| 1. |
- Baranwal, Gaurav, et al.
(författare)
-
Impact of cell wall peptidoglycan O-acetylation on the pathogenesis of Staphylococcus aureus in septic arthritis.
- 2017
-
Ingår i: International journal of medical microbiology : IJMM. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 307:7, s. 388-397
-
Tidskriftsartikel (refereegranskat)abstract
- Staphylococcus aureus (S. aureus) is one of the most common pathogen causing septic arthritis. To colonize the joints and establish septic arthritis this bacterium needs to resist the host innate immune responses. Lysozyme secreted by neutrophils and macrophages is an important defense protein present in the joint synovial fluids. S. aureus is known to be resistant to lysozyme due to its peptidoglycan modification by O-acetylation of N-acetyl muramic acid. In this study we have investigated the role of O-acetylated peptidoglycan in septic arthritis. Using mouse models for both local and hematogenous S. aureus arthritis we compared the onset and progress of the disease induced by O-acetyl transferase mutant and the parenteral wild type SA113 strain. The disease progression was assessed by observing the clinical parameters including body weight, arthritis, and functionality of the affected limbs. Further X-ray and histopathological examinations were performed to monitor the synovitis and bone damage. In local S. aureus arthritis model, mice inoculated with the ΔoatA strain developed milder disease (in terms of knee swelling, motor and movement functionality) compared to mice inoculated with the wild type SA113 strain. X-ray and histopathological data revealed that ΔoatA infected mice knee joints had significantly lesser joint destruction, which was accompanied by reduced bacterial load in knee joints. Similarly, in hematogenous S. aureus arthritis model, ΔoatA mutant strain induced significantly less severe clinical septic arthritis compared to its parental strain, which is in accordance with radiological findings. Our data indicate that peptidoglycan O-acetylation plays an important role in S. aureus mediated septic arthritis.
|
|
| 2. |
|
|
| 3. |
- Engström, Patrik, et al.
(författare)
-
Expansion of the Chlamydia trachomatis inclusion does not require bacterial replication
- 2015
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 305:3, s. 378-382
-
Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis replication takes place inside of a host cell, exclusively within a vacuole known as the inclusion. During an infection, the inclusion expands to accommodate the increasing numbers of C. trachomatis. However, whether inclusion expansion requires bacterial replication and/or de novo protein synthesis has not been previously investigated in detail. Therefore, using a chemical biology approach, we herein investigated C. trachomatis inclusion expansion under varying conditions in vitro. Under normal cell culture conditions, inclusion expansion correlated with C trachomatis replication. When bacterial replication was inhibited using KSK120: an inhibitor that targets C. trachomatis glucose metabolism, inclusions expanded even in the absence of bacterial replication. In contrast, when bacterial protein synthesis was inhibited using chloramphenicol, expansion of inclusions was blocked. Together, these data suggest that de novo protein synthesis is necessary, whereas bacterial replication is dispensable for C trachomatis inclusion expansion. (C) 2015 The Authors. Published by Elsevier GmbH.
|
|
| 4. |
- Joffre, Enrique, et al.
(författare)
-
Identification of new heat-stable (STa) enterotoxin allele variants produced by human enterotoxigenic Escherichia coli (ETEC)
- 2016
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 306:7, s. 586-594
-
Tidskriftsartikel (refereegranskat)abstract
- We describe natural variants of the heat stable toxin (STa) produced by enterotoxigenic Escherichia coli (ETEC) isolates collected worldwide. Previous studies of ETEC isolated from human diarrheal cases have reported the existence of three natural STa gene variants estA1, estA2 and estA3/4 where the first variant encodes STp (porcine, bovine, and human origin) and the two latter ones encode STh (human origin). We identified STa sequences by BLASTn and profiled ST amino acid polymorphisms in a collection of 118 clinical ETEC isolates from children and adults from Asia, Africa and, Latin America that were characterized by whole genome sequencing. Three novel variants of STp and STh were found and designated STa5 and STa6, and STa7, respectively. Presence of glucose significantly decreased the production of STh and STp toxin variants (p < 0.05) as well as downregulated the gene expression (STh: p < 0.001, STp: p < 0.05). We found that the ETEC isolates producing the most common STp variant, STa5, co-expressed coli surface antigen CS6 and was significantly associated with disease in adults in this data set (p < 0.001). Expression of mature STa5 peptide as well as gene expression of tolC, involved in ST secretion, increased in response to bile (p < 0.05). ETEC expressing the common STh variant STa3/4 was associated with disease in children (p < 0.05). The crp gene, that positively regulate estA3/4 encoding STa3/4, and estA3/4 itself had decreased transcriptional levels in presence of bile. Since bile levels in the intestine are lower in children than adults, these results may suggest differences in pathogenicity of ETEC in children and adult populations. (C) 2016 The Author(s). Published by Elsevier GmbH.
|
|
| 5. |
- Kilsgård, Ola, et al.
