Vegetative Endocarditis Research Articles

Platelet-streptococcal interactions in endocarditis.

Infective endocarditis is characterized by the formation of septic masses of platelets on the surfaces of heart valves and is most commonly caused by viridans streptococci. Streptococcal virulence in endocarditis involves factors that promote infectivity and pathogenicity. Adhesins and exopolysaccharide (glycocalyx) contribute to infectivity. Although many factors may contribute to pathogenicity, the platelet aggregation-associated protein (PAAP) of Streptococcus sanguis contributes directly to the development of experimental endocarditis. PAAP is synthesized as a rhamnose-rich glycoprotein of 115 kDa and contains a collagen-like platelet-interactive domain, pro-gly-glu-gln-gly-pro-lys. Expressed on the cell wall of platelet aggregation-inducing strains (Agg+) of S. sanguis, PAAP apparently interacts with a signal-transducing receptor complex on platelets, which includes a novel 175-kDa alpha 2-integrin-associated protein and a 65-kDa collagen-binding component. From available data, the role of PAAP in the pathogenesis of experimental endocarditis may be explained by a proposed mechanistic model. On injured heart valves, PAAP first enhances platelet accumulation into a fibrin-enmeshed thrombus (vegetation), within which S. sanguis colonizes. Colonizing bacteria must resist platelet microbicidal protein (PMPR). The aggregation of platelets on the heart valve may be potentiated by an ectoATPase expressed on the surface of the S. sanguis and platelet alpha-adrenoreceptors that respond to endogenous catecholamines. The expression of PAAP may be modified during infection. Collagen is exposed on damaged heart valves; fever (heat shock) occurs during endocarditis. In response to heat shock or collagen in vitro, PAAP expression is altered. After colonization, streptococcal exotoxin(s) may cause fever. Proteases and other enzymes from streptococci and host sources may directly destroy the heart valves. When PAAP is unexpressed or neutralized with specific antibodies, experimental endocarditis runs a milder course and vegetations are smaller. The data suggest strongly, therefore, that the role of PAAP may overlap the colonization function of putative adhesins such as FimA or SsaB. Finally, PAAP also contributes to the development of the characteristic septic mural thrombus (vegetation) of infective endocarditis and the signs of valvular pathology.

Vegetative endocarditis in a Waldrapp ibis

A case of bacterial vegetative endocarditis in a Waldrapp ibis is described. Lesions were present on both atrio-ventricular valves and there were thromboembolic lesions in brain, lung and myocardium. A streptococcal origin is suspected.

A prospective study to compare transthoracic with transesophageal echocardiography in the detection of vegetation in infective endocarditis: KL Chan MD for the CATIE Investigators, University of Ottawa, Ottawa, Canada

A prospective study to compare transthoracic with transesophageal echocardiography in the detection of vegetation in infective endocarditis: KL Chan MD for the CATIE Investigators, University of Ottawa, Ottawa, Canada

Clinical outcome and echocardiographic findings of native and prosthetic valve endocarditis in the 1990's.

