bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Metronidazole on the Pathogenicity of Resistant
Bacteroides
Strains in Gnotobiotic Mice
Authors: Diniz Claudio Galuppo , Cara Denise Carmona , Nicoli Jacques Robert , Farias Luiz De Macedo , De Carvalho Maria Auxiliadora Roque 
Published: July 2002

ABSTRACT

Metronidazole is widely used to treat protozoan and fungal infections. As an antibacterial drug, it is used mainly against anaerobes. Among anaerobes, the
Bacteroides fragilis
group is the most relevant in terms of frequency of recovery and antimicrobial resistance patterns. The use of metronidazole and other antimicrobial drugs induces morphological changes in this bacterial group. The present study investigated in vivo if these morphological modifications were accompanied by changes in virulence patterns by using germfree mice experimentally challenged with metronidazole-resistant
Bacteroides
strains before and after exposure to metronidazole. It was observed that metronidazole-resistant strains were more virulent after contact with the drug, as demonstrated by anatomicopathologic data for spleen, liver, and small intestine samples. These results suggest that long-term therapy and high metronidazole concentrations could interfere with microbial pathogenicity, resulting in changes to host-bacterium relationships.
Geographical Segregation of the Neurotoxin-Producing Cyanobacterium
Anabaena circinalis
Authors: Beltran E. Carolina , Neilan Brett A. 
Published: July 2002

ABSTRACT

Blooms of the cyanobacterium
Anabaena circinalis
are a major worldwide problem due to their production of a range of toxins, in particular the neurotoxins anatoxin-a and paralytic shellfish poisons (PSPs). Although there is a worldwide distribution of
A. circinalis
, there is a geographical segregation of neurotoxin production. American and European isolates of
A. circinalis
produce only anatoxin-a, while Australian isolates exclusively produce PSPs. The reason for this geographical segregation of neurotoxin production by
A. circinalis
is unknown. The phylogenetic structure of
A. circinalis
was determined by analyzing 16S rRNA gene sequences.
A. circinalis
was found to form a monophyletic group of international distribution. However, the PSP- and non-PSP-producing
A. circinalis
formed two distinct 16S rRNA gene clusters. A molecular probe was designed, allowing the identification of
A. circinalis
from cultured and uncultured environmental samples. In addition, probes targeting the predominantly PSP-producing or non-PSP-producing clusters were designed for the characterization of
A. circinalis
isolates as potential PSP producers.
Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1,2-Dichloroethane by
Xanthobacter autotrophicus
Authors: Hunkeler D. , Aravena R. 
Published: July 2002

ABSTRACT

Carbon isotope fractionation during aerobic mineralization of 1,2-dichloroethane (1,2-DCA) by
Xanthobacter autotrophicus
GJ10 was investigated. A strong enrichment of
13
C in residual 1,2-DCA was observed, with a mean fractionation factor α ± standard deviation of 0.968 ± 0.0013 to 0.973 ± 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon occurred. A mechanistic model that links the fractionation factor α to the rate constants of the first catabolic enzyme was developed. Based on the model, it was concluded that the strong enrichment of
13
C in 1,2-DCA arises because the first irreversible step of the initial enzymatic transformation of 1,2-DCA consists of an S
N
2 nucleophilic substitution. S
N
2 reactions are accompanied by a large kinetic isotope effect. The substantial carbon isotope fractionation between biomass and inorganic carbon could be explained by the kinetic isotope effect associated with the initial 1,2-DCA transformation and by the metabolic pathway of 1,2-DCA degradation. Carbon isotope fractionation during 1,2-DCA mineralization leads to 1,2-DCA, inorganic carbon, and biomass with characteristic carbon isotope compositions, which may be used to trace the process in contaminated environments.
Does Enterohemorrhagic
Escherichia coli
O157:H7 Enter the Viable but Nonculturable State in Salted Salmon Roe?
Authors: Makino Sou-Ichi , Kii Tsutomu , Asakura Hiroshi , Shirahata Toshikazu , Ikeda Tetsuya , Takeshi Kouichi , Itoh Kikuji 
Published: July 2002

