bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Gamma Interferon in Cellular Immune Response against MurineEncephalitozoon cuniculiInfection
Authors: Khan Imtiaz A. , Moretto Magali 
Published: March 2020

ABSTRACTMicrosporidia are obligate intracellular protozoan parasites that cause a wide variety of opportunistic infection in patients with AIDS. Because it is able to grow in vitro,Encephalitozoon cuniculiis currently the best-studied microsporidian. T cells mediate protective immunity against this parasite. Splenocytes obtained from infected mice proliferate in vitro in response to irradiated parasites. A transient state of hyporesponsiveness to parasite antigen and mitogen was observed at day 17 postinfection. This downregulatory response could be partially reversed by addition of nitric oxide (NO) antagonist to the culture. Mice infected withE. cuniculisecrete significant levels of gamma interferon (IFN-γ). Treatment with antibody to IFN-γ or interleukin-2 (IL-12) was able to neutralize the resistance to the parasite. Mutant animals lacking the IFN-γ or IL-12 gene were highly susceptible to infection. However, mice unable to secrete NO withstood high doses of parasite challenge, similar to normal wild-type animals. These studies describe an IFN-γ-mediated protection againstE. cuniculiinfection that is independent of NO production.
Effect of Temperature on Growth, Hemagglutination, and Protease Activity ofPorphyromonas gingivalis
Authors: Percival Rimondia S. , Marsh Philip D. , Devine Deirdre A. , Rangarajan Minnie , Aduse-Opoku Joseph , Shepherd Philip , Curtis Michael A. 
Published: March 2020

ABSTRACTBacteria persisting in periodontal pockets are exposed to elevated temperatures during periods of inflammation. Temperature is an environmental factor that can modulate gene expression. Consequently, in the present study we examined the effect of temperature on the expression of virulence determinants by the periodontopathogen,Porphyromonas gingivalis. P. gingivalisW50 was grown in a complex medium under hemin excess at pH 7.0 and at a constant temperature of either 37, 39, or 41°C; cultures were monitored for protease and hemagglutinin activity.P. gingivalisgrew well at all three temperatures. An increase in growth temperature from 37 to 39°C resulted in a 65% reduction in both total arginine- and lysine-specific activities (P< 0.01). A further rise in growth temperature to 41°C led to even greater reductions in arginine-specific (82%;P< 0.001) and lysine-specific (73%;P< 0.01) activities. These reductions were also associated with an altered distribution of individual arginine-specific enzyme isoforms. At 41°C, there was a disproportionate reduction in the level of the heterodimeric RI protease, which also contains adhesin domains. The reduction also correlated with a markedly diminished hemagglutination activity of cells, especially in those grown at 41°C, and a reduced immunoreactivity with a monoclonal antibody which recognizes gene products involved in hemagglutination. Thus, as the environmental temperature increased,P. gingivalisadopted a less aggressive phenotype, while retaining cell population levels. The coordinate down-regulation of virulence gene expression in response to an environmental cue linked to the intensity of the host inflammatory response is consistent with the clinically observed cyclical nature of disease progression in periodontal diseases.
Adaptive Immune Response toShigella flexneri2acydCin Immunocompetent Mice and Mice Lacking Immunoglobulin A
Authors: Way Sing Sing , Borczuk Alain C. , Goldberg Marcia B. 
Published: March 2020

ABSTRACTShigella flexneri cydC, which is deficient in cytochromebd, was rapidly cleared from the lungs of intranasally inoculated mice and was Sereny negative, yet it induced 93% protection against challenge with wild-typeS. flexneri. Mice that lack immunoglobulin A (IgA) were fully protected, suggesting that IgA may not be required for adaptive immunity in this model system.
Biological Properties of Structurally Related α-Helical Cationic Antimicrobial Peptides
Authors: Scott Monisha G. , Yan Hong , Hancock Robert E. W. 
Published: March 2020

