bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical-Genetic Characterization and Regulation of Expression of an ACC-1-Like Chromosome-Borne Cephalosporinase from
Hafnia alvei
Authors: Girlich Delphine , Naas Thierry , Bellais Samuel , Poirel Laurent , Karim Amal , Nordmann Patrice 
Published: July 2002

ABSTRACT

A naturally occurring AmpC β-lactamase (cephalosporinase) gene was cloned from the
Hafnia alvei
1 clinical isolate and expressed in
Escherichia coli
. The deduced AmpC β-lactamase (ACC-2) had a pI of 8 and a relative molecular mass of 37 kDa and showed 50 and 47% amino acid identity with the chromosome-encoded AmpCs from
Serratia marcescens
and
Providentia stuartii
, respectively. It had 94% amino acid identity with the recently described plasmid-borne cephalosporinase ACC-1 from
Klebsiella pneumoniae
, suggesting the chromosomal origin of ACC-1. The hydrolysis constants (
k
cat
and

K
m

) showed that ACC-2 was a peculiar cephalosporinase, since it significantly hydrolyzed cefpirome. Once its gene was cloned and expressed in
E. coli
(pDEL-1), ACC-2 conferred resistance to ceftazidime and cefotaxime but also an uncommon reduced susceptibility to cefpirome. A divergently transcribed
ampR
gene with an overlapping promoter compared with
ampC
(
bla
ACC-2
) was identified in
H. alvei
1, encoding an AmpR protein that shared 64% amino acid identity with the closest AmpR protein from
P. stuartii
. β-Lactamase induction experiments showed that the
ampC
gene was repressed in the absence of
ampR
and was activated when cefoxitin or imipenem was added as an inducer. From
H. alvei
1 cultures that expressed an inducible-cephalosporinase phenotype, several ceftazidime- and cefpirome-cross-resistant
H. alvei
1 mutants were obtained upon selection on cefpirome- or ceftazidime-containing plates, and
H. alvei
1 DER, a ceftazidime-resistant mutant, stably overproduced cephalosporinase. Transformation of
H. alvei
1 DER or
E. coli
JRG582 (
ampDE
mutant) harboring
ampC
and
ampR
from
H. alvei
1 with a recombinant plasmid containing
ampD
from
E. coli
resulted in a decrease in the MIC of β-lactam and recovery of an inducible phenotype for
H. alvei
1 DER. Thus, AmpR and AmpD proteins may regulate biosynthesis of the
H. alvei
cephalosporinase similarly to other enterobacterial cephalosporinases.
Transcriptional Analyses of Antifungal Drug Resistance in
Candida albicans
Authors: Lyons Chris N. , White Theodore C. 
Published: July 2002

ABSTRACT

Oral infections with the pathogenic yeast
Candida albicans
are one of the most frequent and earliest opportunistic infections in human immunodeficiency virus-infected patients. The widespread use of azole antifungal drugs has led to the development of drug-resistant isolates. Several molecular mechanisms that contribute to drug resistance have been identified, including increased mRNA levels for two types of efflux pump genes: the ATP binding cassette transporter CDRs (
CDR1
and
CDR2
) and the major facilitator
MDR1
. Using Northern blot analyses, the expression patterns of these genes have been determined during logarithmic and stationary phases of cell growth and during growth in different carbon sources in a set of matched susceptible and fluconazole-resistant isolates that have been characterized previously.
MDR1
,
CDR1
, and
CDR2
are expressed early during logarithmic growth,
CDR4
is expressed late during logarithmic growth, and
CDR1
is preferentially expressed in stationary-phase cells. There is a small decrease in expression of these genes when the cells are grown in carbon sources other than glucose. While increased mRNA levels of efflux pump genes are commonly associated with azole resistance, the causes of increased mRNA levels have not yet been resolved. Southern blot analysis demonstrates that the increased mRNA levels in these isolates are not the result of gene amplification. Nuclear run-on assays show that
MDR1
and
CDR
mRNAs are transcriptionally overexpressed in the resistant isolate, suggesting that the antifungal drug resistance in this series is associated with the promoter and
trans
-acting factors of the
CDR1
,
CDR2
, and
MDR1
genes.
Molecular Characterization of the Plasma Membrane H+-ATPase, an Antifungal Target inCryptococcus neoformans
Authors: Soteropoulos Patricia , Vaz Tanya , Santangelo Rosaria , Paderu Padmaja , Huang David Y. , Tamás Markus J. , Perlin David S. 
Published: July 2002

