bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of aLegionella pneumophila relAInsertion Mutant and Roles of RelA and RpoS in Virulence Gene Expression
Authors: Zusman Tal , Gal-Mor Ohad , Segal Gil 
Published: July 2002

ABSTRACTTo investigate the involvement of RelA in the regulation ofLegionella pneumophilavirulence, a deletion substitution was constructed in therelAgene. TherelAknockout resulted in an undetectable level of ppGpp in the cells during the stationary phase, but the original level was restored when therelAgene product was supplied on a plasmid. The effect of therelAmutation was examined with two systems that are known to be expressed during the stationary phase inL. pneumophila. Pigment production was found to be dependent on therelAgene product, and only one-half as much pigment was produced by therelAmutant as by the wild-type strain. Flagellum gene expression was also found to be dependent on therelAgene product, as determined with aflaA::lacZfusion. However, therelAgene product was found to be dispensable for intracellular growth both in HL-60-derived human macrophages and in the protozoan hostAcanthamoeba castellanii. To determine the involvement of therelAgene product in expression ofL. pneumophilagenes required for intracellular growth (icm/dotgenes), nineicm::lacZfusions were constructed, and expression of these fusions in the wild-type strain was compared with their expression inrelAmutant strains. Expression of only one of theicm::lacZfusions was moderately reduced in therelAmutant strain. Expression of the nineicm::lacZfusions was also examined in a strain containing an insertion in the gene that codes for the stationary-phase sigma factor RpoS, and similar results were obtained. We concluded that RelA is dispensable for intracellular growth ofL. pneumophilain the two hosts examined and that both RelA and RpoS play minor roles inL. pneumophila icm/dotgene expression.
Redundancy in Periplasmic Binding Protein-Dependent Transport Systems for Trehalose, Sucrose, and Maltose in
Sinorhizobium meliloti
Authors: Jensen John Beck , Peters N. Kent , Bhuvaneswari T. V. 
Published: July 2002

ABSTRACT

We have identified a cluster of six genes involved in trehalose transport and utilization (
thu
) in
Sinorhizobium meliloti
. Four of these genes,
thuE
, -
F
, -
G
, and -
K
, were found to encode components of a binding protein-dependent trehalose/maltose/sucrose ABC transporter. Their deduced gene products comprise a trehalose/maltose-binding protein (ThuE), two integral membrane proteins (ThuF and ThuG), and an ATP-binding protein (ThuK). In addition, a putative regulatory protein (ThuR) was found divergently transcribed from the
thuEFGK
operon. When the
thuE
locus was inactivated by gene replacement, the resulting
S. meliloti
strain was impaired in its ability to grow on trehalose, and a significant retardation in growth was seen on maltose as well. The wild type and the
thuE
mutant were indistinguishable for growth on glucose and sucrose. This suggested a possible overlap in function of the
thuEFGK
operon with the
aglEFGAK
operon, which was identified as a binding protein-dependent ATP-binding transport system for sucrose, maltose, and trehalose. The

K
m

s for trehalose transport were 8 ± 1 nM and 55 ± 5 nM in the uninduced and induced cultures, respectively. Transport and growth experiments using mutants impaired in either or both of these transport systems show that these systems form the major transport systems for trehalose, maltose, and sucrose. By using a
thuE
′
-lacZ
fusion, we show that
thuE
is induced only by trehalose and not by cellobiose, glucose, maltopentaose, maltose, mannitol, or sucrose, suggesting that the
thuEFGK
system is primarily targeted toward trehalose. The
aglEFGAK
operon, on the other hand, is induced primarily by sucrose and to a lesser extent by trehalose. Tests for root colonization, nodulation, and nitrogen fixation suggest that uptake of disaccharides can be critical for colonization of alfalfa roots but is not important for nodulation and nitrogen fixation per se.
Methylation of Inorganic and Organic Selenium by the Bacterial Thiopurine Methyltransferase
Authors: Ranjard Lionel , Prigent-Combaret Claire , Nazaret Sylvie , Cournoyer Benoit 
Published: July 2002

