bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Susceptibilities of Gram-Negative Bacteria Isolated from Hospitalized Patients in Four European Countries, Canada, and the United States in 2000-2001 to Expanded-Spectrum Cephalosporins and Comparator Antimicrobials: Implications for Therapy
Authors: Wenzel Richard P. , Sahm Daniel F. , Thornsberry Clyde , Draghi Deborah C. , Jones Mark E. , Karlowsky James A. 
Published: September 2003

ABSTRACT

Access to current antimicrobial agent surveillance data is an important prerequisite for the optimal management of patients with hospital-acquired infections. The present study used data collected in 2000 to 2001 from 670 laboratories in Europe (France, Germany, Italy, and Spain), Canada, and the United States to report on the in vitro activities of ceftriaxone, cefotaxime, and comparative agents against >125,000 isolates of gram-negative bacteria from hospitalized patients. All but two isolates of
Enterobacteriaceae
(one isolate of
Proteus mirabilis
from France and one isolate of
Morganella morganii
from Canada) were susceptible to imipenem. The susceptibility of
Escherichia coli
to ceftriaxone or cefotaxime was ≥97% in each country, and for
P. mirabilis
, susceptibility was 99% in each country except Italy. In contrast, susceptibility of
E. coli
to ciprofloxacin varied from 80.5% (Spain) to 94.0% (France); levofloxacin susceptibility ranged from 75.2% (Spain) to 91.6% (United States). Among
Klebsiella pneumoniae
and
Klebsiella oxytoca
isolates, ceftriaxone and cefotaxime susceptibilities ranged from 86.6 to 98.7% and 83.5 to 99.7%, respectively, depending upon the country. Considerable geographic variation in the susceptibilities (generally 85 to 95% susceptible) of
Serratia marcescens
and
M. morganii
to ceftriaxone and cefotaxime were observed. For
S. marcescens
, susceptibility to piperacillin-tazobactam varied from 81.5% (France) to 94.1% (Italy) and susceptibility to ciprofloxacin ranged from 66.2% (Germany) to 90.7% (Spain).
Enterobacter cloacae
and
Enterobacter aerogenes
were less susceptible to ceftriaxone and cefotaxime than were the other species of
Enterobacteriaceae
studied. The present study demonstrated that established parenteral expanded-spectrum cephalosporin antimicrobial agents retain significant in vitro activity against many clinically important gram-negative pathogens.
Rapid Direct Method for Monitoring Antibiotics in a Mouse Model of Bacterial Biofilm Infection
Authors: Kadurugamuwa Jagath L. , Sin Lin V. , Yu Jun , Francis Kevin P. , Kimura Richard , Purchio Tony , Contag Pamela R. 
Published: September 2003

ABSTRACT

We have developed a rapid, continuous method for monitoring the effectiveness of several antibacterial agents in real time, noninvasively, by using a recently described mouse model of chronic biofilm infection (J. L. Kadurugamuwa et al., Infect. Immun. 71:882-890, 2003), which relies on biophotonic imaging of bioluminescent bacteria. To facilitate real-time monitoring of infection, we used a
Staphylococcus aureus
isolate that was made bioluminescent by inserting a modified
lux
operon into the bacterial chromosome. This bioluminescent reporter bacterium was used to study the antimicrobial effects of several antibiotics belonging to different molecular families. Treatment with rifampin, tobramycin, and ciprofloxacin was started 7 days after subcutaneous implantation of catheters precolonized with 10
4
CFU of
S. aureus
. Three different doses of antibiotics were administered twice a day for 4 consecutive days. The number of metabolically active bacteria in untreated mice and the tobramycin- and ciprofloxacin-treated groups remained relatively unchanged over the 4-week observation period, indicating poor efficacies for tobramycin and ciprofloxacin. A rapid dose-dependent decline in metabolic activity in rifampin-treated groups was observed, with almost a 90% reduction after two doses and nearly undetectable levels after three doses. The disappearance of light emission correlated with colony counts. After the final treatment, cell numbers rebounded as a function of concentration in a time-dependent manner. The staphylococci isolated from the catheters of mice treated with rifampin were uniformly resistant to rifampin but retained their in vitro susceptibilities to tobramycin and ciprofloxacin. Since the metabolic activities of viable cells and a postantibiotic effect could be detected directly on the support matrix nondestructively and noninvasively, the methodology is specifically appealing for investigating the effects of antibiotics on biofilms in vivo. Moreover, our study points to the possible use of biophotonic imaging for the detection of the development of resistance to therapeutic agents during treatment of chronic infections in vivo.
Antimicrobial Resistance Genes in Enterotoxigenic
Escherichia coli
O149:K91 Isolates Obtained over a 23-Year Period from Pigs
Authors: Maynard Christine , Fairbrother John M. , Bekal Sadjia , Sanschagrin François , Levesque Roger C. , Brousseau Roland , Masson Luke , Larivière Serge , Harel Josée 
Published: September 2003