Prosthetic valve endocarditis is considered to be associated with a more severe prognosis than native valve endocarditis. Among other factors, inappropriate visualization of vegetations in prosthetic valve endocarditis by transthoracic echocardiography is responsible for this observation. Since the introduction of transoesophageal echocardiography into clinical practice the diagnostic sensitivity and specificity of the detection of vegetations located on prosthetic valves have been enhanced. Therefore we aimed to determine and compare the prognosis of prosthetic valve endocarditis and native valve endocarditis in the era of this improved diagnostic approach. One hundred and six episodes of infective endocarditis in 104 patients were seen at our institution between 1989 and 1993. Eighty patients (77%) had native valve endocarditis and 24 (23%) had late prosthetic valve endocarditis. In the latter group two patients had recurrent infective endocarditis. Patients with prosthetic valve endocarditis were older (mean age 64 vs 54 years in native valve endocarditis; P < 0.001) and the majority was female (62% vs 38% in native valve endocarditis; P < 0.05). In prosthetic valve endocarditis, infection of a valve in the mitral position predominated (65% vs 30% in native valve endocarditis; P < 0.01), whereas in native valve endocarditis more than half the cases had isolated aortic valve endocarditis (51% vs 27% in prosthetic valve endocarditis; P < 0.01). In prosthetic valve endocarditis more cases were caused by Staphylococcus aureus (31% vs 14% in native valve endocarditis; P = 0.08), whereas in native valve endocarditis the most frequent organisms were streptococci (29% vs 19% in prosthetic valve endocarditis; P = 0.12). Differences in the clinical features of native valve endocarditis and prosthetic valve endocarditis could not be found except for a higher rate of embolism in native valve endocarditis (40% vs 19% in prosthetic valve endocarditis; P < 0.05). Vegetations could be detected by transthoracic echocardiography more frequently in native valve endocarditis (71% vs 15% in prosthetic valve endocarditis; P < 0.0001). Transoesophageal echocardiography visualized vegetations in 95% of the episodes of native valve endocarditis and in 80% of the episodes of prosthetic valve endocarditis (P = 0.09). Thus, the diagnostic gain by transoesophageal echocardiography was greatest in prosthetic valve endocarditis. Patients with native valve endocarditis had significantly larger vegetations than patients with prosthetic valve endocarditis (P < 0.05 for length, P < 0.001 for width). The median time to diagnosis was similar in native valve endocarditis and prosthetic valve endocarditis (31 vs 28 days). Surgery was performed in 74% of patients with native valve endocarditis and in 58% of those with prosthetic valve endocarditis; the median time delay between the diagnosis of infective endocarditis and surgery tended to be shorter in prosthetic valve endocarditis than in native valve endocarditis (45 vs 60 days). The in-hospital mortality and the mortality during a follow-up of 22 +/- 10 months did not significantly differ between native valve endocarditis and prosthetic valve endocarditis (21% vs 17%; 28% vs 25%). In summary in the era of transoesophageal echocardiography, late prosthetic valve endocarditis does not seem to carry a worse prognosis than native valve endocarditis. This can be attributed in part to the improved diagnostic accuracy achieved by transoesophageal echocardiography leading to comparable diagnostic latency periods in both patient groups. Finally, better characterization of vegetations on prosthetic valves by transoesophageal echocardiography allows early lifesaving surgery in patients with prosthetic valve endocarditis.

Streptogramins. A unique class of antibiotics.

Streptogramin antibiotics represent a unique class of antibacterials in that each member of the class consists of at least 2 structurally unrelated molecules: group A streptogramins (macrolactones) and group B streptogramins (cyclic hexadepsipeptides). Both group A and group B streptogramins inhibit protein synthesis at the ribosomal level, and they act synergistically against many isolates, their combination generating bactericidal activities and reducing the possibility of emergence of resistant strains. The mechanisms of acquired resistance to group B streptogramins are similar to those induced by erythromycin, but group A streptogramins remain unaffected by target modifications and active efflux. The pharmacokinetic parameters of group A and group B streptogramins in blood are quite similar. In addition, both the A and B groups penetrate and accumulate in macrophages and in the bacterial vegetations of experimental endocarditis. There are important structural and biological differences between the streptogramins and the macrolides. The main differentiating features are the rapid anti-bacterial killing of streptogramins and the rarity of cross-resistance between the 2 groups of antibiotics.

Bacteriologic culture and histologic examination of samples collected from recumbent cattle at slaughter

Objective— To evaluate the potential food safety risks constituted by recumbent cattle that are slaughtered for edible beef. Design— Prospective case series. Animals— Thirty cattle in recumbency that passed a routine antemortem inspection at a US federally inspected abattoir. Procedure— Aerobic, bacteriologic culture of blood samples taken immediately prior to slaughter and of spleens taken during viscera inspection. Gross lesions were recorded, and samples of liver, lung, kidney, and heart were collected from each animal for routine light microscopic examination. Results— Bacteremia caused by Salmonella dublin was documented in 1 cow that had arthritis. Two other cows were condemned after postmortem inspection: 1 because of pneumonia and pleuritis and the other because of vegetative endocarditis. Three carcasses were retained and later condemned because of antibiotic residues in tissues; 1 of these cows had mastitis, 1 had liver abscesses, and 1 was the cow with vegetative endocarditis. Sarcocystosis was found in 27 of 30 hearts, but other clinically important histologic lesions were observed only in liver samples. In 11 of the 30 cows, multifocal, microscopic foci of hepatitis were observed, suggesting that terminal embolic bacterial showering of the liver had occurred in these animals. Liver samples were not submitted for bacteriologic culture. Clinical Implications— Most recumbent cows slaughtered for edible beef are not contaminated by bacteria; however, the viscera from these animals may present a food safety danger. Efforts should be made to develop rapid tests to identify bacteremic animals at slaughter and to more fully evaluate terminal showering of viscera by bacteria in cattle at slaughter.