ABSTRACTEscherichia colicells expressing thetpmgene encoding the bacterial thiopurine methyltransferase (bTPMT) are shown to methylate selenite and (methyl)selenocysteine into dimethylselenide (DMSe) and dimethyldiselenide (DMDSe).E. colicells expressingtpmfrom a gene library cosmid clone (harboring aPseudomonas syringaeinsert of about 20 kb) also methylated selenate into DMSe and DMDSe. bTPMT is the first methyltransferase shown to be involved in the methylation of these selenium derivatives.
The Highly Conserved TldD and TldE Proteins of
Escherichia coli
Are Involved in Microcin B17 Processing and in CcdA Degradation
Authors: Allali Noureddine , Afif Hassan , Couturier Martine , Van Melderen Laurence 
Published: July 2002

ABSTRACT

Microcin B17 (MccB17) is a peptide antibiotic produced by
Escherichia coli
strains carrying the pMccB17 plasmid. MccB17 is synthesized as a precursor containing an amino-terminal leader peptide that is cleaved during maturation. Maturation requires the product of the chromosomal
tldE
(
pmbA
) gene. Mature microcin is exported across the cytoplasmic membrane by a dedicated ABC transporter. In sensitive cells, MccB17 targets the essential topoisomerase II DNA gyrase. Independently,
tldE
as well as
tldD
mutants were isolated as being resistant to CcdB, another natural poison of gyrase encoded by the
ccd
poison-antidote system of plasmid F. This led to the idea that TldD and TldE could regulate gyrase function. We present in vivo evidence supporting the hypothesis that TldD and TldE have proteolytic activity. We show that in bacterial mutants devoid of either TldD or TldE activity, the MccB17 precursor accumulates and is not exported. Similarly, in the
ccd
system, we found that TldD and TldE are involved in CcdA and CcdA41 antidote degradation rather than being involved in the CcdB resistance mechanism. Interestingly, sequence database comparisons revealed that these two proteins have homologues in eubacteria and archaebacteria, suggesting a broader physiological role.
Physical Map of the Linear Chromosome of
Streptomyces hygroscopicus
10-22 Deduced by Analysis of Overlapping Large Chromosomal Deletions
Authors: Pang Xiuhua , Zhou Xiufen , Sun Yuhui , Deng Zixin 
Published: July 2002

ABSTRACT

The chromosomal DNA of
Streptomyces hygroscopicus
10-22, a derivative of strain 5102-6, was digested with several restriction endonucleases and analyzed by pulsed-field gel electrophoresis (PFGE). Digestions with
Ase
I gave 11 fragments with a total length of ca. 7.36 Mb. The
Ase
I sites were mapped by analysis of overlapping chromosomal deletions in different mutants and confirmed by Southern hybridizations using partially digested genome fragments and linking cosmids as probes. PFGE analysis of DNA with and without proteinase K treatment, together with the hybridization results, suggested a linear organization with terminal proteins and large terminal inverted repeats. Some deletion mutants had circular chromosomes.
Regulation of Purine Hydroxylase and Xanthine Dehydrogenase from
Clostridium purinolyticum
in Response to Purines, Selenium, and Molybdenum
Authors: Self William T. 
Published: July 2002

