fibrin and Bacteremia

A neonate with pulmonary hypertension was supported with extracorporeal membrane oxygenation (ECMO). During ECMO support, the patient developed Enterococcus faecalis bacteremia, treated with targeted antibiotics. Despite the maximum dose of antibiotics, routine blood cultures remained positive throughout the ECMO treatment. A circuit change was performed due to buildup of thrombotic material and disseminated intravascular coagulation (DIC) inside the circuit. Thrombus formation was more extensive in the first than the second circuit. Gram-positive diplococci were present in all initial circuit clots and gram-positive masses surrounded by fibrin were found inside thrombi of the second circuit. Scanning electron microscopy (SEM) revealed a dense fibrin network with embedded red blood cells and bacteria in the first circuit. In the second circuit, SEM analysis revealed scattered micro thrombi. Polymerase chain reaction for identification of bacteria in the thrombus of the first circuit showed the same bacteria as found in blood cultures and did not achieve a sufficient signal in the second circuit. This case report shows that bacteria can nestle in thrombi of an ECMO circuit and that there is a rationale for a circuit change in a patient with persistent positive blood cultures and DIC.

Topics: Anti-Bacterial Agents; Bacteremia; Bacteria; Extracorporeal Membrane Oxygenation; Fibrin; Humans; Infant, Newborn; Thrombosis

Formation of intravenous catheter-related thrombosis leads to central venous stenosis in patients requiring renal replacement therapy or chemotherapy infusion, yet the triggers or mechanisms remain unclear, especially in patients without symptoms of infection. In this study, we found that neutrophil extracellular traps (NETs) could be detected in the fibrin sheaths from dialysis patients without clinical manifestations of infection. Confocal microscopy revealed bacteria imbedded in NETs in the fibrin sheaths. Thirty-nine of 50 (78%) fibrin sheath specimens contained bacteria detectable by 16S ribosomal RNA genome typing with a predominance of

Topics: Animals; Bacteremia; Catheters, Indwelling; Constriction, Pathologic; Extracellular Traps; Fibrin; Neutrophils; Rats; Staphylococcus aureus; Thrombosis; Venous Thrombosis

Topics: Adult; Bacteremia; Fibrin; Humans; Male; Methicillin-Resistant Staphylococcus aureus; Staphylococcal Infections

Tissue factor (TF) is a transmembrane glycoprotein that plays an essential role in hemostasis by activating coagulation. TF is also expressed by monocytes/macrophages as part of the innate immune response to infections. In the current study, we determined the role of TF expressed by myeloid cells during Mycobacterium tuberculosis (M. tb) infection by using mice lacking the TF gene in myeloid cells (TF(Δ) ) and human monocyte derived macrophages (MDMs). We found that during M. tb infection, a deficiency of TF in myeloid cells was associated with reduced inducible nitric oxide synthase (iNOS) expression, enhanced arginase 1 (Arg1) expression, enhanced IL-10 production and reduced apoptosis in infected macrophages, which augmented M. tb growth. Our results demonstrate that a deficiency of TF in myeloid cells promotes M2-like phenotype in M .tb infected macrophages. A deficiency in TF expression by myeloid cells was also associated with reduced fibrin deposition and increased matrix metalloproteases (MMP)-2 and MMP-9 mediated inflammation in M. tb infected lungs. Our studies demonstrate that TF expressed by myeloid cells has newly recognized abilities to polarize macrophages and to regulate M. tb growth.

Topics: Animals; Bacteremia; Blood Coagulation; Cell Differentiation; Female; Fibrin; Host-Pathogen Interactions; Humans; Immunity, Innate; Lung; Macrophages; Mice, Inbred C57BL; Mice, Knockout; Mycobacterium tuberculosis; Pneumonia; Thromboplastin; Tuberculoma; Tuberculosis, Pulmonary

Mycobacterium tuberculosis, the causative agent of tuberculosis, drives the formation of granulomas, structures in which both immune cells and the bacterial pathogen cohabit. The most abundant cells in granulomas are macrophages, which contribute as both cells with bactericidal activity and as targets for M. tuberculosis infection and proliferation during the entire course of infection. The mechanisms and factors involved in the regulation and control of macrophage microenvironment-specific polarization and plasticity are not well understood, as some granulomas are able to control bacteria growth and others fail to do so, permitting bacterial spread. In this issue of the European Journal of Immunology, Venkatasubramanian et al. [Eur. J. Immunol. 2016. 46: 464-479] show that mice lacking the tissue factor gene in myeloid cells have augmented M. tuberculosis growth and increased inflammation in the lungs. This suggests that tissue factor, an initiator of coagulation, is important for the generation of fibrin, which supports granuloma formation. This article demonstrates for the first time the involvement of tissue factor in inducing effective immunity against M. tuberculosis, and sheds new lights on the complex interplay between host inflammatory response, the coagulation system, and the control of M. tuberculosis infection.

