Acute infective endocarditis. Diagnostic and therapeutic approach

Left-sided infective endocarditis presenting with pulmonary involvement and liver abscess: A case report

Key Clinical Message

Infective endocarditis is an important differential diagnosis in patients with persistent fever and chills not responding to antibiotics and involvement of multiple organs. It can present without any specific signs such as valvular murmurs and no growth on blood cultures. Therefore, considering an echocardiography can be crucial and helpful in establishing the diagnosis.

Abstract

Infective endocarditis (IE), a rare disease with high mortality, arises from microbial infection affecting the heart valves and endocardium. It exhibits diverse symptoms and can involve various organs, including the brain, lungs, spleen, and liver. Diagnosis is often intricate due to its polymorphic nature, and negative blood cultures can add complexity to the diagnostic process. In this report, we present an unusual case of IE in a 53-year-old male farmer with multi-organ involvement, including liver abscesses and pulmonary infiltration with cavities. Echocardiography showed a nodular mass attached to his bicuspid aortic valve, thus, playing a crucial role in confirming the diagnosis. This atypical manifestation highlights the necessity for increased clinical vigilance and further research to improve diagnostic approaches for uncommon IE cases.

Left Atrial Myxoma Misdiagnosis as Infective Endocarditis: A Case Report

Introduction: Myxomas, as primary cardiac tumors, are rare neoplasms manifesting with constitutional, obstructive, and embolic symptoms. Systemic signs and symptoms make infective endocarditis one of the most common differential diagnoses. Nonspecific systemic signs and symptoms of myxomas can cause great challenges in management and treatment. Case Presentation: A 21-month-old boy was admitted to our center with a high-grade fever and gastrointestinal symptoms, but no significant respiratory complaints were noted. A history of lower limb pain and morning claudication was also present. The patient had leukocytosis with an elevated erythrocyte sedimentation rate (ESR) of two months' duration. Other acute phase reactants were detected despite previous antibiotic therapy; however, his blood culture result was negative. In echocardiography, multiple masses were seen in the left atrium near the mitral valve apparatus. The diagnosis of infective endocarditis was made, and intravenous antibiotics were prescribed for up to two weeks. He then underwent surgery because of poor response to medical treatment and renal complications. During surgery, a small mass was seen in the left atrium, and two other masses were within the mitral chordae. The histopathology report confirmed atrial myxoma. Shortly after surgical resection of the tumors, the patient's symptoms improved, and inflammatory indices returned to normal. Conclusions: Constitutional manifestations of myxoma render it reasonable to consider it as a differential diagnosis of infective endocarditis. Obtaining a complete clinical history and using imaging tools are necessary for the correct diagnosis and prevention of complications of inappropriate treatment.

Dermatologic Conundrum: A Cardiac Condition Masqueraded as a Dermatologic Distraction

A 38-year-old male presented to the emergency department (ED) complaining of extreme pain and a petechial rash on the left ankle for two weeks associated with generalized fatigue, intermittent fevers, and weight loss. He was discharged home from the ED on pain medications. He returned a few days later with a progressive rash that involved the entire left lower extremity to the level of the knee. He was diagnosed with herpes zoster (shingles) and was prescribed acyclovir and steroids. After several days, the patient presented for the third time to the ED. He developed a right lower extremity discomfort this time. The pain in bilateral lower extremities had become unbearable. His cardiac examination revealed a systolic murmur at the apex and a faint diastolic murmur at the left sternal border. Ultimately, he had an echocardiogram that demonstrated both a bicuspid aortic valve and large vegetation on the anterior leaflet of the mitral valve, and his blood culture grew Streptococcus mitis and Streptococcus oralis. The patient was subsequently diagnosed with subacute bacterial endocarditis thought to be sourced from his poor dentition. The diagnosis of infective endocarditis is often delayed due to its nonspecific clinical presentations. Our case displays an unusual skin manifestation of IE that may be present in the absence of other signs and symptoms of the disease.

Intracranial complications of acute bacterial endocarditis

Background:

Infectious endocarditis (IE) clinically manifests as either subacute bacterial endocarditis (SBE) or acute bacterial endocarditis (ABE). Neurologic manifestations are markedly different for these two entities. ABE is caused by invasive, highly virulent pathogens (e.g., Staphylococcus aureus), whereas SBE is attributed to relatively avirulent, non-invasive organisms (e.g., viridans streptococci).

