| 1. |
- de Oliveira, Ana H., 1995-, et al.
(författare)
-
The virulence and infectivity of Listeria monocytogenes are not substantially altered by elevated SigB activity
- 2023
-
Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 91:6
-
Tidskriftsartikel (refereegranskat)abstract
- Listeria monocytogenes is a bacterial pathogen capable of causing severe infections but also thriving outside the host. To respond to different stress conditions, L. monocytogenes mainly utilizes the general stress response regulon, which largely is controlled by the alternative sigma factor Sigma B (SigB). In addition, SigB is important for virulence gene expression and infectivity. Upon encountering stress, a large multicomponent protein complex known as the stressosome becomes activated, ultimately leading to SigB activation. RsbX is a protein needed to reset a "stressed"stressosome and prevent unnecessary SigB activation in nonstressed conditions. Consequently, absence of RsbX leads to constitutive activation of SigB even without prevailing stress stimulus. To further examine the involvement of SigB in the virulence of this pathogen, we investigated whether a strain with constitutively active SigB would be affected in virulence factor expression and/or infectivity in cultured cells and in a chicken embryo infection model. Our results suggest that increased SigB activity does not substantially alter virulence gene expression compared with the wild-type (WT) strain at transcript and protein levels. Bacteria lacking RsbX were taken up by phagocytic and nonphagocytic cells at a similar frequency to WT bacteria, both in stressed and nonstressed conditions. Finally, the absence of RsbX only marginally affected the ability of bacteria to infect chicken embryos. Our results suggest only a minor role of RsbX in controlling virulence factor expression and infectivity under these conditions.
|
|
| 2. |
- Quintana-Hayashi, Macarena P, et al.
(författare)
-
Brachyspira species avidity to colonic mucins from pigs with and without brachyspira hyodysenteriae infection is species specific and varies between strains
- 2021
-
Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 89:12
-
Tidskriftsartikel (refereegranskat)abstract
- Brachyspira hyodysenteriae is commonly associated with swine dysentery (SD), a disease that has an economic impact on the swine industry. B. hyodysenteriae infection results in changes to the colonic mucus niche with massive mucus induction, which substantially increases the number of B. hyodysenteriae binding sites in the mucus. We previously determined that a B. hyodysenteriae strain binds to colon mucins in a manner that differs between pigs and mucin types. Here, we investigated if adhesion to mucins is a trait observed across a broad set of B. hyodysenteriae strains and isolates and furthermore at a genus level (B. innocens, B. pilosicoli, B. murdochii, B. hampsonii, and B. intermedia strains). Our results show that binding to mucins appears to be specific to B. hyodysenteriae, and within this species, the binding ability to mucins varies between strains/isolates, increases for mucins from pigs with SD, and is associated with sialic acid epitopes on mucins. Infection with B. hyodysenteriae strain 8dII results in mucin glycosylation changes in the colon, including a shift in sialic acid-containing structures. Thus, we demonstrate through hierarchical cluster analysis and orthogonal projections to latent structures discriminant analysis (OPLS-DA) models of the relative abundances of sialic acid-containing glycans that sialic acid-containing structures in the mucin O-glycome are good predictors of B. hyodysenteriae strain 8dII infection in pigs. The results emphasize the role of sialic acids in governing B. hyodysenteriae interactions with its host, which may open perspectives for therapeutic strategies.
|
|
| 3. |
- Schneiders, Stephan, et al.
(författare)
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection : Growth rate and plasmid copy number during Yersinia infection
- 2021
-
Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522.
-
Tidskriftsartikel (refereegranskat)abstract
- Pathogenic Yersinia spp. depend on the activity of a potent virulence plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Y. pseudotuberculosis up-regulates the virulence plasmid copy number (PCN) during infection and the resulting elevated gene dose of plasmid-encoded T3SS genes is essential for virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the virulence plasmid during infection is unknown. In the current study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer’s Patches and caecum during the clonal invasive phase of the infection, while the fastest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues, and will be readily applicable to other infection models.
|
|
| 4. |
- Schneiders, Stephan, et al.
(författare)
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection
- 2021
-
Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 89:4
-
Tidskriftsartikel (refereegranskat)abstract
- Pathogenic Yersinia spp. depend on the activity of a potent virulence plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Yersinia pseudotuberculosis upregulates the virulence plasmid copy number (PCN) during infection and that the resulting elevated gene dose of plasmid-encoded T3SS genes is essential for virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the virulence plasmid during infection is unknown. In the present study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer's patches and cecum during the clonal invasive phase of the infection, while the highest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues and will be readily applicable to other infection models.
|
|
| 5. |
- Sheikh, A., et al.
