bluuebunny/crossref_metadata_2025_split huggingface dataset:
Overexpression of the Multidrug Efflux Operon
acrEF
by Insertional Activation with IS
1
or IS
10
Elements in
Salmonella enterica
Serovar Typhimurium DT204
acrB
Mutants Selected with Fluoroquinolones
Authors: Olliver Anne , Vallé Michel , Chaslus-Dancla Elisabeth , Cloeckaert Axel 
Published: December 2004

ABSTRACT

High-level fluoroquinolone (FQ) resistance in
Salmonella enterica
serovar Typhimurium phage type DT204 has been previously shown to be essentially due to both multiple target gene mutations and active efflux by the AcrAB-TolC efflux system. In this study we show that in intermediatly resistant
acrB
-inactivated serovar Typhimurium DT204 mutants, high-level resistance to FQs can be restored on in vitro selection with FQs. In each FQ- resistant mutant selected from serovar Typhimurium DT204
acrB
mutant strains, an insertion sequence (IS
1
or IS
10
) was found integrated upstream of the
acrEF
operon, coding for AcrEF, an efflux pump highly homologous to AcrAB. In one of the strains, transposition of IS
1
caused partial deletion of
acrS
, the putative local repressor gene of the
acrEF
operon. Sequence analysis showed that both IS
1
and IS
10
elements contain putative promoter sequences that might alter the expression of adjacent
acrEF
genes. Indeed, reverse transcription-PCR experiments showed an 8- to 10-fold increase in expression of
acrF
in these insertional mutants, relative to their respective parental strain, which correlated well with the resistance levels observed to FQs and other unrelated drugs. It is noteworthy that AcrEF did not contribute to the intrinsic drug resistance of serovar Typhimurium, since
acrF
deletion in wild-type strains did not result in any increase in drug susceptibility. Moreover, deletion of
acrS
did not cause any
acrF
overexpression or any decrease in drug susceptibility, suggesting that
acrEF
overexpression is mediated solely by the IS
1
and IS
10
promoter sequences and not by inactivity of AcrS. Southern blot experiments showed that the number of chromosomal IS
1
and IS
10
elements in the serovar Typhimurium DT204 genome was about 5 and 15 respectively. None were detected in epidemic serovar Typhimurium DT104 strains or in the serovar Typhimurium reference strain LT2. Carrying IS
1
and/or IS
10
elements in their chromosome may thus be a selective advantage for serovar Typhimurium DT204 strains as opposed to DT104 strains for which no high-level FQ resistance nor insertional mutations were found. Taken together, the results of the present study indicate that the IS
1
- or IS
10
- activated AcrEF efflux pump may relay AcrAB in serovar Typhimurium, and underline the importance of transposable elements in the acquisition of FQ and multidrug resistance.
Molecular Characterization of Cefoxitin-Resistant
Escherichia coli
from Canadian Hospitals
Authors: Mulvey Michael R. , Bryce Elizabeth , Boyd David A. , Ofner-Agostini Marianna , Land Allison M. , Simor Andrew E. , Paton Shirley 
Published: December 2004

ABSTRACT

A study designed to gain baseline information on strains of
Escherichia coli
displaying resistance to cefoxitin in Canada is described. A total of 29,323
E. coli
isolates were screened at 12 participating hospital sites as part of an extended-spectrum beta-lactamase surveillance initiative. A total of 411 clinically significant, nonrepeat isolates displaying reduced susceptibilities to the NCCLS-recommended beta-lactams were submitted to a central laboratory over a 1-year period ending on 30 September 2000. Two hundred thirty-two isolates were identified as resistant to cefoxitin. All cefoxitin-resistant strains were subtyped by pulsed-field gel electrophoresis, and of these, 182 strains revealed a unique fingerprint and 1 strain was untypeable. PCR and sequence analysis of the
ampC
promoter region revealed 51 different promoter or attenuator variants and 14 wild-type promoters. Three promoter regions were interrupted by insertion elements, two contained IS
10
elements, and one contained an IS
911
variant. PCR and sequence analysis for the detection of acquired AmpC resistance (by the acquisition of ACT-1/MIR-1, CMY-2, or FOX) revealed that 25 strains contained CMY-2, including 7 of the strains found to have wild-type promoters. The considerable genetic variability in both the strain fingerprint and the promoter region suggests that AmpC-type resistance may emerge spontaneously by mutation of sensitive strains rather than by the spread of strains or plasmids in the hospital setting.
IS
Ecp1B
-Mediated Transposition of
bla
CTX-M
in
Escherichia coli
Authors: Poirel Laurent , Lartigue Marie-Frédérique , Decousser Jean-Winoc , Nordmann Patrice 
Published: December 2004

