bluuebunny/crossref_metadata_2025_split huggingface dataset:
Treponema pallidumsubsp.pertenueDisplays Pathogenic Properties Different from Those ofT. pallidumsubsp.pallidum
Authors: Wicher Konrad , Wicher Victoria , Abbruscato Frank , Baughn Robert E. 
Published: July 2002

ABSTRACTThe present study described the susceptibility of C4D guinea pigs to cutaneous infection withTreponema pallidumsubsp.pertenueHaiti B strain. The general manifestations of the disease in adults and neonates differ, to a certain degree, from those induced byT. pallidumsubsp.pallidumNichols strain. Noticeable differences between the infections were reflected in the character of the skin lesions, their onset and persistence, and the kinetics of the humoral response. The incidence and dissemination of cutaneous yaws lesions in very young guinea pigs were remarkably different from the low frequency observed in a similar age group of syphilis infection, 100 versus 17%, respectively. Moreover, as opposed toT. pallidumsubsp.pallidum,T. pallidumsubsp.pertenuedoes not cross the placenta. Offspring born to yaws-infected mothers did not produce immunoglobulin M antibodies and their organs, examined by PCR and rabbit infectivity test (RIT), were all negative. Examination of a large number of tissues and organs in adult, neonate, and maternal yaws by PCR and RIT clearly demonstrated that, unlike syphilis, there was a low incidence and short persistence of the yaws pathogen in internal organs. These findings stress the dermotropic rather than the organotropic character of yaws and provide further evidence of distinctive biological and pathological differences between yaws and venereal syphilis.
Pilus-Mediated Adherence ofHaemophilus influenzaeto Human Respiratory Mucins
Authors: Kubiet Martin , Ramphal Reuben , Weber Allan , Smith Arnold 
Published: July 2002

ABSTRACTHaemophilus influenzae, especially the nontypeable strains, are among the most common pathogens encountered in patients with chronic lung disease and otitis media. We and others have demonstrated that respiratory isolates of nontypeableH. influenzaebind to human mucins, but the mechanism of binding is not entirely clear. We have therefore examined the role of pili in the adherence of both type b and nontypeableH. influenzaeto human respiratory mucins. We used isogenicH. influenzaestrains with a mutation in the structural gene for pilin (hifA), a laboratoryH. influenzaestrain transformed with a type b pilus gene cluster (from strain C54), antibodies raised againstH. influenzaeHifA, andEscherichia colistrains carrying a cloned type b pilus gene cluster (from strain AM30) in these studies. All bacteria lacking HifA or the pilus gene cluster had decreased adherence of piliatedH. influenzaeto mucins, and Fab fragments of anti-HifA antibodies inhibited the adherence.E. colistrains carrying the cloned type b pilus gene cluster were six to seven times more adhesive than strains carrying the vector. The role of other putative adhesins was not examined and thus cannot be excluded, but these studies support a role for pili in the binding ofH. influenzaeto human respiratory mucins.
Interaction of
Shigella flexneri
IpaC with Model Membranes Correlates with Effects on Cultured Cells
Authors: Tran Ngoc , Serfis Alexa Barnoski , Osiecki John C. , Picking Wendy L. , Coye Lisette , Davis Rebecca , Picking William D. 
Published: July 2002

ABSTRACT

Invasion of enterocytes by
Shigella flexneri
requires the properly timed release of IpaB and IpaC at the host-pathogen interface; however, only IpaC has been found to possess quantifiable activities in vitro. We demonstrate here that when added to cultured cells, purified IpaC elicits cytoskeletal changes similar to those that occur during
Shigella
invasion. This IpaC effect may correlate with its ability to interact with model membranes at physiological pH and to promote entry by an
ipaC
mutant of
S. flexneri
.
Relationship between the Tsh Autotransporter and Pathogenicity of Avian
Escherichia coli
and Localization and Analysis of the
tsh
Genetic Region
Authors: Dozois Charles M. , Dho-Moulin Maryvonne , Brée Annie , Fairbrother John M. , Desautels Clarisse , Curtiss Roy 
Published: July 2002