A CASE REPORT OF LUNG PYOSIS AFTER NATIVE TRICUSPIDAL VALVE REPLACEMENT DUE TO FUNGAL ENDOCARDITIS

It has been believed that fungal endocarditis is rare in this country, but the number of cases of the disease is increasing. Under a recent background where the operations for cachexic decreased resistance (immune) and these more infectious and severe valve diseases have been increasingly done. However, fungal endocarditis on the tricuspidal valve area in still rare. So far, we have inspected no more than 7 cases of fungal tricuspidal valve endocarditis including this case in Japan. A 66-year-old male with native tricuspidal valve endocarditis associated with acute suppurative cholangitis and pyogenic liver abscess due to Candida glabrata underwent tricuspidal valve replacement with Carpentier-Edwards pericardial bioprosthesis. On the 5th postoperative day bilateral lung pyosis caused by fungal infection developed. Candida glabrata was detected in pus culture from thoracic drains. He died of multiple organ failure 11 days after the operation. The vegetation of fungal endocarditis tends to grow and develop emboli. In this case, it was clear that the reason of postoperative lung pyosis was preoperative lung embolism due to lated surgical operation. We conclude that the principal solution for remedy of fungal endocarditis lies on early diagnosis, early surgical treatment and thorough postoperative chemotherapy.

Therapeutic Advantage of Recombinant Human Plasminogen Activator in Endocarditis: Evidence from Experiments in Rabbits

In infective endocarditis vegetations are stabilized by fibrin. To learn if fibrin digestion would be therapeutic, experimental endocarditis was induced in rabbits by inoculation with a platelet-aggregating strain (Agg+) of Streptococcus sanguis and treated with recombinant tissue plasminogen activator (rt-PA), rt-PA with penicillin, or penicillin alone. Control rabbits were inoculated with saline. All treatments of Agg+ endocarditis reduced the mass of valvular vegetations and clinical signs of endocarditis, including the frequency of left axis deviation and heart ischemia. rt-PA with penicillin was more effective than penicillin or rt-PA alone, reducing the mass of vegetations and clinical signs to that of saline controls. Within 50 min, rt-PA cleared 5-fold more 111Indium-labelled platelets from the heart than untreated rabbits and 1.4-fold more after 3 days. Combined with penicillin, thrombolytic therapy for human endocarditis should be reconsidered.

Characterization of aneurysmal transformation in perimembranous ventricular septal defects: an adhered anterior leaflet of tricuspid valve predisposes to the development of left ventricular-to-right atrial shunt

Background: The most common type of left ventricular-to-right atrial shunts are those associated with perimembranous ventricular septal defect when the defects diminish in size via aneurysmal transformation. This study is to characterize the echocardiographic features and to determine the possible mechanisms. Methods and results: From January 1986 to December 1992, of 930 consecutive patients with isolated perimembranous ventricular septal defect, 692 showed evidence of aneurysmal transformation. Excluding those with subaortic ridge, echocardiographic analysis was based on 664 of them. Of these, 94 patients had left ventricular-to-right atrial shunts, 115 had their defects spontaneously closed and in 455 only interventricular shunt persisted. Four types of echocardiographic findings featured in the aneurysmal transformation process: type A, both the anterior and septal leaflets of tricuspid valve contributed to the process; type B was similar to type A, but the arc-like structure from the anterior leaflet is much less evident; in type C, only the septal leaflet, and in type D, other adjacent tissues, contribute to the aneurysmal transformation. Type A morphology was closely associated with the development of left ventricular-to-right atrial shunt while types C and D were most commonly seen in those spontaneously closed defects and those with only interventricular shunt. The vegetations of infective endocarditis were located at the atrial side of the tricuspid valve in patients with left ventricular-to-right atrial shunts, while they were in the right ventricle in those with only interventricular shunt. Conclusion: The morphology of the aneurysmal transformation in perimembranous ventricular septal defect can be characterized by echocardiograms. Although the septal leaflet of the tricuspid valve is usually involved in this process, it is the incorporation of the anterior leaflet that predisposes to the development of left ventricular-to-right atrial shunts.