ABSTRACTTheCryptococcus neoformans PMA1gene, encoding a plasma membrane H+-ATPase, was isolated from a genomic DNA library of serotype A strain ATCC 6352. An open reading frame of 3,380 nucleotides contains six introns and encodes a predicted protein consisting of 998 amino acids with a molecular mass of approximately 108 kDa. Plasma membranes were isolated, and the H+-ATPase was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be slightly larger than theS. cerevisiaeH+-ATPase, consistent with its predicted molecular mass. The plasma membrane-bound enzyme exhibited a pH 6.5 optimum for ATP hydrolysis,KmandVmaxvalues of 0.5 mM and 3.1 μmol mg−1min−1, respectively, and an apparentKifor vanadate inhibition of 1.6 μM. ATP hydrolysis in plasma membranes and medium acidification by whole cells were inhibited by ebselen, a nonspecific H+-ATPase antagonist which was also fungicidal. The predictedC. neoformansprotein is 35% identical to proton pumps of both pathogenic and nonpathogenic fungi but exhibits more than 50% identity toPMA1genes from plants. Collectively, this study provides the basis for establishing theCryptococcusH+-ATPase as a viable target for antifungal drug discovery.
Astaxanthin-Rich Algal Meal and Vitamin C Inhibit
Helicobacter pylori
Infection in BALB/cA Mice
Authors: Wang Xin , Willén Roger , Wadström Torkel 
Published: July 2002

ABSTRACT

Helicobacter pylori
infection in humans is associated with chronic type B gastritis, peptic ulcer disease, and gastric carcinoma. A high intake of carotenoids and vitamin C has been proposed to prevent development of gastric malignancies. The aim of this study was to explore if the microalga
Haematococcus pluvialis
rich in the carotenoid astaxanthin and vitamin C can inhibit experimental
H. pylori
infection in a BALB/cA mouse model. Six-week-old BALB/cA mice were infected with the mouse-passaged
H. pylori
strain 119/95. At 2 weeks postinoculation mice were treated orally once daily for 10 days (i) with different doses of algal meal rich in astaxanthin (0.4, 2, and 4 g/kg of body weight, with the astaxanthin content at 10, 50, and 100 mg/kg, respectively), (ii) with a control meal (algal meal without astaxanthin, 4 g/kg), or (iii) with vitamin C (400 mg/kg). Five mice from each group were sacrificed 1 day after the cessation of treatment, and the other five animals were sacrificed 10 days after the cessation of treatment. Culture of
H. pylori
and determination of the inflammation score of the gastric mucosae were used to determine the outcome of the treatment. Mice treated with astaxanthin-rich algal meal or vitamin C showed significantly lower colonization levels and lower inflammation scores than those of untreated or control-meal-treated animals at 1 day and 10 days after the cessation of treatment. Lipid peroxidation was significantly decreased in mice treated with the astaxanthin-rich algal meal and vitamin C compared with that of animals not treated or treated with the control meal. Both astaxanthin-rich algal meal and vitamin C showed an inhibitory effect on
H. pylori
growth in vitro. In conclusion, antioxidants may be a new strategy for treating
H. pylori
infection in humans.
Therapeutic Efficacy of Poly(
dl
-Lactide-Co-Glycolide)-Encapsulated Antitubercular Drugs against
Mycobacterium tuberculosis
Infection Induced in Mice
Authors: Dutt Manisha , Khuller G. K. 
Published: July 2002

