bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the HspR-Mediated Stress Response inHelicobacter pylori
Authors: Spohn Gunther , Delany Isabel , Rappuoli Rino , Scarlato Vincenzo 
Published: July 2002

ABSTRACTThe major heat shock genes ofHelicobacter pyloriare regulated by the HspR repressor. In the present study we characterize the transcriptional response of the three known HspR-dependent promoters Pcbp, Pgro, and Phrcto different environmental stresses. A temperature shift from 37 to 42°C causes a typical heat shock response at all three promoters characterized by an immediate and strong induction phase of transcription and a subsequent adaptation phase, which is specific for each promoter and whose onset is determined partially by the half-lives of the respective mRNAs. Exposure to high osmolarity induces a similar response on the Pgroand Pcbppromoters while no such response is detectable at the Phrcpromoter. Puromycin treatment induces transcription from all three HspR-dependent promoters, indicating that different environmental stresses are intracellularly sensed by the regulatory machinery through the accumulation of nonnative proteins. The implications of these data for the regulatory network controlling the heat shock response inH. pyloriare discussed.
Up-Regulation of theYersinia enterocolitica yopRegulon by Deletion of the Flagellum Master OperonflhDC
Authors: Bleves Sophie , Marenne Marie-Noëlle , Detry Gautier , Cornelis Guy R. 
Published: July 2002

ABSTRACTThe Yop virulon enables extracellularly locatedYersinia, in close contact with a eukaryotic target cell, to inject bacterial toxic proteins directly into the cytosol of this cell. Several Ysc proteins, forming the Yop secretion apparatus, display homology with proteins of the flagellar basal body. To determine whether this relationship could extend to the regulatory pathways, we analyzed the influence offlhDC, the master regulatory operon of the flagellum, on theyopregulon. In anflhDCmutant, theyopregulon was up-regulated. The transcription ofvirFand the steady-state level of the transcriptional activator VirF were enhanced.yoptranscription was increased at 37°C and could also be detected at a low temperature. Yop secretion was increased at 37°C and occurred even at a low temperature. The Ysc secretion machinery was thus functional at room temperature in the absence of flagella, implying that in wild-type bacteria, FlhD and/or FlhC, or the product of a gene downstream offlhDC, represses theyopregulon. In agreement with this notion, increased expression offlhDCin wild-type bacteria resulted in the oversecretion of flagellins at room temperature and in decreased Yop secretion at 37°C.
Aerobic-Type Ribonucleotide Reductase in the Anaerobe
Bacteroides fragilis
Authors: Smalley Darren , Rocha Edson R. , Smith C. Jeffrey 
Published: July 2002

ABSTRACT

Bacteroides fragilis
, a component of the normal intestinal flora, is an obligate anaerobe capable of long-term survival in the presence of air. Survival is attributed to an elaborate oxidative stress response that controls the induction of more than 28 peptides, but there is limited knowledge concerning the identities of these peptides. In this report, RNA fingerprinting by arbitrarily primed PCR identified five new genes whose expression increased following exposure to O
2
. Nucleotide sequence analysis of the cloned genes indicated that they encoded an outer membrane protein, an aspartate decarboxylase, an efflux pump, heat shock protein HtpG, and an NrdA ortholog constituting the large subunit of a class Ia ribonucleotide reductase (RRase). Attention was focused on the
nrdA
gene since class I RRases are obligate aerobic enzymes catalyzing the reduction of ribonucleoside 5′-diphosphates by a mechanism that requires molecular oxygen for activity. Sequence analysis of the
nrd
locus showed that two genes,
nrdA
and
nrdB
, are located in the same orientation in a 4.5-kb region. Northern hybridization and primer extension experiments confirmed induction of the genes by O
2
and suggested they are an operon. The
B. fragilis nrdA
and
nrdB
genes were overexpressed in
Escherichia coli
, and CDP reductase assays confirmed that they encoded an active enzyme. The enzyme activity was inhibited by hydroxyurea, and ATP was shown to be a positive effector of CDP reductase activity, while dATP was an inhibitor, indicating that the enzyme was a class Ia RRase. A
nrdA
mutant was viable under anaerobic conditions but had decreased survival following exposure to O
2
, and it could not rapidly resume growth after O
2
treatment. The results presented indicate that during aerobic conditions
B. fragilis
NrdAB may have a role in maintaining deoxyribonucleotide pools for DNA repair and growth recovery.
A ToxR Homolog from
Vibrio anguillarum
Serotype O1 Regulates Its Own Production, Bile Resistance, and Biofilm Formation
Authors: Wang Su-Yan , Lauritz Johan , Jass Jana , Milton Debra L. 
Published: July 2002

