bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasmid-Encoded Metallo-β-Lactamase (IMP-6) Conferring Resistance to Carbapenems, Especially Meropenem
Authors: Yano Hisakazu , Kuga Akio , Okamoto Ryoichi , Kitasato Hidero , Kobayashi Toshimitsu , Inoue Matsuhisa 
Published: July 2002

ABSTRACT

In 1996,
Serratia marcescens
KU3838 was isolated from the urine of a patient with a urinary tract infection at a hospital in northern Japan and was found to contain the plasmid pKU501. Previously, we determined that pKU501 carries
bla
IMP
and the genes for TEM-1-type β-lactamases as well as producing both types of β-lactamases (H. Yano, A. Kuga, K. Irinoda, R. Okamoto, T. Kobayashi, and M. Inoue, J. Antibiot. 52:1135–1139, 1999). pKU502 is a recombinant plasmid that contains a 1.5-kb DNA fragment, including the metallo-β-lactamase gene, and is obtained by PCR amplification of pKU501. The sequence of the metallo-β-lactamase gene in pKU502 was determined and revealed that this metallo-β-lactamase gene differed from the gene encoding IMP-1 by one point mutation, leading to one amino acid substitution: 640-A in the base sequence of the IMP-1 gene was replaced by G, and Ser-196 was replaced by Gly in the mature enzyme. This enzyme was designated IMP-6. The strains that produced IMP-6 were resistant to carbapenems. The MICs of panipenem and especially meropenem were higher than the MIC of imipenem for these strains. The
k
cat
/

K
m

value of IMP-6 was about sevenfold higher against meropenem than against imipenem, although the MIC of meropenem for KU1917, which produced IMP-1, was lower than that of imipenem, and the MIC of panipenem was equal to that of imipenem. These results support the hypothesis that IMP-6 has extended substrate profiles against carbapenems. However, the activity of IMP-6 was very low against penicillin G and piperacillin. These results suggest that IMP-6 acquired high activity against carbapenems, especially meropenem, via the point mutation but in the process lost activity against penicillins. Although IMP-6 has reduced activity against penicillins due to this point mutation, pKU501 confers resistance to a variety of antimicrobial agents because it also produces TEM-1-type enzyme.
Inhibition of Intramacrophage Growth ofPenicillium marneffeiby 4-Aminoquinolines
Authors: Taramelli Donatella , Tognazioli Clara , Ravagnani F. , Leopardi O. , Giannulis G. , Boelaert J. R. 
Published: July 2002

ABSTRACTThe antimicrobial activities of chloroquine (CQ) and several 4-aminoquinoline drugs were tested againstPenicillium marneffei, an opportunistic fungus that invades and grows inside macrophages and causes disseminated infection in AIDS patients. Human THP1 and mouse J774 macrophages were infected in vitro withP. marneffeiconidia and treated with different doses of drugs for 24 to 48 h followed by cell lysis and the counting ofP. marneffeiCFU. CQ and amodiaquine exerted a dose-dependent inhibition of fungal growth, whereas quinine and artemisinin were fungistatic and not fungicidal. The antifungal activity of CQ was not due to an impairment of fungal iron acquisition in that it was not reversed by the addition of iron nitrilotriacetate, FeCl3, or iron ammonium citrate. Perl's staining indicated that CQ did not alter the ability of J774 cells to acquire iron from the medium. Most likely, CQ's antifungal activity is due to an increase in the intravacuolar pH and a disruption of pH-dependent metabolic processes. Indeed, we demonstrate that (i) bafilomycin A1 and ammonium chloride, two agents known to alkalinize intracellular vesicles by different mechanisms, were inhibitory as well and (ii) a newly synthesized 4-amino-7-chloroquinoline molecule (compound 9), lacking the terminal amino side chain of CQ that assists in drug accumulation, did not inhibitP. marneffeigrowth. These results suggest that CQ has a potential for use in prophylaxis ofP. marneffeiinfections in human immunodeficiency virus-infected patients in countries whereP. marneffeiis endemic.
Improved Efficacy of Ciprofloxacin Administered in Polyethylene Glycol-Coated Liposomes for Treatment ofKlebsiella pneumoniaePneumonia in Rats
Authors: Bakker-Woudenberg Irma A. J. M. , ten Kate Marian T. , Guo Luke , Working Peter , Mouton Johan W. 
Published: July 2002