(författare)
-
Differential compartmentalization of Streptococcus pyogenes virulence factors and host protein binding properties as a mechanism for host adaptation
- 2016
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221. ; 306:7, s. 504-516
-
Tidskriftsartikel (refereegranskat)abstract
- . Streptococcus pyogenes is an important human pathogen responsible for substantial morbidity and mortality worldwide. Although . S. pyogenes is a strictly human pathogen with no other known animal reservoir, several murine infection models exist to explore different aspects of the bacterial pathogenesis. Inoculating mice with wild-type . S. pyogenes strains can result in the generation of new bacterial phenotypes that are hypervirulent compared to the original inoculum. In this study, we used a serial mass spectrometry based proteomics strategy to investigate if these hypervirulent strains have an altered distribution of virulence proteins across the intracellular, surface associated and secreted bacterial compartments and if any change in compartmentalization can alter the protein-protein interaction network between bacteria and host proteins. Quantitative analysis of the . S. pyogenes surface and secreted proteomes revealed that animal passaged strains are associated with significantly higher amount of virulence factors on the bacterial surface and in the media. This altered virulence factor compartmentalization results in increased binding of several mouse plasma proteins to the bacterial surface, a trend that was consistent for mouse plasma from several different mouse strains. In general, both the wild-type strain and animal passaged strain were capable of binding high amounts of human plasma proteins. However, compared to the non-passaged strains, the animal passaged strains displayed an increased ability to bind mouse plasma proteins, in particular for M protein binders, indicating that the increased affinity for mouse blood plasma proteins is a consequence of host adaptation of this pathogen to a new host. In conclusion, plotting the total amount of virulence factors against the total amount of plasma proteins associated to the bacterial surface could clearly separate out animal passaged strains from wild type strains indicating a virulence model that could predict the virulence of a . S. pyogenes strain in mice and which could be used to identify key aspects of this bacteria's pathogenesis.
|
|
| 6. |
- Knabl, Ludwig, et al.
(författare)
-
Shiga toxin 2a binds antithrombin and heparin, but does not directly activate platelets
- 2018
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 308:7, s. 969-976
-
Tidskriftsartikel (refereegranskat)abstract
- Escherichia coli-induced hemolytic uremic syndrome (eHUS) is a life-threatening complication of infection with Shiga toxin (Stx), in particular Stx2a-producing Escherichia coli. Enhanced coagulation activation with formation of microthrombi seems to be a key event in development of eHUS. Platelet activation has been postulated as a possible, but controversially debated mechanism. The present study investigated the effect of Stx2a on plasmatic coagulation and platelets. Binding studies were initially performed with ELISA and co-immunoprecipitation and supported by quartz crystal microbalance with dissipation monitoring (QCM-D). Antithrombin (AT) activity was measured using the automated BCS XP (R) system. ROTEM (R) was used for functional coagulation testing. Platelet binding and activation was studied with FACS and light-transmission aggregometry. We found binding of Stx2a to AT, an important inhibitor of blood coagulation, but only a mild albeit significant reduction of AT activity against FXa in the presence of Stx2a. QCM-D analysis also showed binding of Stx2a to heparin and an impaired binding of AT to Stx2a-bound heparin. ROTEM (R) using Stx2a-treated platelet-poor plasma revealed a significant, but only moderate shortening of clotting time. Neither binding nor activation of platelets by Stx2a could be demonstrated. In summary, data of this study suggest that Stx2a binds to AT, but does not induce major effects on plasmatic coagulation. In addition, no interaction with platelets occurred. The well-known non-beneficial administration of heparin in eHUS patients could be explained by the interaction of Stx2a with heparin.
|
|
| 7. |
- Liu, Hui, et al.
(författare)
-
Analysis of a single Helicobacter pylori strain over a 10-year period in a primate model
- 2015
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 305:3, s. 392-403
-
Tidskriftsartikel (refereegranskat)abstract
- Helicobacter pylori from different individuals exhibits substantial genetic diversity. However, the kinetics of bacterial diversification after infection with a single strain is poorly understood. We investigated evolution of H. pylori following long-term infection in the primate stomach; Rhesus macaques were infected with H. pylori strain USU101 and then followed for 10 years. H. pylori was regularly cultured from biopsies, and single colony isolates were analyzed. At 1-year, DNA fingerprinting showed that all output isolates were identical to the input strain; however, at 5-years, different H. pylori fingerprints were observed. Microarray-based comparative genomic hybridization revealed that long term persistence of USU101 in the macaque stomach was associated with specific whole gene changes. Further detailed investigation showed that levels of the BabA protein were dramatically reduced within weeks of infection. The molecular mechanisms behind this reduction were shown to include phase variation and gene loss via intragenomic rearrangement, suggesting strong selective pressure against BabA expression in the macaque model. Notably, although there is apparently strong selective pressure against babA, babA is required for establishment of infection in this model as a strain in which babA was deleted was unable to colonize experimentally infected macaques.
|
|
| 8. |
- Senneby, Erik, et al.