Stimulation of monocyte tissue factor expression in an in vitro model of bacterial endocarditis.

The coagulation system plays a major role in the formation of the infected endocardial vegetation in bacterial endocarditis. Since monocytes can express tissue factor (TF) on their surfaces, they are thought to be responsible for the extrinsic activation of the coagulation cascade during this disease. The present study used an in vitro model in which fibrin plates, isolated adherent monocytes, and Streptococcus sanguis were used as an analog for endocardial vegetations. Adherence to fibrin by itself was found to stimulate TF expression on the monocytes, but stimulation by S. sanguis significantly increased TF expression, which was found to be maximal at a bacterium-to-monocyte ratio of 9 or more.

In vivo activities and penetration of the two components of the streptogramin RP 59500 in cardiac vegetations of experimental endocarditis

We evaluated the in vivo activity and the diffusion of radiolabelled RP 57669 (RPI) and RP 54476 (RPII), the two components of the injectable streptogramin RP 59500, alone or in combination, in aortic vegetations from experimental endocarditis in rabbits. RPI and RPII demonstrated in vitro bacteriostatic and bactericidal synergy against a clinical strain of Staphylococcus aureus resistant to methicillin and susceptible to erythromycin. In experimental staphylococcal endocarditis, RP 59500 was as effective as vancomycin and significantly more effective than RPI (P < 0.01) and RPII (P < 0.05). Autoradiography studies showed different patterns of distribution into cardiac vegetations infected with Streptococcus sanguis for [14C]RPI and [14C]RPII. [14C]RPI was homogeneously distributed throughout the vegetations whereas [14C]RPII showed a decreasing gradient of concentration between the periphery and the core of the vegetation, with an approximately 2:1 ratio. [14C]RPI diffused approximately 2 to 4 times more than [14C]RPII into the core of the vegetations. Since the injected ratio of RPI and RPII is 30:70 in RP 59500, the actual RPI:RPII ratio in the core of the vegetation may range from 0.8 to 1.7, a ratio which remains compatible with the in vivo synergism demonstrated between the two components.

Evaluation of new clinical criteria for the diagnosis of infective endocarditis

purpose: The clinical diagnosis of infective endocarditis (IE) can be difficult. A new diagnostic schema for IE (the Duke criteria) has been proposed, utilizing clinical, microbiologic, and echocardiographic data. We evaluated the Duke criteria in a cohort of prospectively enrolled patients suspected of having IE and compared the diagnostic efficiency of these criteria with the previously published criteria of von Reyn. patients: Sixty-three febrile patients with suspected IE at a nonreferral, municipal hospital were evaluated. All patients had the following parameters defined: the presence and nature of underlying heart disease; recent abuse of intravenous drugs; peripheral stigmata of IE; blood culture results; findings on two-dimensional transthoracic and transesophageal echocardiography (TTE, TEE); and the results of open heart surgery. results: Twelve of 63 patients underwent open heart surgery, at which time IE was pathologically confirmed in 10 patients and excluded in 2 patients. All 10 patients with pathologically confirmed IE were classified as “clinically definite” by Duke criteria, whereas 5 of 10 were rejected by von Reyn criteria (p <0.05). Among the remaining 51 patients suspected of IE and evaluated by both von Reyn and Duke clinical criteria, significantly more cases were classified as “definite” IE by Duke criteria than by von Reyn criteria (p < 10 −5). Similarly, significantly fewer cases were rejected as IE by the Duke criteria as compared with the von Reyn criteria (p < 10 −6). Duke criteria were also significantly better at diagnosing IE than von Reyn criteria in the following clinical settings: suspected right-sided IE (p < 0.01); suspected left-sided IE (p = 0.014); suspected culture-negative IE (p < 10 −2); and IE complicating Staphylococcus aureus or viridans streptococcal bacteremias (p < 10 −5; p < 0.05, respectively). Among 30 cases defined as clinically definite by the Duke criteria, the presence of blood culture positivity and echocardiographically defined vegetations was important in this classification of 77% and 57% of cases, respectively. Among the 17 patients in the clinically definite category with vegetative endocarditis observed by echocardiography, 7 (41%) had vegetations defined only by TEE. conclusion: The Duke criteria are superior to the von Reyn criteria for the clinical diagnosis of IE, predominately reflecting use of two-dimensional echocardiographic demonstration of valvular vegetations in the Duke schema.