ABSTRACT

The discovery that two distinct enzyme catalysts, purine hydroxylase (PH) and xanthine dehydrogenase (XDH), are required for the overall conversion of hypoxanthine to uric acid by
Clostridium purinolyticum
was unexpected. In this reaction sequence, hypoxanthine is hydroxylated to xanthine by PH and then xanthine is hydroxylated to uric acid by XDH. PH and XDH, which contain a labile selenium cofactor in addition to a molybdenum cofactor, flavin adenine dinucleotide, and FeS centers, were purified and partially characterized as reported previously. In the present study, the activities of these two enzymes were measured in cells grown in media containing various concentrations of selenite, molybdate, and various purine substrates. The levels of PH protein in extracts were determined by immunoblot assay. The amount of PH protein, as well as the specific activities of PH and XDH, increased when either selenite or molybdate was added to the culture medium. PH levels were highest in the cells cultured in the presence of either adenine or purine. XDH activity increased dramatically in cells grown with either xanthine or uric acid. The apparent increases in protein levels and activities of PH and XDH in response to selenium, molybdenum, and purine substrates demonstrate that these enzymes are tightly regulated in response to these nutrients.
Serum Interleukin-6 (IL-6), IL-10, Tumor Necrosis Factor (TNF) Alpha, Soluble Type II TNF Receptor, and Transforming Growth Factor Beta Levels in Human Immunodeficiency Virus Type 1-Infected Individuals withMycobacterium aviumComplex Disease
Authors: Havlir Diane V. , Torriani Francesca J. , Schrier Rachel D. , Huang Jimmy Y. , Lederman Michael M. , Chervenak Keith A. , Boom W. Henry 
Published: July 2002

ABSTRACTTo characterize changes in serum cytokine levels in human immunodeficiency virus type 1 (HIV-1)-infected persons withMycobacterium aviumcomplex (MAC) bacteremia, the levels of IL-1α (interleukin-1α), IL-6, IL-10, tumor necrosis factor alpha (TNF-α), soluble type II TNF receptor (sTNF-RII), and transforming growth factorβ(TGF-β) in serum were measured in two cohorts of HIV-1-infected persons with MAC bacteremia. The first cohort was part of a MAC prophylaxis study. Patients with bacteremia were matched with controls without bacteremia. Elevated IL-6, IL-10, TNF-α, sTNF-RII, and TGF-β levels were noted at baseline for all subjects, a result consistent with advanced HIV-1 disease. IL-1α was not detected. No differences in cytokine levels in serum were noted at baseline and at the time of bacteremia between patients with MAC and controls. In the second cohort, subjects had serum samples collected at the time of MAC bacteremia and thereafter while on macrolide therapy. Serum samples at time of bacteremia were collected from HIV-1-infected persons at a time when neither highly active antiretroviral therapy (HAART) nor MAC prophylaxis was used routinely. MAC treatment resulted in decreased levels of IL-6 and TNF-α in serum, which were evident for IL-6 by 4 to 6 weeks and for TNF-α by 8 to 16 weeks. Thus, antibiotic treatment for MAC results in decreased levels of IL-6 and TNF-α in serum in HIV-1-infected persons who are not on HAART.
Comparison of Three Transport Systems (Starplex StarSwab II, the New Copan Vi-Pak Amies Agar Gel Collection and Transport Swabs, and BBL Port-A-Cul) for Maintenance of Anaerobic and Fastidious Aerobic Organisms
Authors: Hindiyeh Musa , Acevedo Victoria , Carroll Karen C. 
Published: July 2002

ABSTRACT

Of utmost importance in evaluations of clinical samples for infectious agents is proper specimen transport to the clinical laboratory. In the present study we compared three transport systems (the new Starplex StarSwab II, the new Copan Vi-Pak Amies Agar Gel collection and transport swabs, and the BBL Port-A-Cul) for survival of anaerobic and fastidious aerobic bacteria. The new Copan Vi-Pak system has been modified by nitrogen gas flushing to keep an ideal low E
h
condition and to prevent oxidation of the transport medium. The Copan Vi-Pak system outperformed the other two swabs evaluated by maintaining the viabilities of both anaerobic and fastidious aerobic bacteria for 24 h for the majority of the organisms evaluated. This time period should be sufficient for transport of specimens to the clinical microbiology laboratory without compromising organism recovery.
PCR for Specific Detection of H7 Flagellar Variant of
fliC
among Extraintestinal Pathogenic
Escherichia coli
Authors: Johnson James R. , Stell Adam L. 
Published: July 2002