(författare)
-
Identification of two abundant Aerococcus urinae cell wall-anchored proteins
- 2019
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 309:7
-
Tidskriftsartikel (refereegranskat)abstract
- Aerococcus urinae is an emerging pathogen that causes urinary tract infections, bacteremia and infective endocarditis. The mechanisms through which A. urinae cause infection are largely unknown. The aims of this study were to describe the surface proteome of A. urinae and to analyse A. urinae genomes in search for genes encoding surface proteins. Two proteins, denoted Aerococcal surface protein (Asp) 1 and 2, were through the use of mass spectrometry based proteomics found to quantitatively dominate the aerococcal surface. The presence of these proteins on the surface was also shown using ELISA with serum from rabbits immunized with the recombinant Asp. These proteins had a signal sequence in the amino-terminal end and a cell wall-sorting region in the carboxy-terminal end, which contained an LPATG-motif, a hydrophobic domain and a positively charged tail. Twenty-three additional A. urinae genomes were sequenced using Illumina HiSeq technology. Six different variants of asp genes were found (denoted asp1-6). All isolates had either one or two of these asp-genes located in a conserved locus, designated Locus encoding Aerococcal Surface Proteins (LASP). The 25 genomes had in median 13 genes encoding LPXTG-proteins (range 6-24). For other Gram-positive bacteria, cell wall-anchored surface proteins with an LPXTG-motif play a key role for virulence. Thus, it will be of great interest to explore the function of the Asp proteins of A. urinae to establish a better understanding of the molecular mechanisms by which A. urinae cause disease.
|
|
| 9. |
- Singh, Birendra, et al.
(författare)
-
Haemophilus influenzae surface fibril (Hsf) is a unique twisted hairpin-like trimeric autotransporter
- 2015
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1618-0607 .- 1438-4221. ; 305:1, s. 27-37
-
Tidskriftsartikel (refereegranskat)abstract
- The Haemophilus surface fibril (Hsf) is an extraordinary large (2413 amino acids) trimeric autotransporter, present in all encapsulated Haemophilus influenzae. It contributes to virulence by directly functioning as an adhesin. Furthermore, Hsf recruits the host factor vitronectin thereby inhibiting the host innate immune response resulting in enhanced survival in serum. Here we observed by electron microscopy that Hsf appears as an 100. nm long fibril at the bacterial surface albeit the length is approximately 200. nm according to a bioinformatics based model. To unveil this discrepancy, we denaturated Hsf at the surface of Hib by using guanidine hydrochloride (GuHCl). Partial denaturation induced in the presence of GuHCl unfolded the Hsf molecules, and resulted in an increased length of fibres in comparison to the native trimeric form. Importantly, our findings were also verified by E. coli expressing Hsf at its surface. In addition, a set of Hsf-specific peptide antibodies also indicated that the N-terminal of Hsf is located near the C-terminal at the base of the fibril. Taken together, our results demonstrated that Hsf is not a straight molecule but is folded and doubled over. This is the first report that provides the unique structural features of the trimeric autotransporter Hsf.
|
|
| 10. |
- Skarp, Astrid, et al.
(författare)
-
Accessory genetic content in Campylobacter jejuni ST21CC isolates from feces and blood
- 2017
-
Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 307:4-5, s. 233-240
-
Tidskriftsartikel (refereegranskat)abstract
- Campylobacter jejuni is an important foodborne pathogen and the most commonly reported bacterial cause of gastroenteritis. C. jejuni is occasionally found in blood, although mechanisms important for invasiveness have remained unclear. C. jejuni is divided into many different lineages, of which the ST21 clonal complex (CC) is widely distributed. Here, we performed comparative genomic and in vitro analyses on 17C. jejuni ST21CC strains derived from human blood and feces in order to identify features associated with isolation site. The ST21CC lineage is divided into two large groups; centered around ST-21 and ST-50. Our clinical strains, typed as ST-50, showed further microevolution into two distinct clusters. These clusters were distinguished by major differences in their capsule loci and the distribution of accessory genetic content, including C. jejuni integrated elements (CJIEs) and plasmids. Accessory genetic content was more common among fecal than blood strains, whereas blood strains contained a hybrid capsule locus which partially consisted of C. jejuni subsp. doylei-like content. In vitro infection assays with human colon cell lines did not show significant differences in adherence and invasion between the blood and fecal strains. Our results showed that CJIEs and plasmid derived genetic material were less common among blood isolates than fecal isolates; in contrast, hybrid capsule loci, especially those containing C. jejuni subsp. doylei-like gene content, were found among many isolates derived from blood. The role of these findings requires more detailed investigation.
|
|