Methods:

Here, we reviewed the clinical and radiographic presentations of a patient with cranial complications attributed to ABE. Such patients typically develop central nervous system (CNS) septic emboli resulting in stroke (with/without intracranial hemorrhage (ICH)) and/or mycotic aneurysms resulting in ICH bleeds.

Results:

With ABE, cerebrospinal fluid (CSF) seeding may result in acute bacterial meningitis (ABM), documented by positive Gram stain and/or culture for S. aureus, decreased glucose, highly elevated lactose acid levels, or ICH. Alternatively, in SBE, the CSF profile reflects an aseptic (viral) meningitis (i.e., Gram stain and culture negative, a normal glucose, and lymphocytic pleocytosis), while septic microemboli to the vasa vasorum contribute to an inflammatory reaction in the adventitia/muscle layer that weakens the vessel wall and results in mycotic aneurysms that may leak but often do not rupture causing ICH.

Conclusion:

Here, we reviewed the literature for intracranial pathology accompanying ABE versus SBE. ABE typically results in acute ischemia, septic emboli, stroke/hemorrhagic infarcts, or ICH. SBE more classically produces septic microemboli and mycotic aneurysms that may leak, but rarely producing ICH. We also presented a patient with ABE attributed to S. aureus whose septic emboli/stroke was accompanied by a mycotic aneurysm; the ruptured resulting in a large right occipital ICH.

Biodegradable nitric oxide precursor-loaded micro- and nanoparticles for the treatment of Staphylococcus aureus biofilms

Bacteria in biofilms are more difficult to eradicate than planktonic bacteria and result in treatment challenges for many chronic infectious diseases. Nitric oxide (NO) is an endogenous molecule that offers potential as an alternative to conventional antibiotics; however its sustained topical delivery to biofilms is not readily achieved. With this in mind, we report the development of biodegradable poly(lactide-co-glycolide) (PLGA) based microparticles (MP) and nanoparticles (NP) for encapsulation of the NO precursor isosorbide mononitrate (ISMN) and the controlled delivery to Staphylococcus aureus (S. aureus) biofilms. Firstly, water-in-oil-in-water (w/o/w) emulsification/solvent evaporation methods for PLGA NP and MP syntheses were experimentally optimised with respect to particle size and ISMN loading/encapsulation efficiency. The influence of various experiment parameters, such as the volume of inner aqueous phase, concentration of surfactants, mixing time on the particle size, drug loading and encapsulation efficiency were investigated systematically. Both PLGA MP and NP formulations enabled sustained ISMN release in physiological media over 3 to 5 days. PLGA MP with diameters of ∼3 μm and ISMN loading of 2.2% (w/w) were identified as the optimum delivery system and demonstrated significant antibacterial activity in S. aureus biofilms. This behaviour is considered to be due to targeted biofilm delivery through a combination of effective penetration and sustained release of ISMN.

Haemophilus parainfluenzae aortic prosthetic valve endocarditis (PVE) successfully treated with oral levofloxacin

Antibiotic treatment of native valve infective endocarditis (IE) traditionally consists of 4-6 weeks of intravenous (IV) antibiotic therapy. Oral (PO) antibiotic therapy is being used more frequently, for part or all of treatment for IE but experience in treating IE with PO antibiotics is limited. Preferable agents for oral therapy of IE are antibiotics with a high degree of activity against the IE pathogen and that have high bioavailability (>90%) so that achievable serum and tissue levels are the same as with equivalent IV antibiotics. Oral antibiotic therapy of IE has several advantages over IV therapy given the long duration of treatment, i.e., 4-6 weeks for IE. Firstly, outpatient oral therapy for IE is easily administered over 4-6 weeks and decreases hospital length of stay (LOS). Secondly, oral antibiotics (administered at the same dose, frequency and duration) costs much less than their IV counterparts. Thirdly, with PO therapy for IE there are no central venous catheter (CVC) associated complications, e.g., phlebitis, bacteremia, fungemia. Compared to native valve IE, prosthetic valve endocarditis (PVE), depending on the IE pathogen, requires prolonged therapy and usually valve replacement. Haemophilus sp. IE is relatively virulent and often complicated by heart failure and/or embolic phenomena. We describe the first reported case of Haemophilus parainfluenzae aortic PVE successfully treated with oral levofloxacin without aortic valve replacement.