ABSTRACT

A newly developed PCR-based assay for the H7 variant of the
Escherichia coli
flagellin gene,
fliC
, was 100% sensitive and specific in comparison with serology and probe hybridization. It revealed broad conservation of the H7
fliC
variant among phylogenetically diverse lineages of extraintestinal pathogenic
E. coli
(ExPEC) and superseded serotyping for certain isolates with ambiguous or non-H7 serotyping results. The H7 primers functioned well when incorporated into a multiplex PCR assay for diverse virulence-associated genes of ExPEC.
Optimal Inoculation Methods and Quality Control for the NCCLS Oxacillin Agar Screen Test for Detection of Oxacillin Resistance in
Staphylococcus aureus
Authors: Swenson Jana M. , Spargo Jean , Tenover Fred C. , Ferraro Mary Jane 
Published: July 2002

ABSTRACT

To define more precisely the inoculation methods to be used in the oxacillin screen test for
Staphylococcus aureus
, we tested agar screen plates prepared in house with 6 μg of oxacillin/ml and 4% NaCl using the four different inoculation methods that would most likely be used by clinical laboratories. The organisms selected for testing were 19 heteroresistant
mecA
-producing strains and 41 non-
mecA
-producing strains for which oxacillin MICs were near the susceptible breakpoint. The inoculation method that was preferred by all four readers and that resulted in the best combination of sensitivity and specificity was a 1-μl loopful of a 0.5 McFarland suspension. A second objective of the study was to then use this method to inoculate plates from five different manufacturers of commercially prepared media. Although all commercial media performed with acceptable sensitivity compared to the reference lot, one of the commercial lots demonstrated a lack of specificity. Those lots of oxacillin screen medium that fail to grow heteroresistant strains can be detected by using
S. aureus
ATCC 43300 as a positive control in the test and by using transmitted light to carefully examine the plates for any growth. However, lack of specificity with commercial lots may be difficult to detect using any of the current quality control organisms.
Selection of a Teicoplanin-Resistant
Enterococcus faecium
Mutant during an Outbreak Caused by Vancomycin-Resistant Enterococci with the VanB Phenotype
Authors: Kawalec Magdalena , Gniadkowski Marek , Ke˛dzierska Jolanta , Skotnicki Aleksander , Fiett Janusz , Hryniewicz Waleria 
Published: July 2002

ABSTRACT

Vancomycin-resistant enterococci (VRE) have recently become an increasing problem in hospitals in Poland, being responsible for a growing number of nosocomial outbreaks. In this work, we have analyzed the second outbreak of VRE with the VanB phenotype to be identified in the country. It was caused by clonal dissemination of a single strain of vancomycin-resistant
Enterococcus faecalis
(VRES) and horizontal transmission of vancomycin resistance genes among several vancomycin-resistant
Enterococcus faecium
(VREM) strains. Two similar restriction fragment length polymorphism types of the
vanB
gene cluster characterized VRES and VREM isolates, and they both contained the same
vanB2
variant of the
vanB
gene. Two vancomycin-susceptible
E. faecium
(VSEM) isolates, recovered from the same wards during the outbreak, proved to be related to certain VREM isolates and could represent endemic strains that had acquired vancomycin resistance. One VSEM and four VREM isolates, all identified in the same patient, belonged to a single clone, although they revealed remarkable diversity in terms of susceptibility, PFGE patterns, plasmid content, and number of
vanB
gene cluster copies. Most probably they reflected the dynamic evolution of an
E. faecium
strain in the course of infection of a single patient. One of the VREM isolates turned out to be resistant to teicoplanin, which coincided with the use of this antibiotic in the patient's therapy. Its
vanB
gene variant differed by a single mutation from that found in other isolates; however, it also lacked a large part of the
vanB
gene cluster, including the regulatory genes
vanR

