bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acquired Bacitracin Resistance in
Enterococcus faecalis
Is Mediated by an ABC Transporter and a Novel Regulatory Protein, BcrR
Authors: Manson Janet M. , Keis Stefanie , Smith John M. B. , Cook Gregory M. 
Published: September 2004

ABSTRACT

Bacitracin resistance (bacitracin MIC, ≥256 μg ml
−1
) has been reported in
Enterococcus faecalis
, and in the present study we report on the genetic basis for this resistance. Mutagenesis was carried out with transposon Tn
917
to select for
E. faecalis
mutants with decreased resistance to bacitracin. Two bacitracin-sensitive mutants (MICs, 32 μg ml
−1
) were obtained and Tn
917
insertions were mapped to genes designated
bcrA
and
bcrB
. The amino acid sequences of BcrA (ATP-binding domain) and BrcB (membrane-spanning domain) are predicted to constitute a homodimeric ATP-binding cassette (ABC) transporter, the function of which is essential for bacitracin resistance in
E. faecalis
. The
bcrA
and
bcrB
genes were organized in an operon with a third gene,
bcrD
, that had homology to undecaprenol kinases. Northern analysis demonstrated that
bcrA
,
bcrB
, and
bcrD
were transcribed as a polycistronic message that was induced by increasing concentrations of bacitracin but not by other cell wall-active antimicrobials (e.g., vancomycin). Upstream of the
bcrABD
operon was a putative regulatory gene,
bcrR
. The
bcrR
gene was expressed constitutively, and deletion of
bcrR
resulted in a bacitracin-sensitive phenotype. No
bcrABD
expression was observed in a
bcrR
mutant, suggesting that BcrR is an activator of genes essential for bacitracin resistance (i.e.,
bcrABD
). The bacitracin resistance genes were found to be located on a plasmid that transferred at a high frequency to
E. faecalis
strain JH2-2. This report represents the first description of genes that are essential for acquired bacitracin resistance in
E. faecalis
.
Cell Wall Composition and Decreased Autolytic Activity and Lysostaphin Susceptibility of Glycopeptide-Intermediate
Staphylococcus aureus
Authors: Koehl Jennifer L. , Muthaiyan Arunachalam , Jayaswal Radheshyam K. , Ehlert Kerstin , Labischinski Harald , Wilkinson Brian J. 
Published: September 2004

ABSTRACT

The cell wall composition and autolytic properties of passage-selected glycopeptide-intermediate
Staphylococcus aureus
(GISA) isolates and their parent strains were studied in order to investigate the mechanism of decreased vancomycin susceptibility. GISA had relatively modest changes in peptidoglycan composition involving peptidoglycan interpeptide bridges and somewhat decreased cross-linking compared to that of parent strains. The cell wall phosphorus content of GISA strains was lower than that of susceptible parent strains, indicating somewhat lower wall teichoic acid levels in the GISA strains. Similar to whole cells, isolated crude cell walls retaining autolytic activity of GISA had drastically reduced autolytic activity compared to that of parent strains, and this arose early in the development of the GISA phenotype. This was due to an alteration in the autolytic enzymes of GISA as revealed by normal susceptibility of GISA-purified cell walls to parental strain autolysin extract and lower activity and altered peptidoglycan hydrolase activity profiles in GISA autolysin extracts compared to those of parent strains. Northern blot analysis indicated that expression of
atl
, the major autolysin gene, was significantly downregulated in a GISA strain compared to that of its parent strain. In contrast to whole cells, which showed decreased lysostaphin susceptibility, purified cell walls of GISA showed increased susceptibility to lysostaphin. We suggest that in our GISA strains, decreased autolytic activity is involved in the tolerance of vancomycin and the activities of endogenous autolysins are important in conferring sensitivity to lysostaphin on whole cells.
Complete Nucleotide Sequence of a 92-Kilobase Plasmid Harboring the CTX-M-15 Extended-Spectrum Beta-Lactamase Involved in an Outbreak in Long-Term-Care Facilities in Toronto, Canada
Authors: Boyd David A. , Tyler Shaun , Christianson Sara , McGeer Allison , Muller Matthew P. , Willey Barbara M. , Bryce Elizabeth , Gardam Michael , Nordmann Patrice , Mulvey Michael R. 
Published: September 2004