ABSTRACT

An outbreak caused by salted salmon roe contaminated with enterohemorrhagic
Escherichia coli
O157 occurred in Japan in 1998. Since about 0.75 to 1.5 viable cells were estimated to cause infection, we presumed that O157 might enter the viable but nonculturable (VNC) state in salted salmon roe and consequently that viable cell numbers might be underestimated. Although patient-originating O157 cells could not grow on agar plates after 72 h of incubation in 13% NaCl, they were resuscitated in yeast extract broth, and more than 90% of the cells were shown to be viable by fluorescent staining, suggesting that almost all of them could enter the VNC state in NaCl water. Roe-originating O157 was resistant to NaCl because it could grow on agar after 72 h of incubation in NaCl water, but about 20% of cells appeared to enter the VNC state. Therefore, germfree mice were infected with O157 to examine the resuscitation of cells in the VNC state and the retention of pathogenicity. O157 that originated in roe, but not patients, killed mice and was isolated from the intestine. However, these isolates had become sensitive to NaCl. O157 cells of roe origin incubated in normal media also killed mice and were isolated from the intestine, but they also became transiently NaCl sensitive. We therefore propose that bacterial cells might enter the VNC state under conditions of stress, such as those encountered in vivo or in high salt concentrations, and then revive when those conditions have eased. If so, the VNC state in food is potentially dangerous from a public health viewpoint and may have to be considered at the time of food inspection. Finally, the establishment of a simple recovery system for VNC cells should be established.
Characterization of AbiR, a Novel Multicomponent Abortive Infection Mechanism Encoded by Plasmid pKR223 of
Lactococcus lactis
subsp.
lactis
KR2
Authors: Twomey Denis P. , De Urraza Patricio J. , McKay Larry L. , O'Sullivan Daniel J. 
Published: July 2002

ABSTRACT

The native lactococcal plasmid pKR223 encodes two distinct phage resistance mechanisms, a restriction and modification (R/M) system designated
Lla
KR2I and an abortive infection mechanism (Abi) which affects prolate-headed-phage proliferation. The nucleotide sequence of a 16,174-bp segment of pKR223 encompassing both the R/M and Abi determinants has been determined, and sequence analysis has validated the novelty of the Abi system, which has now been designated AbiR. Analysis of deletion and insertion clones demonstrated that AbiR was encoded by two genetic loci, separated by the
Lla
KR2I R/M genes. Mechanistic studies on the AbiR phenotype indicated that it was heat sensitive and that it impeded phage DNA replication. These data indicated that AbiR is a novel multicomponent, heat-sensitive, “early”-functioning Abi system and is the first lactococcal Abi system described which is encoded by two separated genetic loci.
Detection and Enumeration of Methanotrophs in Acidic
Sphagnum
Peat by 16S rRNA Fluorescence In Situ Hybridization, Including the Use of Newly Developed Oligonucleotide Probes for
Methylocella palustris
Authors: Dedysh Svetlana N. , Derakshani Manigee , Liesack Werner 
Published: July 2002

ABSTRACT

Two 16S rRNA-targeted oligonucleotide probes, Mcell-1026 and Mcell-181, were developed for specific detection of the acidophilic methanotroph
Methylocella palustris
using fluorescence in situ hybridization (FISH). The fluorescence signal of probe Mcell-181 was enhanced by its combined application with the oligonucleotide helper probe H158. Mcell-1026 and Mcell-181, as well as 16S rRNA oligonucleotide probes with reported group specificity for either type I methanotrophs (probes M-84 and M-705) or the
Methylosinus
/
Methylocystis
group of type II methanotrophs (probes MA-221 and M-450), were used in FISH to determine the abundance of distinct methanotroph groups in a
Sphagnum
peat sample of pH 4.2.
M. palustris
was enumerated at greater than 10
6
cells per g of peat (wet weight), while the detectable population size of type I methanotrophs was three orders of magnitude below the population level of
M. palustris
. The cell counts with probe MA-221 suggested that only 10
4
type II methanotrophs per g of peat (wet weight) were present, while the use of probe M-450 revealed more than 10
6
type II methanotroph cells per g of the same samples. This discrepancy was due to the fact that probe M-450 targets almost all currently known strains of
Methylosinus
and
Methylocystis
, whereas probe MA-221, originally described as group specific, does not detect a large proportion of
Methylocystis
strains. The total number of methanotrophic bacteria detected by FISH was 3.0 (±0.2) × 10
6
cells per g (wet weight) of peat. This was about 0.8% of the total bacterial cell number. Thus, our study clearly suggests that
M. palustris
and a defined population of
Methylocystis
spp. were the predominant methanotrophs detectable by FISH in an acidic
Sphagnum
peat bog.
Epidemiology of
Rhodococcus equi
Strains on Thoroughbred Horse Farms
Authors: Morton Anna C. , Begg Angela P. , Anderson Garry A. , Takai Shinji , Lämmler Christoph , Browning Glenn F. 
Published: July 2002