ABSTRACT

A total of 112
Escherichia coli
O149:K91 strains isolated from pigs with diarrhea in Quebec, Canada, between 1978 and 2000 were characterized for their genotypic antimicrobial resistance profiles. Tests for resistance to 10 antimicrobial agents were conducted. Resistance to tetracycline and sulfonamides was found to be the most frequent, but resistance to cefotaxime and ceftiofur was absent. An increase in the number of isolates resistant to at least three antimicrobials was observed over time. The distribution of 28 resistance genes covering six antimicrobial families (beta-lactams, aminoglycosides, phenicols, tetracycline, trimethoprim, and sulfonamides) was assessed by colony hybridization. Significant differences in the distributions of tetracycline [
tet
(A),
tet
(B),
tet
(C)], trimethoprim (
dhfrI
,
dhfrV
,
dhfrXIII
), and sulfonamide (
sulI
,
sulII
) resistance genes were observed during the study period (1978 to 2000). Sixty percent of the isolates possessed a class 1 integron, illustrating the importance of integrons in the epidemiology of antibiotic resistance in
E. coli
strains from pigs. Amplification of the integron's variable region resulted in four distinct fragments of 1, 1.3, 1.6, and 1.8 kb, with the 1.6- and 1.8-kb fragments appearing only during the last half of the study period. Examination of linkages among the different resistance genes showed a variety of positive and negative associations. Association analysis of isolates divided into two groups, those isolated between 1978 and 1989 and those isolated between 1990 and 2000, revealed the appearance of new positive resistance gene associations. Our genotypic resistance analyses of ETEC isolates from pigs indicate that many of the antibiotic resistance genes behind phenotypic resistance are not static but, rather, are in a state of flux driven by various selection forces such as the use of specific antimicrobials.
Effects of Tylosin on Bacterial Mucolysis,Clostridium perfringensColonization, and Intestinal Barrier Function in a Chick Model of Necrotic Enteritis
Authors: Collier C. T. , van der Klis J. D. , Deplancke B. , Anderson D. B. , Gaskins H. R. 
Published: September 2003

ABSTRACTNecrotic enteritis (NE) is a worldwide poultry disease caused by the alpha toxin-producing bacteriumClostridium perfringens. Disease risk factors include concurrent coccidial infection and the dietary use of cereal grains high in nonstarch polysaccharides (NSP), such as wheat, barley, rye, and oats. Outbreaks of NE can be prevented or treated by the use of in-feed antibiotics. However, the current debate regarding the prophylactic use of antibiotics in animal diets necessitates a better understanding of factors that influence intestinal colonization byC. perfringensas well as the pathophysiological consequences of its growth. We report a study with a chick model of NE, which used molecular (16S rRNA gene [16S rDNA]) and culture-based microbiological techniques to investigate the impact of the macrolide antibiotic tylosin phosphate (100 ppm) and a dietary NSP (pectin) on the community structure of the small intestinal microbiota relative to colonization byC. perfringens. The effects of tylosin and pectin on mucolytic activity of the microbiota andC. perfringenscolonization and their relationship to pathological indices of NE were of particular interest. The data demonstrate that tylosin reduced the percentage of mucolytic bacteria in general and the concentration ofC. perfringensin particular, and these responses correlated in a temporal fashion with a reduction in the occurrence of NE lesions and an improvement in barrier function. The presence of pectin did not significantly affect the variables measured. Thus, it appears that tylosin can control NE through its modulation ofC. perfringenscolonization and the mucolytic activity of the intestinal microbiota.
Effects of Lipid-Based Oral Formulations on Plasma and Tissue Amphotericin B Concentrations and Renal Toxicity in Male Rats
Authors: Risovic Verica , Boyd Michael , Choo Eugene , Wasan Kishor M. 
Published: September 2003