ABSTRACT

Poly(
dl
-lactide-co-glycolide) (PLG) microparticles were developed as carriers for isoniazid and rifampin in order to improve compliance of tuberculous chemotherapy. Antitubercular drugs encapsulated in PLG polymers and injected in a single dose subcutaneously resulted in a sustained release (up to 6 weeks) of drugs in various organs of mice. Further,
Mycobacterium tuberculosis
H
37
Rv-infected animals given a single shot of chemotherapy in PLG microparticles exhibited a better or equivalent clearance of CFU in various organs compared to those given a daily administration of free drugs.
Indication of Transposition of a Mobile DNA Element Containing the
vat
(D) and
erm
(B) Genes in
Enterococcus faecium
Authors: Hammerum Anette M. , Flannagan Susan E. , Clewell Don B. , Jensen Lars Bogø 
Published: July 2002

ABSTRACT

The
vat
(D) and
erm
(B) genes encoding streptogramin resistance in
Enterococcus faecium
transferred together, and a direct physical link between
erm
(B) and
vat
(D) was detected. Both the
vat
(D) and
erm
(B) probes hybridized to fragments of different sizes in the donor and transconjugants, which indicated a transposition event.
Action of Deferoxamine against
Pneumocystis carinii
Authors: Clarkson Allen B. , Turkel-Parrella David , Williams Jonathan H. , Chen Lung Chi , Gordon Terry , Merali Salim 
Published: July 2002

ABSTRACT

We found earlier that deferoxamine (DFO), a drug used for treatment of iron overload, is active against a rat model of
Pneumocystis carinii
pneumonia (PCP). We had assumed a mode of action by deprivation of nutritional iron; however, data here show that DFO penetrates
P
.
carinii
, causing irreversible damage, thus indicating a different mode of action. Penetration was demonstrated by showing DFO uptake by high-pressure liquid chromatography analysis. By using calcein-AM as an indicator, exposure to DFO was shown to cause a reduction in
P
.
carinii
cytoplasmic free iron. Exposure to ≥100 μM DFO for ≥8 h in vitro caused growth to cease and cell numbers to decline over several days. This direct and irreversible damage to
P
.
carinii
led to the prediction that infrequent delivery of DFO to the lungs via an aerosol would be an effective treatment in the animal model of PCP. This prediction was confirmed by demonstrating that a once-a-week aerosol treatment of rats was 100% effective both as a prophylactic and as a curative treatment in a rat model of PCP.
Reduction of NO Synthase Expression and Tumor Necrosis Factor Alpha Production in Macrophages by Amphotericin B Lipid Carriers
Authors: Larabi Malika , Legrand Philippe , Appel Martine , Gil Sophie , Lepoivre Michel , Devissaguet Jean-Philippe , Puisieux Francis , Barratt Gillian 
Published: July 2002

ABSTRACTThe present study compared the abilities of different lipid carriers of amphotericin B (AMB) to activate murine peritoneal macrophages, as assessed by their capacities to produce nitric oxide (NO) and tumor necrosis factor alpha (TNF-α). Although AMB alone did not induce NO production, synergy was observed with gamma interferon but not with lipopolysaccharide. This synergy could not be explained by the mobilization of the nuclear activation factor NF-κB by AMB. On the other hand, AMB induced TNF-α production without a costimulator and no synergy was observed. Anti-TNF-α antibodies did not influence NO production, and an inhibitor of NO synthase did not affect TNF-α production, indicating that the production of one of these effector molecules was independent of that of the other. The incorporation of AMB into lipid carriers reduced NO and TNF-α production with all formulations but more so with liposomes than with lipid complexes. NO production was correlated with the induction of NO synthase II, revealed by Western blotting. The extent of association of AMB with macrophages depended on the formulation, especially on the AMB/lipids ratio: the higher the ratio was, the greater the AMB association with macrophages. However, there was no clear correlation between AMB association with macrophages, whether internalized or bound to the membrane, and immunostimulating effects. These results may explain the reduced toxicities of lipid-based formulations of AMB.
Efficacy of Voriconazole in Treatment of Murine Pulmonary Blastomycosis
Authors: Sugar Alan M. , Liu Xiu-Ping 
Published: July 2002