ABSTRACTAnimal and clinical data show that high ratios of the area under the concentration-time curve and the peak concentration in blood to the MIC of fluoroquinolones for a given pathogen are associated with a favorable outcome. The present study investigated whether improvement of the therapeutic potential of ciprofloxacin could be achieved by encapsulation in polyethylene glycol (PEG)-coated long-circulating sustained-release liposomes. In a rat model of unilateralKlebsiella pneumoniaepneumonia (MIC = 0.1 μg/ml), antibiotic was administered at 12- or 24-h intervals at twofold-increasing doses. A treatment period of 3 days was started 24 h after inoculation of the left lung, when the bacterial count had increased 1,000-fold and some rats had positive blood cultures. The infection was fatal within 5 days in untreated rats. Administration of ciprofloxacin in the liposomal form resulted in delayed ciprofloxacin clearance and increased and prolonged ciprofloxacin concentrations in blood and tissues. The ED50(dosage that results in 50% survival) of liposomal ciprofloxacin was 3.3 mg/kg of body weight/day given once daily, and that of free ciprofloxacin was 18.9 mg/kg/day once daily or 5.1 mg/kg/day twice daily. The ED90of liposomal ciprofloxacin was 15.0 mg/kg/day once daily compared with 36.0 mg/kg/day twice daily for free ciprofloxacin; 90% survival could not be achieved with free ciprofloxacin given once daily. In summary, the therapeutic efficacy of liposomal ciprofloxacin was superior to that of ciprofloxacin in the free form. PEG-coated liposomal ciprofloxacin was well tolerated in relatively high doses, permitting once daily administration with relatively low ciprofloxacin clearance and without compromising therapeutic efficacy.
Clearance of Fungal Burden during Treatment of Disseminated Histoplasmosis with Liposomal Amphotericin B versus Itraconazole
Authors: Wheat L. Joseph , Cloud Gretchen , Johnson Philip C. , Connolly Patricia , Goldman Mitchell , Le Monte Ann , Fuller Deanna E. , Davis Thomas E. , Hafner Richard ,   The AIDS Clinical Trials Group The Mycoses Study Group Of NIAID
Published: July 2002

ABSTRACTAnimal studies have shown that fungal burden correlates with survival during treatment with new antifungal therapies for histoplasmosis. The purpose of this report is to compare the clearance of fungal burden in patients with histoplasmosis treated with liposomal amphotericin B versus itraconazole. In two separate closed clinical trials that evaluated the efficacy of liposomal amphotericin B and itraconazole treatment of disseminated histoplasmosis in patients with AIDS, blood was cultured for fungus and blood and urine were tested forHistoplasmaantigen. The clinical response rates were similar; 86% with liposomal amphotericin B (n= 51) versus 85% with itraconazole (n= 59). Of the patients with positive blood cultures at enrollment, after 2 weeks of therapy cultures were negative in over 85% of the liposomal amphotericin B group versus 53% of the itraconazole group (P= 0.0008). Furthermore, after 2 weeks, median antigen levels in serum fell by 1.6 U in the liposomal amphotericin B group versus 0.1 U in the itraconazole group (P= 0.02), and those in urine fell by 2.1 U in the liposomal amphotericin B group and 0.2 U in the itraconazole group (P= 0.0005). The more rapid clearance of fungemia supports the use of liposomal amphotericin B rather than itraconazole for initial treatment of moderately severe or severe histoplasmosis.
In Vitro Synergy of Caspofungin and Amphotericin B against
Aspergillus
and
Fusarium
spp
Authors: Arikan Sevtap , Lozano-Chiu Mario , Paetznick Victor , Rex John H. 
Published: July 2002

ABSTRACT

We investigated the in vitro interaction of caspofungin and amphotericin B for clinical isolates of
Aspergillus
and
Fusarium
. Synergy tests were performed using the checkerboard method and following the NCCLS M38-P guidelines in Antibiotic Medium 3 broth supplemented to 2% glucose. Antagonism was not observed for any of the isolates tested. Caspofungin and amphotericin B were synergistic or synergistic to additive for at least half of the isolates.
Inhibitory Effect of Adefovir on Viral DNA Synthesis and Covalently Closed Circular DNA Formation in Duck Hepatitis B Virus-Infected Hepatocytes In Vivo and In Vitro
Authors: Delmas Julien , Schorr Olivier , Jamard Catherine , Gibbs Craig , Trépo Christian , Hantz Olivier , Zoulim Fabien 
Published: July 2002