(författare)
-
Enterotoxigenic Escherichia coli Degrades the Host MUC2 Mucin Barrier To Facilitate Critical Pathogen-Enterocyte Interactions in Human Small Intestine
- 2022
-
Ingår i: Infection and Immunity. - : American Society for Microbiology. - 0019-9567 .- 1098-5522. ; 90:2
-
Tidskriftsartikel (refereegranskat)abstract
- Enterotoxigenic Escherichia coli (ETEC) isolates are genetically diverse pathological variants of E. coli defined by the production of heat-labile (LT) and/or heat-stable (ST) toxins. ETEC strains are estimated to cause hundreds of millions of cases of diarrheal illness annually. However, it is not clear that all strains are equally equipped to cause disease, and asymptomatic colonization with ETEC is common in low- to middle-income regions lacking basic sanitation and clean water where ETEC are ubiquitous. Recent molecular epidemiology studies have revealed a significant association between strains that produce EatA, a secreted autotransporter protein, and the development of symptomatic infection. Here, we demonstrate that LT stimulates production of MUC2 mucin by goblet cells in human small intestine, enhancing the protective barrier between pathogens and enterocytes. In contrast, using explants of human small intestine as well as small intestinal enteroids, we show that EatA counters this host defense by engaging and degrading the MUC2 mucin barrier to promote bacterial access to target enterocytes and ultimately toxin delivery, suggesting that EatA plays a crucial role in the molecular pathogenesis of ETEC. These findings may inform novel approaches to prevention of acute diarrheal illness as well as the sequelae associated with ETEC and other pathogens that rely on EatA and similar proteases for efficient interaction with their human hosts. © 2022 American Society for Microbiology. All rights reserved.
|
|
| 6. |
- Sigurlásdóttir, Sara, et al.
(författare)
-
Lactate-Induced Dispersal of Neisseria meningitidis Microcolonies Is Mediated by Changes in Cell Density and Pilus Retraction and Is Influenced by Temperature Change
- 2021
-
Ingår i: Infection and Immunity. - 0019-9567 .- 1098-5522. ; 89:10
-
Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis is the etiologic agent of meningococcal meningitis and sepsis. Initial colonization of meningococci in the upper respiratory tract epithelium is crucial for disease development. The colonization occurs in several steps and expression of type IV pili (Tfp) is essential for both attachment and microcolony formation of encapsulated bacteria. Previously, we have shown that host-derived lactate induces synchronized dispersal of meningococcal microcolonies. In this study, we demonstrated that lactate-induced dispersal is dependent on bacterial concentration but not on the quorum-sensing system autoinducer-2 or the two-component systems NarP/NarQ, PilR/PilS, NtrY/NtrX, and MisR/MisS. Further, there were no changes in expression of genes related to assembly, elongation, retraction, and modification of Tfp throughout the time course of lactate induction. By using pilT and pptB mutants, however, we found that lactate-induced dispersal was dependent on PilT retraction but not on phosphoglycerol modification of Tfp even though the PptB activity was important for preventing reaggregation postdispersal. Furthermore, protein synthesis was required for lactate-induced dispersal. Finally, we found that at a lower temperature, lactate-induced dispersal was delayed and unsynchronized, and bacteria reformed microcolonies. We conclude that lactate-induced microcolony dispersal is dependent on bacterial concentration, PilT-dependent Tfp retraction, and protein synthesis and is influenced by environmental temperature.
|
|
| 7. |
- Alamiri, Feiruz, et al.
