scholarly journals Antibiotics Stimulate Formation of Vesicles inStaphylococcus aureusin both Phage-Dependent and -Independent Fashions and via Different Routes

2018 ◽  
Vol 63 (2) ◽  
pp. e01439-18 ◽  
Author(s):  
Federica Andreoni ◽  
Masanori Toyofuku ◽  
Carmen Menzi ◽  
Ratchara Kalawong ◽  
Srikanth Mairpady Shambat ◽  
...  
Keyword(s):  
Whole Blood ◽  
Ex Vivo ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Vesicle Formation ◽  
Independent Manner ◽  
Content Type ◽  
Lactam Antibiotic ◽  
Underlying Mechanisms

ABSTRACTBacterial membrane vesicle research has so far focused mainly on Gram-negative bacteria. Only recently have Gram-positive bacteria been demonstrated to produce and release extracellular membrane vesicles (MVs) that contribute to bacterial virulence. Although treatment of bacteria with antibiotics is a well-established trigger of bacterial MV formation, the underlying mechanisms are poorly understood. In this study, we show that antibiotics can induce MVs through different routes in the important human pathogenStaphylococcus aureus. DNA-damaging agents and antibiotics inducing the SOS response triggered vesicle formation in lysogenic strains ofS. aureusbut not in their phage-devoid counterparts. The β-lactam antibiotics flucloxacillin and ceftaroline increased vesicle formation in a prophage-independent manner by weakening the peptidoglycan layer. We present evidence that the amount of DNA associated with MVs formed by phage lysis is greater than that for MVs formed by β-lactam antibiotic-induced blebbing. The purified MVs derived fromS. aureusprotected the bacteria from challenge with daptomycin, a membrane-targeting antibiotic, bothin vitroandex vivoin whole blood. In addition, the MVs protectedS. aureusfrom killing in whole blood, indicating that antibiotic-induced MVs function as a decoy and thereby contribute to the survival of the bacterium.

scholarly journals Bacterial Membrane-Derived Vesicles Attenuate Vancomycin Activity against Methicillin-Resistant Staphylococcus aureus

2021 ◽  
Vol 9 (10) ◽  
pp. 2055
Author(s):  
Monika Kumaraswamy ◽  
Kamilla Wiull ◽  
Bishnu Joshi ◽  
George Sakoulas ◽  
Armin Kousha ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Whole Blood ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Ex Vivo ◽  
Membrane Vesicles ◽  
World Health ◽  
Human Neutrophils ◽  
Methicillin Resistant

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved numerous antimicrobial resistance mechanisms and is identified as a serious public health threat by the World Health Organization and U.S. Centers for Disease Control and Prevention. The glycopeptide vancomycin (VAN) remains a cornerstone of therapy for severe MRSA infections despite increasing reports of therapeutic failure in hospitalized patients with bacteremia or pneumonia. Recently, the role of released bacterial-derived membrane vesicles (MVs) in antibiotic resistance has garnered attention. Here we examined the effect of exogenous MRSA-derived MVs on VAN activity against MRSA in vitro, using minimum inhibitory concentration and checkerboard assays, and ex vivo, incorporating components of host innate immunity such as neutrophils and serum complement present in blood. Additionally, the proteome of MVs from VAN-exposed MRSA was characterized to determine if protein expression was altered. The presence of MVs increased the VAN MIC against MRSA to values where clinical failure is commonly observed. Furthermore, the presence of MVs increased survival of MRSA pre-treated with sub-MIC concentrations of VAN in whole blood and upon exposure to human neutrophils but not human serum. Unbiased proteomic analysis also showed an elevated expression of MV proteins associated with antibiotic resistance (e.g., marR) or proteins that are functionally linked to cell membrane/wall metabolism. Together, our findings indicate MRSA-derived MVs are capable of lowering susceptibility of the pathogen to VAN, whole-blood- and neutrophil-mediated killing, a new pharmacodynamic consideration for a drug increasingly linked to clinical treatment failures.