ABSTRACT

The temperature-sensitive hemagglutinin Tsh is a member of the autotransporter group of proteins and was first identified in avian-pathogenic
Escherichia coli
(APEC) strain χ7122. The prevalence of
tsh
was investigated in 300
E. coli
isolates of avian origin and characterized for virulence in a 1-day-old chick lethality test. Results indicate that among the
tsh
-positive APEC isolates, 90.6% belonged to the highest virulence class. Experimental inoculation of chickens with χ7122 and an isogenic
tsh
mutant demonstrated that Tsh may contribute to the development of lesions within the air sacs of birds but is not required for subsequent generalized infection manifesting as perihepatitis, pericarditis, and septicemia. Conjugation and hybridization experiments revealed that the
tsh
gene is located on a ColV-type plasmid in many of the APEC strains studied, including strain χ7122, near the colicin V genes in most of these strains. DNA sequences flanking the
tsh
gene of strain χ7122 include complete and partial insertion sequences and phage-related DNA sequences, some of which were also found on virulence plasmids and pathogenicity islands present in various
E. coli
pathotypes and other pathogenic members of the
Enterobacteriaceae
. These results demonstrate that the
tsh
gene is frequently located on the ColV virulence plasmid in APEC and suggest a possible role of Tsh in the pathogenicity of
E. coli
for chickens in the early stages of infection.
Cryptococcus neoformansIs a Facultative Intracellular Pathogen in Murine Pulmonary Infection
Authors: Feldmesser Marta , Kress Yvonne , Novikoff Phyllis , Casadevall Arturo 
Published: July 2002

ABSTRACTTo produce chronic infection, microbial pathogens must escape host immune defenses. Infection with the human pathogenic fungusCryptococcus neoformansis typically chronic. To understand the mechanism by whichC. neoformanssurvives in tissue after the infection of immunocompetent hosts, we systematically studied the course of pulmonary infection in mice by electron microscopy. The macrophage was the primary phagocytic cell at all times of infection, but neutrophils also ingested yeast. Alveolar macrophages rapidly internalized yeast cells after intratracheal infection, and intracellular yeast cells were noted at all times of infection from 2 h through 28 days. However, the proportion of yeast cells in the intracellular and extracellular spaces varied with the time of infection. Early in infection, yeast cells were found predominantly in the intracellular compartment. A shift toward extracellular predominance occurred by 24 h that was accompanied by macrophage cytotoxicity and disruption. Later in infection, intracellular persistence in vivo was associated with replication, residence in a membrane-bound phagosome, polysaccharide accumulation inside cells, and cytotoxicity to macrophages, despite phagolysosomal fusion. Many phagocytic vacuoles with intracellular yeast had discontinuous membranes. Macrophage infection resulted in cells with a distinctive appearance characterized by large numbers of vacuoles filled with polysaccharide antigen. Similar results were observed in vitro using a macrophage-like cell line. Our results show thatC. neoformansis a facultative intracellular pathogen in vivo. Furthermore, our observations suggest thatC. neoformansoccupies a unique niche among the intracellular pathogens whereby survival in phagocytic cells is accompanied by intracellular polysaccharide production.
Adherence of Isogenic Flagellum-Negative Mutants of
Helicobacter pylori
and
Helicobacter mustelae
to Human and Ferret Gastric Epithelial Cells
Authors: Clyne Marguerite , Ocroinin Tadhg , Suerbaum Sebastian , Josenhans Christine , Drumm Brendan 
Published: July 2002

ABSTRACT

Isogenic flagellum-negative mutants of
Helicobacter pylori
and
Helicobacter mustelae
were screened for their ability to adhere to primary human and ferret gastric epithelial cells, respectively. We also evaluated the adherence of an
H. pylori
strain with a mutation in the
flbA
gene, a homologue of the
flbF/lcrD
family of genes known to be involved in the regulation of
H. pylori
flagellar biosynthesis.
H. pylori
and
H. mustelae
mutants deficient in production of FlaA or FlaB and mutants deficient in the production of both FlaA and FlaB showed no reduction in adherence to primary human or ferret gastric epithelial cells compared with the wild-type parental strains. However, adherence of the
H. pylori flbA
mutant to human gastric cells was significantly reduced compared to the adherence of the wild-type strain. These results show that flagella do not play a direct role in promoting adherence of
H. pylori
or
H. mustelae
to gastric epithelial cells. However, genes involved in the regulation of
H. pylori
flagellar biosynthesis may also regulate the production of an adhesin.
Mutational Analysis of the
Helicobacter pylori
Vacuolating Toxin Amino Terminus: Identification of Amino Acids Essential for Cellular Vacuolation
Authors: Ye Dan , Blanke Steven R. 
Published: July 2002

