bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloning and Characterization of the Gene Encoding the Glutamate Dehydrogenase of
Streptococcus suis
Serotype 2
Authors: Okwumabua Ogi , Persaud Julia S. , Reddy P. G. 
Published: July 2002

ABSTRACT

Given the lack of effective vaccines to control
Streptococcus suis
infection and the lack of a rapid and reliable molecular diagnostic assay to detect its infection, a polyclonal antibody was raised against the whole-cell protein of
S. suis
type 2 and used to screen an
S. suis
gene library in an effort to identify protective antigen(s) and antigens of diagnostic importance. A clone that produced a 45-kDa
S. suis
-specific protein was identified by Western blotting. Restriction analysis showed that the gene encoding the 45-kDa protein was present on a 1.6-kb pair
Dra
I region on the cloned chromosomal fragment. The nucleotide sequence contained an open reading frame that encoded a polypeptide of 448 amino acid residues with a calculated molecular mass of 48.8 kDa, in close agreement with the size observed on Western blots. A GenBank database search revealed that the derived amino acid sequence is homologous to the sequence of glutamate dehydrogenase (GDH) protein isolated from various sources, including conserved motifs and functional domains typical of the family 1-type hexameric GDH proteins, thus placing it in that family. Because of these similarities, the protein was designated the GDH of
S. suis
. Hybridization studies showed that the gene is conserved among the
S. suis
type 2 strains tested. Antiserum raised against the purified recombinant protein was reactive with a protein of the same molecular size as the recombinant protein in
S. suis
strains, suggesting expression of the gene in all of the isolates and antigenic conservation of the protein. The recombinant protein was reactive with serum from pigs experimentally infected with a virulent strain of
S. suis
type 2, suggesting that the protein might serve as an antigen of diagnostic importance to detect
S. suis
infection. Activity staining showed that the
S. suis
GDH activity is NAD(P)H dependent but, unlike the NAD(P)H-dependent GDH from various other sources, that of
S. suis
utilizes
l
-glutamate rather than α-ketoglutarate as the substrate. Highly virulent strains of
S. suis
type 2 could be distinguished from moderately virulent and avirulent strains on the basis of their GDH protein profile following activity staining on a nondenaturing gel. We examined the cellular location of the protein using a whole-cell enzyme-linked immunosorbent assay and an immunogold-labeling technique. Results showed that the
S. suis
GDH protein is exposed at the surface of intact cells.
Immune Responses in Hookworm Infections
Authors: Loukas Alex , Prociv Paul 
Published: July 2002

SUMMARYHookworms infect perhaps one-fifth of the entire human population, yet little is known about their interaction with our immune system. The two major species are Necator americanus, which is adapted to tropical conditions, and Ancylostoma duodenale, which predominates in more temperate zones. While having many common features, they also differ in several key aspects of their biology. Host immune responses are triggered by larval invasion of the skin, larval migration through the circulation and lungs, and worm establishment in the intestine, where adult worms feed on blood and mucosa while injecting various molecules that facilitate feeding and modulate host protective responses. Despite repeated exposure, protective immunity does not seem to develop in humans, so that infections occur in all age groups (depending on exposure patterns) and tend to be prolonged. Responses to both larval and adult worms have a characteristic T-helper type 2 profile, with activated mast cells in the gut mucosa, elevated levels of circulating immunoglobulin E, and eosinoophilia in the peripheral blood and local tissues, features also characteristic of type I hypersensitivity reactions. The longevity of adult hookworms is determined probably more by parasite genetics than by host immunity. However, many of the proteins released by the parasites seem to have immunomodulatory activity, presumably for self-protection. Advances in molecular biotechnology enable the identification and characterization of increasing numbers of these parasite molecules and should enhance our detailed understanding of the protective and pathogenetic mechanisms in hookworm infections.
Extended-Spectrum β-Lactamases in the 21st Century: Characterization, Epidemiology, and Detection of This Important Resistance Threat
Authors: Bradford Patricia A. 
Published: July 2002

SUMMARYβ-Lactamases continue to be the leading cause of resistance to β-lactam antibiotics among gram-negative bacteria. In recent years there has been an increased incidence and prevalence of extended-spectrum β-lactamases (ESBLs), enzymes that hydrolyze and cause resistance to oxyimino-cephalosporins and aztreonam. The majority of ESBLs are derived from the widespread broad-spectrum β-lactamases TEM-1 and SHV-1. There are also new families of ESBLs, including the CTX-M and OXA-type enzymes as well as novel, unrelated β-lactamases. Several different methods for the detection of ESBLs in clinical isolates have been suggested. While each of the tests has merit, none of the tests is able to detect all of the ESBLs encountered. ESBLs have become widespread throughout the world and are now found in a significant percentage of Escherichia coli and Klebsiella pneumoniae strains in certain countries. They have also been found in other Enterobacteriaceae strains and Pseudomonas aeruginosa. Strains expressing these β-lactamases will present a host of therapeutic challenges as we head into the 21st century.
Recent Advances in Biology and Immunobiology ofEimeriaSpecies and in Diagnosis and Control of Infection with These Coccidian Parasites of Poultry
Authors: Allen P. C. , Fetterer R. H. 
Published: July 2002