Liposome-encapsulated ISMN: a novel nitric oxide-based therapeutic agent against Staphylococcus aureus biofilms

Background

Staphylococcus aureus in its biofilm form has been associated with recalcitrant chronic rhinosinusitis with significant resistance to conventional therapies. This study aims to determine if liposomal-encapsulation of a precursor of the naturally occurring antimicrobial nitric oxide (NO) enhances its desired anti-biofilm effects against S. aureus, in the hope that improving its efficacy can provide an effective topical agent for future clinical use.

Methodology

S. aureus ATCC 25923 biofilms were grown in-vitro using the Minimum Biofilm Eradication Concentration (MBEC) device and exposed to 3 and 60 mg/mL of the NO donor isosorbide mononitrate (ISMN) encapsulated into different anionic liposomal formulations based on particle size (unilamellar ULV, multilamellar MLV) and lipid content (5 and 25 mM) at 24 h and 5 min exposure times. Biofilms were viewed using Live-Dead Baclight stain and confocal scanning laser microscopy and quantified using the software COMSTAT2.

Results

At 3 and 60 mg/mL, ISMN-ULV liposomes had comparable and significant anti-biofilm effects compared to untreated control at 24 h exposure (p = 0.012 and 0.02 respectively). ULV blanks also had significant anti-biofilm effects at both 24 h and 5 min exposure (p = 0.02 and 0.047 respectively). At 5 min exposure, 60 mg/mL ISMN-MLV liposomes appeared to have greater anti-biofilm effects compared to pure ISMN or ULV particles. Increasing liposomal lipid content improved the anti-biofilm efficacy of both MLV and ULVs at 5 min exposure.

Conclusion

Liposome-encapsulated “nitric oxide” is highly effective in eradicating S. aureus biofilms in-vitro, giving great promise for use in the clinical setting to treat this burdensome infection. Further studies however are needed to assess its safety and efficacy in-vivo before clinical translation is attempted.

Nosocomial methicillin-sensitive Staphylococcal aureus (MSSA) native mitral valve acute bacterial endocarditis (ABE) due to radiofrequency catheter ablation (RCA) procedure

Nosocomial endocarditis (NE) has been recognized with increasing frequency. Most cases of NE attributable to virulent pathogens (eg, Staphylococcus aureus) present as acute bacterial endocarditis (ABE). The increase in NE is related to the widespread use of cardio-invasive procedures involving cardiac catheterization or temporary or semipermanent central venous catheters. We present a 58-year-old man who developed nosocomial methicillin-sensitive S. aureus native mitral valve ABE a week after a radiofrequency catheter ablation (RCA) procedure. Cardiac valvular vegetations attributable to S. aureus ABE may be visualized by cardiac echocardiography as early as a week after the onset of valvular infection, as was the case here. Clinicians should be alert to the possibility of NE in patients who develop fevers and high-grade/continuous (MSSA / MRSA) bacteremias after cardiac catheterization-related interventions, eg, RCA procedures.

Subacute bacterial endocarditis: making the diagnosis

The presentation of endocarditis varies from patient to patient, making it a difficult infection to diagnose correctly. While some patients will develop symptoms acutely over days, it may take weeks or months for symptoms to develop as in the case of subacute bacterial endocarditis.