ABSTRACTThe purpose of this study was to determine the effects of various lipid and mixed-micelle formulations on the oral absorption and renal toxicity of amphotericin B (AMB) in rats. The maximum concentration of AMB in plasma and the area under the concentration-time curve for 0 to 24 h for AMB were elevated in rats administered triglyceride (TG)-rich AMB formulations in comparison to those in rats given (i) AMB preformulated as a micelle containing sodium deoxycholate with sodium phosphate as a buffer (DOC-AMB), (ii) an AMB-lipid complex suspension, or (iii) AMB solubilized in methanol. Furthermore, our findings suggest that AMB incorporated into TG-based oral formulations has less renal toxicity than DOC-AMB.
Activity of Human β-Defensin 3 Alone or Combined with Other Antimicrobial Agents against Oral Bacteria
Authors: Maisetta Giuseppantonio , Batoni Giovanna , Esin Semih , Luperini Filippo , Pardini Manuela , Bottai Daria , Florio Walter , Giuca Maria Rita , Gabriele Mario , Campa Mario 
Published: September 2003

ABSTRACT

The in vitro activities of human β-defensin 3 (hBD-3) alone or combined with lysozyme, metronidazole, amoxicillin, and chlorhexidine were investigated with the oral bacteria
Streptococcus mutans
,
Streptococcus sanguinis
,
Streptococcus sobrinus
,
Lactobacillus acidophilus
,
Actinobacillus actinomycetemcomitans
, and
Porphyromonas gingivalis
. hBD-3 showed bactericidal activity against all of the bacterial species tested. The bactericidal effect was enhanced when the peptide was used in combination with the antimicrobial agents mentioned above.
Chimeric Analysis of AcrA Function Reveals the Importance of Its C-Terminal Domain in Its Interaction with the AcrB Multidrug Efflux Pump
Authors: Elkins Christopher A. , Nikaido Hiroshi 
Published: August 2003

ABSTRACT

AcrAB-TolC is the major, constitutively expressed efflux protein complex that provides resistance to a variety of antimicrobial agents in
Escherichia coli
. Previous studies showed that AcrA, a periplasmic protein of the membrane fusion protein family, could function with at least two other resistance-nodulation-division family pumps, AcrD and AcrF, in addition to its cognate partner, AcrB. We found that, among other
E
.
coli
resistance-nodulation-division pumps, YhiV, but not MdtB or MdtC, could also function with AcrA. When AcrB was assessed for the capacity to function with AcrA homologs, only AcrE, but not YhiU or MdtA, could complement an AcrA deficiency. Since AcrA could, but YhiU could not, function with AcrB, we engineered a series of chimeric mutants of these proteins in order to determine the domain(s) of AcrA that is required for its support of AcrB function. The 290-residue N-terminal segment of the 398-residue protein AcrA could be replaced with a sequence coding for the corresponding region of YhiU, but replacement of the region between residues 290 and 357 produced a protein incapable of functioning with AcrB. In contrast, the replacement of residues 357 through 397 of AcrA still produced a functional protein. We conclude that a small region of AcrA close to, but not at, its C terminus is involved in the interaction with its cognate pump protein, AcrB.
Mycobacterium tuberculosis
FurA Autoregulates Its Own Expression
Authors: Sala Claudia , Forti Francesca , Di Florio Elisabetta , Canneva Fabio , Milano Anna , Riccardi Giovanna , Ghisotti Daniela 
Published: August 2003

ABSTRACT

The
furA-katG
region of
Mycobacterium tuberculosis
, encoding a Fur-like protein and the catalase-peroxidase, is highly conserved among mycobacteria. Both genes are induced upon oxidative stress. In this work we analyzed the
M. tuberculosis furA
promoter region. DNA fragments were cloned upstream of the luciferase reporter gene, and promoter activity in
Mycobacterium smegmatis
was measured in both the presence and absence of oxidative stress. The shortest fragment containing an inducible promoter extends 45 bp upstream of
furA
. In this region, −35 and −10 promoter consensus sequences can be identified, as well as a 23-bp AT-rich sequence that is conserved in the nonpathogenic but closely related
M. smegmatis
.
M. tuberculosis
FurA was purified and found to bind upstream of
furA
by gel shift analysis. A ca. 30-bp DNA sequence, centered on the AT-rich region, was essential for FurA binding and protected by FurA in footprinting analysis. Peroxide treatment of FurA abolished DNA binding. Three different AT-rich sequences mutagenized by site-directed mutagenesis were constructed. In each mutant, both
M. tuberculosis
FurA binding in vitro and
pfurA
regulation upon oxidative-stress in
M. smegmatis
were abolished. Thus,
pfurA
is an oxidative stress-responsive promoter controlled by the FurA protein.
Arsenic Sensing and Resistance System in the Cyanobacterium
Synechocystis
sp. Strain PCC 6803
Authors: López-Maury Luis , Florencio Francisco J. , Reyes José C. 
Published: August 2003

