bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asaia
sp., an Unusual Spoilage Organism of Fruit-Flavored Bottled Water
Authors: Moore John E. , McCalmont Mark , Xu Jiru , Millar B. Cherie , Heaney Neville 
Published: October 2002

ABSTRACT

A gram-negative bacillus was isolated from a batch of fruit-flavored bottled water, which had spoiled as a result of bacterial overgrowth (>10
6
CFU/ml). The spoilage organism was extremely difficult to identify phenotypically and was poorly identified as
Pasturella
sp. (78.7% identification profile) employing the API 20NE identification scheme, which gave the profile 5040000. Molecular identification through PCR amplification of a partial region of the 16S rRNA gene followed by direct automated sequencing of the PCR amplicon allowed identification of the organism. Due to the sequence identity (100%) between the spoilage organism and a reference strain in GenBank, the spoilage isolate was considered to be an
Asaia
sp., a recently described genus and member of the acetic acid bacteria. This is the first report of
Asaia
sp. causing spoilage of a foodstuff and highlights the benefits of molecular identification techniques based on 16S rRNA gene sequences in the identification of unusual spoilage organisms.
Fluorescent Amplified Fragment Length Polymorphism and Repetitive Extragenic Palindrome-PCR Fingerprinting Reveal Host-Specific Genetic Diversity of
Vibrio halioticoli
-Like Strains Isolated from the Gut of Japanese Abalone
Authors: Sawabe Tomoo , Thompson Fabiano L. , Heyrman Jeroen , Cnockaert Margo , Hayashi Karin , Tanaka Reiji , Yoshimizu Mamoru , Hoste Bart , Swings Jean , Ezura Yoshio 
Published: October 2002

ABSTRACT

When analyzed by fluorescent amplified fragment length polymorphism and repetitive extragenic palindrome-PCR fingerprinting, a total of 47
Vibrio halioticoli
strains isolated from four Japanese abalone species and one turban shell species formed three clusters that roughly reflect the different species of host abalone from which they were isolated. The
V. halioticoli
isolates from turban shells were distributed evenly among the clusters. Representative isolates from two clusters were deemed separate species or subspecies by DNA-DNA hybridization.
Accelerated Death Kinetics ofAspergillus nigerSpores under High-Pressure Carbonation
Authors: Shimoda M. , Kago H. , Kojima N. , Miyake M. , Osajima Y. , Hayakawa I. 
Published: October 2002

ABSTRACTThe death kinetics ofAspergillus nigerspores under high-pressure carbonation were investigated with respect to the concentration of dissolved CO2(dCO2) and treatment temperature. All of the inactivation followed first-order death kinetics. TheDvalue (decimal reduction time, or the time required for a 1-log-cycle reduction in the microbial population) in the saline carbonated at 10 MPa was 0.16 min at 52°C. The logDvalues were linearly related to the treatment temperature and the concentration of dCO2, but a significant interaction was observed between them.
Inactivation of
Cryptosporidium parvum
Oocysts in Fresh Apple Cider by UV Irradiation
Authors: Hanes D. E. , Worobo R. W. , Orlandi P. A. , Burr D. H. , Miliotis M. D. , Robl M. G. , Bier J. W. , Arrowood M. J. , Churey J. J. , Jackson G. J. 
Published: October 2002

ABSTRACT

This study evaluated the efficacy of UV irradiation on the inactivation of
Cryptosporidium parvum
oocysts in fresh apple cider. Cider was inoculated with oocysts and exposed to 14.32 mJ of UV irradiation/cm
2
. Oocyst viability was assessed with the gamma interferon gene knockout (GKO) mouse and infant BALB/cByJ mouse models. All GKO mice challenged with UV-treated cider demonstrated no morbidity or mortality, and infant BALB/c mice challenged with treated cider were negative for the presence of
C. parvum
. In contrast, the GKO mice challenged with non-UV-treated inoculated cider died and the parasite was detected in the ileums of all challenged infant mice. This study shows that UV irradiation can be used to inactivate
C. parvum
in fresh apple cider.
Human Salivary Histatin 5 Causes Disordered Volume Regulation and Cell Cycle Arrest inCandida albicans
Authors: Baev Didi , Li Xuewei S. , Dong Jin , Keng Peter , Edgerton Mira 
Published: October 2002