ABSTRACT

Several expanded-spectrum β-lactamase
bla
CTX-M
genes are associated with IS
Ecp1
-like elements in
Enterobacteriaceae
. We found that IS
Ecp1B
was able to mobilize the adjacent
bla
CTX-M-19
gene by a transpositional mechanism in
Escherichia coli
by recognizing a variety of DNA sequences as right inverted repeats.
The
trans
-Sialidase from
Trypanosoma cruzi
Induces Thrombocytopenia during Acute Chagas' Disease by Reducing the Platelet Sialic Acid Contents
Authors: Tribulatti María Virginia , Mucci Juan , Van Rooijen Nico , Leguizamón María Susana , Campetella Oscar 
Published: December 2004

ABSTRACT

Strong thrombocytopenia is observed during acute infection with
Trypanosoma cruzi
, the parasitic protozoan agent of American trypanosomiasis or Chagas' disease. The parasite sheds
trans
-sialidase, an enzyme able to mobilize the sialyl residues on cell surfaces, which is distributed in blood and is a virulence factor. Since the sialic acid content on the platelet surface is crucial for determining the half-life of platelets in blood, we examined the possible involvement of the parasite-derived enzyme in thrombocytopenia induction. We found that a single intravenous injection of
trans
-sialidase into naïve mice reduced the platelet count by 50%, a transient effect that lasted as long as the enzyme remained in the blood. CD43
−/−
mice were affected to a similar extent. When green fluorescent protein-expressing platelets were treated in vitro with
trans
-sialidase, their sialic acid content was reduced together with their life span, as determined after transfusion into naïve animals. No apparent deleterious effect on the bone marrow was observed. A central role for Kupffer cells in the clearance of
trans
-sialidase-altered platelets was revealed after phagocyte depletion by administration of clodronate-containing liposomes and splenectomy. Consistent with this, parasite strains known to exhibit more
trans
-sialidase activity induced heavier thrombocytopenia. Finally, the passive transfer of a
trans
-sialidase-neutralizing monoclonal antibody to infected animals prevented the clearance of transfused platelets. Results reported here strongly support the hypothesis that the
trans
-sialidase is the virulence factor that, after depleting the sialic acid content of platelets, induces the accelerated clearance of the platelets that leads to the thrombocytopenia observed during acute Chagas' disease.
Fungal Metabolite Gliotoxin Targets Flavocytochrome
b
558
in the Activation of the Human Neutrophil NADPH Oxidase
Authors: Nishida Satoshi , Yoshida Lucia S. , Shimoyama Takashi , Nunoi Hiroyuki , Kobayashi Toshihiro , Tsunawaki Shohko 
Published: December 2004

ABSTRACT

Fungal gliotoxin (GT) is a potent inhibitor of the O
2
−
-generating NADPH oxidase of neutrophils. We reported that GT-treated neutrophils fail to phosphorylate p47

phox

, a step essential for the enzyme activation, because GT prevents the colocalization of protein kinase C βII with p47

phox

on the membrane. However, it remains unanswered whether GT directly affects any of NADPH oxidase components. Here, we examine the effect of GT on the NADPH oxidase components in the cell-free activation assay. The O
2
−
-generating ability of membranes obtained from GT-treated neutrophils is 40.0 and 30.6% lower, respectively, than the untreated counterparts when assayed with two distinct electron acceptors, suggesting that flavocytochrome
b
558
is affected in cells by GT. In contrast, the corresponding cytosol remains competent for activation. Next, GT addition in vitro to the assay consisting of flavocytochrome
b
558
and cytosolic components (native cytosol or recombinant p67