ABSTRACT

Pulsed-field gel electrophoresis of restriction endonuclease-digested genomic DNA from a large collection of clinical isolates of
Rhodococcus equi
, an important pathogen of foals, was used to compare strain distribution between farms and over time. Forty-four strains were found among 209 isolates, with 5 of these accounting for over half the isolates and the 22 strains isolated more than once accounting for 90% of the isolates. The average genotypic diversity on each farm and in each year was found to be less than the genotypic diversity of the isolates taken as a whole, with 5.2% of the total diversity being due to differences between farms and 5.5% to differences between years. A small number of strains on each farm were found to have caused at least half the clinical cases of disease, and these varied between farms and, to a lesser extent, years. Most strains were found on more than one farm, and some very similar restriction patterns were found among isolates from different continents, indicating that strains can be very widespread. Multiple strains were isolated in five of the six cases in which more than one isolate from a single foal was examined, indicating that disease may commonly be caused by simultaneous infection with multiple strains. It was concluded that there are a number of different strains of
R. equi
which carry the
vapA
gene, and these strains tend to be widespread, but individual farms tend to have particular strains associated with them.
Complete Denitration of Nitroglycerin by Bacteria Isolated from a Washwater Soakaway
Authors: Marshall Samantha J. , White Graham F. 
Published: July 2002

ABSTRACTFour axenic bacterial species capable of biodegrading nitroglycerin (glycerol trinitrate [GTN]) were isolated from soil samples taken from a washwater soakaway at a disused GTN manufacturing plant. The isolates were identified by 16S rRNA gene sequence homology asPseudomonas putida, anArthrobacterspecies, aKlebsiellaspecies, and aRhodococcusspecies. Each of the isolates utilized GTN as its sole nitrogen source and removed nitro groups sequentially from GTN to produce glycerol dinitrates and mononitrates (GMN), with the exception of theArthrobacterstrain, which achieved removal of only the first nitro group within the time course of the experiment. TheKlebsiellastrain exhibited a distinct preference for removal of the central nitro group from GTN, while the other five strains exhibited no such regioselectivity. All strains which removed a second nitro group from glycerol 1,2-dinitrate showed regiospecific removal of the end nitro group, thereby producing glycerol 2-mononitrate. Most significant was the finding that theRhodococcusspecies was capable of removing the final nitro group from GMN and thus achieved complete biodegradation of GTN. Such complete denitration of GTN has previously been shown only in mixed bacterial populations and in cultures ofPenicillium corylophilum Dierckxsupplemented with an additional carbon and nitrogen source. Hence, to the best of our knowledge, this is the first report of a microorganism that can achieve complete denitration of GTN.
Role of Serotype-Specific Polysaccharide in the Resistance ofStreptococcus mutansto Phagocytosis by Human Polymorphonuclear Leukocytes
Authors: Tsuda Hiromasa , Yamashita Yoshihisa , Toyoshima Kuniaki , Yamaguchi Noboru , Oho Takahiko , Nakano Yoshio , Nagata Kengo , Koga Toshihiko 
Published: July 2002

ABSTRACTTo clarify the role of cell surface components ofStreptococcus mutansin resistance to phagocytosis by human polymorphonuclear leukocytes (PMNs), several isogenic mutants ofS. mutansdefective in cell surface components were studied with a luminol-enhanced chemiluminescence (CL) assay, a killing assay, and a transmission electron microscope. The CL responses of human PMNs to mutant Xc11 defective in a major cell surface antigen, PAc, and mutant Xc16 defective in two surface glucosyltransferases (GTF-I and GTF-SI) were the same as the response to the wild-type strain, Xc. In contrast, mutant Xc24R, which was defective in serotype c-specific polysaccharide, induced a markedly higher CL response than the other strains. The killing assay showed that human PMNs killed more Xc24R than the parent strain and the other mutants. The transmission electron microscopic observation indicated that Xc24R cells were more internalized by human PMNs than the parental strain Xc. These results may be reflected by the fact that strain Xc24R was more phagocytosed than strain Xc. The CL response of human PMNs to a mutant defective in polysaccharide serotype e or f was similar to the response to Xc24R. Furthermore, mutants defective in serotype-specific polysaccharide were markedly more hydrophobic than the wild-type strains and the other mutants, suggesting that the hydrophilic nature of polysaccharides may protect the bacterium from phagocytosis. We conclude that the serotype-specific polysaccharide, but not the cell surface proteins on the cell surface ofS. mutans, may play an important role in the resistance to phagocytosis.
Depressed CD40 Ligand Expression Contributes to Reduced Gamma Interferon Production in Human Tuberculosis
Authors: Samten Buka , Thomas Elaine K. , Gong Jianhua , Barnes Peter F. 
Published: July 2002