B

and -
S

B

, and the vancomycin-inducible promoter
P

YB

. Expression of the resistance genes
vanH

B

, -
B
, and -
X

B

was constitutive in the mutant, and this phenomenon was responsible for its unusual phenotype.
Multidrug-Resistant
Trichosporon asahii
Infection of Nongranulocytopenic Patients in Three Intensive Care Units
Authors: Wolf Dana G. , Falk Rama , Hacham Moshe , Theelen Bart , Boekhout Teun , Scorzetti Gloria , Shapiro Mervyn , Block Colin , Salkin Ira F. , Polacheck Itzhack 
Published: July 2002

ABSTRACT

Trichosporon asahii
(
Trichosporon beigelii
) infections are rare but have been associated with a wide spectrum of clinical manifestations, ranging from superficial involvement in immunocompetent individuals to severe systemic disease in immunocompromised patients. We report on the recent recovery of
T. asahii
isolates with reduced susceptibility in vitro to amphotericin B (AMB), flucytosine, and azoles from six nongranulocytopenic patients who exhibited risk factors and who developed either superficial infections (four individuals) or invasive infections (two individuals) while in intensive care units. The latter two patients responded clinically and microbiologically to AMB treatment. All six isolates were closely related according to random amplified polymorphic DNA studies and showed 71% similarity by amplified fragment length polymorphism analysis, suggesting a common nosocomial origin. We also review the literature pertaining to
T. asahii
infections and discuss the salient characteristics of this fungus and recent taxonomic proposals for the genus.
Protocol for Detection of Biofilms on Needleless Connectors Attached to Central Venous Catheters
Authors: Donlan R. M. , Murga R. , Bell M. , Toscano C. M. , Carr J. H. , Novicki T. J. , Zuckerman C. , Corey L. C. , Miller J. M. 
Published: July 2002

ABSTRACT
Central venous catheter needleless connectors (NCs) have been shown to develop microbial contamination. A protocol was developed for the collection, processing, and examination of NCs to detect and measure biofilms on these devices. Sixty-three percent of 24 NCs collected from a bone marrow transplant center contained biofilms comprised primarily of coagulase-negative staphylococci.
Comparative Pathogenesis of Infection of Pigs with Hepatitis E Viruses Recovered from a Pig and a Human
Authors: Halbur P. G. , Kasorndorkbua C. , Gilbert C. , Guenette D. , Potters M. B. , Purcell R. H. , Emerson S. U. , Toth T. E. , Meng X. J. 
Published: July 2002

ABSTRACT
Specific-pathogen-free pigs were inoculated with one of two hepatitis E viruses (HEV) (one recovered from a pig and the other from a human) to study the relative pathogenesis of the two viruses in swine. Fifty-four pigs were randomly assigned to three groups. Seventeen pigs in group 1 served as uninoculated controls, 18 pigs in group 2 were intravenously inoculated with the swine HEV recovered from a pig in the United States, and 19 pigs in group 3 were intravenously inoculated with the US-2 strain of human HEV recovered from a hepatitis patient in the United States. Two to four pigs from each group were necropsied at 3, 7, 14, 20, 27, or 55 days postinoculation (DPI). Evidence of clinical disease or elevation of liver enzymes or bilirubin was not found in pigs from any of the three groups. Enlarged hepatic and mesenteric lymph nodes were observed in both HEV-inoculated groups. Multifocal lymphoplasmacytic hepatitis was observed in 9 of 17, 15 of 18, and 16 of 19 pigs in groups 1 to 3, respectively. Focal hepatocellular necrosis was observed in 5 of 17, 10 of 18, and 13 of 19 pigs in groups 1 to 3, respectively. Hepatitis lesions were very mild in group 1 pigs, mild to moderate in group 2 pigs, and moderate to severe in group 3 pigs. Hepatic inflammation and hepatocellular necrosis peaked in severity at 20 DPI and were still moderately severe at 55 DPI in the group inoculated with human HEV. Hepatitis lesions were absent or nearly resolved by 55 DPI in the swine-HEV-inoculated pigs. All HEV-inoculated pigs seroconverted to anti-HEV immunoglobulin G. HEV RNA was detected by reverse transcriptase PCR in feces, liver tissue, and bile of pigs in both HEV-inoculated groups from 3 to 27 DPI. Based on evaluation of microscopic lesions, the US-2 strain of human HEV induced more severe and persistent hepatic lesions in pigs than did swine HEV. Pig livers or cells from the livers of HEV-infected pigs may represent a risk for transmission of HEV from pigs to human xenograft recipients. Since HEV was shed in the feces of infected pigs, exposure to feces from infected pigs represents a risk for transmission of HEV, and pigs should be considered a reservoir for HEV.
Persistence of a Distinct
Corynebacterium diphtheriae
Clonal Group within Two Communities in the United States and Canada Where Diphtheria Is Endemic
Authors: Marston Chung K. , Jamieson Frances , Cahoon Fred , Lesiak Gail , Golaz Anne , Reeves Mike , Popovic Tanja 
Published: July 2002