Vancomycin revisited: a reappraisal of clinical use

Vancomycin has been used for decades to treat serious systemic gram positive infections. Extensive use over time has demonstrated vancomycin is not nephrotoxic even when used in high dosage, i.e., twice the usual dose. Since vancomycin is not nephrotoxic, there is no rationale for dosing vancomycin based on serum vancomycin levels. Since vancomycin is eliminated by GFR, vancomycin dosing should be based on creatinine clearance. Vancomycin obeys "concentration dependent" kinetics and higher than usual doses may be useful in some infections (eg, osteomyelitis). Widespread vancomycin use has resulted in increased VRE prevalence worldwide. Among staphylococci, vancomycin induced cell wall thickening results in "permeability mediated" resistance to vancomycin, as well as other anti-staphylococcal antibiotics. "Permeability mediated" resistance accounts for the common clinical observation that MRSA infections treated with vancomycin often resolve slowly or not at all. Other effective MRSA antibiotics are available (eg, linezolid, daptomycin, minocycline, or tigecycline) and are more reliably effective, do not increase staphylococcal resistance or increase VRE prevalence.

[Clinical review: Fever and arthritis. Diagnosis: endocarditis due to enterococcus]

Clinical signs of infective endocarditis are inespecific. Fever and heart murmur are the most frequent symptoms. Arthralgias's association is fairly common but presentation as polyarthritis is inusual. We report a cse of infective endocarditis that begins with subacute fever and polyarthritis.

Staphylococcus hominis native mitral valve bacterial endocarditis (SBE) in a patient with hypertrophic obstructive cardiomyopathy

There are several species of coagulase-negative Staphylococci (CoNS) that are part of the normal skin flora and are relatively noninvasive/low virulence organisms. CoNS are important pathogens in patients with prosthetic devices and are the most common pathogen associated with prosthetic valve endocarditis. CoNS native valve infective endocarditis (IE) is rare. Patients with hypertrophic obstructive cardiomyopathy and an outflow pressure gradient greater than 30 mm Hg are predisposed to IE. There has been only one reported case of non-mitral valve IE due to CoNS in a patient with hypertrophic obstructive cardiomyopathy. To the best of our knowledge, we report the first case of Staphylococcal hominis mitral valve endocarditis in a patient with hypertrophic obstructive cardiomyopathy.

Quadrivalvular marantic endocarditis (ME) mimicking acute bacterial endocarditis (ABE)

Marantic endocarditis (ME) is defined by noninfectious valvular vegetations. The most common disorders associated with ME are malignancy with or without hypercoagulable state, intercardiac instrumentation, residual vegetations from previously treated infective endocarditis (IE), renal insufficiency, and burns. Another important cause of ME is systemic lupus erythematosus when accompanied by vegetations, that is, Libman-Sacks endocarditis. ME should be differentiated from IE because they may present with similar clinical features. Both ME and IE may present with fever and a heart murmur with or without embolic phenomenon. Leukocytosis and elevated erythrocyte sedimentation rate suggest the diagnosis of IE. The hallmark of IE is a cardiac vegetation and continuous high-grade bacteremia. After exclusion of the causes of culture negative endocarditis, the absence of bacteremia clearly differentiates ME from IE. We present a case of ME mimicking acute bacterial endocarditis (ABE). The differential diagnostic features of ME versus IE are discussed. To the best of our knowledge, this is the first reported case of quadrivalvular ME with massive vegetations on all cardiac valves, as well as the aorta, atria, and pulmonary artery.

Clinicopathological conference: case report--a case of anorexia and weak arm

The authors present the case of a 49-year-old female who presented to the emergency department with a chief complaint of "not eating well." She was found to have a heart murmur, a focal neurological deficit, and large mitral valve vegetation. The patient was later diagnosed with acute Pseudomonal endocarditis with septic emboli to the brain, liver, spleen, and kidneys. A discussion of the patient presentation, diagnostic evaluation, and outcome are reviewed.

Oral antibiotic therapy of serious systemic infections

Traditionally, antibiotics have been administered intravenously (IV) for serious systemic infections. As more potent oral antibiotics were introduced, and their pharmacokinetic aspects studied, orally administered antibiotics have been increasingly used for serious systemic infections. Antibiotics ideal for oral administration are those that have the appropriate spectrum, high degree of activity against the presumed or known pathogen, and have good bioavailability. Oral antibiotics with high bioavailability, that is > or = 90% absorbed, achieve serum/tissue concentrations comparable to IV administered antibiotics at the same dose. The popularity of "IV to PO switch therapy" is possible because of the availability of many potent oral antibiotics with high bioavailability. Initial IV therapy is appropriate in patients who are in shock/have impaired intestinal absorption, but after clinical defervescence, completion of therapy should be accomplished with oral antibiotics. As experience with "IV to PO switch therapy" has accumulated, confidence in oral antimicrobics for therapy of serious systemic infections has continued to increase. The trend in treating serious systemic infections entirely with oral antimicrobial therapy will continue, and is clearly the wave of the future.

