bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions
Authors: Kurabayashi Kumiko , Tanimoto Koichi , Fueki Shinobu , Tomita Haruyoshi , Hirakawa Hidetada 
Published: July 2015

ABSTRACT

Because a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a “last-resort option.” This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed that
Escherichia coli
strains, including enterohemorrhagic
E. coli
(EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth of
E. coli
. Our quantitative PCR analysis and a transport assay showed that
E. coli
cells grown under anaerobic conditions had higher levels of expression of
glpT
and
uhpT
, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream of
glpT
and
uhpT
, suggesting that it is an activator of expression of
glpT
and
uhpT
during anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin toward
E. coli
under anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.
Key Residues of Outer Membrane Protein OprI Involved in Hexamer Formation and Bacterial Susceptibility to Cationic Antimicrobial Peptides
Authors: Chang Ting-Wei , Wang Chiu-Feng , Huang Hsin-Jye , Wang Iren , Hsu Shang-Te Danny , Liao You-Di 
Published: July 2015

ABSTRACT

Antimicrobial peptides (AMPs) are important components of the host innate defense mechanism against invading pathogens. Our previous studies have shown that the outer membrane protein, OprI from
Pseudomonas aeruginosa
or its homologue, plays a vital role in the susceptibility of Gram-negative bacteria to cationic α-helical AMPs (Y. M. Lin, S. J. Wu, T. W. Chang, C. F. Wang, C. S. Suen, M. J. Hwang, M. D. Chang, Y. T. Chen, Y. D. Liao, J Biol Chem 285:8985–8994, 2010,
http://dx.doi.org/10.1074/jbc.M109.078725
; T. W. Chang, Y. M. Lin, C. F. Wang, Y. D. Liao, J Biol Chem
287:
418–428, 2012,
http://dx.doi.org/10.1074/jbc.M111.290361
). Here, we obtained two forms of recombinant OprI: rOprI-F, a hexamer composed of three disulfide-bridged dimers, was active in AMP binding, while rOprI-R, a trimer, was not. All the subunits predominantly consisted of α-helices and exhibited rigid structures with a melting point centered around 76°C. Interestingly, OprI tagged with
Escherichia coli
signal peptide was expressed in a hexamer, which was anchored on the surface of
E. coli
, possibly through lipid acids added at the N terminus of OprI and involved in the binding and susceptibility to AMP as native
P. aeruginosa
OprI. Deletion and mutation studies showed that Cys1 and Asp27 played a key role in hexamer formation and AMP binding, respectively. The increase of OprI hydrophobicity upon AMP binding revealed that it undergoes conformational changes for membrane fusion. Our results showed that OprI on bacterial surfaces is responsible for the recruitment and susceptibility to amphipathic α-helical AMPs and may be used to screen antimicrobials.
Antimicrobial Susceptibility Profiles of Staphylococcus aureus Isolates Recovered from Humans, Environmental Surfaces, and Companion Animals in Households of Children with Community-Onset Methicillin-Resistant S. aureus Infections
Authors: Morelli John J. , Hogan Patrick G. , Sullivan Melanie L. , Muenks Carol E. , Wang Jeffrey W. , Thompson Ryley M. , Burnham Carey-Ann D. , Fritz Stephanie A. 
Published: July 2015

ABSTRACT

Our objective was to determine the antibiotic susceptibility profiles of
Staphylococcus aureus
isolates recovered from 110 households of children with community-onset methicillin-resistant
S. aureus
(MRSA) infections. Cultures were obtained from household members, household objects, and dogs and cats, yielding 1,633
S. aureus
isolates. The
S. aureus
isolates were heterogeneous, although more than half were methicillin resistant. The highest proportion of MRSA was found in bathrooms. The majority of isolates were susceptible to antibiotics prescribed in outpatient settings.
Intestinal Microbiota of Mice Influences Resistance to Staphylococcus aureus Pneumonia
Authors: Gauguet Stefanie , D'Ortona Samantha , Ahnger-Pier Kathryn , Duan Biyan , Surana Neeraj K. , Lu Roger , Cywes-Bentley Colette , Gadjeva Mihaela , Shan Qiang , Priebe Gregory P. , Pier Gerald B. 
Published: July 2015