ABSTRACTExpression of CD40 ligand (CD40L) correlated directly withMycobacterium tuberculosis-stimulated gamma interferon (IFN-γ) production by peripheral blood mononuclear cells (PBMC) from tuberculosis patients and healthy tuberculin reactors. The CD40L agonist increasedM. tuberculosis-induced IFN-γ production by PBMC, and anti-CD40 or anti-CD40L antibodies reduced IFN-γ production. CD40L expression on PBMC was reduced by exposure to B cells and to soluble factors fromM. tuberculosis-infected monocytes. These findings suggest that CD40L dysregulation contributes to reduced IFN-γ production in human tuberculosis.
Expression of Intimin γ from Enterohemorrhagic
Escherichia coli
in
Citrobacter rodentium
Authors: Hartland Elizabeth L. , Huter Veronika , Higgins Lisa M. , Goncalves Nathalie S. , Dougan Gordon , Phillips Alan D. , MacDonald Thomas T. , Frankel Gad 
Published: July 2002

ABSTRACT

The carboxy-terminal 280 amino acids (Int280) of the bacterial adhesion molecule intimin include the receptor-binding domain. At least five different types of Int280, designated α, β, γ, δ, and ɛ, have been described based on sequence variation in this region. Importantly, the intimin types are associated with different evolutionary branches and contribute to distinct tissue tropism of intimin-positive bacterial pathogens. In this study we engineered a strain of
Citrobacter rodentium
, which normally displays intimin β, to express intimin γ from enterohemorrhagic
Escherichia coli
. We show that intimin γ binds to the translocated intimin receptor (Tir) from
C. rodentium
and has the ability to produce attaching and effacing lesions on HEp-2 cells. However,
C. rodentium
expressing intimin γ could not colonize orally infected mice or induce mouse colonic hyperplasia. These results suggest that intimin may contribute to host specificity, possibly through its interaction with a receptor on the host cell surface.
DNA-Based Immunization withTrypanosoma cruziComplement Regulatory Protein Elicits Complement Lytic Antibodies and Confers Protection againstTrypanosoma cruziInfection
Authors: Sepulveda Pilar , Hontebeyrie Mireille , Liegeard Pascal , Mascilli Alexia , Norris Karen A. 
Published: July 2002

ABSTRACTA complement regulatory protein (CRP) ofTrypanosoma cruziwas evaluated as a vaccine candidate in a murine model of experimentalT. cruziinfection. Recombinant CRP derived from anEscherichia coliexpression system and a plasmid encoding the full-lengthcrpstructural gene under the control of a eukaryotic promoter were used to immunize BALB/c mice. Immunization with both protein and DNA vaccines resulted in a Th1-type T-cell response, comparable antibody titers, and similar immunoglobulin G isotype profiles. Only mice immunized with thecrpDNA plasmid produced antibodies capable of lysing the parasites in the presence of complement and were protected against a lethal challenge withT. cruzitrypomastigotes. These results demonstrate the superiority of DNA immunization over protein immunization with the recombinant CRP. The work also supports the further investigation of CRP as a component of a multigene, anti-T. cruziDNA vaccine.
Role of Fc Gamma Receptors in Triggering Host Cell Activation and Cytokine Release byBorrelia burgdorferi
Authors: Talkington Jeffrey , Nickell Steven P. 
Published: July 2002