ABSTRACT

A series of α-helical cationic antimicrobial peptide variants with small amino acid changes was designed. Alterations in the charge, hydrophobicity, or length of the variant peptides did not improve the antimicrobial activity, and there was no statistically significant correlation between any of these factors and the MIC for
Pseudomonas aeruginosa
,
Escherichia coli
, or
Salmonella typhimurium
. Individual peptides demonstrated synergy with conventional antibiotics against antibiotic-resistant strains of
P. aeruginosa
. The peptides varied considerably in the ability to bind
E. coli
O111:B4 lipopolysaccharide (LPS), and this correlated significantly with their antimicrobial activity and ability to block LPS-stimulated tumor necrosis factor and interleukin-6 production. In general, the peptides studied here demonstrated a broad range of activities, including antimicrobial, antiendotoxin, and enhancer activities.
Biological Effects of
Pseudomonas aeruginosa
Type III-Secreted Proteins on CHO Cells
Authors: Vallis Amy J. , Finck-Barbançon Viviane , Yahr Timothy L. , Frank Dara W. 
Published: March 2020

ABSTRACT

A strain of
Pseudomonas aeruginosa
that fails to express known type III-secreted effector proteins was constructed as an expression host. Individual effectors were expressed in
trans
, and their biological effects on CHO cells were assessed in an acute cellular infection model. Intoxication with ExoS, ExoT, or ExoY resulted in alterations in cell morphology. As shown in previous genetic studies, ExoU expression was linked to acute cytotoxicity.
uspB
, a New ς
S
-Regulated Gene in
Escherichia coli
Which Is Required for Stationary-Phase Resistance to Ethanol
Authors: Farewell Anne , Kvint Kristian , Nyström Thomas 
Published: March 2020

ABSTRACT

The open reading frame immediately upstream of
uspA
is demonstrated to encode a 14-kDa protein which we named UspB (universal stress protein B) because of its general responsiveness to different starvation and stress conditions. UspB is predicted to be an integral membrane protein with at least one and perhaps two membrane-spanning domains. Overexpression of UspB causes cell death in stationary phase, whereas mutants of
uspB
are sensitive to exposure to ethanol but not heat in stationary phase. In contrast to
uspA
, stationary-phase induction of
uspB
requires the sigma factor ς
S
. The expression of
uspB
is modulated by H-NS, consistent with the role of H-NS in altering ς
S
levels. Our results demonstrate that a gene of the RpoS regulon is involved in the development of stationary-phase resistance to ethanol, in addition to the regulon’s previously known role in thermotolerance, osmotolerance, and oxidative stress resistance.
The General Stress Sigma Factor ς
S
of
Escherichia coli
Is Induced during Diauxic Shift from Glucose to Lactose
Authors: Fischer Daniela , Teich Antje , Neubauer Peter , Hengge-Aronis Regine 
Published: March 2020

ABSTRACT

The general stress sigma factor ς
S
(RpoS) of
Escherichia coli
is strongly induced in response to glucose starvation. This increase in the cellular ς
S
level is due to stabilization of ς
S
, which under non-stress conditions is subject to rapid proteolysis. In the present study, it is demonstrated that ς
S
is also induced during the diauxic shift from glucose to lactose, i.e., under conditions of glucose exhaustion in the presence of another, less-preferred carbon source that eventually gets utilized. This ς
S
induction, which is due to stabilization, is transient and precedes the induction of β-galactosidase. In parallel, ς
S
-dependent genes are transiently activated, as was shown here for
osmY
. Although ς
S
can mediate transcription of
lacZ
in vitro, ς
S
does not contribute to the induction of β-galactosidase during the diauxic lag phase. Rather, the induction of ς
S
and the general stress response during the diauxic shift plays the role of a rapidly activated emergency system, which is shut off again as soon as the cells are able to cope with the stress situation by utilizing a more specific and more economical system.
Role and Regulation of
Bacillus subtilis
Glutamate Dehydrogenase Genes
Authors: Belitsky Boris R. , Sonenshein Abraham L. 
Published: March 2020