ABSTRACT

The functional importance of the amino terminus of the
Helicobacter pylori
vacuolating cytotoxin (VacA) was investigated by analyzing the relative levels of vacuolation of HeLa cells transfected with plasmids encoding wild-type and mutant forms of the toxin. Notably, VacA's intracellular activity was found to be sensitive to small truncations and internal deletions at the toxin's amino terminus. Moreover, alanine-scanning mutagenesis revealed the first VacA point mutations (at proline 9 or glycine 14) that completely abolish the toxin's intracellular activity.
Phagocytic Cell Killing Mediated by Secreted Cytotoxic Factors ofVibrio cholerae
Authors: Punj Vasu , Zaborina Olga , Dhiman Neelam , Falzari Kim , Bagdasarian M. , Chakrabarty A. M. 
Published: July 2002

ABSTRACTVibrio choleraestrain VB1 secretes a number of enzymes into the outside medium that utilize ATP as a substrate. Such enzymes are found in the outside medium during the mid-log phase of growth, when the optical density at 650 nm is about 0.4, and they demonstrate nucleoside diphosphate kinase (Ndk), 5′ nucleotidase, and adenylate kinase (Ak) activities. We report that the filtered growth medium ofV. cholerae, as well as the flowthrough fraction of a green Sepharose column during fractionation of the growth medium, had very little cytotoxicity by itself towards macrophages and mast cells but exhibited significant cytotoxicity in the presence of exogenous ATP. Such fractions, harboring 5′ nucleotidase, Ndk, and presumably other ATP-utilizing enzymes, demonstrated enhanced macrophage and mast cell death; periodate-oxidized-ATP (oATP)-treated macrophage and mast cells or such cells exposed to 0.1 mM Mg2+, where surface-associated P2Z receptors could not be activated, were not susceptible to subsequent ATP addition. Microscopic visualization of mast cells clearly demonstrated cell morphological changes such as swelling, vacuolization, and nuclear fragmentation following treatment with ATP and the growth medium ofV. cholerae; however, these effects were suppressed if the mast cells were pretreated with oATP. These results strongly imply that the secreted ATP-utilizing enzymes ofV. choleraemodulate the external ATP levels of the macrophage and mast cells, leading to their accelerated death, presumably through activation of P2Z receptors. Thus, development of inhibitors for such enzymes may reduce the level ofV. choleraeinfection; alternatively, mutations in such genes may eliminateV. choleraesurvival in the gut and contribute to a safer live vaccine.
Legionella pneumophila
Major Acid Phosphatase and Its Role in Intracellular Infection
Authors: Aragon Virginia , Kurtz Sherry , Cianciotto Nicholas P. 
Published: July 2002

ABSTRACT

Legionella pneumophila
is an intracellular pathogen of protozoa and alveolar macrophages. This bacterium contains a gene (
pilD
) that is involved in both type IV pilus biogenesis and type II protein secretion. We previously demonstrated that the PilD prepilin peptidase is crucial for intracellular infection by
L. pneumophila
and that the secreted
pilD
-dependent proteins include a metalloprotease, an acid phosphatase, an esterase/lipase, a phospholipase A, and a
p
-nitrophenyl phosphorylcholine hydrolase. Since mutants lacking type IV pili, the protease, or the phosphorylcholine hydrolase are not defective for intracellular infection, we sought to determine the significance of the secreted acid phosphatase activity. Three mutants defective in acid phosphatase activity were isolated from a population of mini-Tn
10
-mutagenized
L. pneumophila
. Supernatants as well as cell lysates from these mutants contained minimal acid phosphatase activity while possessing normal levels of other
pilD
-dependent exoproteins. Genetic studies indicated that the gene affected by the transposon insertions encoded a novel bacterial histidine acid phosphatase, which we designated Map for major acid phosphatase. Subsequent inhibitor studies indicated that Map, like its eukaryotic homologs, is a tartrate-sensitive acid phosphatase. The
map
mutants grew within macrophage-like U937 cells and
Hartmannella
amoebae to the same degree as did wild-type legionellae, indicating that this acid phosphatase is not essential for
L. pneumophila
intracellular infection. However, in the course of characterizing our new mutants, we gained evidence for a second
pilD
-dependent acid phosphatase activity that, unlike Map, is tartrate resistant.
Evaluation of a Tetracycline-Inducible Promoter in
Staphylococcus aureus
In Vitro and In Vivo and Its Application in Demonstrating the Role of
sigB
in Microcolony Formation
Authors: Bateman B. T. , Donegan N. P. , Jarry T. M. , Palma M. , Cheung A. L. 
Published: July 2002