(författare)
-
A role of epithelial cells and virulence factors in biofilm formation by Streptococcus pyogenes in vitro
- 2020
-
Ingår i: Infection and Immunity. - 1098-5522. ; 88:10
-
Tidskriftsartikel (refereegranskat)abstract
- Biofilm formation by Streptococcus pyogenes (GAS) in model systems mimicking the respiratory tract is poorly documented. Most studies have been conducted on abiotic surfaces, which poorly represent human tissues. We have previously shown that GAS forms mature and antibiotic-resistant biofilms on physiologically relevant epithelial cells. However, the role of the substratum, extracellular matrix (ECM) components, or GAS virulence factors for biofilm formation and structure is unclear. In this study, biofilm formation was measured on respiratory epithelial cells and keratinocytes by determining biomass and antibiotic resistance, and biofilm morphology was visualized using scanning electron microscopy. All GAS isolates tested formed biofilms that had similar, albeit not identical, biomass and antibiotic resistance for both cell types. Interestingly, functionally mature biofilms formed more rapidly on keratinocytes but were structurally denser and coated with more ECM on respiratory epithelial cells. The ECM was crucial for biofilm integrity, as protein- and DNA-degrading enzymes induced bacterial release from biofilms. Abiotic surfaces supported biofilm formation, but these biofilms were structurally less dense and organized. No major role of M protein, capsule, or Streptolysin O was observed in biofilm formation on epithelial cells, although some morphological differences were detected. NAD-glycohydrolase was required for optimal biofilm formation, whereas Streptolysin S or cysteine protease SpeB impaired this process. Finally, no correlation was found between cell adherence or auto-aggregation and GAS biofilm formation. Combined, these results provide a better understanding of the role of biofilm formation in GAS pathogenesis and can potentially provide novel targets for future treatments against GAS infections.
|
|
| 8. |
- Bergmann, René, et al.
(författare)
-
Prominent Binding of Human and Equine Fibrinogen to Streptococcus equi subsp. zooepidemicus Is Mediated by Specific SzM Types and Is a Distinct Phenotype of Zoonotic Isolates
- 2020
-
Ingår i: Infection and Immunity. - 1098-5522. ; 88:1
-
Tidskriftsartikel (refereegranskat)abstract
- Streptococcus equi subsp. zooepidemicus is an important pathogen in horses that causes severe diseases such as pneumonia and abortion. Furthermore, it is a zoonotic agent, and contact with horses is a known risk factor. In this study, we investigated the working hypothesis that the zoonotic potential varies among S. equi subsp. zooepidemicus strains in association with differences in M-like protein-mediated binding of host plasma proteins. We demonstrate via in-frame deletion mutagenesis of two different S. equi subsp. zooepidemicus strains that the M-like protein SzM is crucial for the binding of fibrinogen to the bacterial surface and for survival in equine and human blood. S. equi subsp. zooepidemicus isolates of equine and human origins were compared with regard to SzM sequences and binding of equine and human fibrinogens. The N-terminal 216 amino acids of the mature SzM were found to exhibit a high degree of diversity, but the majority of human isolates grouped in three distinct SzM clusters. Plasma protein absorption assays and flow cytometry analysis revealed that pronounced binding of human fibrinogen is a common phenotype of human S. equi subsp. zooepidemicus isolates but much less so in equine S. equi subsp. zooepidemicus isolates. Furthermore, binding of human fibrinogen is associated with specific SzM types. These results suggest that SzM-mediated binding of human fibrinogen is an important virulence mechanism of zoonotic S. equi subsp. zooepidemicus isolates.
|
|
| 9. |
- Enoksson, Frida, et al.
(författare)
-
Niche- and gender-dependent immune reactions in relation to the microbiota profile in pediatric patients with otitis media with effusion
- 2020
-
Ingår i: Infection and Immunity. - 1098-5522. ; 88:10
-
Tidskriftsartikel (refereegranskat)abstract
- Otitis media with effusion (OME) is a common inflammatory disease, primarily affecting children. OME is defined as a chronic low-grade inflammation of the middle ear (ME), without any signs of infection and with effusion persisting in the ME for more than three months. The precise pathogenesis is, however, not fully understood. Here, we comprehensively characterized and compared the host immune responses (inflammatory cells and mediators) and the overall microbial community composition (microbiota) present in matched middle ear effusion samples (MEE), external ear canal lavages, and nasopharynx (NPH) samples from children with OME. Female patients had significantly increased percentages of T lymphocytes and higher levels of a wide array of inflammatory mediators in their MEEs compared to male patients, which was unrelated to microbiota composition. The relative abundances of identified microorganisms were strongly associated with their niche of origin. Furthermore, specific inflammatory mediators were highly correlated with certain bacterial species. Interestingly, some organisms displayed a niche-driven inflammation pattern, where presence of Haemophilus spp and Corynebacterium propinquum in MEEs was accompanied by pro-inflammatory mediators, whereas their presence in NPH was accompanied by anti-inflammatory mediators. For Turicella and Alloiococcus we found exactly the opposite results, i.e., an anti-inflammatory profile when present in MEEs, whereas their presence in the NPH was accompanied by a pro-inflammatory profile. Altogether, our results indicate that immune responses in children with OME are highly niche- and microbiota-driven, but gender-based differences were also observed, providing novel insight into potential pathogenic mechanisms behind OME.
|
|
| 10. |
|
|