ABSTRACT

ToxR, a transmembrane regulatory protein, has been shown to respond to environmental stimuli. To better understand how the aquatic bacterium
Vibrio anguillarum
, a fish pathogen, responds to environmental signals that may be necessary for survival in the aquatic and fish environment,
toxR
and
toxS
from
V. anguillarum
serotype O1 were cloned. The deduced protein sequences were 59 and 67% identical to the
Vibrio cholerae
ToxR and ToxS proteins, respectively. Deletion mutations were made in each gene and functional analyses were done. Virulence analyses using a rainbow trout model showed that only the
toxR
mutant was slightly decreased in virulence, indicating that ToxR is not a major regulator of virulence factors. The
toxR
mutant but not the
toxS
mutant was 20% less motile than the wild type. Like many regulatory proteins, ToxR was shown to negatively regulate its own expression. Outer membrane protein (OMP) preparations from both mutants indicated that ToxR and ToxS positively regulate a 38-kDa OMP. The 38-kDa OMP was shown to be a major OMP, which cross-reacted with an antiserum to OmpU, an outer membrane porin from
V. cholerae
, and which has an amino terminus 75% identical to that of OmpU. ToxR and to a lesser extent ToxS enhanced resistance to bile. Bile in the growth medium increased expression of the 38-kDa OMP but did not affect expression of ToxR. Interestingly, a
toxR
mutant forms a better biofilm on a glass surface than the wild type, suggesting a new role for ToxR in the response to environmental stimuli.
AniA Regulates Reserve Polymer Accumulation and Global Protein Expression in
Rhizobium etli
Authors: Encarnación Sergio , del Carmen Vargas María , Dunn Michael F. , Dávalos Araceli , Mendoza Guillermo , Mora Yolanda , Mora Jaime 
Published: July 2002

ABSTRACT

Previously, it was reported that the oxidative capacity and ability to grow on carbon sources such as pyruvate and glucose were severely diminished in the
Rhizobium etli phaC
::ΩSm
r
/Sp
r
mutant CAR1, which is unable to synthesize poly-β-hydroxybutyric acid (PHB) (M. A. Cevallos, S. Encarnación, A. Leija, Y. Mora, and J. Mora, J. Bacteriol. 178:1646-1654, 1996). By random Tn
5
mutagenesis of the
phaC
strain, we isolated the mutants VEM57 and VEM58, both of which contained single Tn
5
insertions and had recovered the ability to grow on pyruvate or glucose. Nucleotide sequencing of the region surrounding the Tn
5
insertions showed that they had interrupted an open reading frame designated
aniA
based on its high deduced amino acid sequence identity to the
aniA
gene product of
Sinorhizobium meliloti
.
R. etli aniA
was located adjacent to and divergently transcribed from genes encoding the PHB biosynthetic enzymes β-ketothiolase (PhaA) and acetoacetyl coenzyme A reductase (PhaB). An
aniA
::Tn
5
mutant (VEM5854) was constructed and found to synthesize only 40% of the wild type level of PHB. Both VEM58 and VEM5854 produced significantly more extracellular polysaccharide than the wild type. Organic acid excretion and levels of intracellular reduced nucleotides were lowered to wild-type levels in VEM58 and VEM5854, in contrast to those of strain CAR1, which were significantly elevated. Proteome analysis of VEM58 showed a drastic alteration of protein expression, including the absence of a protein identified as PhaB. We propose that the
aniA
gene product plays an important role in directing carbon flow in
R. etli.
Comparative Prevalences of
Brachyspira aalborgi
and
Brachyspira
(
Serpulina
)
pilosicoli
as Etiologic Agents of Histologically Identified Intestinal Spirochetosis in Australia
Authors: Mikosza Andrew S. J. , La Tom , de Boer W. Bastiaan , Hampson David J. 
Published: July 2002

ABSTRACT

DNA from gastrointestinal biopsy specimens from 28 Australian patients with histologic evidence of intestinal spirochetosis (IS) was subjected to PCRs to amplify segments of the 16S rRNA and NADH oxidase genes of
Brachyspira aalborgi
and
Brachyspira (Serpulina) pilosicoli. B. aalborgi
was identified in specimens from 24 (85.7%) patients and
B. pilosicoli
in those from 4 (14.3%) patients (2 of whom were also positive for
B. aalborgi
). For two patients, no product was amplified. This study demonstrates that
B. aalborgi
is much more commonly involved in histologically identified IS in Australian patients than is
B. pilosicoli
. This is the first report of amplification of
B. pilosicoli
DNA from humans with IS.
Validity of Cultures of Fluid Collected through Drainage Catheters versus Those Obtained by Direct Aspiration
Authors: Everts Richard J. , Heneghan Joan P. , Adholla Paul O. , Reller L. Barth 
Published: July 2002