Pacemaker-induced Staphylococcus aureus mitral valve acute bacterial endocarditis complicated by persistent bacteremia from a coronary stent: Cure with prolonged/high-dose daptomycin without toxicity

Continuous high-grade Staphylococcus aureus bacteremia suggests acute bacterial endocarditis (ABE), a protected focus, ie, an abscess, or a device-related infection. Daptomycin was curative of S. aureus ABE and coronary stent-related bacteremia. Prolonged high-dose daptomycin therapy (12 mg/kg per day for 41 days) is not associated with any toxicity. Persistent S. aureus bacteremia in ABE should suggest myocardial or perivalvular abscess. If intracardiac abscess can be ruled out and there is no extracardiac source of the S. aureus bacteremia, then a device-related infection should be considered.

Daptomycin cure after cefazolin treatment failure of Methicillin-sensitive Staphylococcus aureus (MSSA) tricuspid valve acute bacterial endocarditis from a peripherally inserted central catheter (PICC) line

Right-sided acute bacterial endocarditis (ABE) is an infrequent complication of central intravenous (IV) lines. We report a case of methicillin-sensitive Staphylococcus aureus tricuspid valve (TV) ABE related to a peripherally inserted central catheter line (PICC). Patients with right-sided ABE present with symptoms of fever and chills, and symptoms and signs of pulmonary emboli. In the patient presented, the PICC line was removed and high-dose cefazolin therapy, 2 g (IV) every 8 hours, was initiated. Although the patient's blood cultures became negative during the third week of cefazolin therapy, her erythrocyte sedimentation rate and teichoic acid antibody titers remained high. Pulmonary emboli developed. A large TV vegetation (1 x 2 cm) remained unchanged after 4 weeks of cefazolin therapy. For these reasons, cefazolin treatment was considered a treatment failure. Therapy with daptomycin was initiated at a dose of 6 mg/kg (IV) every 24 hours. During daptomycin therapy, the patient's erythrocyte sedimentation rate and teichoic acid antibody titers gradually returned to normal. Repeat transthoracic echocardiograph revealed the TV vegetation was gone and the methicillin-sensitive Staphylococcus aureus ABE was cured with daptomycin. We conclude daptomycin is a rapidly bactericidal antistaphylococcal antibiotic reliably effective even when other usually effective antistaphylococcal antibiotics have failed.

Platelet aggregation induced by serotype polysaccharides from Streptococcus mutans

Platelet aggregation plays an important role in the pathogenesis of infective endocarditis induced by viridans streptococci or staphylococci. Aggregation induced in vitro involves direct binding of bacteria to platelets through multiple surface components. Using platelet aggregometry, we demonstrated in this study that two Streptococcus mutans laboratory strains, GS-5 and Xc, and two clinical isolates could aggregate platelets in an irreversible manner in rabbit platelet-rich plasma preparations. The aggregation was partially inhibited by prostaglandin I(2) (PGI(2)) in a dose-dependent manner. Whole bacteria and heated bacterial cell wall extracts were able to induce aggregation. Cell wall polysaccharides extracted from the wild-type Xc strain, containing serotype-specific polysaccharides which are composed of rhamnose-glucose polymers (RGPs), could induce platelet aggregation in the presence of plasma. Aggregation induced by the serotype-specific RGP-deficient mutant Xc24R was reduced by 50% compared to the wild-type strain Xc. In addition, cell wall polysaccharides extracted from Xc24R failed to induce platelet aggregation. The Xc strain, but not the Xc24R mutant, could induce platelet aggregation when preincubated with plasma. Both Xc and Xc24R failed to induce platelets to aggregate in plasma depleted of immunoglobulin G (IgG), but aggregation was restored by replenishment of anti-serotype c IgG. Analysis by flow cytometry showed that S. mutans RGPs could bind directly to rabbit and human platelets. Furthermore, cell wall polysaccharides extracted from the Xc, but not the Xc24R, strain could induce pseudopod formation of both rabbit and human platelets in the absence of plasma. Distinct from the aggregation of rabbit platelets, bacterium-triggered aggregation of human platelets required a prolonged lag phase and could be blocked completely by PGI(2). RGPs also trigger aggregation of human platelets in a donor-dependent manner, either as a transient and reversible or a complete and irreversible response. These results indicated that serotype-specific RGPs, a soluble product of S. mutans, could directly bind to and activate platelets from both rabbit and human. In the presence of plasma containing IgG specific to RGPs, RGPs could trigger aggregation of both human and rabbit platelets, but the degree of aggregation in human platelets depends on the donors.