ABSTRACTHuman salivary histatin 5 (Hst 5) is a nonimmune salivary protein with antifungal activity against an important human pathogen,Candida albicans.The candidacidal activity of histatins appears to be a distinctive multistep mechanism involving depletion of theC. albicansintracellular ATP content as a result of nonlytic ATP efflux. Hst 5 caused a loss of cell viability concomitant with a decrease in cellular volume as determined both by a classical candidacidal assay with exogenous Hst 5 and by using a genetically engineeredC. albicansstrain expressing Hst 5. Preincubation ofC. albicanscells with pharmacological inhibitors of anion transport provided complete or substantial protection from Hst 5-induced killing and volume reduction of cells. Moreover, intracellular expression of Hst 5 resulted in a reduction in the population mean cell volume that was accompanied by an increase in the percentage of unbudded cells andC. albicanscells in the G1phase. Following expression of Hst 5, the smallest cells sorted by fluorescence-activated cell sorting from the total population did not replicate and were exclusively in the G1phase. Cells with intracellularly expressed Hst 5 had greatly reduced G1cyclin transcript levels, indicating that they arrested in the G1phase before the onset of Start. Our data demonstrate that a key determinant in the mechanism of Hst 5 toxicity inC. albicanscellsis the disruption of regulatory circuits for cell volume homeostasis that is closely coupled with loss of intracellular ATP. This novel process of fungicidal activity by a human salivary protein has highlighted potential interactions of Hst 5 with volume regulatory mechanisms and the process of yeast cell cycle control.
In Vitro Culture of
Borrelia garinii
Results in Loss of Flagella and Decreased Invasiveness
Authors: Sellek Ricela E. , Escudero Raquel , Gil Horacio , Rodríguez Isabel , Chaparro Escolástica , Pérez-Pastrana Esperanza , Vivo Amparo , Anda Pedro 
Published: October 2002

ABSTRACT

A virulent, low-passage culture of a tick-derived strain of
Borrelia garinii
was subjected to serial in vitro passages, from which inoculations were made into C3H/HeN mice. A full display of pathogenicity was observed through passage 4, as measured by cultures of ear punch biopsy samples and internal organs and determination of tibiotarsal joint swelling. Decreased dissemination through skin and infection of internal organs were observed beginning at passage 6. These losses correlated with both the selection of clones harboring 21% less flagella than the parent strain, as seen by electron microscopy, and loss of the motility of the higher passages, as demonstrated by a swarm assay. However, during the chronic phase (3 months after infection), spirochetes were cultured from the bladder and kidney of a mouse inoculated with passage 12. The kidney isolate had the same number of flagella and motility as the original low-passage isolate. Although we can't exclude the possibility that other subtle variations may be arising given the uncloned nature of the isolate, we have found a strong association between loss of flagella and decreased invasiveness. Arthritogenicity progressively decreased with passages, so that only 12.5% of chronically infected mice inoculated with passage 29 still presented with joint swelling, concurrent with a decrease in the staining intensity in a Southern blot with a
vlsE
-based probe. These results suggest a multifactorial model in which the number of flagella drives the invasiveness of this agent, while plasmid-associated factors are responsible for triggering arthritogenicity.
The Regulator PerR Is Involved in Oxidative Stress Response and Iron Homeostasis and Is Necessary for Full Virulence of
Streptococcus pyogenes
Authors: Ricci Susanna , Janulczyk Robert , Björck Lars 
Published: October 2002