SUMMARYAvian coccidiosis, an intestinal disease caused by protozoan parasites of the genus Eimeria, occurs worldwide. It is considered to be one of the most economically important diseases of domestic poultry. For many years, prophylactic use of anticoccidial feed additives has been the primary means of controlling coccidiosis in the broiler industry and has played a major role in the growth of this industry, which now can produce about 7.6 billion chickens annually. However, development of anticoccidial resistance has threatened the economic stability of the broiler industry. Although there has been little effort by the pharmaceutical industry to develop new anticoccidials, the mounting problem of drug resistance of Eimeria species has prompted major research efforts to seek alternative means of control through increased knowledge of parasite biology, host response, and nutritional modulation. As a consequence, important advancements have been made, particularly in defining parasite antigens that have potential use in vaccines, defining the Eimeria genome, understanding the immunology of coccidial infections, and the practical applications of live vaccines. This review describes the progress in these areas, most of which has occurred within the past 10 to 15 years.
Gene Expression and Production of Tumor Necrosis Factor Alpha, Interleukin-1β (IL-1β), IL-8, Macrophage Inflammatory Protein 1α (MIP-1α), MIP-1β, and Gamma Interferon-Inducible Protein 10 by Human Neutrophils Stimulated with Group B Meningococcal Outer Membrane Vesicles
Authors: Lapinet José A. , Scapini Patrizia , Calzetti Federica , Pérez Oliver , Cassatella Marco A. 
Published: July 2002

ABSTRACTAccumulation of polymorphonuclear neutrophils (PMN) into the subarachnoidal space is one of the hallmarks ofNeisseria meningitidisinfection. In this study, we evaluated the ability of outer membrane vesicles (OMV) fromN. meningitidisB to stimulate cytokine production by neutrophils. We found that PMN stimulated in vitro by OMV produce proinflammatory cytokines and chemokines including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-8, macrophage inflammatory protein 1α (MIP-1α), and MIP-1β. A considerable induction of gamma interferon (IFN-γ)-inducible protein 10 (IP-10) mRNA transcripts, as well as extracellular IP-10 release, was also observed when neutrophils were stimulated by OMV in combination with IFN-γ. Furthermore, PMN stimulated by OMV in the presence of IFN-γ demonstrated an enhanced capacity to release TNF-α, IL-1β, IL-8, and MIP-1β compared to stimulation with OMV alone. In line with its downregulatory effects on neutrophil-derived proinflammatory cytokines, IL-10 potently inhibited TNF-α, IL-1β, IL-8, and MIP-1β production triggered by OMV. Finally, a neutralizing anti-TNF-α monoclonal antibody (MAb) did not influence the release of IL-8 and MIP-1β induced by OMV, therefore excluding a role for endogenous TNF-α in mediating the induction of chemokine release by OMV. In contrast, the ability of lipopolysaccharide fromN. meningitidisB to induce the production of IL-8 and MIP-1β was significantly inhibited by anti-TNF-α MAb. Our results establish that, in response to OMV, neutrophils produce a proinflammatory profile of cytokines and chemokines which may not only play a role in the pathogenesis of meningitis but may also contribute to the development of protective immunity to serogroup B meningococci.
Isolation of
Neisseria gonorrhoeae
Mutants That Show Enhanced Trafficking across Polarized T84 Epithelial Monolayers
Authors: Hopper Sylvia , Wilbur J. Scott , Vasquez Brandi L. , Larson Jason , Clary Susan , Mehr Ian J. , Seifert H. S. , So Magdalene 
Published: July 2002