Monitoring Anticoagulant Therapy by Activated Partial Thromboplastin Time: Hirudin Assessment

1994 ◽  
Vol 72 (05) ◽  
pp. 685-692 ◽  
Author(s):  
Michael T Nurmohamed ◽  
René J Berckmans ◽  
Willy M Morriën-Salomons ◽  
Fenny Berends ◽  
Daan W Hommes ◽  
...  
Keyword(s):  
Whole Blood ◽  
Partial Thromboplastin Time ◽  
Ex Vivo ◽  
Fold Increase ◽  
Heparin Therapy ◽  
Activated Partial Thromboplastin Time ◽  
Recombinant Hirudin ◽  
Interindividual Differences ◽  
The Relationship

SummaryBackground. Recombinant hirudin (RH) is a new anticoagulant for prophylaxis and treatment of venous and arterial thrombosis. To which extent the activated partial thromboplastin time (APTT) is suitable for monitoring of RH has not been properly evaluated. Recently, a capillary whole blood device was developed for bed-side monitoring of the APTT and it was demonstrated that this device was suitable to monitor heparin therapy. However, monitoring of RH was not evaluated.Study Objectives. To evaluate in vitro and ex vivo the responsiveness and reproducibility for hirudin monitoring of the whole blood monitor and of plasma APTT assays, which were performed with several reagents and two conventional coagulometers.Results. Large interindividual differences in hirudin responsiveness were noted in both the in vitro and the ex vivo experiments. The relationship between the APTT, expressed as clotting time or ratio of initial and prolonged APTT, and the hirudin concentration was nonlinear. A 1.5-fold increase of the clotting times was obtained at 150-200 ng/ml plasma. However, only a 2-fold increase was obtained at hirudin levels varying from 300 ng to more than 750 ng RH/ml plasma regardless of the assays. The relationship linearized upon logarithmic conversion of the ratio and the hirudin concentration. Disregarding the interindividual differences, and presuming full linearity of the relationship, all combinations were equally responsive to hirudin.Conclusions. All assays were equally responsive to hirudin. Levels up to 300 ng/ml plasma can be reliably estimated with each assay. The manual device may be preferable in situations where rapid availability of test results is necessary.

Monitoring of r-Hirudin Anticoagulation during Cardiopulmonary Bypass – Assessment of the Whole Blood Ecarin Clotting Time

1997 ◽  
Vol 77 (05) ◽  
pp. 0920-0925 ◽  
Author(s):  
Bernd Pötzsch ◽  
Katharina Madlener ◽  
Christoph Seelig ◽  
Christian F Riess ◽  
Andreas Greinacher ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Whole Blood ◽  
Heart Surgery ◽  
Ex Vivo ◽  
Open Heart Surgery ◽  
Clotting Time ◽  
Blood Samples ◽  
Alternative Approach ◽  
Ecarin Clotting Time

SummaryThe use of recombinant ® hirudin as an anticoagulant in performing extracorporeal circulation systems including cardiopulmonary bypass (CPB) devices requires a specific and easy to handle monitoring system. The usefulness of the celite-induced activated clotting time (ACT) and the activated partial thromboplastin time (APTT) for r-hirudin monitoring has been tested on ex vivo blood samples obtained from eight patients treated with r-hirudin during open heart surgery. The very poor relationship between the prolongation of the ACT and APTT values and the concentration of r-hirudin as measured using a chromogenic factor Ila assay indicates that both assays are not suitable to monitor r-hirudin anticoagulation. As an alternative approach a whole blood clotting assay based on the prothrombin-activating snake venom ecarin has been tested. In vitro experiments using r-hirudin- spiked whole blood samples showed a linear relationship between the concentration of hirudin added and the prolongation of the clotting times up to a concentration of r-hirudin of 4.0 µg/ml. Interassay coefficients (CV) of variation between 2.1% and 5.4% demonstrate the accuracy of the ecarin clotting time (ECT) assay. Differences in the interindividual responsiveness to r-hirudin were analyzed on r-hirudin- spiked blood samples obtained from 50 healthy blood donors. CV- values between 1.8% and 6% measured at r-hirudin concentrations between 0.5 and 4 µg/ml indicate remarkably slight differences in r-hirudin responsiveness. ECT assay results of the ex vivo blood samples linearily correlate (r = 0.79) to the concentration of r-hirudin. Moreover, assay results were not influenced by treatment with aprotinin or heparin. These findings together with the short measuring time with less than 120 seconds warrant the whole blood ECT to be a suitable assay for monitoring of r-hirudin anticoagulation in cardiac surgery.