ABSTRACT
We evaluated the efficacy of voriconazole, a new broad-spectrum triazole antifungal compound, in the treatment of murine pulmonary blastomycosis. Since mice metabolize voriconazole rapidly, we took advantage of our previous observation that administration of grapefruit juice to mice resulted in suitable serum voriconazole concentrations so that treatment studies with mice could be done (A. M. Sugar and X.-P. Liu, Med. Mycol. 38:209–121, 2000). Our results show that voriconazole prolonged survival in a dose-dependent fashion and that the fungal burden in the lungs was decreased by voriconazole administered at 40 mg/kg of body weight/day. Voriconazole should be studied in humans with blastomycosis.
IMP-4, a Novel Metallo-β-Lactamase from Nosocomial
Acinetobacter
spp. Collected in Hong Kong between 1994 and 1998
Authors: Chu Yiu-Wai , Afzal-Shah Mariya , Houang Elizabeth T. S. , Palepou Marie-France I. , Lyon Donald J. , Woodford Neil , Livermore David M. 
Published: July 2002

ABSTRACT

Between 1994 and 1998, 97 imipenem-resistant
Acinetobacter
isolates were identified at the Prince of Wales Hospital, Hong Kong, China. A
bla
IMP
PCR product was obtained from 23 of 35 viable cultures; 12 isolates belonged to genomic DNA group 3, 8 belonged to group 2 (
Acinetobacter baumannii
), 2 belonged to group 13TU, and 1 belonged to group 1. The
bla
IMP
homologues were sequenced from two isolates from genomic DNA group 2 and one isolate each from groups 3 and 13TU. The four sequences included an identical 738-bp open reading frame, predicted to encode a polypeptide of 246 amino acids, with 95.6% homology to IMP-1 and 89.3% homology to IMP-2. The new enzyme, designated IMP-4, was partially purified. It had a pI of 8.0 and was strongly active against imipenem and meropenem, with
V
max
values 53 and 8% of that for penicillin G, respectively. Strong activity was also seen against oxyimino-aminothiazolyl cephalosporins but not against aztreonam. Hydrolytic activity was inhibited by EDTA but not by clavulanate or tazobactam. Carbapenem MICs for most
bla
IMP
-positive isolates were 4 to 32 μg/ml, but one isolate with the intact gene was susceptible, with imipenem and meropenem MICs of 0.25 and 0.5 μg/ml, respectively. The latter isolate did not produce the band with a pI of 8.0, and gene expression was inferred to have been lost. None of the isolates studied in detail contained extrachromosomal DNA, and carbapenem resistance was not transmissible to
Escherichia coli
. Nevertheless, the presence of
bla
IMP-4
in different genomic DNA groups implies horizontal transfer, and sequences resembling a GTTRRRY integrase-dependent recombination motif were identified in the flanking regions of
bla
IMP-4
.
Prevalence and Conditions of Selection of E44D/A and V118I Human Immunodeficiency Virus Type 1 Reverse Transcriptase Mutations in Clinical Practice
Authors: Delaugerre Constance , Mouroux Mireille , Yvon-Groussin Anne , Simon Anne , Angleraud Francis , Huraux Jean-Marie , Agut Henri , Katlama Christine , Calvez Vincent 
Published: July 2002

ABSTRACT
Recently, it has been shown that a new mutational pattern (the E44D/A and/or V118I mutation) confers moderate phenotypic lamivudine resistance in the absence of the M184V mutation. The E44D/A and/or the V118I mutation does not exist in drug-naive patients, and the prevalence increases with the number of treatment regimens and lamivudine experience. The mutations can preexist in nucleoside-experienced but lamivudine-naive patients. They are always associated with zidovudine resistance-associated mutations, even in the absence of M184V. These mutations are more stable than the M184V substitution during antiretroviral treatment interruptions.
Potentiation of Inhibition of Wild-Type and Mutant Human Immunodeficiency Virus Type 1 Reverse Transcriptases by Combinations of Nonnucleoside Inhibitors andd- andl-(β)-Dideoxynucleoside Triphosphate Analogs
Authors: Maga Giovanni , Hübscher Ulrich , Pregnolato Massimo , Ubiali Daniela , Gosselin Gilles , Spadari Silvio 
Published: July 2002