ABSTRACT

A major outbreak involving an
Escherichia coli
strain that was resistant to expanded-spectrum cephalosporins occurred in Toronto and surrounding regions in 2000 to 2002. We report the complete sequence of a plasmid, pC15-1a, that was found associated with the outbreak strain. Plasmid pC15-1a is a circular molecule of 92,353 bp consisting of two distinct regions. The first is a 64-kb region that is essentially homologous to the non-R-determinant region of plasmid R100 except for several point mutations, a few small insertions and deletions, and the absence of Tn
10
. The second is a 28.4-kb multidrug resistance region (MDR) that has replaced the R-determinant region of the R100 progenitor and consists mostly of transposons or partial transposons and five copies of the insertion element IS
26
. All drug resistance genes found in pC15-1a, including the beta-lactamase genes
bla
CTX-M-15
,
bla
OXA-1
, and
bla
TEM-1
, the tetracycline resistance gene
tetA
, and aminoglycoside resistance genes
aac
(
6
′)-
Ib
and
aac
(
3
)
-II
, are located in the MDR. The
bla
CTX-M-15
gene was found downstream of IS
Ecp1
as part of a transposition unit, as determined from the surrounding sequence. Examination of the plasmids from CTX-M-15-harboring strains isolated from hospitals across Canada showed that pC15-1a was found in several strains isolated from a site in western Canada. Comparison of pC15-1a and pCTX15, found in an
E. coli
strain isolated in India in 1999, revealed that the plasmids had several features in common, including an R100 backbone and several of the resistance genes, including
bla
CTX-M-15
,
bla
TEM-1
,
bla
OXA-1
,
tetA
, and
aac
(
6
′)
-Ib
.
Ertapenem Pharmacokinetics and Impact on Intestinal Microflora, in Comparison to Those of Ceftriaxone, after Multiple Dosing in Male and Female Volunteers
Authors: Pletz Mathias W. R. , Rau Mareike , Bulitta Juergen , De Roux Andres , Burkhardt Olaf , Kruse Guido , Kurowski Michael , Nord Carl E. , Lode Hartmut 
Published: September 2004

ABSTRACT

The pharmacokinetics of ertapenem and ceftriaxone were investigated in an open, randomized, two-period crossover study after single- and multiple-dose administration in 10 healthy volunteers (five women and five men). Both antibiotics were administered intravenously once daily for 7 days at dosages of 1 g (ertapenem) and 2 g (ceftriaxone). The concentrations of the antibiotics in serum and urine were quantified by the agar well diffusion method bioassay and, in addition, for ertapenem only, by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). For ertapenem the maximum concentration of the drug in plasma (
C
max
) was 256 mg/liter, the half-life was 20.7 h, and the area under the plasma concentration-time curve (AUC) was 830 mg · h/liter. The concentrations in fecal samples were (mean value) 37.2 and 32.7 mg/kg on day 4 and day 8, respectively. Ceftriaxone exhibited a mean
C
max
of 315 mg/liter, a half-life of 7.6 h, and an AUC of 1,556 mg · h/liter. The mean concentrations in fecal samples were 153 and 258 mg/kg on day 4 and day 8, respectively. No accumulation of ertapenem or ceftriaxone was detected at steady state. A slightly but significantly decreased AUC for ertapenem was detected for the female volunteers. No serious adverse event was observed. Both antibiotics induced a marked decrease in the anaerobic microflora (4-log-unit decreases in lactobacilli, bifidobacteria, clostridia, and bacteroides) and
Escherichia coli
, whereas the number of enterococci increased (4 log units). A slight overgrowth of yeasts was observed with both regimens. In all cases the microflora returned to normal levels on days 21 to 35.
Azole Resistance in
Candida glabrata
: Coordinate Upregulation of Multidrug Transporters and Evidence for a Pdr1-Like Transcription Factor
Authors: Vermitsky John-Paul , Edlind Thomas D. 
Published: September 2004

