza Marisol , Capdepuy Michèle , Arpin Corinne , Raymond Nathalie , Caumette Pierre , Quentin Claudine 
Published: April 2009

ABSTRACT

In order to evaluate the impact of an urban effluent on antibiotic resistance of freshwater bacterial populations, water samples were collected from the Arga river (Spain), upstream and downstream from the wastewater discharge of the city of Pamplona. Strains of
Enterobacteriaceae
(representative of the human and animal commensal flora) (110 isolates) and
Aeromonas
(typically waterborne bacteria) (118 isolates) were selected for antibiotic susceptibility testing. Most of the
Aeromonas
strains (72%) and many of the
Enterobacteriaceae
(20%) were resistant to nalidixic acid. Singly nalidixic acid-resistant strains were frequent regardless of the sampling site for
Aeromonas
, whereas they were more common upstream from the discharge for enterobacteria. The most common resistances to antibiotics other than quinolones were to tetracycline (24.3%) and beta-lactams (20.5%) for
Enterobacteriaceae
and to tetracycline (27.5%) and co-trimoxazole (26.6%) for
Aeromonas
. The rates of these antibiotic resistances increased downstream from the discharge at similar degrees for the two bacterial groups; it remained at high levels for enterobacteria but decreased along the 30-km study zone for
Aeromonas
. Genetic analysis of representative strains demonstrated that these resistances were mostly (enterobacteria) or exclusively (
Aeromonas
) chromosomally mediated. Moreover, a reference strain of
Aeromonas caviae
(CIP 7616) could not be transformed with conjugative R plasmids of enterobacteria. Thus, the urban effluent resulted in an increase of the rates of resistance to antibiotics other than quinolones in the riverine bacterial populations, despite limited genetic exchanges between enterobacteria and
Aeromonas
. Quinolone resistance probably was selected by heavy antibiotic discharges of unknown origin upstream from the urban effluent.
Genetic Diversity of
Vibrio cholerae
in Chesapeake Bay Determined by Amplified Fragment Length Polymorphism Fingerprinting
Authors: Jiang Sunny C. , Louis Valerie , Choopun Nipa , Sharma Anjana , Huq Anwar , Colwell Rita R. 
Published: April 2009

ABSTRACT

Vibrio cholerae
is indigenous to the aquatic environment, and serotype non-O1 strains are readily isolated from coastal waters. However, in comparison with intensive studies of the O1 group, relatively little effort has been made to analyze the population structure and molecular evolution of non-O1
V. cholerae
. In this study, high-resolution genomic DNA fingerprinting, amplified fragment length polymorphism (AFLP), was used to characterize the temporal and spatial genetic diversity of 67
V. cholerae
strains isolated from Chesapeake Bay during April through July 1998, at four different sampling sites. Isolation of
V. cholerae
during the winter months (January through March) was unsuccessful, as observed in earlier studies (J. H. L. Kaper, R. R. Colwell, and S. W. Joseph, Appl. Environ. Microbiol. 37:91–103, 1979). AFLP fingerprints subjected to similarity analysis yielded a grouping of isolates into three large clusters, reflecting time of the year when the strains were isolated. April and May isolates were closely related, while July isolates were genetically diverse and did not cluster with the isolates obtained earlier in the year. The results suggest that the population structure of
V. cholerae
undergoes a shift in genotype that is linked to changes in environmental conditions. From January to July, the water temperature increased from 3°C to 27.5°C, bacterial direct counts increased nearly an order of magnitude, and the chlorophyll
a
concentration tripled (or even quadrupled at some sites). No correlation was observed between genetic similarity among isolates and geographical source of isolation, since isolates found at a single sampling site were genetically diverse and genetically identical isolates were found at several of the sampling sites. Thus,
V. cholerae
populations may be transported by surface currents throughout the entire Bay, or, more likely, similar environmental conditions may be selected for a specific genotype. The dynamic nature of the population structure of this bacterial species in Chesapeake Bay provides new insight into the ecology and molecular evolution of
V. cholerae
in the natural environment.
Generation of Novel Bacterial Regulatory Proteins That Detect Priority Pollutant Phenols
Authors: Wise Arlene A. , Kuske Cheryl R. 
Published: April 2009