ABSTRACT

Arsenic is one of the most important global environmental pollutants. Here we show that the cyanobacterium
Synechocystis
sp. strain PCC 6803 contains an arsenic and antimony resistance operon consisting of three genes:
arsB
, encoding a putative arsenite and antimonite carrier,
arsH
, encoding a protein of unknown function, and
arsC
, encoding a putative arsenate reductase. While
arsB
mutant strains were sensitive to arsenite, arsenate, and antimonite,
arsC
mutants were sensitive only to arsenate. The
arsH
mutant strain showed no obvious phenotype under the conditions tested. In vivo the
arsBHC
operon was derepressed by oxyanions of arsenic and antimony (oxidation state, +3) and, to a lesser extent, by bismuth (oxidation state, +3) and arsenate (oxidation state, +5). In the absence of these effectors, the operon was repressed by a transcription repressor of the ArsR/SmtB family, encoded by an unlinked gene termed
arsR
. Thus,
arsR
null mutants showed constitutive derepression of the
arsBHC
operon. Expression of the
arsR
gene was not altered by the presence of arsenic or antimony compounds. Purified recombinant ArsR protein binds to the
arsBHC
promoter-operator region in the absence of metals and dissociates from the DNA in the presence of Sb(III) or As(III) but not in the presence of As(V), suggesting that trivalent metalloids are the true inducers of the system. DNase I footprinting experiments indicate that ArsR binds to two 17-bp direct repeats, with each one consisting of two inverted repeats, in the region from nucleotides −34 to + 17 of the
arsBHC
promoter-operator.
Effect of Translational Signals on mRNA Decay in
Bacillus subtilis
Authors: Sharp Josh S. , Bechhofer David H. 
Published: August 2003

ABSTRACT

A 254-nucleotide model mRNA, designated Δ
ermC
mRNA, was used to study the effects of translational signals and ribosome transit on mRNA decay in
Bacillus subtilis
. Δ
ermC
mRNA features a strong ribosome-binding site (RBS) and a 62-amino-acid-encoding open reading frame, followed by a transcription terminator structure. Inactivation of the RBS or the start codon resulted in a fourfold decrease in the mRNA half-life, demonstrating the importance of ternary complex formation for mRNA stability. Data for the decay of Δ
ermC
mRNAs with stop codons at positions increasingly proximal to the translational start site showed that actual translation—even the formation of the first peptide bond—was not important for stability. The half-life of an untranslated 3.2-kb Δ
ermC
-
lacZ
fusion RNA was similar to that of a translated Δ
ermC
-
lacZ
mRNA, indicating that the translation of even a longer RNA was not required for wild-type stability. The data are consistent with a model in which ribosome binding and the formation of the ternary complex interfere with a 5′-end-dependent activity, possibly a 5′-binding endonuclease, which is required for the initiation of mRNA decay. This model is supported by the finding that increasing the distance from the 5′ end to the start codon resulted in a 2.5-fold decrease in the mRNA half-life. These results underscore the importance of the 5′ end to mRNA stability in
B
.
subtilis
.
YqfS from
Bacillus subtilis
Is a Spore Protein and a New Functional Member of the Type IV Apurinic/Apyrimidinic-Endonuclease Family
Authors: Salas-Pacheco José M. , Urtiz-Estrada Norma , Martínez-Cadena Guadalupe , Yasbin Ronald E. , Pedraza-Reyes Mario 
Published: August 2003

ABSTRACT

The enzymatic properties and the physiological function of the type IV apurinic/apyrimidinic (AP)-endonuclease homolog of
Bacillus subtilis
, encoded by
yqfS
, a gene specifically expressed in spores, were studied here. To this end, a recombinant YqfS protein containing an N-terminal His
6
tag was synthesized in
Escherichia coli
and purified to homogeneity. An anti-His
6
-YqfS polyclonal antibody exclusively localized YqfS in cell extracts prepared from
B
.
subtilis
spores. The His
6
-YqfS protein demonstrated enzymatic properties characteristic of the type IV family of DNA repair enzymes, such as AP-endonucleases and 3′-phosphatases. However, the purified protein lacked both 5′-phosphatase and exonuclease III activities. YqfS showed not only a high level of amino acid identity with
E. coli
Nfo but also a high resistance to inactivation by EDTA, in the presence of DNA containing AP sites (AP-DNA). These results suggest that YqfS possesses a trinuclear Zn center in which the three metal atoms are intimately coordinated by nine conserved basic residues and two water molecules. Electrophoretic mobility shift assays demonstrated that YqfS possesses structural properties that permit it to bind and scan undamaged DNA as well as to strongly interact with AP-DNA. The ability of
yqfS
to genetically complement the DNA repair deficiency of an
E. coli
mutant lacking the major AP-endonucleases Nfo and exonuclease III strongly suggests that its product confers protection to cells against the deleterious effects of oxidative promoters and alkylating agents. Thus, we conclude that YqfS of
B. subtilis
is a spore-specific protein that has structural and enzymatic properties required to participate in the repair of AP sites and 3′ blocking groups of DNA generated during both spore dormancy and germination.
Identification and Characterization of a New Enoyl Coenzyme A Hydratase Involved in Biosynthesis of Medium-Chain-Length Polyhydroxyalkanoates in Recombinant
Escherichia coli
Authors: Park Si Jae , Lee Sang Yup 
Published: August 2003