ABSTRACT

Th17 immunity in the gastrointestinal tract is regulated by the intestinal microbiota composition, particularly the presence of segmented filamentous bacteria (sfb), but the role of the intestinal microbiota in pulmonary host defense is not well explored. We tested whether altering the gut microbiota by acquiring sfb influences the susceptibility to staphylococcal pneumonia via induction of type 17 immunity. Groups of C57BL/6 mice which differed in their intestinal colonization with sfb were challenged with methicillin-resistant
Staphylococcus aureus
in an acute lung infection model. Bacterial burdens, bronchoalveolar lavage fluid (BALF) cell counts, cell types, and cytokine levels were compared between mice from different vendors, mice from both vendors after cohousing, mice given sfb orally prior to infection, and mice with and without exogenous interleukin-22 (IL-22) or anti-IL-22 antibodies. Mice lacking sfb developed more severe
S. aureus
pneumonia than mice colonized with sfb, as indicated by higher bacterial burdens in the lungs, lung inflammation, and mortality. This difference was reduced when sfb-negative mice acquired sfb in their gut microbiota through cohousing with sfb-positive mice or when given sfb orally. Levels of type 17 immune effectors in the lung were higher after infection in sfb-positive mice and increased in sfb-negative mice after acquisition of sfb, as demonstrated by higher levels of IL-22 and larger numbers of IL-22
+
TCRβ
+
cells and neutrophils in BALF. Exogenous IL-22 protected mice from
S. aureus
pneumonia. The murine gut microbiota, particularly the presence of sfb, promotes pulmonary type 17 immunity and resistance to
S. aureus
pneumonia, and IL-22 protects against severe pulmonary staphylococcal infection.
Influenza and Bacterial Superinfection: Illuminating the Immunologic Mechanisms of Disease
Authors: Rynda-Apple Agnieszka , Robinson Keven M. , Alcorn John F. 
Published: July 2015

ABSTRACT

Seasonal influenza virus infection presents a major strain on the health care system. Influenza virus infection has pandemic potential, which was repeatedly observed during the last century. Severe disease may occur in the young, in the elderly, in those with preexisting lung disease, and in previously healthy individuals. A common cause of severe influenza pathogenesis is superinfection with bacterial pathogens, namely,
Staphylococcus aureus
and
Streptococcus pneumoniae
. A great deal of recent research has focused on the immune pathways involved in influenza-induced susceptibility to secondary bacterial pneumonia. Both innate and adaptive antibacterial host defenses are impaired in the context of preceding influenza virus infection. The goal of this minireview is to highlight these findings and synthesize these data into a shared central theme of pathogenesis.
Multiple Plasmodium falciparum Erythrocyte Membrane Protein 1 Variants per Genome Can Bind IgM via Its Fc Fragment Fcμ
Authors: Jeppesen Anine , Ditlev Sisse Bolm , Soroka Vladyslav , Stevenson Liz , Turner Louise , Dzikowski Ron , Hviid Lars , Barfod Lea 
Published: July 2015

ABSTRACTThePlasmodium falciparumerythrocyte membrane protein 1 (PfEMP1) adhesive proteins expressed on the surfaces of infected erythrocytes (IEs) are of key importance in the pathogenesis ofP. falciparummalaria. Several structurally and functionally defined PfEMP1 types have been associated with severe clinical manifestations, such as cerebral malaria in children and placental malaria in pregnant women. PfEMP1 that can bind the Fc part of IgM (Fcμ) characterizes one such type, although the functional significance of this IgM binding to PfEMP1 remains unclear. In this study, we report the identification and functional analysis of five IgM-binding PfEMP1 proteins encoded byP. falciparumNF54. In addition to the VAR2CSA-type PFL0030c protein, already known to bind Fcμ and to mediate chondroitin sulfate A (CSA)-specific adhesion of IEs in the placenta, we found four PfEMP1 proteins not previously known to bind IgM this way. Although they all contained Duffy binding-like ε (DBLε) domains similar to those in VAR2CSA-type PfEMP1, they did not mediate IE adhesion to CSA, and IgM binding did not shield IEs from phagocytosis of IgG-opsonized IEs. In this way, these new IgM-binding PfEMP1 proteins resemble the rosette-mediating and IgM-binding PfEMP1 HB3VAR06, but none of them mediated formation of rosettes. We could map the capacity for Fc-specific IgM binding to DBLε domains near the C terminus for three of the four PfEMP1 proteins tested. Our study provides new evidence regarding Fc-dependent binding of IgM to PfEMP1, which appears to be a common and multifunctional phenotype.
Dot/Icm Effector Translocation by Legionella longbeachae Creates a Replicative Vacuole Similar to That of Legionella pneumophila despite Translocation of Distinct Effector Repertoires
Authors: Wood Rebecca E. , Newton Patrice , Latomanski Eleanor A. , Newton Hayley J. 
Published: July 2015