ABSTRACT

Ferric uptake regulator (Fur) and Fur-like proteins form an important family of transcriptional regulators in many bacterial species. In this work we have characterized a Fur-like protein, the peroxide regulator PerR, in an M1 serotype of
Streptococcus pyogenes
. To determine the role of PerR in
S. pyogenes
, we inactivated the gene by allelic replacement. PerR-deficient bacteria showed 48% reduction of
55
Fe incorporation from the culture medium. Transcriptional analysis revealed that
mtsA
, encoding a metal-binding protein of an ABC transporter in
S. pyogenes
, was transcribed at lower levels than were wild-type cells. Although total iron accumulation was reduced, the growth of the mutant strain was not significantly hampered. The mutant showed hyperresistance to hydrogen peroxide, and this response was induced in wild-type cells by growth in aerobiosis, suggesting that PerR acts as an oxidative stress-responsive repressor. PerR may also participate in the response to superoxide stress, as the
perR
mutant was more sensitive to the superoxide anion and had a reduced transcription of
sodA
, which encodes the sole superoxide dismutase of
S. pyogenes
. Complementation of the mutation with a functional
perR
gene restored
55
Fe incorporation, response to peroxide stress, and transcription of both
mtsA
and
sodA
to levels comparable to those of wild-type bacteria. Finally, the
perR
mutant was attenuated in virulence in a murine air sac model of infection (
P
< 0.05). These results demonstrate that PerR is involved in the regulation of iron homeostasis and oxidative stress responses and that it contributes to the virulence of
S. pyogenes
.
Structure-Function Relationships for Human Antibodies to Pneumococcal Capsular Polysaccharide from Transgenic Mice with Human Immunoglobulin Loci
Authors: Chang Q. , Zhong Z. , Lees A. , Pekna M. , Pirofski L. 
Published: October 2002

ABSTRACTTo investigate the influence of antibody structure and specificity on antibody efficacy againstStreptococcus pneumoniae, human monospecific antibodies (MAbs) to serotype 3 pneumococcal capsular polysaccharide (PPS-3) were generated from transgenic mice reconstituted with human immunoglobulin loci (XenoMouse mice) vaccinated with a PPS-3-tetanus toxoid conjugate and their molecular genetic structures, epitope specificities, and protective efficacies in normal and complement-deficient mice were determined. Nucleic acid sequence analysis of three MAbs (A7, 1A2, and 7C5) revealed that they use two different VH3 genes (A7 and 1A2 both use V3-15) and three different Vκgene segments. The MAbs were found to have similar affinities for PPS-3 but different epitope specificities and CDR3 regions. Both A7 and 7C5 had a lysine at the VH-D junction, whereas 1A2 had a threonine. Challenge experiments with serotype 3S. pneumoniaein BALB/c mice revealed that both 10- and 1-μg doses of A7 and 7C5 were protective, while only a 10-μg dose of 1A2 was protective. Both A7 and 7C5 were also protective in mice lacking either an intact alternative (FB−/−) or classical (C4−/−) complement pathway, but 1A2 was not protective in either strain. Our data suggest that PPS-3 consists of epitopes that can elicit both highly protective and less protective antibodies and that the superior efficacies of certain antibodies may be a function of their structures and/or specificities. Further investigation of relationships between structure, specificity, and efficacy for defined MAbs to PPS may identify antibody features that might be useful surrogates for antibody (and vaccine) efficacy.
Virulent Combinations of Adhesin and Toxin Genes in Natural Populations of
Staphylococcus aureus
Authors: Peacock Sharon J. , Moore Catrin E. , Justice Anita , Kantzanou Maria , Story Lisa , Mackie Kathryn , O'Neill Gael , Day Nicholas P. J. 
Published: October 2002

