Antibiotic prophylaxis - The debate goes on in infective endocarditis 

Bernard Prendergast: 'The latest guidelines have gone too far'

'The latest guidelines have gone too far'  says Bernard Prendergast, John Radcliffe Hospital Oxford, UK

Cardiologists, who frequently see patients with severe complications of infective endocarditis (IE) destined for complex cardiac surgery or post mortem, naturally fear the disease and have maintained the dogma of prevention by means of antibiotic prophylaxis prior to invasive procedures. However, the supportive evidence is limited and revision of international guidelines has resulted in a major shift of emphasis with resulting controversy and confusion. In the minds of many, the latest recommendations have overstepped the mark.

Is prophylaxis necessary?
The demography of IE is changing rapidly with increasing frequency of Staphylococcus aureus (often acquired as a result of nosocomial infection or IV drug abuse), and falling incidence of IE secondary to oral streptococci.  Prophylaxis before planned invasive procedures (classically involving the dentist) is therefore less and less relevant.
   Furthermore, IE often arises in patients without documented cardiac disease when prophylaxis is inapplicable. These considerations, coupled with a lack of evidence to support its efficacy, recognise that day-to-day bacteraemia is probably of greater importance and concerns regarding antibiotic-induced anaphylaxis and microbial resistance, have led to increasing scepticism of the role of prophylaxis.

Guidelines and philosophy
The original “treat all” philosophy was based upon an understandable fear of IE and its complications. However, the efficacy of this approach is low, routine antibiotic administration carries risks and cost-effectiveness is questionable.

Revised European and US guidelines advocate the “number needed to treat” philosophy, restricting prophylaxis to high-risk patients undergoing high-risk procedures. The 2006 British Society of Antimicrobial Chemotherapy guidelines were met with anger by British cardiologists but preceded a global shift in practice stimulated by the 2007 AHA guidelines (which seem likely to be endorsed by the ESC).

The most recent (and potentially most controversial) NICE guidelines in the UK suggest an end to antibiotic prophylaxis altogether – the “proof of principle” philosophy. Whilst NICE identifies patients at increased risk of developing IE, they do not advocate prophylaxis for any dental or respiratory procedures.  Reflecting the virulence of enterococcal IE, NICE recommends that at-risk patients undergoing GI or GU procedures when there is pre-existing infection receive an antibiotic that covers IE-causative organisms. Although the British Cardiovascular Society and British Heart Foundation contributed to the development of these guidelines, the debate rumbles on.

Concerns and the need for consensus
Many in the dental profession have praised the new guidelines as “a victory for science and common sense”. Conversely, many cardiologists maintain that they are a dangerous departure from established practice which will expose patients to the devastating risks of IE. At the 2007 BCS Annual Scientific Congress, 70% of participants attending an IE debate expressed concern regarding the safety of the AHA guidelines and their reluctance to change current practice. To date, UK reaction to the NICE declaration has been guarded, but hostile in some quarters. This genuine concern for the welfare of patients is admirable and careful monitoring of the incidence and presentation of IE using local and national registries will be essential. Moreover, unanimous interpretation by the relevant professional societies and an open minded attitude of individual clinicians are required to stem further confusion and debate.

Gilbert Habib: 'The Widespread use of antiobiotic prophylaxis is no longer accepted'

'The Widespread use of antiobiotic prophylaxis is no longer accepted' says  Gilbert Habib, Hopital de la Timone Marseille, France

The use of antimicrobial agents to prevent infective endocarditis (IE) was proposed more than 60 years ago and is still applied by the majority of cardiologists from that time. In the past 20 years several recommendations have been published concerning the best use of antimicrobial prophylaxis to prevent IE in patients underging dental, gastrointestinal or genitourinary tract procedures. 

However, it's my view that the widespread use of antibiotics in patients considered to be at risk of IE should no longer be accepted for the following reasons:

1. The link between a dental procedure and IE is unclear. Case-control studies have failed to identify any relationship and no randomised trial exists to prove the efficacy of antibiotic prophylaxis in such circumstances.
2. The risk of IE after a dental procedure is very rare; daily activities like tooth brushing cause repeated bacteremia - potentially more frequently responsible for IE. Thus, IE is much more likely to result from frequent exposure to repeat, daily bacteremia than from bacteremia caused by a dental, gastrointestinal or genitourinary tract procedure.
3. The widespread use of antibiotics may be associated with adverse effects and the selection of resistant bacteria
4. Good oral hygiene is much more important than antibiotic prophylaxis to prevent IE

From one guideline to another
In 2002 the French infectious disease specialists, cardiologists and dentists proposed that antibiotic prophylaxis should only be used in highest risk patients and should be optional in patients at intermediate risk of IE. Other societies (British Society of Antimicrobial Therapy and more recently the AHA) subsequently followed suit and adopted these fundamental changes.

The American recommendations represent a considerable change:

1. Patients at risk. Only patients with the highest risk of adverse outcome in IE are considered for prophylaxis - which includes prosthetic cardiac valves, previous endocarditis, unrepaired congenital heart disease and cardiac transplants who develop cardiac valvulopathy. Thus, the majority of patients with valvular heart disease are no longer considered candidates for antibiotic prophylaxis.
2. Dental procedures. All procedures involving manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa are considered high risk and require prophylaxis when performed in at-risk patients.
3. GU or GI tract procedures. Antibiotic prophylaxis is no longer recommended in these procedures.

A new set of British guidelines from the National Institute for Health and Clinical Excellence (NICE) has even recommended this year that at-risk patients undergoing interventional procedures should no longer be given antibiotic prophylaxis against IE.

What about Europe?
Such radical modifications will probably be difficult to accept and understand by both patients and practitioners. Much education will be necessary to explain both the reasons for these changes and the need to shift from prophylaxis in dental procedures towards more dental care and oral health in patients with cardiac disease associated with IE. 

In addition, patients and practitioners must accept the idea that, although several procedures - dental or non-dental - may produce bacteremia, there is no clear evidence that they cause IE, and even less evidence that prophylaxis might be useful.

The ESC is currently working on a new version of the 2004 guidelines on IE, which are due for publication in 2009. I don’t know to what extent recommendations on the use of antibiotic prophylaxis will be modified in these new guidelines, but we should remember that, until strong evidence in favour of antibiotic prophylaxis is produced, we should stop giving antibiotics systematically before dental procedures in all at-risk patients.