phox

, p47

phox

, and Rac2) causes a striking inhibition (50% inhibitory concentration = 3.3 μM) when done prior to the stimulation with myristic acid. NADPH consumption is also prevented by GT, but the in vitro assembly of p67

phox

, p47

phox

, and Rac2 with flavocytochrome
b
558
is normal. Posterior addition of GT to the activated enzyme is ineffective. The separate treatment of membranes with GT also causes a marked loss of flavocytochrome
b
558
's ability to reconstitute O
2
−
generation, supporting the conclusion at the cellular level. The flavocytochrome
b
558
heme spectrum of the GT-treated membranes stays, however, unchanged, showing that hemes remain intact. These results suggest that GT directly harms site(s) crucial for electron transport in flavocytochrome
b
558
, which is accessible only before oxidase activation.
Association of a Major Protein Antigen of
Mycoplasma arthritidis
with Virulence
Authors: Tu A.-H. T. , Clapper B. , Schoeb T. R. , Elgavish A. , Zhang J. , Liu L. , Yu H. , Dybvig K. 
Published: December 2004

ABSTRACT

Mycoplasma arthritidis
causes acute polyarthritis in rats and chronic proliferative arthritis in mice.
M. arthritidis
-induced arthritis serves as a model for arthritis caused by infectious agents and as a model for examining the role of the superantigen MAM (
M. arthritidis
T-cell mitogen) in the development of autoimmunity.
M. arthritidis
strain 158-1 is a spontaneous mutant of strain 158 that has a drastic reduction in virulence. We show that the mutant is missing a major antigen of 47 kDa (P47) and has acquired a protein of 67 kDa (P67). P47 and P67 partitioned into the detergent phase by extraction with Triton X-114. Coomassie blue staining of sodium dodecyl sulfate-polyacrylamide gels show that P67 is produced in abundance. Analysis of gel-purified P67 by mass spectrometry led to its identification as a lipoprotein (the open reading frame [ORF] 619 gene product) predicted from the genome sequence of
M. arthritidis
. PCR analysis of genomic DNA from 158 and 158-1 indicates that P47 and P67 are encoded by the same ORF 619 gene and differ only in the number of repeats in a tandem repeat region. By two-dimensional polyacrylamide gel analysis, no protein differences were detectable between 158 and 158-1 other than P47 and P67. Collectively, the data suggest that the tandem repeat region of P47 and P67 influences disease outcome.
Invasiveness of Serotypes and Clones of
Streptococcus pneumoniae
among Children in Finland
Authors: Hanage William P. , Kaijalainen Tarja H. , Syrjänen Ritva K. , Auranen Kari , Leinonen Maija , Mäkelä P. Helena , Spratt Brian G. 
Published: December 2004

ABSTRACT

Streptococcus pneumoniae
(the pneumococcus) causes diseases from otitis media to life-threatening invasive infection. The species is extremely antigenically and clonally diverse. We wished to determine odds ratios (ORs) for serotypes and clones of
S. pneumoniae
that cause invasive disease in Finland. A total of 224 isolates of
S. pneumoniae
from cases of invasive disease in children <2 years of age in Finland between 1995 and 1999 were serotyped, and sequence types (STs) were determined by multilocus sequence typing. These STs were compared with a previously published carriage data set. STs from invasive disease were significantly less diverse than those from carriage (invasive disease, 0.038 ± 0.01; carriage, 0.019 ± 0.005). The ORs of serotypes 14, 18C, 19A, and 6B were significantly greater than 1, indicating association with invasive disease. The ORs of 6A and 11A were significantly less than 1. The difference between 6A and 6B is significant, which suggests that relatively subtle changes in the capsule may have a dramatic effect upon disease potential. We found that ST 156, the Spain
9V
-3 clone which mainly expressed serotype 14 in Finland, is strongly associated with invasive disease (OR, 10.1; 95% confidence interval, 1.3 to 79.5). Significant associations with invasive disease were also detected for STs 482, 191, 124, and 138, and associations with carriage were detected for STs 485 and 62. These results demonstrate the invasive phenotype of the serotype 14 variant of the Spain
9V
-3 clone and differences between members of the same serogroup in invasive disease potential.
Cytolethal Distending Toxin from Shiga Toxin-Producing
Escherichia coli
O157 Causes Irreversible G
2
/M Arrest, Inhibition of Proliferation, and Death of Human Endothelial Cells
Authors: Bielaszewska Martina , Sinha Bhanu , Kuczius Thorsten , Karch Helge 
Published: December 2004