ABSTRACT

Legionella
organisms are environmental bacteria and accidental human pathogens that can cause severe pneumonia, termed Legionnaires' disease. These bacteria replicate within a pathogen-derived vacuole termed the
Legionella
-containing vacuole (LCV). Our understanding of the development and dynamics of this vacuole is based on extensive analysis of
Legionella pneumophila
. Here, we have characterized the
Legionella longbeachae
replicative vacuole (
longbeachae
-LCV) and demonstrated that, despite important genomic differences, key features of the replicative LCV are comparable to those of the LCV of
L. pneumophila
(
pneumophila
-LCV). We constructed a Dot/Icm-deficient strain by deleting
dotB
and demonstrated the inability of this mutant to replicate inside THP-1 cells.
L. longbeachae
does not enter THP-1 cells as efficiently as
L. pneumophila
, and this is reflected in the observation that translocation of BlaM-RalF
LLO
(where RalF
LLO
is the
L. longbeachae
homologue of RalF) into THP-1 cells by the
L. longbeachae
Dot/Icm system is less efficient than that by
L. pneumophila
. This difference is negated in A549 cells where
L. longbeachae
and
L. pneumophila
infect with similar entry dynamics. A β-lactamase assay was employed to demonstrate the translocation of a novel family of proteins, the
R
ab-
l
ike
e
ffector (Rle) proteins. Immunofluorescence analysis confirmed that these proteins enter the host cell during infection and display distinct subcellular localizations, with RleA and RleC present on the
longbeachae
-LCV. We observed that the host Rab GTPase, Rab1, and the v-SNARE Sec22b are also recruited to the
longbeachae
-LCV during the early stages of infection, coinciding with the LCV avoiding endocytic maturation. These studies further our understanding of the
L. longbeachae
replicative vacuole, highlighting phenotypic similarities to the vacuole of
L. pneumophila
as well as unique aspects of LCV biology.
Activation of Hepatic STAT3 Maintains Pulmonary Defense during Endotoxemia
Authors: Hilliard Kristie L. , Allen Eri , Traber Katrina E. , Kim Yuri , Wasserman Gregory A. , Jones Matthew R. , Mizgerd Joseph P. , Quinton Lee J. 
Published: July 2015

ABSTRACTPneumonia and infection-induced sepsis are worldwide public health concerns. Both pathologies elicit systemic inflammation and induce a robust acute-phase response (APR). Although APR activation is well regarded as a hallmark of infection, the direct contributions of liver activation to pulmonary defense during sepsis remain unclear. By targeting STAT3-dependent acute-phase changes in the liver, we evaluated the role of liver STAT3 activity in promoting host defense in the context of sepsis and pneumonia. We employed a two-hit endotoxemia/pneumonia model, whereby administration of 18 h of intraperitoneal lipopolysaccharide (LPS; 5 mg/kg of body weight) was followed by intratrachealEscherichia coli(106CFU) in wild-type mice or those lacking hepatocyte STAT3 (hepSTAT3−/−). Pneumonia alone (without endotoxemia) was effectively controlled in the absence of liver STAT3. Following endotoxemia and pneumonia, however, hepSTAT3−/−mice, with significantly reduced levels of circulating and airspace acute-phase proteins, exhibited significantly elevated lung and blood bacterial burdens and mortality. These data suggested that STAT3-dependent liver responses are necessary to promote host defense. While neither recruited airspace neutrophils nor lung injury was altered in endotoxemic hepSTAT3−/−mice, alveolar macrophage reactive oxygen species generation was significantly decreased. Additionally, bronchoalveolar lavage fluid from this group of hepSTAT3−/−mice allowed greater bacterial growthex vivo. These results suggest that hepatic STAT3 activation promotes both cellular and humoral lung defenses. Taken together, induction of liver STAT3-dependent gene expression programs is essential to countering the deleterious consequences of sepsis on pneumonia susceptibility.
Propionibacterium acnes Recovered from Atherosclerotic Human Carotid Arteries Undergoes Biofilm Dispersion and Releases Lipolytic and Proteolytic Enzymes in Response to Norepinephrine Challenge
In Vitro
Authors: Lanter Bernard B. , Davies David G. 
Published: July 2015