ABSTRACT

Most cases of severe
Staphylococcus aureus
disease cannot be explained by the action of a single virulence determinant, and it is likely that a number of factors act in combination during the infective process. This study examined the relationship between disease in humans and a large number of putative virulence determinants, both individually and in combination.
S. aureus
isolates (
n
= 334) from healthy blood donors and from patients with invasive disease were compared for variation in the presence of 33 putative virulence determinants. After adjusting for the effect of clonality, seven determinants (
fnbA
,
cna
,
sdrE
,
sej
,
eta
,
hlg
, and
ica
) were significantly more common in invasive isolates. All seven factors contributed independently to virulence. No single factor predominated as the major predictor of virulence, their effects appearing to be cumulative. No combinations of the seven genes were either more or less likely to cause disease than others with the same number of virulence-associated genes. There was evidence of considerable horizontal transfer of genes on a background of clonality. Our findings also suggested that allelic variants of a polymorphic locus can make different contributions to the disease process, further study of which is likely to expand our understanding of staphylococcal disease pathogenesis.
Bovine CD18 Is Necessary and Sufficient To Mediate
Mannheimia
(
Pasteurella
)
haemolytica
Leukotoxin-Induced Cytolysis
Authors: Deshpande M. S. , Ambagala T. C. , Ambagala A. P. N. , Kehrli M. E. , Srikumaran S. 
Published: October 2002

ABSTRACT

Leukotoxin (Lkt) secreted by
Mannheimia
(
Pasteurella
)
haemolytica
is an RTX toxin which is specific for ruminant leukocytes. Lkt binds to β
2
integrins on the surface of bovine leukocytes. β
2
integrins have a common β subunit, CD18, that associates with three distinct α chains, CD11a, CD11b, and CD11c, to give rise to three different β
2
integrins, CD11a/CD18 (LFA-1), CD11b/CD18 (Mac-1), and CD11c/CD18 (CR4), respectively. Our earlier studies revealed that Lkt binds to all three β
2
integrins, suggesting that the common β subunit, CD18, may be the receptor for Lkt. In order to unequivocally elucidate the role of bovine CD18 as a receptor for Lkt, a murine cell line nonsusceptible to Lkt (P815) was transfected with cDNA for bovine CD18. One of the transfectants, 2B2, stably expressed bovine CD18 on the cell surface. The 2B2 transfectant was effectively lysed by Lkt in a concentration-dependent manner, whereas the P815 parent cells were not. Immunoprecipitation of cell surface proteins of 2B2 with monoclonal antibodies specific for bovine CD18 or murine CD11a suggested that bovine CD18 was expressed on the cell surface of 2B2 as a heterodimer with murine CD11a. Expression of bovine CD18 and the Lkt-induced cytotoxicity of 2B2 cells were compared with those of bovine polymorphonuclear neutrophils and lymphocytes. There was a strong correlation between cell surface expression of bovine CD18 and percent cytotoxicity induced by Lkt. These results indicate that bovine CD18 is necessary and sufficient to mediate Lkt-induced cytolysis of target cells.
Cruzipain Induces Both Mucosal and Systemic Protection againstTrypanosoma cruziin Mice
Authors: Schnapp Anita R. , Eickhoff Chris S. , Sizemore Donata , Curtiss Roy , Hoft Daniel F. 
Published: October 2002