ABSTRACT

Candida glabrata
has emerged as a common cause of fungal infection. This yeast has intrinsically low susceptibility to azole antifungals such as fluconazole, and mutation to frank azole resistance during treatment has been documented. Potential resistance mechanisms include changes in expression or sequence of
ERG11
encoding the azole target. Alternatively, resistance could result from upregulated expression of multidrug transporter genes; in
C. glabrata
these include
CDR1
and
PDH1
. By RNA hybridization, 10 of 12 azole-resistant clinical isolates showed 6- to 15-fold upregulation of
CDR1
compared to susceptible strains. In 4 of these 10 isolates
PDH1
was similarly upregulated, and in the remainder it was upregulated three- to fivefold, while
ERG11
expression was minimally changed. Laboratory mutants were selected on fluconazole-containing medium with glycerol as carbon source (to eliminate mitochondrial mutants). Similar to the clinical isolates, six of seven laboratory mutants showed unchanged
ERG11
expression but coordinate
CDR1-PDH1
upregulation ranging from 2- to 20-fold. Effects of antifungal treatment on gene expression in susceptible
C. glabrata
strains were also studied: azole exposure induced
CDR1-PDH1
expression 4- to 12-fold. These findings suggest that these transporter genes are regulated by a common mechanism. In support of this, a mutation associated with laboratory resistance was identified in the
C. glabrata
homolog of
PDR1
which encodes a regulator of multidrug transporter genes in
Saccharomyces cerevisiae
. The mutation falls within a putative activation domain and was associated with
PDR1
autoupregulation. Additional regulatory factors remain to be identified, as indicated by the lack of
PDR1
mutation in a clinical isolate with coordinately upregulated
CDR1-PDH1
.
Effect of Glycine on
Helicobacter pylori
In Vitro
Authors: Minami Masaaki , Ando Takafumi , Hashikawa Shin-nosuke , Torii Keizo , Hasegawa Tadao , Israel Dawn A. , Ina Kenji , Kusugami Kazuo , Goto Hidemi , Ohta Michio 
Published: September 2004

ABSTRACT

Glycine is the simplest amino acid and is used as a metabolic product in some bacteria. However, an excess of glycine inhibits the growth of many bacteria, and it is used as a nonspecific antiseptic agent due to its low level of toxicity in animals. The effect of glycine on
Helicobacter pylori
is not precisely known. The present study was conducted to investigate (i) the effect of glycine on clarithromycin (CLR)-resistant and -susceptible strains of
H. pylori
, (ii) the effect of glycine in combination with amoxicillin (AMX), and (iii) the postantibiotic effect (PAE). The MIC at which 90% of strains are inhibited for glycine was almost 2.5 mg/ml for 31 strains of
H. pylori
, including CLR-resistant strains. We constructed isogenic CLR-resistant mutant strains by natural transformation and investigated the difference between clinical wild-type strains and isogenic mutants. There were no differences in the MICs between CLR-resistant and -susceptible strains or between clinical wild-type and mutant strains. The combination of AMX and glycine showed synergistic activity, with the minimum bactericidal concentration of AMX with glycine decreasing to 1/10 that of AMX alone. Glycine showed no PAE against
H. pylori
. These results suggest that glycine may be a useful antimicrobial agent against
H. pylori
not only alone but also in combination with antibacterial drugs for the treatment of
H. pylori
-associated diseases. Glycine may represent a component of a new type of eradication therapy for CLR-resistant
H. pylori
.
Increasing Prevalence of Quinolone Resistance in Human Nontyphoid
Salmonella enterica
Isolates Obtained in Spain from 1981 to 2003
Authors: Marimón José M. , Gomáriz María , Zigorraga Carmen , Cilla Gustavo , Pérez-Trallero Emilio 
Published: September 2004

ABSTRACT

From January 1981 to December 2003, susceptibility to nalidixic acid was tested in 10,504 nontyphoid
Salmonella enterica
isolates from patients with acute enteric disease in Gipuzkoa, Spain. The prevalence of nalidixic acid resistance steadily increased from less than 0.5% before 1991 to 38.5% in 2003, mainly due to the increase in resistance among isolates of the most prevalent serovar,
S. enterica
serovar Enteritidis. For nalidixic acid-resistant isolates, the ciprofloxacin MIC was eightfold higher than that for susceptible isolates, and the nalidixic acid-resistant isolates contained a single point mutation in the
gyrA
gene (at codons for Ser83 or Asp87). The same mutations were found in a sample of nalidixic acid-resistant nontyphoid
Salmonella
strains isolated between 1999 and 2003 from retail food for human consumption. In 2003, we identified five
S. enterica
serovar Typhimurium clinical isolates with high-level fluoroquinolone resistance (ciprofloxacin MIC, 16 μg/ml) with two point mutations in the
gyrA
gene (coding for Ser83→Phe and Asp87→Asn) and one point mutation in the
parC
gene (coding for Ser80→Arg). Strict sanitary controls are needed to avoid the spread of ciprofloxacin-resistant serovar Typhimurium isolates, and a more efficient veterinary policy must be adopted to decrease the large burden of
Salmonella
serovar Enteritidis infections in humans in our region.
Population Pharmacokinetics of Pyrimethamine and Sulfadoxine in Children Treated for Congenital Toxoplasmosis
Authors: Corvaisier Stéphane , Charpiat Bruno , Mounier Cyril , Wallon Martine , Leboucher Gilles , Al Kurdi Mounzer , Chaulet Jean-François , Peyron François 
Published: September 2004