Infective Endocarditis in Elderly Patients

Infective endocarditis (IE) in elderly patients is a serious disease with significant morbidity and mortality. IE presents unique diagnostic and therapeutic challenges in the elderly. A heightened index of suspicion is necessary due to the atypical presentations of IE among the elderly. Underlying degenerative valvular disease, mitral valve prolapse, and presence of a prosthetic valve are important predisposing risk factors for IE in the elderly. IE in the elderly is somewhat more common in men. The mitral valve is affected somewhat more frequently compared with the aortic valve. Streptococci and staphylococci are the predominant organisms, recovered in approximately 80% of elderly patients with IE. The presence of calcific valvular lesions and prosthetic valves often confound echocardiographic findings in the elderly. Aggressive diagnostic and therapeutic approaches are mandatory for a favorable outcome of IE in this group of patients.

Iris abscess as an unusual presentation of endogenous endophthalmitis in a patient with bacterial endocarditis

PURPOSE

To report the clinical findings and management of a case of endogenous endophthalmitis in a patient with bacterial endocarditis presenting with a septic metastasis to the iris.

DESIGN

Observational case report.

METHODS

Review of clinical findings and treatment.

RESULTS

A 37-year-old intravenous drug user hospitalized with bacterial endocarditis secondary to methicillin-sensitive Staphylococcus aureus bacteremia presented with a painful red left eye, hypopyon, and iris abscess. Roth spots were noted in the fundus of the right eye. Aqueous culture was positive for methicillin-sensitive S aureus. The patient was treated with intravitreal, topical, and intravenous antibiotics. The hypopyon and iris abscess resolved within 2 weeks, and the patient achieved a final visual acuity of 20/25 in the left eye.

CONCLUSIONS

Septic metastasis to the iris is a rare occurrence. To our knowledge this is the first reported case of an iris abscess secondary to bacterial endocarditis.

Infective endocarditis in elderly patients

Infective endocarditis (IE) in elderly patients presents a unique diagnostic and therapeutic challenge. Atypical presentations frequently lead to delayed diagnosis and poor outcome. IE in elderly persons is somewhat more common among men. Underlying degenerative valvular disease, mitral valve prolapse, and the presence of a prosthetic valve are important risk factors predisposing elderly persons to IE. Streptococci and staphylococci are the predominant organisms, which are recovered from approximately 80% of elderly patients with IE. In older patients, IE occurs somewhat more frequently on the mitral valve than it does on the aortic valve. The presence of calcific valvular lesions and the prosthetic valves often confound the echocardiographic findings in elderly patients. A high index of suspicion and an aggressive diagnostic approach are required to ensure timely diagnosis and appropriate therapy.

Embolization of a huge tricuspid valve bacterial vegetation

A case of a woman who had tricuspid valve bacterial endocarditis is presented. Her course was complicated by persistent disseminated intravascular coagulation and acute renal failure, followed by pulmonary embolization of the vegetation. Transthoracic echocardiography showed almost complete obstruction of the right pulmonary artery. The case demonstrates the impressive size to which right-sided infective vegetations can progress and the relative paucity of symptoms and hemodynamic derangements with which they may be associated, even in the context of potentially life-threatening complications.

Etiology of fever and opportunities for reduction of antibiotic use in a pediatric intensive care unit

OBJECTIVE

To determine the cause of fever in critically ill children and to identify opportunities for reducing antibiotic use in this population.

DESIGN

Prospective case series.