ABSTRACTCombinations of reverse transcriptase (RT) inhibitors are currently used in anti-human immunodeficiency virus therapy in order to prevent or delay the emergence of resistant virus and to improve the efficacy against viral enzymes carrying resistance mutations. Drug-drug interactions can result in either positive (additive or synergistic inhibition) or adverse (antagonistic interaction, synergistic toxicity) effects. Elucidation of the nature of drug interaction would help to rationalize the choice of antiretroviral agents to be used in combination. In this study, different combinations of nucleoside and nonnucleoside inhibitors, includingd- andl-(β)-deoxy- and -dideoxynucleoside triphosphate analogues, have been tested in in vitro RT assays against either recombinant wild-type RT or RT bearing clinically relevant nonnucleoside inhibitor resistance mutations (L100I, K103N, Y181I), and the nature of the interaction (either synergistic or antagonistic) of these associations was evaluated. The results showed that (i) synergy of a combination was not always equally influenced by the individual agents utilized, (ii) a synergistic combination could improve the sensitivity profile of a drug-resistant mutant enzyme to the single agents utilized, (iii)l-(β)-enantiomers of nucleoside RT inhibitors were synergistic when combined with nonnucleoside RT inhibitors, and (iv) inter- and intracombination comparisons of the relative potencies of each drug could be used to highlight the different contributions of each drug to the observed synergy.
Inhibition of Group A Streptococcus Infection by Carboxyfullerene
Authors: Tsao Nina , Luh Tien-Yau , Chou Chen-Kung , Wu Jiunn-Jong , Lin Yee-Shin , Lei Huan-Yao 
Published: July 2002

ABSTRACTThe effect of a water-soluble trimalonic acid derivative of fullerene, carboxyfullerene, againstStreptococcus pyogenesinfection was tested. Pretreatment with carboxyfullerene was able to protect mice fromS. pyogenesinfection in an air pouch model.S. pyogenes-induced death and skin injury were inhibited dose dependently by carboxyfullerene. Administration of carboxyfullerene via the peritoneum and air pouch at 3 h post-S. pyogenesinfection was able to protect 33% of mice from death. Surveys of exudates of the air pouch of carboxyfullerene-treated mice revealed that survival of infiltrating neutrophils was prolonged and that the bacteria were eliminated as a result of enhanced bactericidal activity of the neutrophils. Furthermore, carboxyfullerene was able to directly inhibit in vitro growth ofS. pyogenes. These data suggest that carboxyfullerene can be considered an antimicrobial agent for group A streptococcus infection.
In Vitro Activities of Ertapenem (MK-0826) against Recent Clinical Bacteria Collected in Europe and Australia
Authors: Livermore David M. , Carter Michael W. , Bagel Simone , Wiedemann Bernd , Baquero Fernando , Loza Elena , Endtz Hubert P. , van den Braak Nicole , Fernandes Clarence J. , Fernandes Lorna , Frimodt-Moller Niels , Rasmussen Laura S. , Giamarellou Helen , Giamarellos-Bourboulis Evangelos , Jarlier Vincent , Nguyen Jacqueline , Nord Carl-Erik , Struelens Marc J. , Nonhoff Caire , Turnidge John , Bell Jan , Zbinden Reinhard , Pfister Stefan , Mixson Lori , Shungu Daniel L. 
Published: July 2002