Topics: Animals; Bacteremia; Blood Coagulation; Cell Differentiation; Fibrin; Host-Pathogen Interactions; Humans; Immunity, Innate; Lung; Macrophages; Mice; Mice, Knockout; Mycobacterium tuberculosis; Pneumonia; Thromboplastin; Tuberculoma; Tuberculosis, Pulmonary

In this study, silver/copper (Ag/Cu)-coated catheters were investigated for their efficacy in preventing methicillin-resistant Staphylococcus aureus (MRSA) infection in vitro and in vivo Ag and Cu were sputtered (67/33% atomic ratio) on polyurethane catheters by direct-current magnetron sputtering. In vitro, Ag/Cu-coated and uncoated catheters were immersed in phosphate-buffered saline (PBS) or rat plasma and exposed to MRSA ATCC 43300 at 10(4) to 10(8) CFU/ml. In vivo, Ag/Cu-coated and uncoated catheters were placed in the jugular vein of rats. Directly after, MRSA (10(7) CFU/ml) was inoculated in the tail vein. Catheters were removed 48 h later and cultured. In vitro, Ag/Cu-coated catheters preincubated in PBS and exposed to 10(4) to 10(7) CFU/ml prevented the adherence of MRSA (0 to 12% colonization) compared to uncoated catheters (50 to 100% colonization; P < 0.005) and Ag/Cu-coated catheters retained their activity (0 to 20% colonization) when preincubated in rat plasma, whereas colonization of uncoated catheters increased (83 to 100%; P < 0.005). Ag/Cu-coating protection diminished with 10(8) CFU/ml in both PBS and plasma (50 to 100% colonization). In vivo, Ag/Cu-coated catheters reduced the incidence of catheter infection compared to uncoated catheters (57% versus 79%, respectively; P = 0.16) and bacteremia (31% versus 68%, respectively; P < 0.05). Scanning electron microscopy of explanted catheters suggests that the suboptimal activity of Ag/Cu catheters in vivo was due to the formation of a dense fibrin sheath over their surface. Ag/Cu-coated catheters thus may be able to prevent MRSA infections. Their activity might be improved by limiting plasma protein adsorption on their surfaces.

Topics: Adsorption; Animals; Anti-Infective Agents; Bacteremia; Catheters, Indwelling; Coated Materials, Biocompatible; Colony Count, Microbial; Copper; Fibrin; Jugular Veins; Methicillin-Resistant Staphylococcus aureus; Nanoparticles; Polyurethanes; Rats; Silver; Staphylococcal Infections

To unravel the strategy by which Brucella abortus establishes chronic infections, we explored its early interaction with innate immunity.. Brucella did not induce proinflammatory responses as demonstrated by the absence of leukocyte recruitment, humoral or cellular blood changes in mice. Brucella hampered neutrophil (PMN) function and PMN depletion did not influence the course of infection. Brucella barely induced proinflammatory cytokines and consumed complement, and was strongly resistant to bactericidal peptides, PMN extracts and serum. Brucella LPS (BrLPS), NH-polysaccharides, cyclic glucans, outer membrane fragments or disrupted bacterial cells displayed low biological activity in mice and cells. The lack of proinflammatory responses was not due to conspicuous inhibitory mechanisms mediated by the invading Brucella or its products. When activated 24 h post-infection macrophages did not kill Brucella, indicating that the replication niche was not fusiogenic with lysosomes. Brucella intracellular replication did not interrupt the cell cycle or caused cytotoxicity in WT, TLR4 and TLR2 knockout cells. TNF-alpha-induction was TLR4- and TLR2-dependent for live but not for killed B. abortus. However, intracellular replication in TLR4, TLR2 and TLR4/2 knockout cells was not altered and the infection course and anti-Brucella immunity development upon BrLPS injection was unaffected in TLR4 mutant mice.. We propose that Brucella has developed a stealth strategy through PAMPs reduction, modification and hiding, ensuring by this manner low stimulatory activity and toxicity for cells. This strategy allows Brucella to reach its replication niche before activation of antimicrobial mechanisms by adaptive immunity. This model is consistent with clinical profiles observed in humans and natural hosts at the onset of infection and could be valid for those intracellular pathogens phylogenetically related to Brucella that also cause long lasting infections.

