PHARMACOKINETIC AND PHARMACODYNAMIC ASPECTS OF THERAPY OF EXPERIMENTAL ENDOCARDITIS

Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications: A Scientific Statement for Healthcare Professionals From the American Heart Association

BACKGROUND

Infective endocarditis is a potentially lethal disease that has undergone major changes in both host and pathogen. The epidemiology of infective endocarditis has become more complex with today's myriad healthcare-associated factors that predispose to infection. Moreover, changes in pathogen prevalence, in particular a more common staphylococcal origin, have affected outcomes, which have not improved despite medical and surgical advances.

METHODS AND RESULTS

This statement updates the 2005 iteration, both of which were developed by the American Heart Association under the auspices of the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease of the Young. It includes an evidence-based system for diagnostic and treatment recommendations used by the American College of Cardiology and the American Heart Association for treatment recommendations.

CONCLUSIONS

Infective endocarditis is a complex disease, and patients with this disease generally require management by a team of physicians and allied health providers with a variety of areas of expertise. The recommendations provided in this document are intended to assist in the management of this uncommon but potentially deadly infection. The clinical variability and complexity in infective endocarditis, however, dictate that these recommendations be used to support and not supplant decisions in individual patient management.

Comparison of six generic vancomycin products for treatment of methicillin-resistant Staphylococcus aureus experimental endocarditis in rabbits

Concerns have recently emerged about the potency and the quality of generic vancomycin (VAN) products approved for use in humans, based on experiments in a neutropenic mouse thigh infection model. However, other animal models may be more appropriate to decipher the bactericidal activities of VAN generics in vivo and to predict their efficacy in humans. We aimed to compare the bactericidal activities of six generic VAN products currently used in France (Mylan and Sandoz), Spain (Hospira), Switzerland (Teva), and the United States (Akorn-Strides and American Pharmaceutical Products [APP]) in a rabbit model of aortic valve endocarditis induced by 8 × 10(7) CFU of methicillin-resistant Staphylococcus aureus (MRSA) strain COL (VAN MIC, 1.5 μg/ml). In vitro, there were no significant differences in the time-kill curve studies performed with the six generic VAN products. Ten rabbits in each group were treated with intravenous (i.v.) VAN, 60 mg/kg of body weight twice a day (b.i.d.) for 4 days. Mean peak serum VAN levels, measured 45 min after the last injection, ranged from 35.5 (APP) to 45.9 μg/ml (Teva). Mean trough serum VAN levels, measured 12 h after the last injection, ranged from 2.3 (Hospira) to 9.2 (APP) μg/ml. All generic VAN products were superior to controls (no treatment) in terms of residual organisms in vegetations (P < 0.02 for each comparison) and in the spleen (P < 0.005 for each comparison). Pairwise comparisons of generic VAN products found no significant differences. In conclusion, a stringent MRSA endocarditis model found no significant differences in the bactericidal activities of six generic VAN products currently used in Europe and America.

Antibacterials for the prophylaxis and treatment of bacterial endocarditis in children

Although the overall incidence of infective endocarditis in the paediatric population is considered to be low, over the last 20 years a rising trend in infective endocarditis has been observed among children. This could be due to several reasons including the availability of improved diagnostic techniques, use of continuous central venous catheters and cardiac implants increasing the risk of infection, and the survival of a greater number of infants with congenital heart disease as a result of improved medical management. The predominant causative organisms of paediatric endocarditis include staphylococci and streptococci. There is increased concern surrounding the emergence of endocarditis in children caused by methicillin-resistant Staphylococcus aureus and drug resistant strains of Streptococcus pneumoniae. The treatment approach to paediatric endocarditis is similar to that for adult patients with endocarditis because of similarities in disease pathogenesis and aetiology. The therapeutic goal is to achieve sterilisation of the cardiac vegetations. The choice of antibacterial is dependent upon the susceptibility profile of the causative organism. Vancomycin or gentamicin is recommended for enterococcal endocarditis, according to guidelines from the American Heart Association. For staphylococcal endocarditis in patients with no prosthetic valve, oxacillin or nafcillin with or without gentamicin is the treatment of choice. In the case of endocarditis caused by methicillin-resistant S. aureus, vancomycin is commonly used in patients with no prosthetic valve and a combination of vancomycin, gentamicin and rifampicin (rifampin) for patients with prosthetic material. Cefazolin or ceftriaxone is the treatment of choice for penicillin allergic paediatric patients with endocarditis caused by viridans streptococci. While there have been no major changes in endocarditis therapy for the last decade, the current focus is on the recognition of multiple-drug resistant pathogens and the use of newer agents such as quinupristin/dalfopristin in the treatment of resistant bacterial endocarditis. Prophylactic antibacterial therapy is recommended for procedures thought to be associated with the occurrence of bacteraemia involving organisms commonly associated with endocarditis. These include dental extractions and oral, respiratory tract, genitourinary, gastrointestinal or oesophageal procedures. Prophylactic antibacterials recommended by the American Heart Association during genitourinary and gastrointestinal surgical procedures in high risk patients include ampicillin + gentamicin or vancomycin + gentamicin in high risk patients with penicillin allergy. Ampicillin has been recommended for prophylaxis of bacterial endocarditis in children undergoing oral, respiratory tract or oesophageal procedures. In the case of penicillin allergy in these patients, cephalosporins, clindamycin, azithromycin or clarithromycin have been recommended. The general consensus is that antibacterial prophylaxis during dental procedure is unnecessary, and in fact propagates bacterial resistance.

Acute infective endocarditis. Diagnostic and therapeutic approach

Acute bacterial endocarditis (ABE) is clinically distinct from subacute bacterial endocarditis in terms of pathologic virulence, acuteness and severity of illness, complications, and prognosis. The term infectious endocarditis may be useful as a general term but conveys no meaningful clinical information. ABE presents as an acute, fulminant intracardiac infection with fevers (temperature > 102 degrees F) that are caused by highly virulent known pathogens. Septic embolic phenomena, valve dysfunction, and congestive heart failure are characteristic. Parenteral and oral antibiotic treatment regimens are discussed.

Oral antibiotic therapy in infective endocarditis

The mortality of IE remains fairly high despite the aggressive use of intravenous antibiotics. Oral treatment of IE is an intriguing concept with many potential advantages over conventional intravenous therapy. Unfortunately, there are insufficient data to justify predominantly oral regimens for the treatment of IE. Trials have shown that oral therapy may have a role in follow-up to short courses of parenteral antibiotics, but these trials are limited by the small number of patients studied. It is important to note that most data for oral treatment of IE have been obtained from studies in patients with histories of IVDA and right-sided S. aureus endocarditis. As mentioned previously, the course of IE in this patient population tends to be less severe, which makes extrapolation of these data to the general population difficult. A need exist for the development of oral antimicrobials with the properties previously mentioned, making them appropriate for use in IE. Currently available oral agents require further study before general recommendations regarding their use in patients with IE can be made. Although successful oral treatment of prosthetic valve endocarditis has been reported, such patients in general should not be considered as appropriate candidates for oral therapy. For now, oral antimicrobial therapy may be appropriate only as follow-up to short-course intravenous therapy, or use in combination with intravenous therapy for IE in select populations whose disease course is less severe or in whom prolonged intravenous therapy is impractical (i.e., intravenous drug users).