Thrombin-Activatable Fibrinolysis Inhibitor Binds To Streptococcus Pyogenes By Interacting With Collagen-Like Proteins A And B

Regulation of proteolysis is a critical element of the host immune system and plays an important role in the induction of pro- and anti-inflammatory reactions in response to infection. Some bacterial species take advantage of these processes and recruit host proteinases to their surface in order to counteract the host attack. Here we show that Thrombin-activatable Fibrinolysis Inhibitor (TAFI), a zinc-dependent procarboxypeptidase, binds to the surface of group A streptococci of an M41 serotype. The interaction is mediated by the streptococcal collagen-like surface proteins A and B (Sc1A and Sc1B), and the streptococcal-associated TAFI is then processed at the bacterial surface via plasmin and thrombin-thrombomodulin. These findings suggest an important role for TAFI in the modulation of host responses by streptococci

Thrombin-Activatable Fibrinolysis Inhibitor Binds To Streptococcus Pyogenes By Interacting With Collagen-Like Proteins A And B

Regulation of proteolysis is a critical element of the host immune system and plays an important role in the induction of pro- and anti-inflammatory reactions in response to infection. Some bacterial species take advantage of these processes and recruit host proteinases to their surface in order to counteract the host attack. Here we show that Thrombin-activatable Fibrinolysis Inhibitor (TAFI), a zinc-dependent procarboxypeptidase, binds to the surface of group A streptococci of an M41 serotype. The interaction is mediated by the streptococcal collagen-like surface proteins A and B (Sc1A and Sc1B), and the streptococcal-associated TAFI is then processed at the bacterial surface via plasmin and thrombin-thrombomodulin. These findings suggest an important role for TAFI in the modulation of host responses by streptococci

Evaluation of penicillin G susceptibility testing methods for Staphylococcus lugdunensis

BACKGROUND: Staphylococcus lugdunensis belongs to the CoNS group, but is regarded to be more virulent than most other CoNS. It is also remarkably susceptible to antibiotics, including penicillin G. OBJECTIVES: To evaluate different methods for penicillin susceptibility testing, to assess penicillin susceptibility rates among S. lugdunensis and to describe the clinical presentation including antibiotic treatment. METHODS: Clinical isolates of S. lugdunensis were tested for penicillin susceptibility using disc diffusion according to CLSI (10 U disc) and EUCAST (1 U disc), assessment of zone-edge appearance, nitrocefin test and Etest for MIC determination. PCR of the blaZ gene was used as a reference method. RESULTS: Of the 112 isolates included in the study, 67% were susceptible to penicillin G according to blaZ PCR. The EUCAST disc diffusion test had 100% sensitivity, whereas the CLSI method had one very major error with a false-susceptible isolate. When zone-edge appearance was included in the assessment, the false-susceptible isolate was correctly classified as resistant. Foreign-body infection was the most common focus of infection, affecting 49% of the participants. Only 4% of the patients were treated with penicillin G. CONCLUSIONS: Penicillin susceptibility is common in S. lugdunensis and the disc diffusion method according to EUCAST had a higher sensitivity than that of CLSI. Assessment of zone-edge appearance could increase the sensitivity of the disc diffusion test. Penicillin susceptibility testing and treatment should be considered in S. lugdunensis infections

Urine concentrations of human beta-defensins and ribonuclease 7 in urinary tract infection and asymptomatic bacteriuria

Antimicrobial peptides (AMPs) provide a first line of defense against bacterial infections. Here we report that urine levels of AMPs, locally produced in the urinary tract, are lower in individuals with asymptomatic bacteriuria (ABU) compared to patients with urinary tract infection (UTI)

Penicillin-susceptible Staphylococcus aureus : susceptibility testing, resistance rates and outcome of infection

Background: Staphylococcus aureus (SA) is an important human pathogen that causes both superficial and invasive infections. Penicillin is now rarely used in the treatment of SA infections due to widespread resistance and a concern about the accuracy of existing methods for penicillin susceptibility testing. The aims of the present study were to determine the frequency of penicillin-susceptible SA isolates from blood and wound cultures in Lund, Sweden, and to evaluate methods for penicillin testing in SA. We also wanted to investigate if penicillin-susceptible isolates are associated with higher mortality. Methods: Hundred blood culture isolates collected 2008/2009, 140 blood culture isolates from 2014/2015, and 141 superficial wound culture strains from 2015 were examined. Penicillin susceptibility was tested with disk diffusion according to EUCAST guidelines, and results were confirmed with a cloverleaf assay and PCR amplification of the BlaZ gene. Patient data for all bacteraemia cases were extracted from medical records. Results: The disk diffusion method with assessment of both zone size and zone edge appearance had high accuracy in our study. About 57% of bacteraemia isolates from 2008/2009 were sensitive to penicillin compared to 29% in 2014/2015 (p < .0001). In superficial wound cultures, 21% were penicillin susceptible. There was no difference in co-morbidity or mortality rates between patients with penicillin resistant and penicillin sensitive SA bacteraemia. Conclusion: Disk-diffusion is a simple and reliable method to detect penicillin resistance in SA, and susceptibility rates are significant. Penicillin has many theoretical advantages and should be considered in the treatment of SA bacteraemia when susceptible