ABSTRACT
To examine the validity of cultures of fluid collected through drainage catheters, we reviewed retrospectively fluid specimens that had been collected through catheters in place for at least 2 days. These specimens were taken from patients at a large tertiary-care hospital. A total of 974 specimens representing 620 patient episodes were received. For 554 (89%) episodes there was no reliable imaging evidence for localized infection, rendering the results uninterpretable. The remaining 66 (11%) episodes were followed within 2 days by radiologically guided or open aspiration of one or more fluid collections (predominantly in the abdomen or pelvis) near the drainage catheter, allowing comparison of culture results of 59 direct aspirates with those of prior catheter drainage. In 33 (56%) of these 59 cases, matched culture results were equivalent for therapeutic decision making. However, relying on results of catheter drainage cultures would have led to inadequate antimicrobial therapy in 13 (22%) cases, to excessive therapy in 11 (19%) cases, and to both in 2 cases (3%). We conclude that radiological imaging should be standard practice in the assessment of deep-tissue infections in patients with drainage catheters, and that direct aspiration of potentially infected fluid collections is the most reliable method of obtaining specimens for culture that should be used to guide therapy.
Sequence Polymorphism in the
rrs
Gene of
Mycobacterium tuberculosis
Is Deeply Rooted within an Evolutionary Clade and Is Not Associated with Streptomycin Resistance
Authors: Victor Thomas C. , van Rie Annelies , Jordaan Annemie M. , Richardson Madalene , van der Spuy Gian D. , Beyers Nulda , van Helden Paul D. , Warren Robin 
Published: July 2002

ABSTRACT

A mutation (C-to-T transition) at position 491 of the
rrs
gene was identified in a
Mycobacterium tuberculosis
strain family (
n
= 208 isolates) that was predominant in a suburb of Cape Town, South Africa. This nucleotide change is not involved in streptomycin resistance, and we suggest caution in assuming that all mutations in genes targeted by antituberculosis drugs confer drug resistance.
Prevalence and Antifungal Susceptibility of 442
Candida
Isolates from Blood and Other Normally Sterile Sites: Results of a 2-Year (1996 to 1998) Multicenter Surveillance Study in Quebec, Canada
Authors: St-Germain G. , Laverdière M. , Pelletier R. , Bourgault A.-M. , Libman M. , Lemieux C. , Noël G. 
Published: July 2002

ABSTRACT

During a 2-year surveillance program (1996 to 1998) in Quebec, Canada, 442 strains of
Candida
species were isolated from 415 patients in 51 hospitals. The distribution of species was as follows:
Candida albicans,
54%;
C. glabrata,
15%;
C. parapsilosis,
12%;
C. tropicalis,
9%;
C. lusitaniae,
3%;
C. krusei,
3%; and
Candida
spp., 3%. These data, compared to those of a 1985 survey, indicate variations in species distribution, with the proportions of
C. glabrata
and
C. parapsilosis
increasing by 9 and 4%, respectively, and those of
C. albicans
and
C. tropicalis
decreasing by 10 and 7%, respectively. However, these differences are statistically significant for
C. glabrata
and
C. tropicalis
only. MICs of amphotericin B were ≥4 μg/ml for 3% of isolates, all of which were non-
C. albicans
species. Three percent of
C. albicans
isolates were resistant to flucytosine (≥32 μg/ml). Resistance to itraconazole (≥1 μg/ml) and fluconazole (≥64 μg/ml) was observed, respectively, in 1 and 1% of
C. albicans
, 14 and 9% of
C. glabrata
, 5 and 0% of
C. tropicalis,
and 0% of
C. parapsilosis
and
C. lusitaniae
isolates. Clinical data were obtained for 343 patients. The overall crude mortality rate was 38%, reflecting the multiple serious underlying illnesses found in these patients. Bloodstream infections were documented for 249 patients (73%). Overall, systemic triazoles had been administered to 10% of patients before the onset of candidiasis. The frequency of isolation of non-
C. albicans
species was significantly higher in this group of patients. Overall, only two
C. albicans
isolates were found to be resistant to fluconazole. These were obtained from an AIDS patient and a leukemia patient, both of whom had a history of previous exposure to fluconazole. At present, it appears that resistance to fluconazole in Quebec is rare and is restricted to patients with prior prolonged azole treatment.
Serologic Detection of
Actinobacillus pleuropneumoniae
in Swine by Capsular Polysaccharide-Biotin-Streptavidin Enzyme-Linked Immunosorbent Assay
Authors: Inzana Thomas J. , Fenwick Brad 
Published: July 2002