ABSTRACT

In the present study, human atherosclerotic carotid arteries were examined following endarterectomy for the presence of the Gram-positive bacterium
Propionibacterium acnes
and its potential association with biofilm structures within the arterial wall. The
P. acnes
16S rRNA gene was detectable in 4 of 15 carotid artery samples, and viable
P. acnes
was one among 10 different bacterial species recoverable in culture. Fluorescence
in situ
hybridization analysis of 5 additional atherosclerotic carotid arteries demonstrated biofilm bacteria within all samples, with
P. acnes
detectable in 4 samples. We also demonstrated that laboratory-grown cultures of
P. acnes
biofilms were susceptible to induction of a biofilm dispersion response when challenged with physiologically relevant levels of norepinephrine in the presence of iron-bound transferrin or with free iron. The production and release of lipolytic and proteolytic extracellular enzymes by
P. acnes
were shown to increase in iron-induced dispersed biofilms, and these dispersion-induced
P. acnes
VP1 biofilms showed increased expression of mRNAs for the triacylglycerol lipases PPA2105 and PPA1796 and the hyaluronate lyase PPA380 compared to that in untreated biofilms. These results demonstrate that
P. acnes
can infect the carotid arteries of humans with atherosclerosis as a component of multispecies biofilms and that dispersion is inducible for this organism, at least
in vitro
, with physiologically relevant levels of norepinephrine resulting in the production and release of degradative enzymes.
Acylation Enhances, but Is Not Required for, the Cytotoxic Activity of Mannheimia haemolytica Leukotoxin in Bighorn Sheep
Authors: Batra Sai A. , Shanthalingam Sudarvili , Munske Gerhard R. , Raghavan Bindu , Kugadas Abirami , Bavanthasivam Jegarubee , Highlander Sarah K. , Srikumaran Subramaniam 
Published: July 2015

ABSTRACT

Mannheimia haemolytica
causes pneumonia in domestic and wild ruminants. Leukotoxin (Lkt) is the most important virulence factor of the bacterium. It is encoded within the four-gene
lktCABD
operon:
lkt
A encodes the structural protoxin, and
lktC
encodes a
trans
-acylase that adds fatty acid chains to internal lysine residues in the protoxin, which is then secreted from the cell by a type 1 secretion system apparatus encoded by
lktB
and
lktD
. It has been reported that LktC-mediated acylation is necessary for the biological effects of the toxin. However, an LktC mutant that we developed previously was only partially attenuated in its virulence for cattle. The objective of this study was to elucidate the role of LktC-mediated acylation in Lkt-induced cytotoxicity. We performed this study in bighorn sheep (
Ovis canadensis
) (BHS), since they are highly susceptible to
M. haemolytica
infection. The LktC mutant caused fatal pneumonia in 40% of inoculated BHS. On necropsy, a large number of necrotic polymorphonuclear leukocytes (PMNs) were observed in the lungs. Lkt from the mutant was cytotoxic to BHS PMNs in an
in vitro
cytotoxicity assay. Flow cytometric analysis of mutant Lkt-treated PMNs revealed the induction of necrosis. Scanning electron microscopic analysis revealed the presence of pores and blebs on mutant-Lkt-treated PMNs. Mass spectrometric analysis confirmed that the mutant secreted an unacylated Lkt. Taken together, these results suggest that acylation is not necessary for the cytotoxic activity of
M. haemolytica
Lkt but that it enhances the potency of the toxin.
The Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Active Subunit CdtB Contains a Cholesterol Recognition Sequence Required for Toxin Binding and Subunit Internalization
Authors: Boesze-Battaglia Kathleen , Walker Lisa P. , Zekavat Ali , Dlakić Mensur , Scuron Monika Damek , Nygren Patrik , Shenker Bruce J. 
Published: July 2015