Divergent airway microbiomes in lung transplant recipients with or without pulmonary infection

BACKGROUND: Lung transplant (LTx) recipients are at increased risk for airway infections, but the cause of infection is often difficult to establish with traditional culture-based techniques. The objectives of the study was to compare the airway microbiome in LTx patients with and without ongoing airway infection and identify differences in their microbiome composition.METHODS: LTx recipients were prospectively followed with bronchoalveolar lavage (BAL) during the first year after transplantation. The likelihood of airway infection at the time of sampling was graded based on clinical criteria and BAL cultures, and BAL fluid levels of the inflammatory markers heparin-binding protein (HBP), IL-1β and IL-8 were determined with ELISA. The bacterial microbiome of the samples were analysed with 16S rDNA sequencing and characterized based on richness and evenness. The distance in microbiome composition between samples were determined using Bray-Curtis and weighted and unweighted UniFrac.RESULTS: A total of 46 samples from 22 patients were included in the study. Samples collected during infection and samples with high levels of inflammation were characterized by loss of bacterial diversity and a significantly different species composition. Burkholderia, Corynebacterium and Staphylococcus were enriched during infection and inflammation, whereas anaerobes and normal oropharyngeal flora were less abundant. The most common findings in BAL cultures, including Pseudomonas aeruginosa, were not enriched during infection.CONCLUSION: This study gives important insights into the dynamics of the airway microbiome of LTx recipients, and suggests that lung infections are associated with a disruption in the homeostasis of the microbiome

Biofilm formation is associated with poor outcome in prosthetic joint infections caused by Staphylococcus lugdunensis

Background: Staphylococcus lugdunensis has been described as a pathogen of increasing importance in prosthetic joint infections (PJI). Our aim was to describe the clinical presentation of PJI caused by S. lugdunensis, and to correlate the biofilm-forming ability of the bacterial isolates to clinical outcome. Method: S. lugdunensis isolates from PJI episodes during 2015–2019 were included and analysed for biofilm formation using a microtiter plate assay. Medical records from the corresponding patients were reviewed. Results: We identified 36 patients with PJI caused by S. lugdunensis during the study period. Early postoperative PJIs were most frequent (n = 20, 56%). Surgical intervention was performed in a majority of the patients (n = 33, 92%), and the dominating type of antibiotic treatment was a combination of rifampicin and ciprofloxacin (n = 27, 75%). The treatment success-rate was 81% (n = 29). All isolates causing PJI were able to form biofilm in vitro. Biofilm formation was significantly stronger in isolates causing relapsing vs non-relapsing PJI (mean OD550 3.1 ± 0.23 vs 1.14 ± 0.73 p =.001) and strong biofilm formation was also associated with late acute hematogenic PJI (mean OD550 1.8 ± 0.93 vs. 0.93 ± 0.81, p =.01). Conclusion: Strong biofilm production in S. lugdunensis isolates was associated with relapse in PJI

Streptococcal M1 protein induces hyporesponsiveness and cytokine release from human arteries in a fibrinogen-dependent manner : A translational study

Background: Streptococcus pyogenes is a Gram positive bacterial species commonly involved in sepsis. Invasive strains express virulence factors such as the M1 protein. M1 protein forms complexes with fibrinogen leading to a cytokine storm in plasma contributing to the development of septic shock and organ failure. In experimental animals M1 protein causes vascular nitric oxide production and hyporesponsiveness to pressors, but it is not known whether it affects the human vascular wall. Methods: Human omental arteries obtained during surgery were incubated in vitro with M1 protein or lipopolysaccharide (LPS) as positive control, with or without plasma. After 48h, contractile response to noradrenaline was measured, and levels of nitrite/nitrate and the cytokines interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α in the incubation medium were measured. A second set of arteries were incubated with or without main components of plasma (immunoglobulin G, albumin or fibrinogen), in the presence of M1 protein followed by cytokine measurement. Results: Artery segments incubated with M1 protein and plasma contracted weaker in response to noradrenaline, and levels of IL-6 and IL-8 were significantly higher compared to after incubation with M1 protein alone. Incubation with M1 protein and fibrinogen resulted in elevated levels of IL-6 and IL-8, while incubation with M1 protein and albumin or immunoglobulin G did not affect the levels. Neither any of the other cytokines nor nitrite/nitrate was detected in the medium in any of the incubation conditions. Conclusions: The study shows that M1 protein of Streptococcus pyogenes has a direct effect on the human vascular wall in the presence of plasma, demonstrated both as a diminished contractile response to noradrenaline and increased cytokine production. The effect of plasma was attributed to fibrinogen. The findings suggest that M1 protein contributes to the development of septic shock through impairment of the contractility of the vascular wall

