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» Articles -> Smile Magazine Issue 5 September 2007-> Current Thinking on Prophylaxis for Infective Endocarditis: Development of the New Guidelines
Dated : 2007-09-01
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Current Thinking on Prophylaxis for Infective Endocarditis: Development of the New Guidelines


» By: Dr Victoria S Lucas PhD, MSc, BDS (Hons), DDPH.RCS (Eng), ILTM, Senior Clinical Research Fellow

» Dr. Graham J Roberts BDS, PhD, FDSRCS (Eng), MDS (London), ILTM, Professor & Head of Department
Department of Paediatric Dentistry, King’s College London Dental Institute, Bessemer Road London SE5 9RS, UK

Correspondence to: Dr Victoria S Lucas
Department of Paediatric dentistry
King’s College London Dental Institute
Bessemer Road
London SE5 9RS
Tel: +44 (0) 2399 3375



Until very recently, the traditional approach to the prevention of Infective Endocarditis (IE) has been based on assessment of cardiac risk factors, dental risk factors and antibiotic prophylaxis (Table 1) The European cardiac society published their new guidelines in 2004(1) and recommend antibiotic prophylaxis for any procedures which cause mucosal bleeding. The British Cardiac Society (BCS) also published new guidelines in 2004(2). The main thrust of these BCS guidelines are the prescription of  antibiotic prophylaxis for dental procedures that cause a statistically significantly greater bacteraemia compared with baseline in the high and medium cardiac risk groups. It is unfortunate that the BCS  have insisted on IV antibiotic prophylaxis for the high risk group which is clearly inappropriate in general dental practice.
More recently, the British Society for Antimicrobial Chemotherapy (BSAC)(3) published their guidelines which recommend antibiotic prophylaxis for all dental procedures which cause a  bacteraemia. Only the Paediatric British National Formulary (2006) have currently accepted these guidelines. The National Institute for Clinical Excellence (NICE) aredeliberating on this issue and will report by January 2008.

Development of the New Guidlines

Detection and Quantification of Bacteraemia
One of the difficulties with early bacteraemia investigations has been the lack of quantitative data. That is, the prevalence and identity of the infecting organism can be detected but not the number of colony forming units (cfu) of bacteria causing the infection. The usual method of detecting a bacteraemia is the broth culture (Figure 1). This provides bacterial identification but not the number of bacteria, or intensity of bacteraemia, in the original blood sample. The technique of Lysis Filtration (LF) has been developed for clinical purposes(4,5) because it not only estimates the prevalence of bacteraemia but also the intensity in colony forming units per millilitre of blood. It differs from the broth culture because the blood is drawn through a micropore filter by negative pressure. Because of the small pore size the bacteria are trapped and grow on the filter. It is a sensitive method which provides a significantly higher bacterial yield from blood than other techniques(5). The technique has been validated by comparing test samples of known bacterial intensity(6)

» (Fig. 1)

Broth Culture Bottles (BACTEC Pediatric)







Bacteraemia following Dental Treatment Procedures
Most of the recent work was carried out on children undergoing comprehensive dental treatment under general anaesthesia
(7,8,9,10). Following induction of anaesthesia, a baseline blood sample was taken. The procedure under investigation was carried out as an isolated procedure and  a 2nd 6 ml blood sample withdrawn 30 seconds following the maximum manipulation of the gingival tissues(11,12)(Figure 3). The dental treatment was then carried out. The blood samples were transported to the microbiology laboratory and processed by LF within 30 to 60 minutes(Figure 2)

(Fig. 2): Demonstrates maximum intensity of bacteraemia at 30 seconds and 60 seconds after the maximum dento – gingival manipulation.

Prevalence and Intensity of Bacteraemia
If these results are considered in the context of the traditional guidelines for IE prophylaxis, it can be seen clearly that procedures other than extractions have a similar or greater bacteraemia compared with baseline (Table 2). For example, the prevalence of bacteraemia following the placement of ‘rubber dam’ or ‘matrix band and wedge’ is significantly greater than a ‘single extraction’. Similarly, the range of intensity for these procedures is greater than for a single extraction (Table 3).


» (Table. 1)












Any increase in bacteraemia is important in individuals at risk of developing IE. This leads onto the concept of cumulative bacteraemia in which a series of small but frequent episodes of bacteraemia lead to very large numbers of bacteria passing through the gingival crevicular tissue into the systemic blood stream. Persistently inadequate oral hygiene provides a large reservoir of bacteria which may either steadily enter the blood stream, or enter as a bolus during extra thorough toothbrushing immediately before a dental appointment.