ABSTRACT

An inducible promoter system provides a powerful tool for studying the genetic basis for virulence. A variety of inducible systems have been used in other organisms, including pXyl-
xylR
-inducible promoter, the pSpac-
lacI
system, and the arabinose-inducible P
BAD
promoter, but each of these systems has limitations in its application to
Staphylococcus aureus
. In this study, we demonstrated the efficacy of a tetracycline-inducible promoter system in inducing gene expression in
S. aureus
in vitro and inside epithelial cells as well as in an animal model of infection. Using the
xyl/tetO
promoter::
gfp
uvr
fusion carried on a shuttle plasmid, we demonstrated that dose-dependant tetracycline induction, as measured by bacterial fluorescence, occurred in each of the above environments while basal activation under noninduced conditions remained low. To ascertain how the system can be used to elucidate the genetic basis of a pathogenic phenotype, we cloned the
sigB
gene downstream of the inducible promoter. Induction of SigB expression led to dose-dependent attachment of the tested strain to polystyrene microtiter wells. Additionally, bacterial microcolony formation, an event preceding mature biofilm formation, also increased with tetracycline induction of SigB.
Identification and Characterization of a Second Extracellular Collagen-Like Protein Made by Group A
Streptococcus
: Control of Production at the Level of Translation
Authors: Lukomski Slawomir , Nakashima Kazumitsu , Abdi Iman , Cipriano Vincent J. , Shelvin Bobby J. , Graviss Edward A. , Musser James M. 
Published: July 2002

ABSTRACT

A recent study found that group A
Streptococcus
(GAS) expresses a cell surface protein with similarity to human collagen (S. Lukomski, K. Nakashima, I. Abdi, V. J. Cipriano, R. M. Ireland, S. R. Reid, G. G. Adams, and J. M. Musser, Infect. Immun. 68:6542–6553, 2000). This streptococcal collagen-like protein (Scl) contains a long region of Gly-X-X motifs and was produced by serotype M1 GAS strains. In the present study, a second member of the
scl
gene family was identified and designated
scl2
. The Scl2 protein also has a collagen-like region, which in M1 strains is composed of 38 contiguous Gly-X-X triplet motifs. The
scl2
gene was present in all 50 genetically diverse GAS strains studied. The Scl2 protein is highly polymorphic, and the number of Gly-X-X motifs in the 50 strains studied ranged from 31 in one serotype M1 strain to 79 in serotype M28 and M77 isolates. The
scl1
and
scl2
genes were simultaneously transcribed in the exponential phase, and the Scl proteins were also produced. Scl1 and Scl2 were identified in a cell-associated form and free in culture supernatants. Production of Scl1 is regulated by Mga, a positive transcriptional regulator that controls expression of several GAS virulence factors. In contrast, production of Scl2 is controlled at the level of translation by variation in the number of short-sequence pentanucleotide repeats (CAAAA) located immediately downstream of the GTG (Val) start codon. Control of protein production by this molecular mechanism has not been identified previously in GAS. Together, the data indicate that GAS simultaneously produces two extracellular human collagen-like proteins in a regulated fashion.
Plasminogen Binding and Activation by
Mycoplasma fermentans
Authors: Yavlovich Amichai , Higazi Abd A.-R. , Rottem Shlomo 
Published: July 2002

ABSTRACT

The binding of plasminogen to
Mycoplasma fermentans
was studied by an immunoblot analysis and by a binding assay using iodine-labeled plasminogen. The binding of
125
I-labeled plasminogen was inhibited by unlabeled plasminogen, lysine, and lysine analog ɛ-aminocaproic acid. Partial inhibition was obtained by a plasminogen fragment containing kringles 1 to 3 whereas almost no inhibition was observed with a fragment containing kringle 4. Scatchard analysis revealed a dual-phase interaction, one with a dissociation constant (