ABSTRACT

The complete
Bacillus subtilis
genome contains two genes with the potential to encode glutamate dehydrogenase (GlutDH) enzymes. Mutations in these genes were constructed and characterized. The
rocG
gene proved to encode a major GlutDH whose synthesis was induced in media containing arginine or ornithine or, to a lesser degree, proline and was repressed by glucose. A
rocG
null mutant was impaired in utilization of arginine, ornithine, and proline as nitrogen or carbon sources. The
gudB
gene was expressed under all growth conditions tested but codes for a GlutDH that seemed to be intrinsically inactive. Spontaneous mutations in
gudB
that removed a 9-bp direct repeat within the wild-type
gudB
sequence activated the GudB protein and allowed more-efficient utilization of amino acids of the glutamate family.
A Homolog of CcpA Mediates Catabolite Control in
Listeria monocytogenes
but Not Carbon Source Regulation of Virulence Genes
Authors: Behari Jaideep , Youngman Philip 
Published: March 2020

ABSTRACT

Readily utilizable sugars down-regulate virulence gene expression in
Listeria monocytogenes
, which has led to the proposal that this regulation may be an aspect of global catabolite regulation (CR). We recently demonstrated that the metabolic enzyme α-glucosidase is under CR in
L. monocytogenes
. Here, we report the cloning and characterization from
L. monocytogenes
of an apparent ortholog of
ccpA
, which encodes an important mediator of CR in several low-G+C-content gram-positive bacteria.
L. monocytogenes ccpA
(
ccpA
Lm
) is predicted to encode a 335-amino-acid protein with nearly 65% identity to the gene product of
Bacillus subtilis ccpA
(
ccpA
Bs
). Southern blot analysis with a probe derived from
ccpA
Lm
revealed a single strongly hybridizing band and also a second band of much lower intensity, suggesting that there may be other closely related sequences in the
L. monocytogenes
chromosome, as is the case in
B. subtilis
. Disruption of
ccpA
Lm
resulted in the inability of the mutant to grow on glucose-containing minimal medium or increase its growth rate in the presence of preferred sugars, and it completely eliminated CR of α-glucosidase activity in liquid medium. However, α-glucosidase activity was only partially relieved from CR on solid medium. These results suggest that
ccpA
is an important element of carbon source regulation in
L. monocytogenes
. Nevertheless, utilizable sugars still down-regulate the expression of
hly
, which encodes the virulence factor hemolysin, in a
ccpA
Lm
mutant, indicating that CcpA is not involved in carbon source regulation of virulence genes.
N -Acyl-
l
-Homoserine Lactone Autoinducers Control Production of an Extracellular Lipopeptide Biosurfactant Required for Swarming Motility of
Serratia liquefaciens
MG1
Authors: Lindum P. W. , Anthoni U. , Christophersen C. , Eberl L. , Molin S. , Givskov M. 
Published: March 2020

ABSTRACT

A nonswarming
Serratia liquefaciens
mutant deficient in serrawettin W2 production was constructed by transposon mutagenesis. Sequence homology indicated that insertion had occurred in gene
swrA
, which encodes a putative peptide synthetase. Expression of
swrA
is controlled by quorum sensing.
Monoclonal Antibodies Directed against Conserved Epitopes on the Nucleocapsid Protein and the Major Envelope Glycoprotein of Equine Arteritis Virus
Authors: Weiland Emilie , Bolz Sylvia , Weiland Frank , Herbst Werner , Raamsman Martin J. B. , Rottier Peter J. M. , De Vries Antoine A. F. 
Published: March 2020