A case with isolated pulmonary valve vegetation in infectious endocarditis

A case with isolated pulmonary valve vegetation in infectious endocarditis

Clinical and echocardiographic findings in 10 dogs with vegetative bacterial endocarditis

ABSTRACTTen cases of bacterial endocarditis in the dog were studied by retrospective analysis of case records. Diagnosis of bacterial endocarditis was based on either strict clinical criteria or post mortem examination. A wide spectrum of presenting signs was seen including pyrexia, lameness, epistaxis, haemoptysis and dyspnoea. Haematological and biochemical abnormalities were non‐specific and were attributed to the effects of septicaemia, embolism or chronic inflammation. Haemostatic abnormalities and, or, severe dysrhythmias appeared to be associated with a significantly poorer prognosis. Blood cultures were positive in four cases of eight that were cultured. Lesions compatible with bacterial endocarditis were detected in all eight cases that underwent echocardiographic examination. Right‐sided vegetations present in two dogs were not detected by echocardiography. Two‐dimensional echocardiography is a useful technique for the detection of vegetative endocarditis in the dog and allows rapid therapeutic intervention while blood culture results are pending.

Cerebral healing after craniotomy to evacuate a coenurus cerebralis cyst

An 11-month-old ewe developed neurological signs caused by a space-occupying lesion in the left cerebral hemisphere. Successful surgical evacuation of a Coenurus cerebralis cyst was carried out, the neurological signs regressed and the ewe produced twins in the following breeding season. Sixteen months after the surgical treatment the ewe was found dead and necropsy revealed a vegetative endocarditis. In the brain, at the site of cyst evacuation, there was a collapsed subcortical cavity lined by siderotic fibrovascular tissue and surrounded by a modest glial reaction. These observations confirm that the clinical signs of cerebral coenuriasis are related to the space-occupying effect of the parasitic cyst and indicate that partial replacement by gliomesodermal tissue plays a part in healing of the collapsed cyst.

Selective endovascular techniques in the treatment of cerebral mycotic aneurysms

The aim of this study was to evaluate the role of endovascular treatment for intracranial mycotic aneurysms. The clinical and angiographic features of three patients with endocarditic vegetation (two with Streptococcus viridans and one with Staphylococcus) were reviewed retrospectively. Patients were selected for this treatment according to the clinical setting and aneurysm location. In two cases, selective catheterization of a distal middle cerebral and posterior cerebral artery branch with a microcatheter followed by superselective amobarbital testing of the parent vessel was preliminary to the occlusion of that vessel with autologous clot or glue. The third patient was treated by selective occlusion of the aneurysm by intra-aneurysmal placement of platinum minicoils. Two patients presented with intracranial hemorrhage and in one the lesion was found on computerized tomography. All three aneurysms had been excluded from the circulation at the 6-month follow-up review. The only complication from the procedure, despite the septic nature and distal localization, was balloon deflation in one patient, who was successfully retreated with coils. Endovascular embolization is indicated in patients who are at risk of hemorrhage and cannot undergo the standard procedure. The superselective amobarbital test allows selection of patients who will tolerate distal vessel occlusion. This endovascular procedure represents a safe and effective treatment for these lesions.