Topics: Animals; Bacteremia; Blood Coagulation; Brucella abortus; Brucellosis; Fibrin; Fibrinogen; Immunity, Innate; Leukocytes; Mice; Neutrophils; Platelet Aggregation; Sepsis; Shock, Septic

Inhibition of fibrin sheath formation by enoxaparin decreases catheter colonization. Fibrin-binding radioactive tracer and catheter weights quantify fibrin reduction.. Controlled experimental study of central venous line colonization.. Animal laboratory.. Adult male Sprague-Dawley rats.. Central venous lines were introduced into right external jugular veins of 254 animals in three groups: enoxaparin, Fibrimage, and catheter weight. The enoxaparin group (n = 196) received daily enoxaparin injections (n = 97) or catheter implantation only (n = 99); 176 received tail vein injections of Staphylococcus epidermidis on postoperative day (POD) 10. Twenty rats received saline injections as a control. On POD 13, catheters were removed and incubated in broth at 37 degrees C for 48 hrs. Turbid samples were plated. In the Fibrimage group (n = 39), 20 rats receiving enoxaparin were compared with 19 controls without enoxaparin; all received S. epidermidis injections on POD 10. Fibrimage, fibrin-binding radiolabeled tracer, was given 1 hr before catheter removal. In the weight group (n = 19), six rats received enoxaparin; 13 did not. All received injections of S. epidermidis on POD 10.. Positive plates underwent analytic profile index testing, ensuring correlation with inoculum. Results were compared using Fisher's exact or chi-square tests. Gamma counts were determined in the Fibrimage group. Catheter tip weights were recorded. Results from the Fibrimage and weight groups were compared using Student's t-test. The enoxaparin group had fewer catheters colonized (17 of 77) vs. no enoxaparin (42 of 99; p < .01). Pericatheter sheaths contained less fibrin compared with controls. Fibrimage group gamma counts were significantly decreased for the enoxaparin subgroup (x = 2244 counts per minute) vs. controls (x = 3767 counts per minute; p < .0002). The weight of catheter tips treated with enoxaparin (x = 39 mg) vs. controls (x = 90 mg) was also significantly decreased (p < .0001).. Enoxaparin decreases the amount of fibrin surrounding central venous catheters. The incidence of catheter colonization decreases when the amount of fibrin within the pericatheter sheath decreases.

Topics: Animals; Anticoagulants; Bacteremia; Catheterization, Central Venous; Catheters, Indwelling; Enoxaparin; Fibrin; Male; Rats; Rats, Sprague-Dawley

Adherence of bacteria and subsequent catheter-related infections (CRI) are greatly enhanced by the fibrin sheath that develops on indwelling catheters. Since the infection rate of catheters without fibrin sheaths is low and the fibrin sheath mediates bacterial adherence, catheter material is not thought to affect the incidence of late catheter-related infection.. A total of 276 rats had catheters placed in the right jugular vein with the proximal end buried subcutaneously to eliminate exit site infection. Rats were divided into two groups: silastic catheters (SC; n = 133) and polyurethane catheters (PC; n = 143). Injections of 1 x 10(8) CFU/mL of Staphylococcus epidermidis were given via the tail vein on either the day of surgery, day 0 (n = 53 SC, n = 51 PC), or on postoperative day 10 (n = 50 SC, n = 62 PC). Thirty animals from each group (SC, PC) received sterile saline injections on day 10 and served as controls. Animals were sacrificed on postinjection day 3. Catheters were removed via the chest and placed into trypticase soy broth. Broth was incubated at 37 degrees C for 48 h. Microscopy for the fibrin sheath was done on 20 randomly selected catheters (10/group). Data were compared using Fisher's exact test, with p < 0.05 considered significant.. Incidence of CRI was equal prior to the formation of the fibrin sheath, while CRI was significantly higher in silastic catheters in the presence of a fibrin sheath. Without a fibrin sheath (day 0), 8/53 silastic catheters and 3/51 polyurethane catheters were infected (p = NS). With a fibrin sheath (day 10), 31/50 silastic catheters were infected versus 20/62 polyurethane catheters (p < 0.05). Control catheters were all culture negative (30/group). With light microscopy, 20/20 catheters had fibrin sheaths at day 10 with no visible difference between silastic and polyurethane catheters.. Catheter material does affect the incidence of catheter-related infection even when catheters are coated with a fibrin sheath. This difference may relate to a difference in the fibrin sheath itself as it forms on different catheter materials.