ABSTRACT

We recently developed a highly effective immunization procedure for the generation of monoclonal antibodies (MAbs) directed against the porcine reproductive and respiratory syndrome virus (E. Weiland, M. Wieczorek-Krohmer, D. Kohl, K. K. Conzelmann, and F. Weiland, Vet. Microbiol. 66:171–186, 1999). The same method was used to produce a panel of 16 MAbs specific for the equine arteritis virus (EAV). Ten MAbs were directed against the EAV nucleocapsid (N) protein, and five MAbs recognized the major viral envelope glycoprotein (G
L
). Two of the EAV G
L
-specific MAbs and one antibody of unknown specificity neutralized virus infectivity. A comparison of the reactivities of the MAbs with 1 U.S. and 22 newly obtained European field isolates of EAV demonstrated that all N-specific MAbs, the three nonneutralizing anti-G
L
MAbs, and the weakest neutralizing MAb (MAb E7/d15-c9) recognized conserved epitopes. In contrast, the two MAbs with the highest neutralization titers bound to 17 of 23 (MAb E6/A3) and 10 of 23 (MAb E7/d15-c1) of the field isolates. Ten of the virus isolates reacted with only one of these two MAbs, indicating that they recognized different epitopes. The G
L
-specific MAbs and the strongly neutralizing MAb of unknown specificity (MAb E6/A3) were used for the selection of neutralization-resistant (NR) virus variants. The observation that the E6/A3-specific NR virus variants were neutralized by MAb E7/d15-c1 and that MAb E6/A3 blocked the infectivity of the E7/d15-c1-specific NR escape mutant confirmed that these antibodies reacted with distinct antigenic sites. Immunoelectron microscopy revealed for the first time that the antigenic determinants recognized by the anti-G
L
MAbs were localized on the virion surface. Surprisingly, although the immunofluorescence signal obtained with the neutralizing antibodies was relatively weak, they mediated binding of about three times as much gold granules to the viral envelope than the nonneutralizing anti-G
L
MAbs.
Use of PCR with Universal Primers and Restriction Endonuclease Digestions for Detection and Identification of Common Bacterial Pathogens in Cerebrospinal Fluid
Authors: Lu Jang-Jih , Perng Cherng-Lih , Lee Shih-Yi , Wan Chih-Chieng 
Published: March 2020

ABSTRACT

We have designed a universal PCR capable of amplifying a portion of the 16S rRNA gene of eubacteria, including
Staphylococcus aureus
,
Staphylococcus epidermidis
,
Streptococcus pyogenes
,
Streptococcus agalactiae
,
Streptococcus pneumoniae
,
Enterococcus faecium
,
Enterococcus faecalis
,
Mycobacterium tuberculosis
,
Legionella pneumophila
,
Escherichia coli
,
Klebsiella pneumoniae
,
Serratia marcescens
,
Enterobacter cloacae
,
Pseudomonas aeruginosa
,
Acinetobacter baumannii
,
Proteus mirabilis
,
Haemophilus influenzae
, and
Neisseria meningitidis
. The sizes of the amplified products from various bacteria were the same (996 bp), but the restriction patterns of most PCR products generated by
Hae
III digestion were different. PCR products from
S. aureus
and
S. epidermidis
could not be digested by
Hae
III but yielded different patterns when they were digested with
Mnl
I. PCR products from
S. pneumoniae
,
E. faecium
, and
E. faecalis
yielded the same
Hae
III digestion pattern but could be differentiated by
Alu
I digestion. PCR products from
E. coli
,
K. pneumoniae
,
S. marcescens
, and
E. cloacae
also had the same
Hae
III digestion pattern but had different patterns when digested with
Dde
I or
Bst
BI. This universal PCR could detect as few as 10
E. coli
or 250
S. aureus
organisms. Compared with culture, the sensitivity of this universal PCR for detection and identification of bacteria directly from 150 cerebrospinal fluids was 92.3%. These results suggest that this universal PCR coupled with restriction enzyme analysis can be used to detect and identify bacterial pathogens in clinical specimens.
False Molecular Clusters due to Nonrandom Association of IS
6110
with
Mycobacterium tuberculosis
Authors: Gillespie S. H. , Dickens A. , McHugh T. D. 
Published: March 2020