ABSTRACT

Recently, cytolethal distending toxin V (CDT-V), a new member of the CDT family, was identified in Shiga toxin-producing
Escherichia coli
(STEC) O157 and particular non-O157 serotypes. Here we investigated the biological effects of CDT-V from STEC O157:H
−
(strain 493/89) on human endothelial cells, which are believed to be major pathogenetic targets in severe STEC-mediated diseases. CDT-V caused dose-dependent G
2
/M cell cycle arrest leading to distension, inhibition of proliferation, and death in primary human umbilical vein endothelial cells (HUVEC) and two endothelial cell lines, EA.hy 926 cells (HUVEC derived) and human brain microvascular endothelial cells (HBMEC). The cell cycle effects of CDT-V were cell type specific. In HUVEC and EA.hy 926 cells, CDT-V caused a slowly developing but persistent G
2
/M block which resulted in delayed nonapoptotic cell death. In contrast, in HBMEC, CDT-V induced a rapidly evolving but transient G
2
/M block which was followed by progressive, mostly apoptotic cell death. In both HBMEC and EA.hy 926 cells, G
2
/M arrest was preceded by the early accumulation of a phosphorylated inactive form of cdc2 kinase. Significant G
2
/M arrest and inhibition of proliferation in both HUVEC and each of the endothelial cell lines were induced by 2 to 15 min of exposure to CDT-V, indicating that the effects of the toxin are irreversible. CDT-V-treated HBMEC and EA.hy 926 cells displayed fragmented nuclei and expressed phosphorylated histone protein H2AX, indicative of DNA damage followed by a DNA repair response. Our data demonstrate that CDT-V causes irreversible damage to human endothelial cells and thus may contribute to the pathogenesis of STEC-mediated diseases.
A Mutation in the
sap
Operon Attenuates Survival of Nontypeable
Haemophilus influenzae
in a Chinchilla Model of Otitis Media
Authors: Mason Kevin M. , Munson Robert S. , Bakaletz Lauren O. 
Published: December 2004

ABSTRACT

Bacteria have evolved strategies to resist killing by antimicrobial peptides (APs), important effectors of innate immunity. The
sap
(sensitivity to antimicrobial peptides) operon confers resistance to AP-mediated killing of
Salmonella
. We have recently shown that
sapA
gene expression is upregulated in the middle ear in a chinchilla model of nontypeable
Haemophilus influenzae
(NTHI)-induced otitis media. Based on these findings, we constructed an NTHI strain containing a Lux reporter plasmid driven by the
sapA
promoter and demonstrated early yet transient expression of the
sap
operon within sites of the chinchilla upper airway upon infection. We hypothesized that the
sap
operon products mediate NTHI resistance to APs. In order to test this hypothesis, we constructed a nonpolar mutation in the
sapA
gene of NTHI strain 86-028NP, a low-passage-number clinical isolate. The
sapA
mutant was approximately eightfold more sensitive than the parent strain to killing by recombinant chinchilla β-defensin 1. We then assessed the ability of this mutant to both colonize and cause otitis media in chinchillas. The
sapA
mutant was significantly attenuated compared to the parent strain in its ability to survive in both the nasopharynx and the middle ear of the chinchilla. In addition, the mutant was impaired in its ability to compete with the parent strain in a dual-strain challenge model of infection. Our results indicate that the products of the
sap
operon are important for resisting the activity of APs and may regulate, in part, the balance between normal carriage and disease caused by NTHI.
Truncated Internalin A and Asymptomatic
Listeria monocytogenes
Carriage: In Vivo Investigation by Allelic Exchange
Authors: Olier Maïwenn , Garmyn Dominique , Rousseaux Sandrine , Lemaître Jean-Paul , Piveteau Pascal , Guzzo Jean 
Published: December 2004