» (Table. 2)















» (Fig. 3)

Bacterial colonies on Lysis Filtration filter from a blood sample 30 seconds after toothbrushing




New Guidelines for Infective Endocarditis

Everyday Procedures
The emphasis on bacteraemia from everyday procedures such as toothbrushing is an important factor in the new guidelines from the American Heart Association (AHA), published in April 2007(13). The consensus view of the AHA is that individuals are more at risk from the persistent bacteraemia that occurs as a result of persistently poor oral hygiene than a single infrequent dental operative procedure. Antibiotic prophylaxis is recommended for high risk cardiac conditions only which are:

1- Prosthetic Valves
2- Previous IE
3- Unrepaired Cyanotic Congenital Heart Disease, including palliative shunts and conduits

These guidelines are very similar to those published by the BSAC(3). This is not surprising as the BSAC guidelines were based on the draft AHA guidelines proposed at the International Symposium on Modern Concepts in Endocarditis and Cardiovascular Infections, 2005. All procedures, except for a simple examination with a mirror should have antibiotic prophylaxis in the high risk (AHA) or ‘at risk’ (BSAC). This means that only a small group of patients will need prophlyaxis for a wider range of treatment procedures. In the United Kingdom, only the Paediatric BNF has published the new dental recommendations. The National Institute for Clinical Excellence  will decide in the near future which guidelines the BNF should accept. However, it is difficult to envisage NICE not accepting the  BSAC recommendations in view of the recent AHA publication.

During the last 10 years or so, it has become increasingly obvious that a ‘single event bacteraemia’ has a low probability of seeding a vegetation on a damaged heart valve. It is far more likely that one of the many small bacteraemia episodes occurring during ‘everyday’ activities will seed a vegetation thus leading to IE. It is not possible to identify precisely the causative bacteraemia.

The new guidelines from both the BSAC(3) and the AHA(13) provide dentists and doctors with a simple scheme which will be easy to implement. In addition, there will be the enormous benefit of reducing antibiotic prescription thus minimising the risk of proliferation of antibiotic resistant microorganisms in the population. Both the BASC and the AHA have been sensitive to the development of antibiotic resistance in children within the community(14).

1. Horstkotte D, Follah F, Gutschik E et al.  Guidelines on prevention, diagnosis and treatment of infective endocarditis.  Europ Heart J. 2004;25:267-276.

2. Ramsdale DR, Turner-Stokes L.  prophylaxis and treatment of infective endocarditis in adults:  a concise guide.  Clin Med.  2004;6:545-550.

3. Gould FK, Elliott TSJ, Foweraker J, Fulford M, Perry JD, Roberts GJ et al:  Guidelines for the prevention of endocarditis:  report of the Working Party of the British Society for Antimicrobial Chemotherapy.  J Antimicrob Chemoth.  2006;57:1035-1042. 

4. Heimdahl A, Josefsson K, von Konow L, Nord CE.  Detection of anaerobic bacteria in blood cultures by lysis filtration. Europ J Clin Microbiol. 1985;4:404-407.

5. Heimdahl A, Hall G, Hedberg M, Sandberg H, Soder P O, Tuner K, Nord CE.Detection and quantitation by lysis-filtration of bacteraemia after different oral surgical  procedures.J Clin Microbiol. 1990;28:2205-2209

6. Lucas VS, Lytra V, Hassan T, Tatham H, Wilson M, Roberts GJ.  Comparison of lysis filtration and an automated blood culture system (BACTEC) for detection, quantification and identification of odontogenic bacteraemia in children.  J Clin Microbiol. 2002;40:3416-3420.

7. Roberts GJ, Gardner P, Longhurst P, Black A, Lucas VS. Intensity of bacteraemia associated with conservative dental procedures in children.  Br Dent J.  2000;188: 95-98.

8. Lucas VS, Omar J, Vieira A, Roberts GJ. The relationship between odontogenic bacteraemia and orthodontic treatment procedures.  Europ J  Orthodont  2002;24:293-301.

9. Sonbol H.  the prevalence and intensity of bacteraemia following conservative dento – gingival manipulative procedures in children. Phd thesis.  2005 University of London.

10. Lucas VS, Kyriazidou A, Gelbier M, Roberts GJ.  Bacteramia following debanding and gold chain adjustment.   Europ J Orthodont 2007;29:161-165.

11. Roberts GJ, Gardner P, Simmons NA. Optimum sampling time for detection of odontogenic bacteraemia in children.  Int J Cardiol. 1992;35:311-315.

12. Roberts GJ, Jaffray EC, Spratt DA, Petrie A, Greville C, Wilson M et al.  Duration, prevalence and intensity of bacteraemia following dental extractions in children Heart.

13. Wilson W, Taubert K, Gewitz M, Lockhart PB, Baddour LM, Levison M et al.  Prevention of Infective Endocarditis.  Guidelines from the American Heart Association. 
J Am Dent Assoc.  2007;138:739-760
14. Ready  D, Lancaster H, Mullany P, Bedi R, Wilson M.  Antibiotic resistance in the cultivable microbiota in children in different ethnic groups.  Int J Antimicrob Agents.  2006;27:376-382.

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