ABSTRACT

Ertapenem (MK-0826, L-749,345) is a 1-β-methyl carbapenem with a long serum half-life. Its in vitro activity was determined by broth microdilution against 3,478 bacteria from 12 centers in Europe and Australia, with imipenem, cefepime, ceftriaxone, and piperacillin-tazobactam used as comparators. Ertapenem was the most active agent tested against members of the family
Enterobacteriaceae
, with MICs at which 90% of isolates are inhibited (MIC
90
s) of ≤1 μg/ml for all species. Ertapenem also was more active than imipenem against fastidious gram-negative bacteria and
Moraxella
spp.; on the other hand, ertapenem was slightly less active than imipenem against streptococci, methicillin-susceptible staphylococci, and anaerobes, but its MIC
90
s for these groups remained ≤0.5 μg/ml.
Acinetobacter
spp. and
Pseudomonas aeruginosa
were also much less susceptible to ertapenem than imipenem, and most
Enterococcus faecalis
strains were resistant. Ertapenem resistance, based on a provisional NCCLS MIC breakpoint of ≥16 μg/ml, was seen in only 3 of 1,611 strains of the family
Enterobacteriaceae
tested, all of them
Enterobacter aerogenes
. Resistance was also seen in 2 of 135 anaerobes, comprising 1
Bacteroides fragilis
strain and 1
Clostridium difficile
strain. Ertapenem breakpoints for streptococci have not been established, but an unofficial susceptibility breakpoint of ≤2 μg/ml was adopted for clinical trials to generate corresponding clinical response data for isolates for which MICs were as high as 2 μg/ml. Of 234
Streptococcus pneumoniae
strains tested, 2 required ertapenem MICs of 2 μg/ml and one required an MIC of 4 μg/ml, among 67 non-
Streptococcus pyogenes
, non-
Streptococcus pneumoniae
streptococci, single isolates required ertapenem MICs of 2 and 16 μg/ml. These streptococci also had diminished susceptibilities to other β-lactams, including imipenem as well as ertapenem. The Etest and disk diffusion gave susceptibility test results in good agreement with those of the broth microdilution method for ertapenem.
gyrA
Mutations Associated with Quinolone Resistance in
Bacteroides fragilis
Group Strains
Authors: Oh Herin , El Amin Nagwa , Davies Todd , Appelbaum Peter C. , Edlund Charlotta 
Published: July 2002

ABSTRACT

Mutations in the
gyrA
gene contribute considerably to quinolone resistance in
Escherichia coli
. Mechanisms for quinolone resistance in anaerobic bacteria are less well studied. The
Bacteroides fragilis
group are the anaerobic organisms most frequently isolated from patients with bacteremia and intraabdominal infections. Forty-four clinafloxacin-resistant and-susceptible fecal and clinical isolates of the
B. fragilis
group (eight
Bacteroides fragilis
, three
Bacteroides ovatus
, five
Bacteroides thetaiotaomicron
, six
Bacteroides uniformis
, and 22
Bacteroides vulgatus
) and six ATCC strains of the
B. fragilis
group were analyzed as follows: (i) determination of susceptibility to ciprofloxacin, levofloxacin, moxifloxacin, and clinafloxacin by the agar dilution method and (ii) sequencing of the
gyrA
quinolone resistance-determining region (QRDR) located between amino acid residues equivalent to Ala-67 through Gln-106 in
E. coli
. Amino acid substitutions were found at hotspots at positions 82 (
n
= 15) and 86 (
n
= 8). Strains with Ser82Leu substitutions (
n
= 13) were highly resistant to all quinolones tested. Mutations in other positions of
gyrA
were also frequently found in quinolone-resistant and -susceptible isolates. Eight clinical strains that lacked mutations in their QRDR were susceptible to at least two of the quinolones tested. Although newer quinolones have good antimicrobial activity against the
B. fragilis
group, quinolone resistance in
B. fragilis
strains can be readily selected in vivo. Mutational events in the QRDR of
gyrA
seem to contribute to quinolone resistance in
Bacteroides
species.
Novel Mutations in
ndh
in Isoniazid-Resistant
Mycobacterium tuberculosis
Isolates
Authors: Lee Ann S. G. , Teo Audrey S. M. , Wong Sin-Yew 
Published: July 2002

ABSTRACT

Novel mutations in NADH dehydrogenase (
ndh
) were detected in 8 of 84 (9.5%) isoniazid (INH)-resistant isolates (T110A [
n
= 1], R268H [
n
= 7]), but not in 22 INH-susceptible isolates of
Mycobacterium tuberculosis
. Significantly, all eight isolates with mutations at
ndh
did not have mutations at
katG, kasA
, or the promoter regions of
inhA
or
ahpC
, except for one isolate. Mutations in
ndh
appear to be an additional molecular mechanism for isoniazid resistance in
M. tuberculosis
.