ABSTRACT

Initiation of a gonococcal infection involves attachment of
Neisseria gonorrhoeae
to the plasma membrane of an epithelial cell in the mucosal epithelium and its internalization, transepithelial trafficking, and exocytosis from the basal membrane. Piliation and expression of certain Opa proteins and the immunoglobulin A1 protease influence the transcytosis process. We are interested in identifying other genetic determinants of
N. gonorrhoeae
that play a role in transcellular trafficking. Using polarized T84 monolayers as a model epithelial barrier, we have assayed an
N. gonorrhoeae
FA1090 minitransposon (mTn) mutant bank for isolates that traverse the monolayer more quickly than the isogenic wild-type (WT) strain. From an initial screen, we isolated four mutants, defining three genetic loci, that traverse monolayers significantly more quickly than their WT parent strain. These mutants adhere to and invade cells normally and do not affect the integrity of the monolayer barrier. Backcrosses of the mutations into the WT FA1090 strain yielded mutants with a similar fast-trafficking phenotype. In two mutants, the mTns had inserted 370 bp apart into the same locus, which we have named
fit
, for fast intracellular trafficker. Backcrosses of one of these mutants into the MS11A genetic background also yielded a fast-trafficking mutant. The
fit
locus contains two overlapping open reading frames,
fitA
and
fitB
, whose deduced amino acid sequences have predicted molecular weights of 8.6 and 15.3, respectively. Neither protein contains a signal sequence. FitA has a potential helix-turn-helix motif, while the deduced sequence of FitB offers no clues to its function.
fitA
or
fitB
homologues are present in the genomes of
Pseudomonas syringae
and
Rhizobium meliloti
, but not
Neisseria meningitidis
. Replication of the MS11A
fitA
mutant in A431 and T84 cells is significantly accelerated compared to that of the isogenic WT strain. In contrast, growth of this mutant in liquid media is normal. Taken together, these results strongly suggest that traversal of
N. gonorrhoeae
across an epithelial barrier is linked to intracellular bacterial growth.
Humanized In Vivo Model for Streptococcal Impetigo
Authors: Scaramuzzino Dominick A. , McNiff Jennifer M. , Bessen Debra E. 
Published: July 2002

ABSTRACTAn in vivo model for group A streptococcal (GAS) impetigo was developed, whereby human neonatal foreskin engrafted onto SCID mice was superficially damaged and bacteria were topically applied. Severe infection, indicated by a purulent exudate, could be induced with as few as 1,000 CFU of a virulent strain. Early findings (48 h) showed a loss of stratum corneum and adherence of short chains of gram-positive cocci to the external surface of granular keratinocytes. This was followed by an increasing infiltration of polymorphonuclear leukocytes (neutrophils) of mouse origin, until a thick layer of pus covered an intact epidermis, with massive clumps of cocci accumulated at the outer rim of the pus layer. By 7 days postinoculation, the epidermis was heavily eroded; in some instances, the dermis contained pockets (ulcers) filled with cocci, similar to that observed for ecthyma. Importantly, virulent GAS underwent reproduction, resulting in a net increase in CFU of 20- to 14,000-fold. The majority ofemmpattern D strains had a higher gross pathology score thanemmpattern A, B, or C (A–C) strains, consistent with epidemiological findings that pattern D strains have a strong tendency to cause impetigo, whereas pattern A–C strains are more likely to cause pharyngitis.
Production of Toxic Shock Syndrome Toxin 1 by
Staphylococcus aureus
Requires Both Oxygen and Carbon Dioxide
Authors: Ross Robin A. , Onderdonk Andrew B. 
Published: July 2002

ABSTRACT

The effect of O
2
and CO
2
on expression of toxic shock syndrome toxin 1 (TSST-1) by
Staphylococcus aureus
was investigated under controlled growth conditions with continuous-culture techniques. To stimulate TSST-1 production, air and anaerobic gas were premixed before delivery to the culture vessel. At a growth rate—or mass doubling time (
t
d
)—of 3 h, production of specific TSST-1 (expressed as micrograms per milligram of cell dry weight) was 5.9-fold greater at an O
2
concentration of 4% than under anaerobic conditions. Increasing the O
2
concentration to 11% did not result in a significant increase (
P
> 0.05) in the rate of toxin production over that during growth in 4% O
2
but did result in a significant increase (4.9-fold;
P
< 0.001) in the rate of toxin production over that during anaerobic growth. At a
t
d
of 9 h, addition of 3.5% O
2
resulted in a 7.6-fold increase in specific TSST-1 production. When room air was sparged through a culture growing at a
t
d
of 9 h, TSST-1 production increased significantly (by 3.4-fold) over that during anaerobic growth. When a growth environment of 4% O
2
–remainder N
2
was studied, no increase in TSST-1 production was observed; this was also the case with 8% O
2
at gas-flow rates of 0.1, 0.2, and 0.4 liters/min. In all experiments, production of biomass (expressed as milligrams of cell dry weight per milliliter) increased, indicating that O
2
was metabolized by
S. aureus
. Addition of CO
2
to the gas mix (4% O
2
, 10% CO
2
, 86% N
2
) resulted in a 5.1- to 6.8-fold increase in TSST-1 production over that during anaerobic growth and a 3.6-fold increase over that during growth in an environment of 4% O
2
–remainder N
2
. The
agr
mutant strain tested produced 6.1-fold more specific TSST-1 in a growth environment of 4% O
2
–10% CO
2
–86% N
2
than during anaerobic growth. These data suggest that in this system, O
2
alone does not trigger production of TSST-1; rather, both CO
2
and O
2
are required.
ς
B
Activity in
Staphylococcus aureus
Is Controlled by RsbU and an Additional Factor(s) during Bacterial Growth
Authors: Palma Marco , Cheung Ambrose L. 
Published: July 2002

