Epidemiology and antibiotic treatment of infective endocarditis: an update

he epidemiological profile of infective endocarditis (IE) has changed dramatically over the last few years. 1 Once a disease affecting young adults with previously well-identified valve disease-mostly rheumatic disease-IE is now affecting older patients, a significant proportion of whom has no previously known valve disease and develop IE as the result of healthcare associated procedures. 2 A CHANGING EPIDEMIOLOGY cUntil the end of the 1970s, rheumatic valvulopathies and congenital cyanotic cardiopathies were the two most frequent predisposing factors for IE.Then, a few years after the effective eradication of rheumatic fever, post-rheumatic valvulopathies gradually disappeared.However, other predisposing factors emerged, such as intravenous drug use, valve prostheses, degenerative valve sclerosis, and invasive procedures at risk for bacteraemia, which resulted in nosocomial and health care-associated endocarditis.3 These changes had at least two consequences: (1) the absence of a reduction in the incidence of IE; and (2) major changes in the microbiological profile of IE.In a meta-analysis of 26 articles published between 1993 and 2003, including a total of 3784 episodes of IE, Moreillon and Que showed that oral streptococci (also known as viridans streptococci) are now only second to staphylococci as the leading cause of IE. 1 As a result, it is now critical to regard the epidemiology of IE as a set of various clinical situations sometimes differing greatly from one another.Thus, at least five categories of IE have been identified: native valve endocarditis; prosthetic valve endocarditis; endocarditis in intravenous drug users (IVDUs); nosocomial endocarditis; and healthcare-related endocarditis resulting from invasive procedures such as endovascular investigations, haemodialysis, and implanted endovascular or intracardiac devices.Significant geographical variations have also been shown, with the highest increases in the rate of staphylococcal endocarditis being reported in the United States.4 In a prospective study of 1779 cases of IE collected in 16 countries, Staphylococcus aureus was the primary cause.5 In this study, S aureus IE was more frequent in the United States, and also in Australia/New Zealand and South America, than in Europe.In the USA, chronic haemodialysis, diabetes mellitus, and intravascular devices are the three main factors associated with the development of S aureus endocarditis.4 5 In other countries, the main predisposing factor for S aureus endocarditis is intravenous drug use.6 INCIDENCE OF INFECTIVE ENDOCARDITISThe incidence of IE varies from country to country, which may reflect more methodological differences in surveys than true incidence variations.In an epidemiologic study conducted in Sweden from 1984 to 1988 the incidence of IE was 5.9 episodes/100 000 person-years after adjusting for both age and sex.7 During a similar time period, the total incidence of IE was 9.29 episodes/100 000 person-years in the Philadelphia metropolitan area, which fell to 5.02 episodes/ 100 000 person-years when cases involving intravenous drug users were excluded.8 In the 1990s, French investigators performed two epidemiologic surveys in three regions of France that represented about 25% of the whole French population.In 1991 their survey found the crude incidence to be 2.24 episodes/100 000 person-years, which increased to 2.43 episodes/100 000 person-years after adjustment for age and sex.9 When this study was repeated in 1999 the crude and adjusted incidence rates were 3.0 and 3.1 episodes/100 000 person-years. 2 Of note, in these two surveys, as in others, the incidence of IE was very low in young patients whereas it increased dramatically with age.In France, the peak incidence was 14.5 episodes/100 000 person-years in patients aged between 70-80 years. MICROBIOLOGYAccording to the contribution of blood cultures to the diagnosis of IE, the following classification can be proposed.