ABSTRACT

We sought to determine whether nonrandom association of IS
6110
with
Mycobacterium tuberculosis
could result in false-positive clustering in unselected collections of isolates. We typed 196 strains of
M. tuberculosis
from an unselected community-based study in northern Tanzania by IS
6110
and polymorphic GC-rich repetitive-sequence (PGRS) methodologies. The strains were analyzed by Gelcompar computer software. Analysis of 13 out of 25 groups showed that isolates with identical IS
6110
and PGRS patterns were likely to be the same strain. Some IS
6110
groups containing strains with identical PGRS patterns had similar IS
6110
patterns that differed only by movement of the element. Isolates assigned to a single group (i.e., group 11) on the basis of sharing an identical IS
6110
fingerprint pattern did not share identical PGRS fingerprint patterns. Six out of the nine bands in these isolates were in hot-spot locations, as previously defined. This indicates that nonrandom association may result in false-positive clustering in unselected community-based studies. Only strains with identical PGRS and IS
6110
patterns are likely to be recently transmitted.
High Rate of Tetracycline Resistance in
Streptococcus pyogenes
in Iran: an Epidemiological Study
Authors: Jasir A. , Tanna A. , Noorani A. , Mirsalehian A. , Efstratiou A. , Schalen C. 
Published: March 2020

ABSTRACT

Streptococcus pyogenes
, a major human pathogen, is still considered susceptible to beta-lactams, but for other relevant antibiotics, highly variable resistance rates have been reported. Since no data were available from Iran, we tested 1,335 throat isolates from two different regions of the country for their antibiotic susceptibilities and, for comparison, a collection of 80 strains isolated from 1989 to 1991. Erythromycin resistance was uncommon (0.6%), whereas an overall high rate of tetracycline resistance was found, increasing between 1989–1991 and 1995–1997 from 23 to 42%. The tetracycline-resistant strains belonged to more than 10 different T types, the majority being types 4, 11, and B3264. By conventional M typing of 406 tetracycline-resistant isolates, more than 20 different M types were found. Approximately 50% of the strains were nontypeable by T agglutination as well as serological M typing; however, by genotyping by a combined PCR–capture-enzyme-linked immunosorbent assay, many of these strains were successfully
emm
typed. We conclude that the high rate of tetracycline resistance among Iranian
S. pyogenes
isolates is due to multiclonal dissemination of resistance within the streptococcal population rather than epidemic spread of single clones.
Isolation and Characterization of Glycopeptide-Resistant Enterococci from Hospitalized Patients over a 30-Month Period
Authors: Nelson R. R. S. , McGregor K. F. , Brown A. R. , Amyes S. G. B. , Young H.-K. 
Published: March 2020

ABSTRACT

In February 1996, a Hospital Infection Control Practices Advisory Committee-style screening program was commenced to isolate and subsequently characterize glycopeptide-resistant enterococci (GRE) from patients at a hospital trust in Glasgow, Scotland. Over the next 30 months, GRE were isolated from 154 patients. GRE were isolated from patients in traditionally high-risk areas such as the renal unit and intensive care unit and also in areas considered to be lower risk, including medical wards and associated long-stay geriatric hospitals. The majority (90%) of isolates were
Enterococcus faecium vanB
. The remaining isolates consisted of seven
E. faecalis
(
vanA
), three
E. gallinarum
(
vanC
), and a further six
E. faecium
(five
vanA
, one both
vanA
and
vanB
) isolates. Analysis of
Sma
I-digested DNA by pulsed-field gel electrophoresis revealed that 34 of 40 (85%) VanB
E. faecium
isolates were identical or closely related, while 11 of 13 (85%) VanA GRE were distinct. High-level aminoglycoside resistance was seen in less than 8% of isolates. VanB
E. faecium
isolates were almost uniformly resistant to ampicillin and tetracycline. In this study, GRE have been isolated over a prolonged period from a broad range of patients. Glycopeptide resistance within the study hospital trust appeared to be mainly due to the clonal dissemination of a single strain of
E. faecium
VanB.
Molecular Characteristics and Epidemiological Significance of Shiga Toxin-Producing
Escherichia coli
O26 Strains
Authors: Zhang Wen-Lan , Bielaszewska Martina , Liesegang Almut , Tschäpe Helmut , Schmidt Herbert , Bitzan Martin , Karch Helge 
Published: March 2020