ABSTRACT

Two genes of the
sigB
operon,
rsbU
and
rsbV
, were deleted in an
rsbU
+
strain (FDA486) to evaluate the contribution of these two genes to ς
B
activity in
Staphylococcus aureus.
The ς
B
protein level and the transcription of two ς
B
-dependent promoters (
sigB
and
sarA
P3 transcripts) were analyzed in the constructed mutants. A deletion of the first gene (
rsbU
) within the
sigB
operon led only to a partial reduction in ς
β
activity. A deletion of the second gene (
rsbV
) resulted in a more dramatic reduction in the ς
B
protein level and its activity than did the deletion of
rsbU
, thus indicating that RsbV can be activated independent of RsbU. In the parental strain, the ς
B
-dependent transcript initiated upstream of
rsbV
was 28-fold higher than the ς
A
-dependent transcript originating from the
rsbU
promoter. The level of the ς
B
-dependent transcript decreased up to 50% in the
rsbU
mutant and up to 90% in the
rsbV
mutant compared with the transcript in the wild type. The yellow pigment of
S
.
aureus
colonies, a ς
B
-dependent phenotype, was partially reduced in the
rsbU
and
rsbV
mutants, whereas alpha-hemolysin was increased. Additionally, the
sarA
P3 promoter activity of the parental strain was induced to a higher level in response to pH 5.5 than was that of the
rsbU
or
rsbV
mutant, indicating that RsbU is the major activator of the ς
B
response to acid stress. Using a tetracycline-inducible system to modulate the expression of RsbW, we progressively repressed pigment production, presumably by reducing the free ς
B
level. Collectively, our data indicated that RsbU and RsbV in
S
.
aureus
contributed to different levels of ς
B
protein expression and varying ς
B
activities. Although RsbV can activate ς
B
independent of RsbU, RsbU remains the major activator of ς
B
during acid stress.
Cu,Zn Superoxide Dismutase ofMycobacterium tuberculosisContributes to Survival in Activated Macrophages That Are Generating an Oxidative Burst
Authors: Piddington Debra L. , Fang Ferric C. , Laessig Tracey , Cooper Andrea M. , Orme Ian M. , Buchmeier Nancy A. 
Published: July 2002

ABSTRACTMacrophages produce reactive oxygen species and reactive nitrogen species that have potent antimicrobial activity. Resistance to killing by macrophages is critical to the virulence ofMycobacterium tuberculosis. M. tuberculosishas two genes encoding superoxide dismutase proteins,sodAandsodC. SodC is a Cu,Zn superoxide dismutase responsible for only a minor portion of the superoxide dismutase activity ofM. tuberculosis. However, SodC has a lipoprotein binding motif, which suggests that it may be anchored in the membrane to protectM. tuberculosisfrom reactive oxygen intermediates at the bacterial surface. To examine the role of the Cu,Zn superoxide dismutase in protectingM. tuberculosisfrom the toxic effects of exogenously generated reactive oxygen species, we constructed a null mutation in thesodCgene. In this report, we show that theM. tuberculosis sodCmutant is readily killed by superoxide generated externally, while the isogenic parentalM. tuberculosisis unaffected under these conditions. Furthermore, thesodCmutant has enhanced susceptibility to killing by gamma interferon (IFN-γ)-activated murine peritoneal macrophages producing oxidative burst products but is unaffected by macrophages not activated by IFN-γ or by macrophages from respiratory burst-deficient mice. These observations establish that the Cu,Zn superoxide dismutase contributes to the resistance ofM. tuberculosisagainst oxidative burst products generated by activated macrophages.
Comparative Immune Response to PE and PE_PGRS Antigens of
Mycobacterium tuberculosis
Authors: Delogu Giovanni , Brennan Michael J. 
Published: July 2002