Topics: Animals; Bacteremia; Bacterial Adhesion; Catheters, Indwelling; Coated Materials, Biocompatible; Dimethylpolysiloxanes; Fibrin; Male; Models, Animal; Polyurethanes; Rats; Rats, Sprague-Dawley; Silicones; Staphylococcal Infections; Staphylococcus epidermidis

Topics: Bacteremia; Catheterization, Central Venous; Citrobacter freundii; Contrast Media; Enterobacteriaceae Infections; Fibrin; Humans; Jugular Veins; Male; Middle Aged; Pulmonary Embolism; Radiography; Radionuclide Imaging; Renal Dialysis

During episodes of dental bacteremia, viridans group streptococci encounter platelets. Among these microorganisms, certain Streptococcus sanguis induce human and rabbit platelets to aggregate in vitro. In experimental rabbits, circulating streptococci induced platelets to aggregate, triggering the accumulation of platelets and fibrin into the heart valve vegetations of endocarditis. At necropsy, affected rabbit hearts showed ischemic areas. We therefore hypothesized that circulating S. sanguis might cause coronary thrombosis and signs of myocardial infarction (MI). Signs of MI were monitored in rabbits after infusion with platelet-aggregating doses of 4 to 40 x 10(9) cells of S. sanguis 133-79. Infusion resulted in dose-dependent changes in electrocardiograms, blood pressure, heart rate, and cardiac contractility. These changes were consistent with the occurrence of MI. Platelets isolated from hyperlipidemic rabbits showed an accelerated in vitro aggregation response to strain 133-79. Cultured from immunosuppressed children with septic shock and signs of disseminated intravascular coagulation, more than 60% of isolates of viridans streptococci induced platelet aggregation when tested in vitro. The data are consistent with a thrombogenic role for S. sanguis in human disease, contributing to the development of the vegetative lesion in infective endocarditis and a thrombotic mechanism to explain the additional contributed risk of periodontitis to MI.

Topics: Animals; Bacteremia; Bacterial Physiological Phenomena; Blood Platelets; Blood Pressure; Cells, Cultured; Child; Coronary Thrombosis; Disseminated Intravascular Coagulation; Electrocardiography; Endocarditis, Bacterial; Fibrin; Heart Diseases; Heart Rate; Humans; Hyperlipidemias; Immunocompromised Host; Mouth; Myocardial Contraction; Myocardial Infarction; Myocardial Ischemia; Periodontitis; Platelet Aggregation; Rabbits; Shock, Septic; Streptococcus sanguis; Thrombosis

The purpose of this study was to determine whether the fibrin sheath that develops around an intravenous silicone catheter influences catheter-related sepsis. A rat model with a central intravenous silicone catheter was used. Staphylococcus aureus, dose 1 x 10(7) colony forming units (cfu), were injected via the tail vein, either immediately after catheter insertion (group 1, n = 23) or after the catheter had been in situ for at least 7 days (group 2, n = 22). Blood cultures were done on at 24 hours and 7 days. Animals were killed on day 7 and the catheter was removed for culture (Maki and broth) and scanning electronmicroscopy (SEM). The was no significant difference (P > .05) between the number of positive blood cultures in groups 1 and 2 at 24 hours (16 v 9) and 7 days (12 v 6). In group 1 there were significantly more positive catheter cultures by both methods (23 v 16 in group 2; P < .05) and more cfu/per centimeter catheter (group 1 mean, 520, range, 197 to 600; group 2 mean 195, range 9 to 600; P < .001). In group 1, 12 animals had catheter sepsis compared with 5 in group 2 (P = NS). On SEM a fibrinous sheath was identified on all catheters removed on day 7 but not on 5 catheters inserted and removed after 10 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Bacteremia; Catheterization, Central Venous; Fibrin; Male; Microscopy, Electron, Scanning; Models, Biological; Random Allocation; Rats; Rats, Inbred Strains; Staphylococcal Infections

Injury severity score and hypothermia can lead to a high level of mortality when combined clinically. In acute trauma, the presence of a coagulopathy is difficult to treat and the aim is prevention. Aliquots of whole blood from healthy human volunteers (n = 9) were added to saline (control) and saline plus endotoxin (activated). The control and activated groups were divided and subjected to 60 minutes of normothermia (24 degrees C) or hypothermia (0 degrees C). The samples were returned to 37 degrees C; then the recalcification times were determined using fibrin formation and the viscous drag as the determining factors. The activated hypothermic group showed a decreased recalcification time of 345 (+/- 48.9) seconds compared to 405 (+/- 60.8) for the activated normothermic group (P less than 0.001). When the normothermic and hypothermic groups were compared without endotoxin added, the differences were not significant. The authors conclude that the effects of endotoxin on clotting time are worsened by hypothermia in vitro and act synergistically to possibly cause the coagulopathy seen in trauma patients.

Topics: Bacteremia; Blood Viscosity; Disseminated Intravascular Coagulation; Endotoxins; Escherichia coli Infections; Evaluation Studies as Topic; Fibrin; Humans; Hypothermia; Injury Severity Score; Multiple Trauma; Whole Blood Coagulation Time