ABSTRACTThe elimination of viral covalently closed circular DNA (CCC DNA) from the nucleus of infected hepatocytes is an obstacle to achieving sustained viral clearance during antiviral therapy of chronic hepatitis B virus (HBV) infection. The aim of our study was to determine whether treatment with adefovir, a new acyclic nucleoside phosphonate, the prodrug of which, adefovir dipivoxil, is in clinical evaluation, is able to suppress viral CCC DNA both in vitro and in vivo using the duck HBV (DHBV) model. First, the effect of adefovir on viral CCC DNA synthesis was examined with primary cultures of DHBV-infected fetal hepatocytes. Adefovir was administered for six consecutive days starting one day before or four days after DHBV inoculation. Dose-dependent inhibition of both virion release in culture supernatants and synthesis of intracellular viral DNA was observed. Although CCC DNA amplification was inhibited by adefovir, CCC DNA was not eliminated by antiviral treatment and the de novo formation of CCC DNA was not prevented by pretreatment of the cells. Next, preventive treatment of experimentally infected ducklings with lamivudine or adefovir revealed that both efficiently suppressed viremia and intrahepatic DNA. However, persistence of viral DNA even when detectable only by PCR was associated with a recurrence of viral replication following drug withdrawal. Taken together, our results demonstrate that adefovir is a potent inhibitor of DHBV replication that inhibits CCC DNA amplification but does not effectively prevent the formation of CCC DNA from incoming viral genomes.
Plasma Protein Binding of Amphotericin B and Pharmacokinetics of Bound versus Unbound Amphotericin B after Administration of Intravenous Liposomal Amphotericin B (AmBisome) and Amphotericin B Deoxycholate
Authors: Bekersky Ihor , Fielding Robert M. , Dressler Dawna E. , Lee Jean W. , Buell Donald N. , Walsh Thomas J. 
Published: July 2002

ABSTRACT

Unilamellar liposomal amphotericin B (AmBisome) (liposomal AMB) reduces the toxicity of this antifungal drug. The unique composition of liposomal AMB stabilizes the liposomes, producing higher sustained drug levels in plasma and reducing renal and hepatic excretion. When liposomes release their drug payload, unbound, protein-bound, and liposomal drug pools may exist simultaneously in the body. To determine the amounts of drug in these pools, we developed a procedure to measure unbound AMB in human plasma by ultrafiltration and then used it to characterize AMB binding in vitro and to assess the pharmacokinetics of nonliposomal pools of AMB in a phase IV study of liposomal AMB and AMB deoxycholate in healthy subjects. We confirmed that AMB is highly bound (>95%) in human plasma and showed that both human serum albumin and α
1
-acid glycoprotein contribute to this binding. AMB binding exhibited an unusual concentration dependence in plasma: the percentage of bound drug increased as the AMB concentration increased. This was attributed to the low solubility of AMB in plasma, which limits the unbound drug concentration to <1 μg/ml. Subjects given 2 mg of liposomal AMB/kg of body weight had lower exposures (as measured by the maximum concentration of drug in serum and the area under the concentration-time curve) to both unbound and nonliposomal drug than those receiving 0.6 mg of AMB deoxycholate/kg. Most of the AMB in plasma remained liposome associated (97% at 4 h, 55% at 168 h) after liposomal AMB administration, so that unbound drug concentrations remained at <25 ng/ml in all liposomal AMB-treated subjects. Although liposomal AMB markedly reduces the total urinary and fecal recoveries of AMB, urinary and fecal clearances based on unbound AMB were similar (94 to 121 ml h
−1
kg
−1
) for both formulations. Unbound drug urinary clearances were equal to the glomerular filtration rate, and tubular transit rates were <16% of the urinary excretion rate, suggesting that net filtration of unbound drug, with little secretion or reabsorption, is the mechanism of renal clearance for both conventional and liposomal AMB in humans. Unbound drug fecal clearances were also similar for the two formulations. Thus, liposomal AMB increases total AMB concentrations while decreasing unbound AMB concentrations in plasma as a result of sequestration of the drug in long-circulating liposomes.
Antitrypanosomal Activities of Tryptanthrins
Authors: Scovill John , Blank Elizabeth , Konnick Michael , Nenortas Elizabeth , Shapiro Theresa 
Published: July 2002

ABSTRACT

New drugs and molecular targets are needed against
Trypanosoma brucei
, the protozoan that causes African sleeping sickness. Tryptanthrin (indolo[2,1-b]quinazoline-6,12-dione), a traditional antifungal agent, and 11 analogs were tested against
T. brucei
in vitro. The greatest activity was conferred by electron-withdrawing groups in the 8 position of the tryptanthrin ring system; the most potent compound had a 50% effective concentration of 0.40 μM.
Lack of Catheter Infection by the
efg1
/
efg1
cph1
/
cph1
Double-Null Mutant, a
Candida albicans
Strain That Is Defective in Filamentous Growth
Authors: Lewis Russell E. , Lo Hsiu-Jung , Raad Issam I. , Kontoyiannis Dimitrios P. 
Published: July 2002