ABSTRACT

Fifty-five Shiga toxin (Stx)-producing
Escherichia coli
(STEC) O26:H11 and O26:H
−
strains isolated from humans between 1965 and 1999 in Germany and the Czech Republic were investigated for their chromosomal and plasmid characteristics. All motile (
n
= 23) and nonmotile (
n
= 32) STEC O26 strains were shown to possess the identical flagellin subunit-encoding gene (
fliC
). We observed a striking recent shift of the
stx
genotype from

stx
1

to

stx
2

among the STEC O26 isolates. While

stx
1

was the exclusive genotype identified in our collection until 1994, 94% of the isolates obtained after 1997 possessed

stx
2

either alone (71%) or together with

stx
1

(23%). Plasmid profiling demonstrated a remarkable heterogeneity with respect to plasmid sizes and combinations. Southern blot analysis of plasmid DNA with probes specific to potential accessory virulence genes revealed considerable additional variability in gene composition and arrangement. Pulsed-field gel electrophoresis (PFGE) differentiated 16 subgroups among the 55 STEC O26 strains. Using these techniques we demonstrate the emergence of a new clonal subgroup characterized by PFGE pattern A and a unique combination of virulence markers including

stx
2

and a single, approximately 90-kb plasmid harboring the enterhemorrhagic
E. coli hlyA
and
etp
genes. The proportion of PFGE subgroup A strains among STEC O26 isolates rose from 30% in 1996 to more than 50% in 1999. Four clusters of infections with the clonal subgroup A were identified. We conclude that the STEC serogroup O26 is diverse and that pathogenic clonal subgroups can rapidly emerge during short intervals. The extensive genetic diversity of STEC O26 provides a basis for molecular subtyping of this important non-O157 STEC serogroup.
PCR-Based Quantification ofBorrelia burgdorferiOrganisms in Canine Tissues over a 500-Day Postinfection Period
Authors: Straubinger Reinhard K. 
Published: March 2020

ABSTRACTBorrelia burgdorferiinfection in beagle dogs was studied quantitatively with skin punch biopsy samples and blood samples collected at 4- and 2-week intervals, respectively, over a 500-day period. Thereafter, 25 tissue samples of each dog were collected for further analysis. Starting at day 120 after tick challenge, 12 dogs were treated with antibiotics (azithromycin, ceftriaxone, or doxycycline) for 30 consecutive days. Four dogs received no antibiotic therapy. Quantification ofB. burgdorferiDNA was done with an ABI Prism 7700 Sequence Detection System with oligonucleotide primers and a fluorescence-labeled probe designed to specifically amplify a fragment of theospAgene ofB. burgdorferistrain N40. All 16 dogs became infected withB. burgdorferiafter tick challenge. In skin biopsy samples, spirochete numbers peaked at day 60 postinfection (<1.5 × 106organisms per 100 μg of extracted DNA), at the same time when clinical signs of arthritis developed in 11 of 16 dogs, and decreased to almost undetectable levels during the following 6 months. The number ofB. burgdorferiorganisms detected in skin biopsy samples was inversely correlated with the antibody levels measured by enzyme-linked immunosorbent assay. Antibiotic treatment reduced the amount of detectable spirochete DNA in skin tissue by a factor of 1,000 or more. At the end of the experiment,B. burgdorferiDNA was detectable at low levels (102to 104organisms per 100 μg of extracted DNA) in multiple tissue samples regardless of treatment. However, more tissue samples of untreated dogs than of antibiotic-treated dogs were positive, and tissue samples of untreated dogs also were positive by culture. Only 1.6% of 576 blood samples of all dogs were positive forB. burgdorferiby PCR.