ABSTRACT

The genetic systems of bacteria that have the ability to use organic pollutants as carbon and energy sources can be adapted to create bacterial biosensors for the detection of industrial pollution. The creation of bacterial biosensors is hampered by a lack of information about the genetic systems that control production of bacterial enzymes that metabolize pollutants. We have attempted to overcome this problem through modification of DmpR, a regulatory protein for the phenol degradation pathway of
Pseudomonas
sp. strain CF600. The phenol detection capacity of DmpR was altered by using mutagenic PCR targeted to the DmpR sensor domain. DmpR mutants were identified that both increased sensitivity to the phenolic effectors of wild-type DmpR and increased the range of molecules detected. The phenol detection characteristics of seven DmpR mutants were demonstrated through their ability to activate transcription of a
lacZ
reporter gene. Effectors of the DmpR derivatives included phenol, 2-chlorophenol, 2,4-dichlorophenol, 4-chloro-3-methylphenol, 2,4-dimethylphenol, 2-nitrophenol, and 4-nitrophenol.
Microcystin Production byMicrocystis aeruginosain a Phosphorus-Limited Chemostat
Authors: Oh Hee-Mock , Lee Seog June , Jang Min-Ho , Yoon Byung-Dae 
Published: April 2009

ABSTRACTThe production of microcystins (MC) fromMicrocystis aeruginosaUTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilizedM. aeruginosawere extracted with 5% acetic acid, purified by a Sep-Pak C18cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C18reverse-phase column. The specific growth rate (μ) ofM. aeruginosawas within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing μ. The MC-LR and MC-RR contents on a dry weight basis were highest at μ of 0.1/day at 339 and 774 μg g−1, respectively, while MC-YR was not detected. The MC content ofM. aeruginosawas higher at a lower μ, whereas the MC-producing rate was linearly proportional to μ. The C fixation rate at an ambient irradiance (160 microeinsteins m−2s−1) increased with μ. The ratios of the MC-producing rate to the C fixation rate were higher at a lower μ. Accordingly, the growth ofM. aeruginosawas reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions.
Autumnal Biomass and Potential Productivity of Salt Marsh Fungi from 29° to 43° North Latitude along the United States Atlantic Coast
Authors: Newell Steven Y. , Blum Linda K. , Crawford Richard E. , Dai Ting , Dionne Michele 
Published: April 2009

ABSTRACT

It has been established that substantial amounts of fungal mass accumulate in standing decaying smooth cordgrass (
Spartina alterniflora
) marshes in the southeastern United States (e.g., in standing decaying leaf blades with a total fungal organic mass that accounts for about 20% of the decay system organic mass), but it has been hypothesized that in marshes farther north this is not true. We obtained samples of autumnal standing decaying smooth cordgrass from sites in Florida to Maine over a 3-year period. The variation in latitude could not explain any of the variation in the living fungal standing crop (as determined by ergosterol content) or in the instantaneous rates of fungal growth (as determined by acetate incorporation into ergosterol at a standard temperature, 20°C), which led to the conclusion that the potential levels of fungal production per unit of naturally decaying grass are not different in northern and southern marshes. Twenty-one percent of the variation in the size of the living fungal standing crop could be explained by variation in the C/N ratio (the higher the C/N ratio the smaller the fungal crop), but the C/P ratio was not related to the size of the fungal crop. Instantaneous rates of fungal growth were negatively related to the size of the living fungal crop (
r
= −0.35), but these rates were not correlated with C/nutrient ratios. The same two predominant species of ascomycetes (one
Phaeosphaeria
species and one
Mycosphaerella
species) were found ejecting ascospores from standing decaying smooth cordgrass blades at all of the sites examined from Florida to Maine.
Kinetic and Nuclear Magnetic Resonance Studies of Xylose Metabolism by Recombinant
Zymomonas mobilis
ZM4(pZB5)
Authors: Kim In Seop , Barrow Kevin D. , Rogers Peter L. 
Published: April 2009

ABSTRACT

The specific rates of growth, substrate utilization, and ethanol production as well as yields of biomass and ethanol production on xylose for the recombinant
Zymomonas mobilis
ZM4(pZB5) were shown to be much less than those on glucose or glucose-xylose mixtures. Typical fermentations with ZM4(pZB5) growing on glucose-xylose mixtures followed two-phase growth kinetics with the initial uptakes of glucose and xylose being followed by slower growth and metabolic uncoupling on xylose after glucose depletion. The reductions in rates and yields from xylose metabolism were considered in the present investigation and may be due to a number of factors, including the following: (i) the increased metabolic burden from maintenance of plasmid-related functions, (ii) the production of by-products identified as xylitol, acetate, lactate, acetoin, and dihydroxyacetone by
13
C-nuclear magnetic resonance (NMR) spectroscopy and high-performance liquid chromatography, (iii) growth inhibition due to xylitol by the putative inhibitory compound xylitol phosphate, and (iv) the less energized state of ZM4(pZB5). In vivo
31
P-NMR studies have established that the levels of NTP and UDP sugars on xylose were less than those on glucose, and this energy limitation is likely to restrict the growth of the recombinant strain on xylose media.