ABSTRACTBorrelia burgdorferi, the spirochetal bacterium that causes human Lyme disease, encodes numerous lipoproteins which have the capacity to trigger the release of proinflammatory cytokines from a variety of host cell types, and it is generally believed that these cytokines contribute to the disease process in vivo. We previously reported that low-passage-number infectiousB. burgdorferispirochetes express a novel lipidation-independent activity which induces secretion of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α) by the mouse MC/9 mast cell line. Using RNase protection assays, we determined that mast cells exposed in vitro to low-passage-number, but not high-passage-number,B. burgdorferispirochetes show increased expression of additional mRNAs representing several chemokines, including macrophage-inflammatory protein 1α (MIP-1α), MIP-1β, and TCA3, as well as the proinflammatory cytokine interleukin-6. Furthermore, mast cell TNF-α secretion can be inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin and also by preincubation with purified mouse immunoglobulin G1 (IgG1) and IgG2a, but not mouse IgG3, and by a mouse Fc gamma receptor II and III (FcγRII/III)-specific rat monoclonal antibody, suggesting the likely involvement of host FcγRIII inB. burgdorferi-mediated signaling. A role for passively adsorbed rabbit or bovine IgG or serum components inB. burgdorferi-mediated FcγR signaling was excluded in control experiments. These studies confirm that low-passage-numberB. burgdorferispirochetes express a novel activity which upregulates the expression of a variety of host cell chemokine and cytokine genes, and they also establish a novel antibody-independent role for FcγRs in transduction of activation signals by bacterial products.
Minor Nucleotide Substitutions in the
omp31
Gene of
Brucella ovis
Result in Antigenic Differences in the Major Outer Membrane Protein That It Encodes Compared to Those of the Other
Brucella
Species
Authors: Vizcaı́no Nieves , Kittelberger Reinhold , Cloeckaert Axel , Marı́n Clara M. , Fernández-Lago Luis 
Published: July 2002

ABSTRACT

The gene coding for the major outer membrane protein Omp31 was sequenced in five
Brucella
species and their biovars. Although the
omp31
genes appeared to be highly conserved in the genus
Brucella
, nine nucleotide substitutions were detected in the gene of
Brucella ovis
compared to that of
Brucella melitensis
. As shown by differential binding properties of monoclonal antibodies (MAbs) to the two
Brucella
species, these nucleotide substitutions result in different antigenic properties of Omp31. The antigenic differences were also evidenced when sera from
B. ovis
-infected rams were tested by Western blotting with the recombinant
B. melitensis
or
B. ovis
Omp31 proteins. Twelve available sera reacted with recombinant
B. ovis
Omp31, but only four of them reacted with recombinant
B. melitensis
Omp31. These results validate previous evidence for the potential of Omp31 as a diagnostic antigen for
B. ovis
infection in rams and demonstrate that
B. ovis
Omp31, instead of
B. melitensis
Omp31, should be used to evaluate this point. The antigenic differences between the
B. melitensis
and
B. ovis
Omp31 proteins should also be taken into account when Omp31 is evaluated as a candidate for the development of subcellular vaccines against
B. ovis
infection. No reactivity against recombinant
B. melitensis
Omp31 was detected, by Western blotting, with sera from
B. melitensis
-infected sheep. Accordingly, Omp31 does not seem to be a good diagnostic antigen for
B. melitensis
infections in sheep. Two immunodominant regions were identified on the
B. ovis
Omp31 protein by using recombinant DNA techniques and specific MAbs. Sera from
B. ovis
-infected rams that reacted with the recombinant protein were tested by Western blotting against one of these immunodominant regions shown to be exposed at the bacterial surface. Only 4 of the 12 sera reacted, but with strong intensity.
Induction of Epithelial Cell Death Including Apoptosis by Enteropathogenic
Escherichia coli
Expressing Bundle-Forming Pili
Authors: Abul-Milh Maan , Wu Ying , Lau Bedy , Lingwood Clifford A. , Foster Debora Barnett 
Published: July 2002

ABSTRACT

Infection with enteropathogenic
Escherichia coli
(EPEC) is a major cause of severe infantile diarrhea, particularly in parts of the developing world. The bundle-forming pilus (BFP) of EPEC is an established virulence factor encoded on the EPEC adherence factor plasmid (EAF) and has been implicated in both localized adherence to host cells and bacterial autoaggregation. We investigated the role of BFP in the ability of EPEC binding to kill host epithelial cells. BFP-expressing strains killed all three cell lines tested, comprising HEp-2 (laryngeal), HeLa (cervical), and Caco-2 (colonic) cells. Analysis of phosphatidylserine expression, internucleosomal cleavage of host cell DNA, and morphological changes detected by electron microscopy indicated evidence of apoptosis. The extent of cell death was significantly greater for BFP-expressing strains, including E2348/69, a wild-type clinical isolate, as well as for a laboratory strain, HB101, transformed with a
bfp
-carrying plasmid. Strains which did not express BFP induced significantly less cell death, including a
bfpA
disruptional mutant of E2348/69, EAF plasmid-cured E2348/69, HB101, and HB101 complemented with the locus of enterocyte effacement pathogenicity island. These results indicate a direct correlation between BFP expression and induction of cell death, including apoptosis, an event which may involve the targeting of host cell membrane phosphatidylethanolamine.