Early Platelet-Collagen Interactions in Whole Blood and Their Modifications by Aspirin and Dipyridamole Evaluated by a New Method (Basic Wave)

1985 ◽  
Vol 54 (04) ◽  
pp. 799-803 ◽  
Author(s):  
José Luís Pérez-Requejo ◽  
Justo Aznar ◽  
M Teresa Santos ◽  
Juana Vallés
Keyword(s):  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
White Blood Cells ◽  
Reversible Aggregation ◽  
Inhibitory Compounds ◽  
Rapid Generation ◽  
Stimulation Of ◽  
Collagen Stimulation

SummaryIt is shown that the supernatant of unstirred whole blood at 37° C, stimulated by 1 μg/ml of collagen for 10 sec, produces a rapid generation of pro and antiaggregatory compounds with a final proaggregatory activity which can be detected for more than 60 min on a platelet rich plasma (PRP) by turbidometric aggregometry. A reversible aggregation wave that we have called BASIC wave (for Blood Aggregation Stimulatory and Inhibitory Compounds) is recorded. The collagen stimulation of unstirred PRP produces a similar but smaller BASIC wave. BASIC’s intensity increases if erythrocytes are added to PRP but decreases if white blood cells are added instead. Aspirin abolishes “ex vivo” the ability of whole blood and PRP to generate BASIC waves and dipyridamole “in vitro” significantly reduces BASIC’s intensity in whole blood in every tested sample, but shows little effect in PRP.

Dipyridamole Inhibits Platelet Aggregation in Whole Blood

1983 ◽  
Vol 50 (04) ◽  
pp. 852-856 ◽  
Author(s):  
P Gresele ◽  
C Zoja ◽  
H Deckmyn ◽  
J Arnout ◽  
J Vermylen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Significant Negative Correlation ◽  
Significant Inhibition ◽  
Oral Drug ◽  
Human Blood Samples ◽  
Induced Aggregation

SummaryDipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine- 5’-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p <0.001). A statistically significant inhibition of both collagen (p <0.0025) and ADP-induced (p <0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37° C with dipyridamole (3.9 μM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood.Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.

scholarly journals In Vitro Incorporation of GPI-Anchored Proteins Into Human Erythrocytes and Their Fate in the Membrane

Blood ◽  
1998 ◽  
Vol 91 (5) ◽  
pp. 1784-1792 ◽  
Author(s):  
Gianluca Civenni ◽  
Samuel T. Test ◽  
Urs Brodbeck ◽  
Peter Bütikofer
Keyword(s):  
Membrane Vesicle ◽  
Human Erythrocytes ◽  
Membrane Extraction ◽  
Membrane Microdomains ◽  
Membrane Insertion ◽  
Vesicle Formation ◽  
Calcium Loading ◽  
Lipid Moiety ◽  
Triton X

Abstract In many different cells, glycosylphosphatidylinositol (GPI)-anchored molecules are clustered in membrane microdomains that resist extraction by detergents at 4°C. In this report, we identified the presence of such domains in human erythrocytes and examined the ability of exogenously-added GPI-anchored molecules to colocalize with the endogenous GPI-anchored proteins in these detergent-insoluble complexes. We found that the addition to human erythrocytes of three purified GPI-anchored proteins having different GPI lipid moieties resulted in their efficient and correct incorporation into the membrane. The extent of membrane insertion was dependent on the intactness of the GPI lipid moiety. However, unlike the endogenous GPI-anchored proteins, the in vitro incorporated GPI molecules were not resistant to membrane extraction by Triton X-100 at 4°C. In addition, in contrast to the endogenous GPI-anchored proteins, they were not preferentially released from erythrocytes during vesiculation induced by calcium loading of the cells. These results suggest that in vitro incorporated GPI-linked molecules are excluded from pre-existing GPI-enriched membrane areas in human erythrocytes and that these microdomains may represent the sites of membrane vesicle formation.

scholarly journals Membrane Vesicle Release in Bacteria, Eukaryotes, and Archaea: a Conserved yet Underappreciated Aspect of Microbial Life

2012 ◽  
Vol 80 (6) ◽  
pp. 1948-1957 ◽  
Author(s):  
Brooke L. Deatherage ◽  
Brad T. Cookson
Keyword(s):  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Host Immune System ◽  
Vesicle Release ◽  
Communication Signals ◽  
Microbial Life ◽  
Functional Features