ABSTRACT

Serologic detection of
Actinobacillus pleuropneumoniae
infections in swine have been problematic due to antigenic cross-reactivity of Apx toxins, lipopolysaccharide, and outer membrane proteins between
A. pleuropneumoniae
serotypes and other bacterial species. To maximize serologic specificity and sensitivity, we developed an assay that uses highly purified
A. pleuropneumoniae
capsular polysaccharide (CP) conjugated to biotin, which is then bound to streptavidin-coated enzyme-linked immunosorbent assay (CP-BS-ELISA) plates. This assay was used to test a panel of 240 serum samples from pigs prior to challenge, after challenge with bacterial species other than
A. pleuropneumoniae
, or after challenge with
A. pleuropneumoniae
serotype 1, 5, or 7. Overall assay results for the individual sera tested were reproducible on the same day and on separate days. The sensitivity of the assay was 100% by ELISAs with biotin-CPs of serotypes 1 and 7 and 87.5% by ELISAs with biotin-CP of serotype 5. Specificity was 100% by ELISAs with biotin-CPs of serotypes 1 and 5 and 94.5% by ELISAs with biotin-CP of serotype 7. The biotin-CPs of at least three
A. pleuropneumoniae
serotypes could be combined for use in a screening assay to detect antibodies to CPs from strains of different serotypes. In conclusion, the CP-BS-ELISA proved to be a serotype-specific and species-specific assay with high sensitivity for the identification of pigs exposed to
A. pleuropneumoniae
.
Weissella confusa
(Basonym:
Lactobacillus confusus
) Bacteremia: a Case Report
Authors: Olano Arrel , Chua Jimmy , Schroeder Suzanne , Minari Afaf , La Salvia Margaret , Hall Gerri 
Published: July 2002

ABSTRACT

Infection with
Lactobacillus
is rare, and only a handful of species have been identified as being clinically significant:
Lactobacillus casei, Lactobacillus rhamnosus
, and
Lactobacillus leichmannii
. The literature contains one case report of bacteremia caused by
Weissella confusa
(basonym:
Lactobacillus confusus
), but the clinical significance of the infection was unclear. We describe a case of
W. confusa
bacteremia in a 46-year-old man with a history of abdominal aortic dissection and repair. This procedure was complicated by gut ischemia, which necessitated massive small bowel resection. He subsequently developed short-bowel syndrome, which required him to have total parenteral nutrition. He later developed an
Enterococcus faecalis
aortic valve endocarditis that required a coronary artery bypass graft and aortic root replacement with homograft and 6 weeks of intravenous ampicillin and gentamicin. Three months prior to his most recent admission, he was diagnosed with
Klebsiella pneumoniae
bacteremia and candidemia. At the present admission, he had fever (
T
max
, 39.5°C) and chills of 2 days' duration and was admitted to the intensive care unit because of hemodynamic instability. Blood cultures grew
K. pneumoniae
and
W. confusa
in four of four blood culture bottles (both aerobe and anaerobe bottles). Imaging studies failed to find any foci of infection. A transesophageal echocardiogram revealed no vegetations. A culture of the patient's Hickman catheter tip was negative. The patient was treated with piperacillin-tazobactam and gentamicin. His condition improved, and he was discharged home, where he completed 4 weeks of piperacillin-tazobactam therapy. Lactobacillemia seldom results in mortality; however, it may be a marker of a serious underlying disease. It is usually seen in patients who have a complex medical history or in patients who receive multiple antibiotics.
Lactobacillus
spp. are generally associated with polymicrobial infections, and when isolated from the blood, they need to be considered possible pathogens. The presence of a vancomycin-resistant, gram-positive coccobacilli on a blood culture should alert clinicians to the possibility of bacteremia caused by
W. confusa
or other small gram-positive rods.
Evaluation of Biosite Triage
Clostridium difficile
Panel for Rapid Detection of
Clostridium difficile
in Stool Samples
Authors: Landry Marie L. , Topal Jeffrey , Ferguson David , Giudetti Darlene , Tang Yajarayma 
Published: July 2002