ABSTRACTCruzipain, the major cysteinyl proteinase ofTrypanosoma cruzi, is expressed by all developmental forms and strains of the parasite and stimulates potent humoral and cellular immune responses during infection in both humans and mice. This information suggested that cruzipain could be used to develop an effectiveT. cruzivaccine. To study whether cruzipain-specific T cells could inhibitT. cruziintracellular replication, we generated cruzipain-reactive CD4+Th1 cell lines. These T cells produced large amounts of gamma interferon when cocultured with infected macrophages, resulting in NO production and decreased intracellular parasite replication. To study the protective effects in vivo of cruzipain-specific Th1 responses against systemicT. cruzichallenges, we immunized mice with recombinant cruzipain plus interleukin 12 (IL-12) and a neutralizing anti-IL-4 MAb. These immunized mice developed potent cruzipain-specific memory Th1 cell responses and were significantly protected against normally lethal systemicT. cruzichallenges. Although cruzipain-specific Th1 responses were associated withT. cruziprotective immunity in vitro and in vivo, adoptive transfer of cruzipain-specific Th1 cells alone did not protect BALB/c histocompatible mice, indicating that additional immune mechanisms are important for cruzipain-specific immunity. To study whether cruzipain could induce mucosal immune responses relevant for vaccine development, we prepared recombinant attenuatedSalmonella entericaserovar Typhimurium vaccines expressing cruzipain. BALB/c mice immunized with salmonella expressing cruzipain were significantly protected againstT. cruzimucosal infection. Overall, these data indicate that cruzipain is an importantT. cruzivaccine candidate and that protectiveT. cruzivaccines will need to induce more than CD4+Th1 cells alone.
AChlamydia trachomatis-Specific Th2 Clone Does Not Provide Protection against a Genital Infection and Displays Reduced Trafficking to the Infected Genital Mucosa
Authors: Hawkins Raymond A. , Rank Roger G. , Kelly Kathleen A. 
Published: October 2002

ABSTRACTA T helper type 1 (Th1) response is essential for resolving genital infections with the mouse pneumonitis biovar ofChlamydia trachomatis(MoPn). However, T-cell-dependent anti-chlamydial antibody is produced and may also contribute to protective immunity. We produced a MoPn-specific CD4 Th2 clone (Th2-MoPn) to study the role of a Th2 response during infection. We found that Th2-MoPn was unable to eradicate chlamydiae from the genital tract (GT) when it was transferred into MoPn-infected nude mice. Mice that received Th2-MoPn produced greater titers of MoPn-specific serum immunoglobulin G (IgG) antibody than mice that received a MoPn-specific Th1 clone (Th1-MoPn) (log10titers, 1.89 ± 0.84 and 0.58 ± 0.76 [mean ± standard deviation], respectively [P< 0.01]). Also, the IgG isotypes were different for the two groups; whereas IgG1 was associated with Th2-MoPn, IgG2a was associated with Th1-MoPn. Also, infected nude mice that received Th2-MoPn produced higher levels of IgA in vaginal secretions. Although clone Th2-MoPn was detected in the GT, it was less efficient at migrating (112 ± 35.6 labeled Th2 clone cells/105GT cells) than Th1-MoPn (505 ± 51.6 Th1 clone cells/105GT cells) (P< 0.001, as determined by attest). This may have been due to reduced expression of α4β7 and P-selectin ligand 1 on Th2-MoPn. However, Th2-MoPn cells were retained in the GT during chronic infection and comprised 10 to 15% of the total GT cells 80 days after transfer. The data show that the MoPn-specific Th2 cells are important for serum and vaginal antibody production and may accumulate in the GT during chronic infection.
Efa1 Influences Colonization of the Bovine Intestine by Shiga Toxin-ProducingEscherichia coliSerotypes O5 and O111
Authors: Stevens Mark P. , van Diemen Pauline M. , Frankel Gad , Phillips Alan D. , Wallis Timothy S. 
Published: October 2002