ABSTRACT

The molecular controls regulating the successful colonization of
Candida albicans
on foreign materials are not known. Here we show that a mutant
C. albicans
strain defective in filamentous growth and lacking the transcription factors Efg1p and Cph1p has a profoundly deficient potential for colonizing on polyurethane catheters.
Vesicle-Mediated Transfer of Virulence Genes from
Escherichia coli
O157:H7 to Other Enteric Bacteria
Authors: Yaron Sima , Kolling Glynis L. , Simon Lee , Matthews Karl R. 
Published: July 2002

ABSTRACT

Membrane vesicles are released from the surfaces of many gram-negative bacteria during growth. Vesicles consist of proteins, lipopolysaccharide, phospholipids, RNA, and DNA. Results of the present study demonstrate that membrane vesicles isolated from the food-borne pathogen
Escherichia coli
O157:H7 facilitate the transfer of genes, which are then expressed by recipient
Salmonella enterica
serovar Enteritidis or
E. coli
JM109. Electron micrographs of purified DNA from
E. coli
O157:H7 vesicles showed large rosette-like structures, linear DNA fragments, and small open-circle plasmids. PCR analysis of vesicle DNA demonstrated the presence of specific genes from host and recombinant plasmids (
hly
, L7095,
mobA
, and
gfp
), chromosomal DNA (
uidA
and
eaeA
), and phage DNA (
stx1
and
stx2
). The results of PCR and the Vero cell assay demonstrate that genetic material, including virulence genes, is transferred to recipient bacteria and subsequently expressed. The cytotoxicity of the transformed enteric bacteria was sixfold higher than that of the parent isolate (
E. coli
JM109). Utilization of the nonhost plasmid (pGFP) permitted the evaluation of transformation efficiency (ca. 10
3
transformants μg of DNA
−1
) and demonstrated that vesicles can deliver antibiotic resistance. Transformed
E. coli
JM109 cells were resistant to ampicillin and fluoresced a brilliant green. The role vesicles play in genetic exchange between different species in the environment or host has yet to be defined.
Anaerobic Oxidation of
n
-Dodecane by an Addition Reaction in a Sulfate-Reducing Bacterial Enrichment Culture
Authors: Kropp Kevin G. , Davidova Irene A. , Suflita Joseph M. 
Published: July 2002

ABSTRACT

We identified trace metabolites produced during the anaerobic biodegradation of H
26
- and D
26
-
n
-dodecane by an enrichment culture that mineralizes these compounds in a sulfate-dependent fashion. The metabolites are dodecylsuccinic acids that, in the case of the perdeuterated substrate, retain all of the deuterium atoms. The deuterium retention and the gas chromatography-mass spectrometry fragmentation patterns of the derivatized metabolites suggest that they are formed by C—H or C—D addition across the double bond of fumarate. As trimethylsilyl esters, two nearly coeluting metabolites of equal abundance with nearly identical mass spectra were detected from each of H
26
- and D
26
-dodecane, but as methyl esters, only a single metabolite peak was detected for each parent substrate. An authentic standard of protonated
n
-dodecylsuccinic acid that was synthesized and derivatized by the two methods had the same fragmentation patterns as the metabolites of H
26
-dodecane. However, the standard gave only a single peak for each ester type and gas chromatographic retention times different from those of the derivatized metabolites. This suggests that the succinyl moiety in the dodecylsuccinic acid metabolites is attached not at the terminal methyl group of the alkane but at a subterminal position. The detection of two equally abundant trimethylsilyl-esterified metabolites in culture extracts suggests that the analysis is resolving diastereomers which have the succinyl moiety located at the same subterminal carbon in two different absolute configurations. Alternatively, there may be more than one methylene group in the alkane that undergoes the proposed fumarate addition reaction, giving at least two structural isomers in equal amounts.
Effects of pH and Trace Minerals on Long-Term Starvation ofLeuconostoc mesenteroides
Authors: Kim Dong-Shik , Thomas Steven , Fogler H. Scott 
Published: July 2002

