tailieunhanh - Chapter 118. Infective Endocarditis (Part 2)

Prosthetic valve endocarditis arising within 2 months of valve surgery is generally the result of intraoperative contamination of the prosthesis or a bacteremic postoperative complication. The nosocomial nature of these infections is reflected in their primary microbial causes: coagulase-negative staphylococci (CoNS), S. aureus, facultative gram-negative bacilli, diphtheroids, and fungi. The portals of entry and organisms causing cases beginning 12 months after surgery are similar to those in community-acquired native valve endocarditis. Epidemiologic evidence suggests that prosthetic valve endocarditis due to CoNS that presents 2–12 months after surgery often represents delayed-onset nosocomial infection. . | Chapter 118. Infective Endocarditis Part 2 Prosthetic valve endocarditis arising within 2 months of valve surgery is generally the result of intraoperative contamination of the prosthesis or a bacteremic postoperative complication. The nosocomial nature of these infections is reflected in their primary microbial causes coagulase-negative staphylococci CoNS S. aureus facultative gram-negative bacilli diphtheroids and fungi. The portals of entry and organisms causing cases beginning 12 months after surgery are similar to those in community-acquired native valve endocarditis. Epidemiologic evidence suggests that prosthetic valve endocarditis due to CoNS that presents 2-12 months after surgery often represents delayed-onset nosocomial infection. At least 85 of CoNS strains that cause prosthetic valve endocarditis within 12 months of surgery are methicillin-resistant the rate of methicillin resistance decreases to 25 among CoNS strains causing prosthetic valve endocarditis that presents 1 year after valve surgery. Transvenous pacemaker lead- and or implanted defibrillator-associated endocarditis is usually nosocomial. The majority of episodes occur within weeks of implantation or generator change and are caused by S. aureus or CoNS. Endocarditis occurring among injection drug users especially when infection involves the tricuspid valve is commonly caused by S. aureus strains many of which are methicillin-resistant. Left-sided valve infections in addicts have a more varied etiology and involve abnormal valves often ones damaged by prior episodes of endocarditis. A number of these cases are caused by Pseudomonas aeruginosa and Candida species and sporadic cases are due to unusual organisms such as Bacillus Lactobacillus and Corynebacterium species. Polymicrobial endocarditis is more common among injection drug users than among patients who do not inject drugs. The presence of HIV in the former population does not significantly influence the causes of endocarditis. From 5