ABSTRACT

The population pharmacokinetics of pyrimethamine (PYR) and sulfadoxine (SDX) for a group of 32 children with congenital toxoplasmosis was investigated by nonparametric modeling analysis. A one-compartment model was used as the structural model, and individual pharmacokinetic parameters were estimated by Bayesian modeling. PYR (1.25 mg/kg of body weight) and SDX (25 mg/kg) were administered orally every 10 days for 1 year, with adjustment of the dose to body weight every 3 months. Drug concentrations were measured by high-performance liquid chromatography. A total of 101 measurements in serum were available for both drugs. Mean absorption rate constants, volumes of distribution, elimination rate constants, and half-lives were 0.915 h
−1
, 4.379 liters/kg, 0.00839 h
−1
, and 5.5 days for PYR and 1.659 h
−1
, 0.392 liters/kg, 0.00526 h
−1
, and 6.6 days for SDX, respectively. Wide interindividual variability was observed. The estimated minimum and maximum concentrations of PYR in serum differed 8- and 25-fold among patients, respectively, and those of SDX differed 4- and 5-fold, respectively. Increases in the concentration of PYR were observed for eight children, and increases in the SDX concentration were observed for seven children. Serum PYR-SDX concentrations are unpredictable even when the dose is standardized for body weight. The concentrations of the PYR-SDX combination that are most efficacious for children have not yet been established. A model such as ours, associated with long-term follow-up, is needed to study the correlation between exposure to these two drugs and clinical outcome in children.
Antifungal Activities of Posaconazole and Granulocyte-Macrophage Colony-Stimulating Factor Ex Vivo and in Mice with Disseminated Infection Due to
Scedosporium prolificans
Authors: Simitsopoulou M. , Gil-Lamaignere C. , Avramidis N. , Maloukou A. , Lekkas S. , Havlova E. , Kourounaki L. , Loebenberg D. , Roilides E. 
Published: September 2004

ABSTRACT

Invasive infection due to
Scedosporium prolificans
is characterized by drug resistance and a high rate of mortality. The effects of posaconazole (POS), an investigational antifungal triazole, murine granulocyte-macrophage colony-stimulating factor (GM-CSF), and their combination against
S. prolificans
were evaluated ex vivo and in a newly developed murine model of disseminated infection due to this organism. When POS was combined with polymorphonuclear leukocytes from untreated or GM-CSF-treated mice (
P
< 0.01) ex vivo, it had increased activity in terms of the percentage of hyphal damage. Immunocompetent BALB/c mice were infected with 4 × 10
4
conidia of
S. prolificans
via the lateral tail vein. At 24 h postinfection the mice were treated with GM-CSF (5 μg/kg of body weight/day subcutaneously), POS (50 mg/kg/day by gavage), both agents, or saline only. Half of the brain, lung, liver, and kidney from each animal were cultured; and the other half of each organ was processed for histopathology. The mean survival times were 7.0 ± 0.3 days for the controls, 7.4 ± 0.4 days for POS-treated mice, 8.0 ± 0.3 days for GM-CSF-treated mice (
P
= 0.08 compared with the results for the controls), and 7.3 ± 0.3 days for POS-GM-CSF-treated mice. Fungal burdens (determined as the numbers of CFU per gram of tissue) were found in descending orders of magnitude in the kidneys, brains, livers, and lungs. The burdens were significantly reduced in the brains of GM-CSF-treated mice (
P
< 0.05) and the livers of POS-treated mice (
P
< 0.05). The numbers of lesions in the organs closely corresponded to the fungal burdens. GM-CSF tended to prolong survival (
P
= 0.08 compared with the results for the controls). While the combination of POS and GM-CSF showed enhanced activity ex vivo, it did not increase the activities of the two agents against this highly refractory filamentous fungus in mice.
Variant
Salmonella
Genomic Island 1 Antibiotic Resistance Gene Cluster Containing a Novel 3′-
N
-Aminoglycoside Acetyltransferase Gene Cassette,
aac
(3)-
Id
, in
Salmonella enterica
Serovar Newport
Authors: Doublet Benoît , Weill François-Xavier , Fabre Laetitia , Chaslus-Dancla Elisabeth , Cloeckaert Axel 
Published: September 2004