ABSTRACT

Allelic exchange of the region coding for the C terminus of InlA between one epidemic (with an 80-kDa InlA) and one asymptomatic (with a 47-kDa InlA) carriage
Listeria monocytogenes
strain confirmed the need for this region for internalin entry in vitro. Interestingly, restoration of internalin A functionality did not result in full virulence in chicken embryo assays.
Homocysteine Is Lower in the Third Trimester of Pregnancy in Women with Enhanced Folate Status from Continued Folic Acid Supplementation
Authors: Holmes Valerie A , Wallace Julie MW , Alexander H Denis , Gilmore William S , Bradbury Ian , Ward Mary , Scott John M , McFaul Peter , McNulty Helene 
Published: December 2004

Abstract
Background: In many countries, current recommendations are that women take a daily 400-μg folic acid supplement from before conception until the end of the 12th week of gestation for the prevention of neural tube defects. Low folate status is associated with an increased concentration of plasma total homocysteine (tHcy), a risk factor associated with pregnancy complications such as preeclampsia.
Methods: In a longitudinal study, we determined tHcy and corresponding folate status in 101 pregnant women at 12, 20, and 35 weeks of gestation, in 35 nonpregnant controls sampled concurrently, and in a subgroup (n = 21 pregnant women and 19 nonpregnant controls) at 3 days postpartum.
Results: Plasma tHcy was significantly lower throughout pregnancy compared with nonpregnant controls, with values lowest in the second trimester before increasing toward nonpregnant values in the third trimester. Importantly, mean tHcy concentrations were lower in pregnant women taking folic acid supplements than in those not, an effect that reached significance in the third trimester (5.45 vs 7.40 μmol/L; P &lt;0.05). During the third trimester, tHcy concentrations were significantly higher in pregnant women with a history of miscarriage than in women with no previous history (8.15 vs 6.38 μmol/L; P &lt;0.01).
Conclusions: This is the first longitudinal study to show that homocysteine concentrations increase in late pregnancy toward nonpregnant values; an increase that can be limited by enhancing folate status through continued folic acid supplementation. These results indicate a potential role for continued folic acid supplementation in reducing pregnancy complications associated with hyperhomocysteinemia.
Das antarktische Ozonloch — anthropogene Ursachen??
Authors: Zabel Friedhelm 
Published: December 2004

AbstractSeit etwa 15 Jahren werden die globalen Auswirkungen diskutiert, die vom Menschen verursachte (anthropogene) Veränderungen in der Zusammensetzung der Erdatmosphäre hervorrufen können. Vor allem die mögliche Zerstörung der stratosphärischen Ozonschicht, die das organische Leben an der Erdoberfläche vor der harten UV‐Strahlung der Sonne schützt, durch die anthropogenen Chlorfluorkohlenwasserstoffe hat große Aufmerksamkeit erregt. Der Verbrauch dieser und anderer reaktionsträger Chlorkohlenwasserstoffe, die vom Erdboden aus bis in die Stratosphäre vordringen können, steigt insgesamt immer noch kontinuierlich an ‐ dennoch konnte ein globaler Trend in der atmosphärischen Ozonmenge bisher noch nicht nachgewiesen werden. Vor zwei Jahren wurde nun entdeckt, daß über dem Südpol während des antarktischen Frühlings ein großer Teil des Ozons verschwindet. Dieses antarktische „Ozonloch”︁ wird seit 1979 Jahr für Jahr größer. Haben wir es hier mit den ersten Anzeichen ver vorausgesagten globalen Abnahme des atmosphärischen Ozons zu tun? Im vorliegenden Artikel werden die Meßergebnisse aus der Antarktis vorgestellt und die bisherigen Hypothesen zur Erklärung des Ozonlochs diskutiert.
Das Portrait: Agnes Pockels (1862‐1935) und die Oberflächenchemie
Authors: Beisswanger Gabriele 
Published: December 2004