ABSTRACTShiga toxin-producingEscherichia coli(STEC) comprises a broad group of bacteria, some of which cause attaching and effacing (AE) lesions and enteritis in animals and humans. Non-O157 STEC serotypes contain a gene (efa1) that mediates attachment to cultured epithelial cells. An almost-identical gene in enteropathogenicE. coli(lifA) encodes lymphostatin, which inhibits the proliferation of mitogen-activated lymphocytes and the synthesis of proinflammatory cytokines. We have investigated the role of theefa1gene in colonization of 4- and 11-day-old conventional calves by STEC serotypes O5 and O111. Our findings show that Efa1 is required for efficient colonization of the bovine intestinal tract by STEC, sinceefa1deletion and insertion mutants were shed in the feces in significantly lower numbers. In addition,efa1mutations dramatically reduced the number of bacteria associated with the intestinal epithelium. Expression and secretion of locus for enterocyte effacement-encoded type III secreted proteins that are required for adhesion and AE-lesion formation were impaired by mutation ofefa1in STEC but not by mutation oflifAin enteropathogenicE. coli. However, STECefa1mutants retain the ability to nucleate filamentous actin under sites of bacterial attachment to cultured eukaryotic cells. Efa1 is only the second STEC factor shown to influence carriage of the bacteria in the bovine intestine. Our data may have implications for strategies to reduce the prevalence of STEC in cattle.
Analysis of Pathogen-Host Cell Interactions in Purpura Fulminans: Expression of Capsule, Type IV Pili, and PorA by
Neisseria meningitidis
In Vivo
Authors: Harrison O. B. , Robertson B. D. , Faust S. N. , Jepson M. A. , Goldin R. D. , Levin M. , Heyderman R. S. 
Published: October 2002

ABSTRACT
The pattern of meningococcal surface structure expression in different microenvironments following bloodstream invasion in vivo is not known. We used immunohistochemistry to determine the expression of capsule, type IV pili, and PorA by meningococci residing in the skin lesions of children with purpura fulminans. All the skin biopsy samples showed evidence of thrombosis and, frequently, a perivascular inflammatory cell infiltrate consisting of neutrophils (elastase positive) and monocytes/macrophages (CD68 positive). Modified Gram staining revealed 20 to over 100 gram-negative diplococci in each 4-μm-thick section, usually grouped into microcolonies. Immunoperoxidase staining demonstrated that the invading meningococci expressed PorA, capsule, and type IV pilin. Expression of these antigens was not restricted to any particular environment and was found in association with meningococci located in leukocytes, small blood vessels, and the dermal interstitium. Confocal laser scanning microscopy demonstrated coexpression of pilin and capsule by numerous microcolonies. However, there was some discordance in capsule and pilin expression within the microcolonies, suggesting phase variation. The strategy employed in this study will be helpful in investigating invasive bacterial diseases where antigenic and phase variation has a significant impact on virulence and on vaccine design.
Hydrogen Peroxide-Mediated Killing ofCaenorhabditis elegansbyStreptococcus pyogenes
Authors: Jansen W. T. M. , Bolm M. , Balling R. , Chhatwal G. S. , Schnabel R. 
Published: October 2002

ABSTRACTCaenorhabditis elegansis currently introduced as a new, facile, and cheap model organism to study the pathogenesis of gram-negative bacteria such asPseudomonas aeruginosaandSalmonella entericaserovar Typhimurium. The mechanisms of killing involve either diffusible exotoxins or infection-like processes. Recently, it was shown that also some gram-positive bacteria killC. elegans, although the precise mechanisms of killing remained open. We examinedC. elegansas a pathogenesis model for the gram-positive bacteriumStreptococcus pyogenes, a major human pathogen capable of causing a wide spectrum of diseases. We demonstrate thatS. pyogeneskillsC. elegans, both on solid and in liquid medium. UnlikeP. aeruginosaandS. entericaserovar Typhimurium, the killing byS. pyogenesis solely mediated by hydrogen peroxide. Killing required live streptococci; the killing capacity depends on the amount of hydrogen peroxide produced, and killing can be inhibited by catalase. Major exotoxins ofS. pyogenesare not involved in the killing process as confirmed by using specific toxin inhibitors and knockout mutants. Moreover, no accumulation ofS. pyogenesinC. elegansis observed, which excludes the involvement of infection-like processes. Preliminary results show thatS. pneumoniaecan also killC. elegansby hydrogen peroxide production. Hydrogen peroxide-mediated killing might represent a common mechanism by which gram-positive, catalase-negative pathogens killC. elegans.