ABSTRACTInteraction of microbes with their environment depends on features of the dynamic microbial surface throughout cell growth and division. Surface modifications, whether used to acquire nutrients, defend against other microbes, or resist the pressures of a host immune system, facilitate adaptation to unique surroundings. The release of bioactive membrane vesicles (MVs) from the cell surface is conserved across microbial life, in bacteria, archaea, fungi, and parasites. MV production occurs not onlyin vitrobut alsoin vivoduring infection, underscoring the influence of these surface organelles in microbial physiology and pathogenesis through delivery of enzymes, toxins, communication signals, and antigens recognized by the innate and adaptive immune systems. Derived from a variety of organisms that span kingdoms of life and called by several names (membrane vesicles, outer membrane vesicles [OMVs], exosomes, shedding microvesicles, etc.), the conserved functions and mechanistic strategies of MV release are similar, including the use of ESCRT proteins and ESCRT protein homologues to facilitate these processes in archaea and eukaryotic microbes. Although forms of MV release by different organisms share similar visual, mechanistic, and functional features, there has been little comparison across microbial life. This underappreciated conservation of vesicle release, and the resulting functional impact throughout the tree of life, explored in this review, stresses the importance of vesicle-mediated processes throughout biology.

scholarly journals Ex VivoMaturation Assay for Testing Antimalarial Sensitivity of Rodent Malaria Parasites

2016 ◽  
Vol 60 (11) ◽  
pp. 6859-6866 ◽  
Author(s):  
Zi Wei Chang ◽  
Benoit Malleret ◽  
Bruce Russell ◽  
Laurent Rénia ◽  
Carla Claser
Keyword(s):  
Ex Vivo ◽  
Single Step ◽  
Parasite Development ◽  
Ring Stage ◽  
Malaria Parasites ◽  
Rodent Malaria ◽  
Content Type ◽  
Parasite Biology

ABSTRACTEx vivoassay systems provide a powerful approach to studying human malaria parasite biology and to testing antimalarials. For rodent malaria parasites, short-termin vitroculture andex vivoantimalarial susceptibility assays are relatively cumbersome, relying onin vivopassage for synchronization, since ring-stage parasites are an essential starting material. Here, we describe a new approach based on the enrichment of ring-stagePlasmodium berghei,P. yoelii, andP. vinckei vinckeiusing a single-step Percoll gradient. Importantly, we demonstrate that the enriched ring-stage parasites develop synchronously regardless of the parasite strain or species used. Using a flow cytometry assay with Hoechst and ethidium or MitoTracker dye, we show that parasite development is easily and rapidly monitored. Finally, we demonstrate that this approach can be used to screen antimalarial drugs.

Evidence of the role of hemolysis in experimental cerebral vasospasm

1990 ◽  
Vol 72 (5) ◽  
pp. 775-781 ◽  
Author(s):  
John W. Peterson ◽  
Lawrence Roussos ◽  
Byung-Duk Kwun ◽  
John D. Hackett ◽  
Christopher J. Owen ◽  
...  
Keyword(s):  
Cerebral Vasospasm ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Canine Model ◽  
Initial Reaction ◽  
Basal Cistern ◽  
Content Type ◽  
Vascular Reaction ◽  
Erythrocyte Lysis

✓ The short-term (≤ 72-hour) reaction to subarachnoid injections of various blood components was determined in a canine model of cerebral vasospasm. Platelet-rich plasma (PRP) formed durable clots in the basal cistern surrounding the basilar artery and provoked no vascular reaction in 72 hours or more. Freshly isolated autologous erythrocytes resuspended in PRP likewise provoked no vasoconstriction in 72 hours, although a second injection of fresh erythrocytes in PRP induced significant reaction, as in the conventional “double subarachnoid hemorrhage (SAH)” canine model. Hemolysate of fresh erythrocytes led to a severe immediate vascular reaction after introduction into the basal cistern using PRP as the carrier/clotting medium, as did the injection of intact erythrocytes incubated ex vivo for 72 hours. Resolution of the initial reaction was rapid for hemolysate, but slow and (depending on hematocrit) incomplete for intact “aged” erythrocytes. In vitro measurements of erythrocyte lysis in these media and histological examination indicate that the production of erythrocyte lysate was responsible for the vascular reaction observed, suggesting that the rate of lysis of erythrocytes in the subarachnoid clot is a major factor in the genesis of vasospasm after SAH.

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