ABSTRACT

The biosynthetic pathway of medium-chain-length (MCL) polyhydroxyalkanoates (PHAs) from fatty acids has been established in
fadB
mutant
Escherichia coli
strain by expressing the MCL-PHA synthase gene. However, the enzymes that are responsible for the generation of (
R
)-3-hydroxyacyl coenzyme A (R3HA-CoAs), the substrates for PHA synthase, have not been thoroughly elucidated.
Escherichia coli
MaoC, which is homologous to
Pseudomonas aeruginosa
(
R
)-specific enoyl-CoA hydratase (PhaJ1), was identified and found to be important for PHA biosynthesis in a
fadB
mutant
E. coli
strain. When the MCL-PHA synthase gene was introduced, the
fadB maoC
double-mutant
E. coli
WB108, which is a derivative of
E. coli
W3110, accumulated 43% less amount of MCL-PHA from fatty acid compared with the
fadB
mutant
E. coli
WB101. The PHA biosynthetic capacity could be restored by plasmid-based expression of the

maoC
Ec

gene in
E. coli
WB108. Also,
E. coli
W3110 possessing fully functional β-oxidation pathway could produce MCL-PHA from fatty acid by the coexpression of the

maoC
Ec

gene and the MCL-PHA synthase gene. For the enzymatic analysis, MaoC fused with His
6
-Tag at its C-terminal was expressed in
E. coli
and purified. Enzymatic analysis of tagged MaoC showed that MaoC has enoyl-CoA hydratase activity toward crotonyl-CoA. These results suggest that MaoC is a new enoyl-CoA hydratase involved in supplying (
R
)-3-hydroxyacyl-CoA from the β-oxidation pathway to PHA biosynthetic pathway in the
fadB
mutant
E. coli
strain.
Extracellular Polysaccharides Associated with Thin Aggregative Fimbriae ofSalmonella entericaSerovar Enteritidis
Authors: White A. P. , Gibson D. L. , Collinson S. K. , Banser P. A. , Kay W. W. 
Published: August 2003

ABSTRACTLipopolysaccharide (LPS) O polysaccharide was identified as the principle factor impeding intercellular formation of intact thin aggregative fimbriae (Tafi) inSalmonella entericaserovar Enteritidis. The extracellular nucleation-precipitation assembly pathway for these organelles was investigated by quantifying fimbrial formation between ΔagfA(AgfA recipient) and ΔagfB(AgfA donor) cells harboring mutations in LPS (galE::Tn10) and/or cellulose (ΔbcsA) synthesis. Intercellular complementation could be detected between ΔagfAand ΔagfBstrains only when both possessed thegalEmutation. LPS O polysaccharide appears to be an impenetrable barrier to AgfA assembly between cells but not within individual cells. The presence of cellulose did not restrict Tafi formation between cells. Transmission electron microscopy ofw+S. entericaserovar Enteritidis 3b cells revealed diffuse Tafi networks without discernible fine structure. In the absence of cellulose, however, individual Tafi fibers were clearly visible, appeared to be occasionally branched, and showed the generally distinctive appearance described forEscherichia coliK-12 curli. A third extracellular matrix component closely associated with cellulose and Tafi was detected on Western blots by using immune serum raised to whole, purified Tafi aggregates. Cellulose was required to tightly link this material to cells. Antigenically similar material was also detected inS. entericaserovar Typhimurium and one diarrheagenicE. coliisolate. Preliminary analysis indicated that this material represented an anionic, extracellular polysaccharide that was distinct from colanic acid. Therefore, Tafi in their native state appear to exist as a complex with cellulose and at least one other component.