SETTING

A tertiary-care medical-surgical pediatric intensive care unit (PICU).

PATIENTS

Children admitted to the PICU who experienced fever (axillary temperature >38.3 degrees C).

MEASUREMENTS

Consecutive children who were febrile at any point in their PICU stay were investigated over two winter seasons. Etiology of the fever was determined by physical examination and routine microbiology and radiographic tests. Three subgroups were reviewed to approximate the number of antibiotic-days that could have been reduced; namely, those with an indeterminate source, those with a documented viral infection, and those receiving a prolonged course of antibiotics. A set of standards reflecting common antibiotic use then was applied to these three patient groups.

RESULTS

Of 211 subjects, the majority (83.3%) had either a definitive or suspected focus for their fever, and nearly all of these patients were judged to have an infectious etiology. The study population received a total of 2,036 antibiotic-days. Despite the high incidence of infectious causes of fever in our subjects, however, approximately 15% of total antibiotic-days could have been reduced by applying common-use standards.

CONCLUSIONS

Fever in the PICU was usually of defined focus and infectious in origin. However, among febrile patients in the PICU, substantial opportunity exists for reduction of antibiotic use. Trials determining the safety of antibiotic reduction in this population should be pursued vigorously.

Role of monocytes in experimental Staphylococcus aureus endocarditis

In the pathogenesis of bacterial endocarditis (BE), the clotting system plays a cardinal role in the formation and maintenance of the endocardial vegetations. The extrinsic pathway is involved in the activation of the coagulation pathway with tissue factor (TF) as the key protein. Staphylococcus aureus is a frequently isolated bacterium from patients with BE. We therefore investigated whether S. aureus can induce TF activity (TFA) on fibrin-adherent monocytes, used as an in vitro model of BE. We also assessed in vivo in rabbits with catheter induced vegetations, the effect of S. aureus infection on vegetational TFA. In vitro experiments showed that adherent S. aureus induced TFA on fibrin-adherent monocytes which was optimal at a bacterium/monocyte ratio of 1 to 1. Monocyte damage occurred when this ratio exceeded 4 to 1 (visually) or 6 to 1 (propidium iodide influx) Consequently, TFA decreased. In vivo S. aureus led to very high bacterial numbers in the vegetations and a significant increase of their weight. However, TFA of infected vegetations was the same as of sterile ones. This may be due to the high bacteria to monocyte ratio as well as bacterium-induced monocyte damage. Teicoplanin treatment of infected rabbits reduced bacterial numbers in the blood and in the vegetations. Two-day treatment resulted in an increase of vegetational TFA, but after four-day treatment vegetational TFA dropped, most probably due to a suboptimal bacterium/monocyte ratio. S. aureus endocarditis in etoposide (Vepesid)-treated rabbits, leading to a selective monocytopenia, caused a rapid death of the animals. In these rabbits no vegetations were found at all. We conclude that, like Streptococcus sanguis and Staphylococcus epidermidis, S. aureus is able to induce TFA in fibrin-adherent blood monocytes. In addition, monocytes have a protective effect during the course of S. aureus endocarditis.

Differential diagnosis of infective endocarditis

Infective endocarditis (IE) is a deadly disease if left untreated. Early detection and treatment of IE reduces the high mortality rate. Mitral valve prolapse is now the leading risk factor for development of IE. The Duke (1994) criteria includes echocardiography as a diagnostic tool. Outclient i.v. therapy is increasing due to once-daily dosing regimens, which reduces the cost of treatment. Identifying at risk clients and educating them is vital to the prevention of IE. This article familiarizes the primary care provider with the pathophysiology, clinical presentation, diagnostic testing, complications, medical treatment, prophylactic management, and client education of IE.