BACTERIAL ENDOCARDITIS WITH THROMBUS FORMATION AND ABSCESSATION IN A HORSE

A 2.5 year old Appaloosa stallion with progressive weight loss and a heart murmur was diagnosed as having vegetative endocarditis of the right atrioventricular valves with a mass in the right atrium. The ultrasonographic appearance of the lesion was characterized by extreme reverberation. On postmortem examination, a 9 cm diameter thrombus was found within the right atrium and auricle, occupying approximately 80% of the chamber volume. Additionally, a lenticular abscess extended throughout the parietal cusp of the right atrioventricular valve. Histologic examination revealed that the lesions were septic with numerous gram positive cocci in short chains, suggestive of Streptococcus equi, and gram negative rods.

Bacteremia and Vegetative Endocarditis Associated with a Heart Murmur in a Blue-and-Gold Macaw

A 6-year-old male blue-and-gold macaw (Ara ararauna) was presented with severe weakness, anorexia, and weight loss of 2 weeks duration. Cardiac auscultation revealed a soft systolic murmur. Blood cultures collected both antemortem and postmortem yielded pure isolates of Enterobacter cloacae. At necropsy, vegetative endocarditis was found involving the left atrioventricular valve. Microscopically, the lesion on the valve was characterized by a mixture of necrotic material, colonies of gram-negative bacteria, fibrosis, and inflammatory infiltrate consisting primarily of heterophils.

Evaluation of strategies for central venous catheter replacement

To assess the consequences of leaving a bacterially colonized central venous catheter in place and to compare the effects of three catheter replacement strategies for catheter repair control in an animal model. Prospective study. Laboratory and animal facility of a large university. Eighteen healthy, female, adult sheep. Radiopaque-siliconized elastomer central venous catheters were inserted into the jugular veins and colonized with either Escherichia coli or Staphylococcus epidermidis. After 7 days of infection, the catheters were either: a) exchanged using a guidewire; b) removed and replaced with a new catheter in a new jugular vein site after a 48-hr interval; or c) exchanged using a guidewire and antibiotics (tobramycin, cephaloridine) injected into the catheter. Animals were euthanized 7 days after insertion of the new catheter. Quantitative microbiology was performed on blood samples collected daily from the catheters and a peripheral vein, as well as from catheters and tissue recovered from the sheep at the time of autopsy. When catheters were changed using a guidewire, they became colonized by bacteria within 48 hrs, and the sheep had embolic pneumonia and vegetative endocarditis at autopsy. Similar consequences were observed when antibiotics were administered into the catheter lumen. If colonized catheters were removed and a new catheter was inserted after a 48-hr interval, recolonization, pneumonia, and endocarditis were not observed. Replacement of a biofilm-colonized central venous catheter over a guidewire is associated with rapid colonization of the replacement catheter and production of detached, slime-enclosed, antibiotic-resistant aggregates that colonize other catheters or initiate endocarditis or pneumonia by dissemination in the bloodstream.

Identification of factors affecting in vivo aminoglycoside activity in an experimental model of gram-negative endocarditis.

Aminoglycoside bactericidal activity during the first 24 h of treatment probably is a determining parameter in the prognosis of severe gram-negative infections in immunocompromised patients. To identify the predictive factors involved in the definition of the best therapeutic regimen for Enterobacter cloacae and Serratia marcescens infections, we studied different gentamicin, tobramycin, and amikacin regimens by using an experimental model of rabbit endocarditis. Two factors appear to play an important role in predicting in vivo efficacy: (i) the level of in vivo bactericidal activity, which can differ widely from one aminoglycoside to another for the same bacterial strain and from one strain to another of the same species, and (ii) the critical serum drug concentration (CSC, in milligrams per liter), defined as the lowest serum antibiotic concentration capable of producing a significant CFU reduction (P less than 0.05) in endocarditis vegetations 24 h after the beginning of a continuous infusion. Stepwise regression analysis showed that for gentamicin and S. marcescens, the area under the concentration-time curve above the CSC and then the time above the CSC are the determining parameters for efficacy (R = 0.69; F = 13.5; P = 0.001), whereas for amikacin and S. marcescens, the time above the CSC and then the area under the concentration-time curve above the CSC predict efficacy (R = 0.74; F = 24.0; P = 0.0001). The lowest CSC is that of amikacin (about 8 mg/liter); those of gentamicin and tobramycin are about 15 mg/liter. In severe S. marcescens infections, intermittent amikacin dosing offers excellent bactericidal activity within the first 24 h.