ABSTRACT

Sequencing of the entire genome of
Mycobacterium tuberculosis
identified a novel multigene family composed of two closely related subfamilies designated PE and PE_PGRS. The major difference between these two families is the presence of a domain containing numerous Gly-Ala repeats extending to the C terminus of the PE_PGRS genes. We have used a representative PE_PGRS gene from
M. tuberculosis, Rv1818c
(1818
PE_PGRS
), and its amino-terminal PE region (1818
PE
), to investigate the immunological response to these proteins during experimental tuberculosis and following immunization with DNA constructs. During infection of mice with
M. tuberculosis
, a significant humoral immune response was observed against recombinant 1818
PE_PGRS
but not toward the 1818
PE
protein. Similarly, immunization with a 1818
PE_PGRS
DNA construct induced antibodies directed against 1818
PE_PGRS
but not against 1818
PE
proteins, and no humoral response was induced by 1818
PE
DNA. These results suggest that certain PE_PGRS genes are expressed during infection of the host with
M. tuberculosis
and that an antibody response is directed solely against the Gly-Ala-rich PGRS domain. Conversely, splenocytes from 1818
PE
-vaccinated mice but not mice immunized with 1818
PE_PGRS
secreted gamma interferon following in vitro restimulation and demonstrated protection in the mouse tuberculosis challenge model. These results suggest that the PE vaccine can elicit an effective cellular immune response and that immune recognition of the PE antigen is influenced by the Gly-Ala-rich PGRS domain.
NhaA, an Na
+
/H
+
Antiporter Involved in Environmental Survival of
Vibrio cholerae
Authors: Vimont Sophie , Berche Patrick 
Published: July 2002

ABSTRACT

Vibrio cholerae
, the agent of cholera, is a normal inhabitant of aquatic environments, in which it survives under a wide range of conditions of pH and salinity. In this work, we identified the
nhaA
gene in a wild-type epidemic strain of
V. cholerae
O1.
nhaA
encodes a protein of 382 amino acids that is very similar to the proteins NhaA of
Vibrio parahaemolyticus
,
Vibrio alginolyticus
(∼87% identity), and
Escherichia coli
(56% identity).
V. cholerae
NhaA complements an
E. coli nhaA
mutant, enabling it to grow in 700 mM NaCl, pH 7.5, indicating functional homology to
E. coli
NhaA. However, unlike
E. coli
, the growth of a
nhaA
-inactivated mutant of
V. cholerae
was not restricted at various pH and NaCl concentrations, although it was inhibited in the presence of 120 mM LiCl at pH 8.5. Nevertheless, using a
nhaA′-lacZ
transcriptional fusion, we observed induction of
nhaA
transcription by Na
+
, Li
+
, and K
+
. These results strongly suggest that NhaA is an Na
+
/H
+
antiporter contributing to the Na
+
/H
+
homeostasis of
V. cholerae. nhaA
-related sequences were detected in all strains of
V. cholerae
from the various serogroups. This gene is presumably involved in the survival and persistence of free-living bacteria in their natural habitat.
Population Studies of Methicillin-Resistant and -Sensitive
Staphylococcus aureus
Strains Reveal a Lack of Variability in the
agrD
Gene, Encoding a Staphylococcal Autoinducer Peptide
Authors: van Leeuwen Willem , van Nieuwenhuizen Wendy , Gijzen Christel , Verbrugh Henri , van Belkum Alex 
Published: July 2002

ABSTRACT

The virulence of
Staphylococcus aureus
is controlled by the accessory gene regulator (
agr
) system, including an extracellular inducer encoded by
agrD
. Variable
agr
PCR restriction fragment length polymorphism (RFLP) patterns of unique
S. aureus
strains (
n
= 192) were determined for a region comprising
agrD
and parts of the neighboring
agrC
and
agrB
genes. Twelve unique RFLP patterns were identified among
S. aureus
strains in general; these patterns were further specified by sequencing. All sequences could be catalogued in the three current
agr
groups. A major proportion of the
S. aureus
strains belong to
agr
group 1, whereas only 6% of the methicillin-susceptible
S. aureus
strains and 5% of the methicillin-resistant
S. aureus
strains belong to
agr
groups 2 and 3, respectively. The homology between groups varied from 75 to 80%, and within groups it varied from 96 to 100%. Different levels of sequence variability were observed in the different
agr
genes.
agr
-related bacterial interference among colonizing
S. aureus
strains in the noses of persistent and intermittent human carriers was studied.
S. aureus
strains belonging to different agr groups were encountered in the same individual. This may suggest that the activity of the
agrD
gene product does not define colonization dynamics, which is further substantiated by the rarity of
agr
group 2 and 3 strains.