ABSTRACTInduction of cell cycle arrest in lymphocytes following exposure to theAggregatibacter actinomycetemcomitanscytolethal distending toxin (Cdt) is dependent upon the integrity of lipid membrane microdomains. Moreover, we have previously demonstrated that the association of Cdt with target cells involves the CdtC subunit which binds to cholesterol via a cholesterol recognition amino acid consensus sequence (CRAC site). In this study, we demonstrate that the active Cdt subunit, CdtB, also is capable of binding to large unilamellar vesicles (LUVs) containing cholesterol. Furthermore, CdtB binding to cholesterol involves a similar CRAC site as that demonstrated for CdtC. Mutation of the CRAC site reduces binding to model membranes as well as toxin binding and CdtB internalization in both Jurkat cells and human macrophages. A concomitant reduction in Cdt-induced toxicity was also noted, indicated by reduced cell cycle arrest and apoptosis in Jurkat cells and a reduction in the proinflammatory response in macrophages (interleukin 1β [IL-1β] and tumor necrosis factor alpha [TNF-α] release). Collectively, these observations indicate that membrane cholesterol serves as an essential ligand for both CdtC and CdtB and, further, that this binding is necessary for both internalization of CdtB and subsequent molecular events leading to intoxication of cells.
Comparable Genital Tract Infection, Pathology, and Immunity in Rhesus Macaques Inoculated with Wild-Type or Plasmid-Deficient Chlamydia trachomatis Serovar D
Authors: Qu Yanyan , Frazer Lauren C. , O'Connell Catherine M. , Tarantal Alice F. , Andrews Charles W. , O'Connor Shelby L. , Russell Ali N. , Sullivan Jeanne E. , Poston Taylor B. , Vallejo Abbe N. , Darville Toni 
Published: July 2015

ABSTRACT

Rhesus macaques were studied to directly address the potential for plasmid-deficient
Chlamydia trachomatis
to serve as a live attenuated vaccine in the genital tract. Five repeated cervical inoculations of rhesus macaques with wild-type serovar D strain D/UW-3/Cx or a plasmid-deficient derivative of this strain, CTD153, resulted in infections with similar kinetics and induced comparable levels of protective immunity. After all animals received five challenges with D/UW-3/Cx, levels of inflammation observed grossly and histologically were similar between the groups. Animals in both groups developed evidence of oviduct dilatation; however, reduced oviduct dilatation was observed for “controllers,” i.e., animals without detectable chlamydial DNA in the fimbriae at weeks 5 and 12. Grouping animals into “ascenders” and “controllers” revealed that elevated early T cell responses were associated with protection, whereas higher antibody responses were associated with ascension. Protected animals shared common major histocompatibility complex (MHC) alleles. Overall, genetic differences of individual animals, rather than the presence or absence of the chlamydial plasmid in the primary infecting strain, appeared to play a role in determining the outcome of infection.
Adherent-Invasive Escherichia coli Production of Cellulose Influences Iron-Induced Bacterial Aggregation, Phagocytosis, and Induction of Colitis
Authors: Ellermann Melissa , Huh Eun Young , Liu Bo , Carroll Ian M. , Tamayo Rita , Sartor R. Balfour 
Published: July 2015

ABSTRACT

Adherent-invasive
Escherichia coli
(AIEC), a functionally distinct subset of resident intestinal
E. coli
associated with Crohn's disease, is characterized by enhanced epithelial adhesion and invasion, survival within macrophages, and biofilm formation. Environmental factors, such as iron, modulate
E. coli
production of extracellular structures, which in turn influence the formation of multicellular communities, such as biofilms, and bacterial interactions with host cells. However, the physiological and functional responses of AIEC to variable iron availability have not been thoroughly investigated. We therefore characterized the impact of iron on the physiology of AIEC strain NC101 and subsequent interactions with macrophages. Iron promoted the cellulose-dependent aggregation of NC101. Bacterial cells recovered from the aggregates were more susceptible to phagocytosis than planktonic cells, which corresponded with the decreased macrophage production of the proinflammatory cytokine interleukin-12 (IL-12) p40. Prevention of aggregate formation through the disruption of cellulose production reduced the phagocytosis of iron-exposed NC101. In contrast, under iron-limiting conditions, where NC101 aggregation is not induced, the disruption of cellulose production enhanced NC101 phagocytosis and decreased macrophage secretion of IL-12 p40. Finally, abrogation of cellulose production reduced NC101 induction of colitis when NC101 was monoassociated in inflammation-prone
Il10
−/−
mice. Taken together, our results introduce cellulose as a novel physiological factor that impacts host-microbe-environment interactions and alters the proinflammatory potential of AIEC.