Bacterial species- and strain-dependent induction of tissue factor in human vascular endothelial cells

A cardinal process in bacterial endocarditis (BE) is the activation of the clotting system and the formation of a fibrin clot on the inner surface of the heart, the so-called endocardial vegetation. The processes that lead to the activation of the clotting system on endothelial surfaces upon exposure to bacteria are largely unknown. In the present study, we investigated in an in vitro model whether infection of human endothelial cells (EC) with bacteria that are relevant to BE, such as Staphylococcus aureus, Streptococcus sanguis, and Staphylococcus epidermidis, leads to induction of tissue factor (TF)-dependent procoagulant activity (TFA) and whether this process is influenced by host factors, such as interleukin-1 (IL-1), that are produced in response to the bacteremia in vivo. The results show that S. aureus binds to and is internalized by EC, resulting in expression of TF mRNA and TF surface protein as well as generation of TFA within 4 to 8 h after infection. No TFA was found when EC were exposed to UV-irradiated S. aureus or bacterial cell wall fragments. S. sanguis and S. epidermidis, although also binding to EC, did not induce endothelial TFA. This indicates a species and strain dependency. EC also expressed TFA after exposure to IL-1. The enhanced TFA of EC after exposure to S. aureus was not prevented by IL-1 receptor antagonist, arguing against an auto- or paracrine contribution of endogenous IL-1. When IL-1 was applied together with bacteria, this had a synergistic effect on the induction of EC TFA. This was found in particular with S. aureus but also, although to a lesser degree, with S. sanguis and S. epidermidis. This influence of IL-1 on the species- and strain-dependent induction of EC TFA suggests that bacterial factors as well as host factors orchestrate the induction of coagulation in an early stage in the pathogenesis of endovascular disease, such as BE.

Nonculture Laboratory Methods for the Diagnosis of Infectious Endocarditis

Over the past few years new techniques have been developed to improve the diagnosis of infectious diseases. However, despite the various available culture systems, culture-negative endocarditis currently represents a challenge for physicians. In our laboratory, in an effort to reduce the rate of endocarditis of unknown etiology, we have used several recent histologic, serologic, and molecular tests. We review the latest technical developments for the diagnosis of infectious endocarditis, including those that we are currently using.

Cranial magnetic resonance imaging findings in bacterial endocarditis: the neuroimaging spectrum of septic brain embolization demonstrated in twelve patients

Infective endocarditis (IE) is an elusive systemic disorder that is often associated with neurologic complications. The contribution of brain magnetic resonance imaging (MRI) to the diagnosis of IE and the spectrum of such findings has been only sparsely described previously. The authors report cranial MRI findings in 12 patients with IE. Each of the patients had MRI evidence of cerebral embolization, with multiple brain lesions noted in most patients (n = 10). Cortical branch infarction was the most common lesion (n = 8), which usually involved the distal middle cerebral artery tree. The next most common finding (n = 7) was numerous small embolic lesions which typically lodged in the supratentorial gray-white junction, some of which were clinically silent and many of which enhanced (probable microabscesses). Brain hemorrhages were noted in four patients, most commonly subarachnoid hemorrhage (n = 3). Two patients developed multiple frank parenchymal macroabscesses/cerebritis lesions. A previously unreported finding in septic embolization, a stroke that became infected with abscess formation ("septic infarction"), was noted in two patients. MRI showed orbital cellulitis in two patients. Most patients studied with gadolinium showed enhancement of lesions (n = 5/8). The authors conclude that cranial MRI may be a valuable tool in the evaluation of patients with IE. The presence of characteristic cranial MRI lesions, especially of multiple types, may prompt early diagnosis and treatment.

Cardiac infections: medical and surgical therapies

Infections of the heart can be acute or subacute, depending on host susceptibility, the cause and associated virulence, early diagnosis, and effective therapy. The following review will discuss the causes, clinical manifestations, diagnosis, and medical or surgical management of infective endocarditis, prosthetic valve endocarditis, myocarditis, and pericarditis. Nursing considerations emphasize understanding the pathogenesis, early recognition of signs and symptoms, and appropriate prevention and intervention.

Fever in the critical care unit

Fever in the critical care unit (CCU) may be on an infectious or noninfectious basis. Many noninfectious disorders have clinical and laboratory features mimicking infections. The main clinical dilemma in the febrile CCU patient is to differentiate between noninfectious and infectious disease. Antibiotic treatment of colonization or noninfectious conditions is unnecessary, wasteful, likely to cause resistance problems, and may result in serious side effects. Selection of appropriate antibiotic therapy is straightforward once the likely source of sepsis is determined. This article provides a clinical diagnostic approach.