ABSTRACT

One hundred two stool samples were tested by both the rapid Triage
Clostridium difficile
Panel (Triage Panel) and the cytotoxin cell culture assay. Five samples positive by both the
C. difficile
toxin A (Tox A) and common antigen components of the Triage Panel had cytotoxin titers of ≥10,000. Twenty-three samples were Triage Panel Tox A negative but common antigen positive. Ten of these had cytotoxin titers of 10 to 1,000, but 13 were cytotoxin negative. Bacterial isolates obtained from 8 of these 13 specimens were analyzed for Tox A and B genes by PCR, and only two contained toxigenic bacteria. Thus, the majority of samples positive only for
C. difficile
common antigen contained nontoxigenic bacteria. A Triage Panel Tox A-positive result indicated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 33.3, 100, 100, and 88.2%, respectively. A Triage Panel common antigen-positive result indicated a sensitivity, specificity, PPV, and NPV of 100, 82.7, 53.6, and 100%, respectively. The high NPV of the Triage Panel common antigen, together with rapid reporting of results, should prove useful in avoiding unnecessary use of contact precautions and antibiotic treatment for
C. difficile
-negative patients. However, with Triage Panel common antigen-positive patients, a sensitive cytotoxin assay should be used to distinguish true cytotoxin-positive patients from
C. difficile
carriers.
Mycobacterium triplex
Infection in a Liver Transplant Patient
Authors: Hoff E. , Sholtis M. , Procop G. , Sabella C. , Goldfarb J. , Wyllie R. , Cunningham R. , Stockman L. , Hall G. 
Published: July 2002

ABSTRACT

Mycobacterium triplex
was first named in 1996 as an acid-fast bacillus with features that most resemble
Mycobacterium simiae
and
Mycobacterium avium-intracellulare
complex but which possesses a distinct mycolic acid pattern as well as a distinctive 16S rRNA hypervariable region. It has been isolated from lymph node, sputum, and cerebrospinal fluid specimens, but to date only rare clinical cases of this organism have been reported in the literature. The following is a case report of
M. triplex
that was isolated from the pericardial and peritoneal fluid of a 13-year-old female liver transplant patient.
Molecular Cloning and Sequencing of the Circumsporozoite Protein Gene fromPlasmodium falciparumStrain FCC-1/HN and Expression of the Gene in Mycobacteria
Authors: Zheng Chunfu , Xie Peimei , Chen Yatang 
Published: July 2002

ABSTRACTMycobacterium bovisbacillus Calmette-Guérin (BCG) has been used as a live bacterial vaccine to immunize more than 2 billion people against tuberculosis. In an attempt to use this vaccine strain as a vehicle for protective antigens, thePlasmodium falciparumgene from strain FCC-1/HN encoding circumsporozoite protein (CSP) was amplified from theP. falciparumgenome, sequenced, and expressed inM. bovisBCG under the control of an expression cassette carrying the promoter of heat shock protein 70 (HSP70) fromMycobacterium tuberculosis. The recombinant shuttle plasmid pBCG/CSP was introduced into mycobacteria by electroporation, and the recombinant mycobacteria harboring pBCG/CSP could be induced by heating to express CSP; the molecular mass of recombinant CSP was about 42 kDa. This report of expression of the almost-full-lengthP. falciparumCSP gene in BCG provides scientific evidence for the application of the HSP70 promoter in expressing a foreign gene in BCG and in development of BCG as a multivalent vectoral vaccine for malaria.
Outbreak of Infection with Extended-Spectrum β-Lactamase-Producing
Klebsiella pneumoniae
in a Mexican Hospital
Authors: Silva Jesus , Gatica Rodolfo , Aguilar Cecilia , Becerra Zita , Garza-Ramos Ulises , Velázquez Manuel , Miranda Guadalupe , Leaños Blanca , Solórzano Fortino , Echániz Gabriela 
Published: July 2002

ABSTRACT

Thirty-one strains of
Klebsiella pneumoniae
(including 10 duplicates) from 21 septicemic pediatric patients (age, <2 months) were studied during a 4-month period (June to October 1996) in which the fatality rate was 62% (13 of 21). These isolates identified by the API 20E system yielded the same biotype. Pulsed-field gel electrophoresis experiments revealed the same clone in 31 strains. The isolates were multidrug-resistant but were still susceptible to ciprofloxacin, imipenem, and cefoxitin. A 135-kb plasmid was harbored in all of the isolates. No transconjugants were obtained that were resistant to ampicillin, cefotaxime, tetracycline, or gentamicin. Isoelectric focusing for β-lactamases was performed on all strains, and three bands with pIs of 5.4, 7.6, and 8.2 were obtained. Of these, the pI 8.2 β-lactamase had an extended-spectrum β-lactamase phenotype. PCR amplification of both TEM- and SHV-type genes was obtained. The sequence analysis of the SHV PCR product indicated a mutation corresponding to the SHV-5 β-lactamase.