ABSTRACT

Salmonella
genomic island 1 (SGI1) harbors an antibiotic resistance gene cluster and was previously identified in the multidrug-resistant
Salmonella enterica
serovars Typhimurium DT104, Agona, Paratyphi B, and Albany. This antibiotic resistance gene cluster is a complex class 1 integron and most often confers resistance to ampicillin (Ap), chloramphenicol (Cm)/florfenicol (Ff), streptomycin (Sm)/spectinomycin (Sp), sulfonamides (Su), and tetracycline (Tc) (ApCmFfSmSpSuTc profile). Recently, variant SGI1 antibiotic resistance gene clusters conferring different antibiotic resistance profiles have been identified in several
S. enterica
serovars and were classified as SGI1-A to -G. We identified a new variant SGI1 antibiotic resistance gene cluster in two multidrug-resistant
S. enterica
serovar Newport strains isolated from humans in France. In these strains, the Sm/Sp resistance gene cassette
aadA2
inserted at the first
attI1
site was replaced by two other aminoglycoside resistance gene cassettes. The first one contains a new resistance gene encoding an AAC(3)-I aminoglycoside 3-
N
-acetyltransferase that confers resistance to gentamicin (Gm) and sisomicin (Sc). This gene has been named
aac
(3)-
Id
. The second one harbors the Sm/Sp resistance gene
aadA7
. This gene cassette replacement in the SGI1 complex integron of serovar Newport strains constitutes a new variant SGI1 antibiotic resistance gene cluster named SGI1-H. The occurrence of SGI1 in different
S. enterica
serovars, now including serovar Newport, strengthens the hypothesis of horizontal transfer of SGI1.
Liquid Chromatography Assay for Routine Monitoring of Cellular Ribavirin Levels in Blood
Authors: Inoue Yoichi , Homma Masato , Matsuzaki Yasushi , Shibata Minoru , Matsumura Takuya , Ito Takayoshi , Mitamura Keiji , Tanaka Naomi , Kohda Yukinao 
Published: September 2004

ABSTRACTRibavirin-induced hemolytic anemia is one cause for cessation of combination therapy with alpha interferon 2b and ribavirin for hepatitis C infection. Determining cellular ribavirin levels in blood, including the levels of its phosphorylated metabolites, might be useful for predicting ribavirin-induced anemia, because the metabolites accumulate in erythrocytes. We simplified an assay method developed previously to make it suitable for routine monitoring of cellular ribavirin. Whole blood diluted with a sixfold volume of ice-cold distilled water was subjected to acid phosphatase digestion to convert phosphorylated ribavirin metabolites to free ribavirin. The resulting mixture, spiked with an internal standard, was treated by phenyl boronic acid column extraction, followed by reverse-phase high-performance liquid chromatography analysis. The calibration curve for ribavirin levels in whole blood was linear at concentrations of 5.3 to 1,024 μM (r2= 0.9999). Validation coefficients of variation for intra- and interday assays were 2.9 to 5.8% and 4.3 to 8.3%, respectively. We tested this method by monitoring blood ribavirin concentrations in two hepatitis C patients receiving alpha interferon 2b-plus-ribavirin combination therapy.
Therapy of Experimental
Pseudomonas
Infections with a Nonreplicating Genetically Modified Phage
Authors: Hagens Steven , Habel André , von Ahsen Uwe , von Gabain Alexander , Bläsi Udo 
Published: September 2004

ABSTRACT

Bacteriophage therapy of bacterial infections has received renewed attention owing to the increasing prevalence of antibiotic-resistant pathogens. A side effect of many antibiotics as well as of phage therapy with lytic phage is the release of cell wall components, e.g., endotoxins of gram-negative bacteria, which mediate the general pathological aspects of septicemia. Here we explored an alternative strategy by using genetically engineered nonreplicating, nonlytic phage to combat an experimental
Pseudomonas aeruginosa
infection. An export protein gene of the
P. aeruginosa
filamentous phage Pf3 was replaced with a restriction endonuclease gene. This rendered the Pf3 variant (Pf3R) nonreplicative and concomitantly prevented the release of the therapeutic agent from the target cell. The Pf3R phage efficiently killed a wild-type host in vitro, while endotoxin release was kept to a minimum. Treatment of
P. aeruginosa
infections of mice with Pf3R or with a replicating lytic phage resulted in comparable survival rates upon challenge with a minimal lethal dose of 3. However, the survival rate after phage therapy with Pf3R was significantly higher than that with the lytic phage upon challenge with a minimal lethal dose of 5. This higher survival rate correlated with a reduced inflammatory response elicited by Pf3R treatment relative to that with the lytic phage. Therefore, this study suggests that the increased survival rate of Pf3R-treated mice could result from reduced endotoxin release. Thus, the use of a nonreplicating modified phage for the delivery of genes encoding proteins toxic to bacterial pathogens may open up a new avenue in antimicrobial therapy.