k
d

) of 0.5 μM and the second with a

k
d

of 7.5 μM. The estimated numbers of plasminogen molecules bound were calculated to be 110 and 790 per cell, respectively. Autoradiograms of ligand blots containing
M. fermentans
membrane proteins incubated with
125
I-labeled plasminogen identified two plasminogen-binding proteins of about 32 and 55 kDa. The binding of plasminogen to
M. fermentans
enhances the activation of plasminogen to plasmin by the urokinase-type plasminogen activator (uPA), as monitored by measuring the breakdown of chromogenic substrate S-2251. Enhancement was more pronounced with the low-molecular-weight and the single-chain uPA variants, known to have low plasminogen activator activities. The binding of plasminogen also promotes the invasion of HeLa cells by
M. fermentans
. Invasion was more pronounced in the presence of uPA, suggesting that the ability of the organism to invade host cells stems not only from its potential to bind plasminogen but also from the activation of plasminogen to plasmin.
Stage-Dependent Role of Nitric Oxide in Control ofTrypanosoma cruziInfection
Authors: Saeftel Michael , Fleischer Bernhard , Hoerauf Achim 
Published: July 2002

ABSTRACTTrypanosoma cruzi, the causative agent of Chagas' disease, is known to be susceptible to nitric oxide (NO)-dependent killing by gamma interferon-activated macrophages. Mice deficient for inducible nitric oxide synthase (iNOS) are highly susceptible toT. cruzi, and inhibition of iNOS from the beginning of infection was reported to lead to an increase in trypomastigotes in the blood and to high mortality. In the present study, we investigated whether NO production is essential for the control ofT. cruziin all phases of the infection. BALB/c mice were treated at different time intervals afterT. cruziinfection with an iNOS inhibitor, aminoguanidine orl-N6-(1-iminoethyl)-lysine (L-NIL). Treatment initiated with the beginning of the infection resulted in 100% mortality by day 16 postinfection (p.i.). If treatment was started later during the acute phase at the peak of parasitemia (day 20 p.i.), all the mice survived. Parasitemia was cleared and tissue amastigotes became undetectable in these mice even in the presence of the iNOS inhibitor L-NIL. Inhibition of iNOS in the chronic phase of the infection, i.e., from day 60 to day 120 p.i., with L-NIL did not result in a reappearance of parasitemia. These data suggest that while NO is essential forT. cruzicontrol in the early phase of acute infection, it is dispensable in the late acute and chronic phase, revealing a fundamental difference in control mechanisms compared to those in infections by other members of the orderKinetoplastida, e.g.,Leishmania major.
HtrA Homologue of
Legionella pneumophila
: an Indispensable Element for Intracellular Infection of Mammalian but Not Protozoan Cells
Authors: Pedersen Lisa L. , Radulic Marina , Doric Miljenko , Abu Kwaik Yousef 
Published: July 2002

ABSTRACT

Legionella pneumophila
replicates within alveolar macrophages, and possibly, alveolar epithelial cells and also within protozoa in the aquatic environment. Here we characterize an
L. pneumophila
mutant defective in the HtrA/DegP stress-induced protease/chaperone homologue and show that HtrA is indispensable for intracellular replication within mammalian macrophages and alveolar epithelial cells and for intrapulmonary replication in A/J mice. Importantly, amino acid substitutions of two conserved residues in the catalytic domain of (H
103
➤R and S
212
➤A) and in-frame deletions of either or both of the two conserved PDZ domains of HtrA abolish its function. Interestingly, the
htrA
mutant exhibits a parental-type phenotype in intracellular replication within the protozoan host
Acanthamoeba polyphaga
. We used a promoterless
lacZ
fusion to the
htrA
promoter to probe the phagosomal microenvironment harboring
L. pneumophila
within macrophages and within
A. polyphaga
for the exposure to stress stimuli. The data show that expression through the
htrA
promoter is induced by 12,000- to 20,000-fold throughout the intracellular infection of macrophages but its induction is by 120- to 500-fold within protozoa compared to in vitro expression. Data derived from confocal laser scanning microscopy reveal that in contrast to the parental strain, phagosomes harboring the
htrA
mutant within U937 macrophages colocalize with the late endosomal-lysosomal marker LAMP-2, similar to killed
L. pneumophila
. Coinfection experiments examined by confocal laser scanning microscopy show that in communal phagosomes harboring both the parental strain and the
htrA
mutant, replication of the mutant is not rescued, while replication of a
dotA
mutant control, which is normally trafficked into a phagolysosome, is rescued by the parental strain. Our data show, for the first time, that the stress response by
L. pneumophila
(mediated, at least in part, by HtrA) is indispensable for intracellular replication within mammalian but not protozoan cells.