Antimicrobial endocarditis

Antimicrobials also can be classified as possessing bactericidal or bacteriostatic activity in vitro. Bactericidal antibiotics generally kill at least 99.9% (3 log reduction) of a bacterial population, whereas bacteriostatic antibiotics possess antimicrobial activity but reduce bacterial load by less than 3 logs. Clinically, bactericidal antibiotics may be necessary to achieve success in infections such as endocarditis or meningitis. A full discussion of the application of antimicrobial pharmacodynamics is beyond the scope of this chapter, but excellent sources of information are available.15... 

Reculture of specimens is not performed routinely except in few cases (e.g., endocarditis) or where a secondary infection is suspected because data may be misleading and lead to the addition of broader or more powerful antimicrobials... 

Baddour LM, Wilson WR, Bayer AS, et al. Infective endocarditis Diagnosis, antimicrobial therapy, and management of complications a statement for healthcare professionals from the Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease, Council on Cardiovascular Disease in the Young, and the Councils on Clinical Cardiology, Stroke, and Cardiovascular Surgery and Anesthesia, American Heart Association endorsed by the Infectious Diseases Society of America. Circulation 2005 111(23) 394M34. 

Baddour LM, Wilson WR, Bayer AS, et al. Infective endocarditis Diagnosis, antimicrobial therapy, and management of complications. American Heart Association scientific statement. Circulation 2005 111 e394—433. 

The goal of antimicrobial prophylaxis in dental procedures is to prevent endocarditis. According to American Heart Association guidelines, at-risk individuals should receive 2 g of amoxicillin 1 hour prior to the procedure.23 Patients with a (5-lactam allergy may receive clindamycin 600 mg 1 hour prior to the procedure. Interested readers should refer to the American Heart Association guidelines for a complete discussion on risk stratification and recommendations. 

Serum concentrations of the antimicrobial should generally exceed the MBC of the organism however, in practice this principle is usually not helpful in monitoring patients with endocarditis. 

The use of antimicrobials for this purpose requires consideration of the types of patients who are at risk the procedures causing bacteremia the organisms that are likely to cause endocarditis and the pharmacokinetics, spectrum, cost, and ease of administration of available agents. The objective... 

For parenteral therapy, nafciUin and oxacillin offer comparable efficacy and antimicrobial spectra of activity. Although both drugs undergo hepatic metabolism, only nafcillin requires dose adjustment in patients with combined hepatic and renal insufficiency. Other pharmacokinetic data for nafcillin and oxacillin appear in Table 45.1. Indications for nafcillin or oxacillin include severe staphylococcal infections like cellulitis, empyema, endocarditis, osteomyelitis, pneumonia, septic arthritis, and toxic shock syndrome. 

Various antimicrobials agents is used in dentistry for prevention of local oral wound infection and prevention of distant infection i.e., bacterial endocarditis. Generally, prophylaxis by the use of antibiotics is not required for routine type of dental surgery... 

The intravenous route is preferred in the following situations (1) for critically ill patients (2) for patients with bacterial meningitis or endocarditis (3) for patients with nausea, vomiting, gastrectomy, or diseases that may impair oral absorption and (4) when giving antimicrobials that are poorly absorbed following oral administration. 

Bacterial endocarditis. An aminoglycoside, usually gentamicin, should comprise part of the antimicrobial combination for enterococcal, streptococcal or staphylococcal infection of the heart valves, and for the therapy of clinical endocarditis which fails to yield a positive blood culture. 

Simmons N A1993 Recommendations for endocarditis prophylaxis. Journal of Antimicrobial Chemotherapy 31 437. Littler W A, McGowan D A, Shanson D C 1997 Changes in recommendations about amoxycillin prophylaxis for prevention of endocarditis. Lancet 350 1100. 

Rifampin is effective against Staph, aureus, Haemophilus spp., R. equi and a variety of mycobacteria. At very high concentrations, it has activity against poxviruses and adenoviruses. Rifampin also has antifungal activity when combined with other antifungal agents. Resistance develops rapidly therefore, it is usually administered concurrently with another antimicrobial agent. In equine practice, is most commonly used in combination with erythromycin for the treatment of R. equi infections in foals. It may also be used in the treatment of refractory osteomyelitis and endocarditis caused by Staph, aureus. 

Antimicrobial combination therapy is used frequently to treat serious infections. Combination therapy may be used prior to knowing the pathogen or antibiotic susceptibility for the treatment of infections in neutropenic patients and in patients with enterococcal endocarditis or bacteremia, sepsis, or pneumonia caused by P. aeruginosa. In these cases, it is important to know whether the combination will have beneficial (or detrimental) effects on the overall antibacterial activity of the regimen. For example, the combination may result in activity that is... 

The proper route of administration for an antimicrobial depends on the site of infection. Parenteral therapy is warranted when patients are being treated for febrile neutropenia or deep-seated infections such as meningitis, endocarditis, and osteomyelitis. Severe pneumonia often is treated initially with intravenous antibiotics and switched to oral therapy as clinical improvement is evident. Patients treated in the ambulatory setting for upper respiratory tract infections (e.g., pharyngitis, bronchitis, sinusitis, and otitis media), lower respiratory tract infections, skin and soft tissue infections, uncomplicated urinary tract infections, and selected sexually transmitted diseases may receive oral therapy. 

All enterococci causing endocarditis must be tested for antimicrobial susceptibility in order to select optimal therapy (see text). This table is for endocarditis due to gentamicin- or vancomycin-susceptible enterococci, viridans streptococci with a minimum inhibitory concentration of >0.5 mcg/mL, nutritionally variant viridans streptococci, or prosthetic valve endocarditis caused by viridans streptococci or Streptococcus bovis. Antibiotic dosages are for patients with normal renal function. 

After 12 months, the likely organism for PVE parallels that of native-valve endocarditis. As with native-valve endocarditis, antimicrobial therapy should be based on the identified organism and... 

Shorter-course antimicrobial regimens are advocated when possible. For instance, in exquisitely sensitive streptococcal endocarditis (MICs <0.1 mcg/mL), a 2-week regimen of high-dose parenteral penicillin G in combination with an aminoglycoside is as effective as 4 weeks of penicillin alone. Uncomplicated right-sided MSSA endocarditis in the intravenous drug abuser also may be treated with... 

Patients with certain cardiac lesions, particularly those with prosthetic heart valves or a history of bacterial endocarditis, are at high risk for developing IE (see Table 109-10). Nevertheless, only 15% to 25% of patients who develop IE are in a definable high-risk category. Few cases of IE are preventable with antibiotic prophylaxis, even with 100% effectiveness. The concern of antibiotic resistance also questions the routine use of antimicrobials in this setting. Despite the low probability that IE will develop, prophylaxis is recommended for some dental, respiratory, gastrointestinal, and genitourinary pro-... 

Korzeniowski O, Sande MA. The National Collaborative Endocarditis Study Group Combination antimicrobial therapy for Staphylococcus aureus endocarditis in patients addicted to parenteral drugs and in nonaddicts. Ann Intern Med 1982 97 496-503. 

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