Commercial albumin solution enhances endotoxin-induced vasoplegia and inflammation

BACKGROUND: The Gram-negative bacterium Escherichia coli, commonly involved in severe sepsis and septic shock, shed endotoxin that upon detection by the host triggers an inflammatory cascade. Efficiency of albumin solutions to restore hypovolemia during sepsis has been debated. To aid identification of subgroups of sepsis patients that may respond positively or negatively to treatment with albumin we investigated if preparations of albumin for medical use could affect endotoxin-induced inflammatory response.METHODS: Isolated human omental arteries obtained during surgery were incubated with endotoxin in the presence or absence of albumin solution. Isolated human monocytes were incubated with endotoxin in the presence or absence of five different commercially available albumin solutions. Vascular contractile response to noradrenaline and release of interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α were measured.RESULTS: Incubation with albumin together with endotoxin decreased median maximum contraction and increased release of IL-6 and IL-8 from the arteries compared to incubation with endotoxin alone. All albumin solutions except one significantly increased endotoxin-induced TNF-α release from monocytes. IL-6 and IL-10 were also increased and no concentration dependency of TNF-α release was observed above 2 mg mL-1 . Incubation with albumin alone did not affect contraction or release of cytokines while no potentially endotoxin-enhancing contaminant could be identified.CONCLUSION: We have shown that albumin solution in combination with endotoxin cause vasoplegia in human omental arteries, paralleled by an inflammatory response. This finding could explain the variable efficiency of albumin solutions for sepsis treatment

Exoproducts of the Most Common Achromobacter Species in Cystic Fibrosis Evoke Similar Inflammatory Responses In Vitro

ABSTRACT Achromobacter is a genus of Gram-negative rods, which can cause persistent airway infections in people with cystic fibrosis (CF). The knowledge about virulence and clinical implications of Achromobacter is still limited, and it is not fully established whether Achromobacter infections contribute to disease progression or if it is a marker of poor lung function. The most commonly reported Achromobacter species in CF is A. xylosoxidans. While other Achromobacter spp. are also identified in CF airways, the currently used Matrix-Assisted Laser Desorption/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) method in routine diagnostics cannot distinguish between species. Differences in virulence between Achromobacter species have consequently not been well studied. In this study, we compare phenotypes and proinflammatory properties of A. xylosoxidans, A. dolens, A. insuavis, and A. ruhlandii using in vitro models. Bacterial supernatants were used to stimulate CF bronchial epithelial cells and whole blood from healthy individuals. Supernatants from the well-characterized CF-pathogen Pseudomonas aeruginosa were included for comparison. Inflammatory mediators were analyzed with ELISA and leukocyte activation was assessed using flow cytometry. The four Achromobacter species differed in morphology seen in scanning electron microscopy (SEM), but there were no observed differences in swimming motility or biofilm formation. Exoproducts from all Achromobacter species except A. insuavis caused significant IL-6 and IL-8 secretion from CF lung epithelium. The cytokine release was equivalent or stronger than the response induced by P. aeruginosa. All Achromobacter species activated neutrophils and monocytes ex vivo in a lipopolysaccharide (LPS)-independent manner. Our results indicate that exoproducts of the four included Achromobacter species do not differ consistently in causing inflammatory responses, but they are equally or even more capable of inducing inflammation compared with the classical CF pathogen P. aeruginosa. IMPORTANCE Achromobacter xylosoxidans is an emerging pathogen among people with cystic fibrosis (CF). Current routine diagnostic methods are often unable to distinguish A. xylosoxidans from other Achromobacter species, and the clinical relevance of different species is still unknown. In this work, we show that four different Achromobacter species relevant to CF evoke similar inflammatory responses from airway epithelium and leukocytes in vitro, but they are all equally or even more proinflammatory compared to the classic CF-pathogen Pseudomonas aeruginosa. The results suggest that Achromobacter species are important airway pathogens in CF, and that all Achromobacter species are relevant to treat