Abstract„Agnes Pockels? Kenne ich nicht. Ist nach ihr nicht die Pockelsstraße benannt, die Straße, an der die Universität liegt?”︁ Viel wissen die Studenten und Studentinnen der Technischen Universität Braunschweig heute nicht mehr über Agnes Pockels. Das Wenige ist zudem noch falsch. Denn Namensgeber der Pockelsstraße ist ein entfernter Verwandter von ihr, der Oberbürgermeister Wilhelm Pockels (1832‐1904).
Von der Idee zum Herstellungsverfahren. Der Produktentwickler in der Kosmetikindustrie
Authors: Rudolph Martin 
Published: December 2004

AbstractFür den Einstieg als Naturwissenschaftler in die Produktentwicklung der kosmetischen Industrie gibt es keinen vorgezeichneten Weg, und daher kommen in der Produktentwicklung eines großen Industrieunternehmens Naturwissenschaftler unterschiedlichster Fachrichtungen zum Einsatz: Chemiker, Pharmazeuten, Lebensmitteltechniker, Physiker und Mathematiker. Nicht alle beginnen direkt nach dem Studium im Kosmetikbereich.
Das gelbe Element und seine erstaunliche Vielseitigkeit
Authors: Steudel Ralf 
Published: December 2004

AbstractElemental sulfur ‐ both in the solid, liquid, and gaseous state ‐ shows highly unusual physical and chemical properties not matched by any other element. The reason for this unique behavior is the formation of molecules of different size ‐from S2 to S6, S7, and S8 up to macromolecules („S,”︁) ‐ every size is possible. Which mixture is obtained depends on the temperature and other reaction conditions. These findings are important for the understanding of elemental sulfur produced industrially in huge quantities, certain astonishing observations made with bacteria that oxidize sulfur, the Stretford process for sulfur production, and the sulfur covering Ios surface.
Nachweisreaktionen mit Indikatorstäbchen
Authors: Roesky Herbert W. , Kusche Christian 
Published: December 2004

AbstractDie Verwendung von Indikatorstäbchen zur Durchführung von Nachweisreaktionen bie‐ tet viele Vorteile. Sie ist eine gute Alternative zu den klassischen Methoden, da nur ein Bruchteil der üblicherweise verwendeten Chemikalien benötigt wird. Die Nachweise können problem‐ und gefahrlos durchgeführt werden und sind daher auch für Anfänger sehr gut geeignet. Zudem können die Indikatorstäbchen vorab präpariert werden, was den Zeitaufwand für die Durchführung einer Reaktion verringert. Dies ist sowohl für den Experimentator vor einem Auditorium als auch für Schülerexperimente von großer Bedeutung, da im Vergleich zu den klassischen Nachweismethoden im gleichen Zeitintervall sehr vie1 mehr Reaktionen durchgefuhrt werden können. Aufgrund der geringen Chemikalienmengen wird die Umwelt weniger belastet, und die Kosten für den Unterricht sinken. Darüber hinaus werden die gesetzlichen Auflagen durch die Gefahrstoffverordnung bei dieser Methode eingehalten. Dadurch kann Chemie en miniature mit dam beitragen, einen attraktiven Chemieunterricht an Schulen zu ermöglichen.
100. Geburtstag von Erich Hückel
Authors: Frenking Gernot 
Published: December 2004

AbstractThe theoretical physicist Erich Hückel, who would have become 100 years old on August 9, 1996, was one of the pioneers of quantum chemistry. The theory of conductivity of strong electrolytes (“Debye‐Hückel theory”) and particularly his fundamental work about the electronic structure of benzene, which has unbroken actuality for modern chemistry, are the early highlights of his peculiar scientific career. His life was strongly characterized by the late recognition of his achievements in theoretical chemistry, which can partly be explained by the dominance of experimental chemistry in the history of the science, and by the long uncertainty of his academic position.