ABSTRACTLaboratory experiments have definitively shown that exopolymer-producing bacteria have the potential to modify the flow of fluids in oil reservoirs to enhance oil production. Once injected into the reservoir, they will be subjected to a wide range of pH values and to starvation resulting from nutrient depletion. For successful field implementation it is necessary to have a fundamental understanding of these effects on the viability of bacteria. This paper addresses the effects of pH and trace minerals on cell viability ofLeuconostoc mesenteroidesduring carbon source depletion. Two different carbon sources were used to grow cells before transferring the cells to starvation conditions: sucrose and a combination of glucose and fructose. These substrates were chosen becauseL. mesenteroidesproduces a significant amount of water-insoluble exopolymers (dextran) under sucrose-fed conditions, which may enhance cell survival under harsh conditions. The effects of dextran on the cell viability were tested at different pH values with and without trace minerals. The rate of cell death followed an exponential-decay law for different values of the solution pH. The optimal solution pH for survival was pH 5, whereas cells died rapidly at pH 3 and below and at pH 13 and above. The sucrose-fed cells showed a greater viability than cells fed glucose and fructose for all pH ranges tested. The results indicated that water-insoluble exopolymers help cells survive for longer periods of time under starvation conditions. The effects of trace minerals on cell culturability were tested at two pH values, 4.5 and 7. For both cases, cells showed a greater culturability (smaller decay rate constant) in the presence of trace minerals than without trace minerals. It was also found that the effects of trace minerals on cell culturability were greater for glucose-fructose-fed cells than for sucrose-fed cells. The Michaelis pH function theory was used for comparing the relationships between the cell decay rate and pH.
Molecular Diversity within
Lactobacillus helveticus
as Revealed by Genotypic Characterization
Authors: Giraffa Giorgio , Gatti Monica , Rossetti Lia , Senini Lucia , Neviani Erasmo 
Published: July 2002

ABSTRACT

Lactobacillus helveticus
is a homofermentative thermophilic lactic acid bacterium that is used in the manufacture of Swiss type and long-ripened Italian cheeses, such as Emmental, Grana, and Provolone cheeses. Substantial differences in several technologically important characteristics are found among
L. helveticus
strains isolated from natural dairy starter cultures. In the present study we investigated the genotypic diversity of 74 strains isolated from different dairy cultures used for manufacturing Grana and Provolone cheeses and six collection strains. A restriction fragment length polymorphism analysis of both total genomic DNA and the 16S rRNA gene (ribotyping) was used as genotypic fingerprinting. A multivariate statistical analysis of the data enabled us to identify significant genotypic heterogeneity in
L. helveticus
. We found that genotypic fingerprinting could be used to distinguish strains; in particular, it was possible to associate the presence of specific strain genotypes with dairy ecosystem sources (e.g., Grana or Provolone cheese). Our data contribute to the description of microbial heterogeneity in
L. helveticus
and provide a more solid basis for understanding the functional and ecological significance of the presence of different
L. helveticus
biotypes in natural dairy starter cultures.
Survival and Filamentation of
Salmonella enterica
Serovar Enteritidis PT4 and
Salmonella enterica
Serovar Typhimurium DT104 at Low Water Activity
Authors: Mattick K. L. , Jørgensen F. , Legan J. D. , Cole M. B. , Porter J. , Lappin-Scott H. M. , Humphrey T. J. 
Published: July 2002

ABSTRACT

In this study we investigated the long-term survival of and morphological changes in
Salmonella
strains at low water activity (a
w
).
Salmonella enterica
serovar Enteritidis PT4 and
Salmonella enterica
serovar Typhimurium DT104 survived at low a
w
for long periods, but minimum humectant concentrations of 8% NaCl (a
w
, 0.95), 96% sucrose (a
w
, 0.94), and 32% glycerol (a
w
, 0.92) were bactericidal under most conditions.
Salmonella rpoS
mutants were usually more sensitive to bactericidal levels of NaCl, sucrose, and glycerol. At a lethal a
w
, incubation at 37°C resulted in more rapid loss of viability than incubation at 21°C. At a
w
values of 0.93 to 0.98, strains of
S. enterica
serovar Enteritidis and
S. enterica
serovar Typhimurium formed filaments, some of which were at least 200 μm long. Filamentation was independent of
rpoS
expression. When the preparations were returned to high-a
w
conditions, the filaments formed septa, and division was complete within approximately 2 to 3 h. The variable survival of
Salmonella
strains at low a
w
highlights the importance of strain choice when researchers produce modelling data to simulate worst-case scenarios or conduct risk assessments based on laboratory data. The continued increase in
Salmonella
biomass at low a
w
(without a concomitant increase in microbial count) would not have been detected by traditional microbiological enumeration tests if the tests had been performed immediately after low-a
w
storage. If
Salmonella
strains form filaments in food products that have low a
w
values (0.92 to 0.98), there are significant implications for public health and for designing methods for microbiological monitoring.