ABSTRACT

Molecular characterization of 53 U.S. and Canadian
Corynebacterium diphtheriae
isolates by multilocus enzyme electrophoresis, ribotyping, and random amplified polymorphic DNA showed that strains with distinct molecular subtypes have persisted in the United States and Canada for at least 25 years. These strains are endemic rather than imported from countries with current endemic or epidemic diphtheria.
Bacteremia by
Dermabacter hominis
, a Rare Pathogen
Authors: Gómez-Garcés José Luis , Oteo Jesús , Garcı́a Guadalupe , Aracil Belén , Alós Juan Ignacio , Funke Guido 
Published: July 2002

ABSTRACT

Dermabacter hominis
is a gram-positive, catalase-positive, glucose-fermenting rod, which, as it grows forms small greyish-white colonies with a characteristic pungent odor. Previously known as coryneform Centers for Disease Control and Prevention groups 3 and 5, it was catalogued as
D. hominis
in 1994. Various strains isolated in blood cultures, abscesses, or wounds in the 1970s were retrospectively characterized in referral centers as
D. hominis
. In this report we describe two patients with severe underlying pathology who developed bacteremias by
D. hominis
within the context of their clinical pictures.
Experimental Paratuberculosis in Calves following Inoculation with a Rabbit Isolate of
Mycobacterium avium
subsp.
paratuberculosis
Authors: Beard P. M. , Stevenson K. , Pirie A. , Rudge K. , Buxton D. , Rhind S. M. , Sinclair M. C. , Wildblood L. A. , Jones D. G. , Sharp J. M. 
Published: July 2002

ABSTRACT

The role of wildlife species in the epidemiology of paratuberculosis has been the subject of increased research efforts following the discovery of natural paratuberculosis in free-living rabbits from farms in east Scotland. This paper describes the experimental inoculation of young calves with an isolate of
Mycobacterium avium
subsp.
paratuberculosis
recovered from a free-living rabbit. After a 6-month incubation period, all eight calves inoculated with the rabbit isolate had developed histopathological and/or microbiological evidence of
M. avium
subsp.
paratuberculosis
infection. Similar results were obtained from a group of calves infected with a bovine isolate of
M. avium
subsp.
paratuberculosis
. The virulence of the rabbit isolate for calves demonstrated in this study suggests that rabbits are capable of passing paratuberculosis to domestic ruminants and that wildlife reservoirs of
M. avium
subsp.
paratuberculosis
should therefore be considered when formulating control plans for the disease.
Murine Monoclonal Antibodies against
Escherichia coli
O4 Lipopolysaccharide and H5 Flagellin
Authors: Rivera-Betancourt Mildred , Keen James E. 
Published: July 2002

ABSTRACT

Two murine monoclonal antibodies (MAb), 2C5-F10 and 8D1-H10, reactive with
Escherichia coli
O4 and H5 antigens, respectively, were generated and characterized. Enzyme immunoassays and immunoblots demonstrated that MAb 2C5-F10 reacted specifically with lipopolysaccharide O antigen of
E. coli
O4 isolates, while MAb 8D1-H10 reacted with
E. coli
strains expressing H5 flagella.