The Normal Bacterial Flora of oral cavityFlora of the mouth refers to the bacteria and othermicroorganisms that can and do live inside themouth. There are literally hundreds of differentspecies of microorganisms that live inside themouth. Most are relatively harmless. Others havebeen implicated in a variety of health disorders.The two most common disease states that areattributed primarily to oral flora are dental caries(cavities) and periodontitis (gum disease). Otherless common conditions are oral yeast infectionsand oral herpes.
The presence of nutrients, epithelial debris, and secretions makes themouth a favorable habitat for a great variety of bacteria.The normal flora occupy available colonization sites which makes itmore difficult for other microorganisms (nonindigenous species) tobecome established. Also, the oral flora contribute to host nutritionthrough the synthesis of vitamins, and they contribute to immunity byinducing low levels of circulating and secretory antibodies that maycross react with pathogens. Finally, the oral bacteria exert microbialantagonism against nonindigenous species by production of inhibitorysubstances such as fatty acids, peroxides and bacteriocins.
Oral flora are able to live and thrive in the mouth because theconditions are nearly ideal. The mouth is warm, dark, moist, andusually provides a good food supply to the flora.Most microorganisms live in the periodontal sulcus between the teethand gums. Others can hide in the small pits and fissures of the teethwhere it is difficult to remove them with a toothbrush.If oral streptococci are introduced into wounds created by dentalmanipulation or treatment, they may adhere to heart valves and initiatesubacute bacterial endocarditis.
Subacute Bacterial EndocarditisSubacute Bacterial Endocarditis (SBE) is a bacterialinfection that produces growths on the endocardium (the cells lining the inside of the heart). Subacute bacterial endocarditis usually (but not always) is caused by a viridans streptococci (a type of bacteria); it occurs on damaged valves, and, if untreated, can become fatalwithin six weeks to a year.
Causes and Risk Factors of Subacute BacterialEndocarditisSubacute bacterial endocarditis (SBE) is usually caused bystreptococcal species (especially viridans streptococci),and less often by staphylococci.SBE often develops on abnormal valves afterasymptomatic bacteremias (bacteria traveling through thebloodstream) from infected gums, or from gastrointestinal,urinary, or pelvic procedures.
Symptoms of Subacute Bacterial EndocarditisMost patients present with a fever that lasts several daysto 2 weeks. Nonspecific symptoms are common. Cough,shortness of breath, joint pain, diarrhea, and abdominal orflank pain may be present,anaemiaand blood in urine.About 90 percent of patients will have heart murmurs, butmurmurs may be absent in patients with right-sided heartinfections. A changing murmur is common only in acuteendocarditis.
Diagnosis of Subacute Bacterial EndocarditisEndocarditis is suspected in a patient with a heartmurmur and unexplained fever for at least one week, andin an intravenous drug abuser with a fever, even in theabsence of hearing a murmur.A definitive clinical diagnosis requires blood cultures thatgrow bacteria. Echocardiography (ultrasound study of theheart) may visualize vegetations (growths) on heart valves.
Treatment of Subacute Bacterial EndocarditisCure of endocarditis requires eradication of all microorganisms fromthe vegetation(s), usually on the heart valve.Bacterial endocarditis almost always requires hospitalization forantibiotic therapy, generally given intravenously, at least at theoutset. Most patients respond rapidly to appropriate antibiotictherapy, with over 70 percent of patients becoming afebrile (without afever) within one week. Occasionally, therapy with oral antibiotics athome will be successful.Antibiotic therapy must usually continue for at least a month.In unusual cases, surgery may be necessary to repair or replace adamaged heart valve.
Patients are categorized as:-High risk patients for bacterial endocarditis-Moderate risk patients for bacterial -endocarditis-Negligible risk patients for bacterial endocarditis
Patients at high risk for bacterial endocarditis• Prosthetic cardiac valves, including bioprosthetic and homograft valves• Previous bacterial endocarditis• Complex cyanotic congenital heart disease (e.g., Tetralogy of Fallot)• Surgically constructed systematic pulmonary shunts or conduits
Patients at moderate risk for bacterial endocarditis• Acquired valvular dysfunction (e.g., rheumatic heart disease)• Hypertrophic cardiomyopathy• Mitral valve prolapse with valvular regurgitation and/or thickened leaflets• Most other congenital cardiac malformations (other than those cited as high or low risk)
Patients at negligible risk for bacterial endocarditis• Mitral Valve Prolapse without valvar regurgitation• Rheumatic Heart Disease or Kawasaki Disease without valvar dysfunction• Physiologic, functional or innocent heart murmurs• Previous coronary artery bypass surgery• Cardiac pacemakers or defibrillators• Isolated secundum atrial septal defect• Surgical repair of atrial septal defect, ventricular septal defect, or patent ductus arteriosus (without• residua beyond 6 months)
ComplicationsIf bacterial endocarditis is not adequately treated, it can befatal. This is dependent on the infecting organism. Evenwhen treated, further damage to a heart valve may can toheart failure. In addition, blood clots can form and travelthroughout the bloodstream to the brain or lungs.
In Adults, the new antibiotic regime recommended for theprevention of bacterial endocarditis is: Amoxycillin: 2.0grams, 1 hour prior to the procedure (Four 500 mg tablets)For those patients allergic to penicillin, Clindamycin: 600mg, 1 hour to the procedure (Four 150 mg tablets)The guidelines for Children are: Amoxycillin: 50 mg/kg, 1hour prior to the procedure.For those patients allergic to penicillin, Clindamycin: 20mg/kg, 1 hour prior to the procedure.
- Cannot use oral medicationsAmpicillin Adults, 2.0 g IM or IV ;Children, 50 mg/kg IM or IVwithin 30 minutes beforeprocedure.Cephalexin or cefadroxilAdults, 2.0 g;Children, 50 mg/kg orallyone hour before procedure- Allergic to penicillin Azithromycin orClarithromycinAdults, 500 mg;Children, 15 mg/kg orallyone hour before procedure
Clindamycin Adults, 600 mg;Children, 15 mg/kg IV onehour before procedure- Allergic to penicillin andunable to take oralmedicationsCefazolin Adults, 1.0 g;Children, 25 mg/kg IM or IVwithin 30 minutes beforeprocedure.†Cephalosporins should not be used in patients with immediate-type hypersensitivityreaction (urticaria, angioedeman or anaphylaxis) to penicillins.‡Total children’s dose should not exceed adult dose.§ IM: intramuscular; IV: intravenous
Patients at risk requiring antibiotic prophylaxis who arealready receiving an antibiotic for a preexisting condition should receive an antibiotic for prophylaxis from a differentclassification.For example, a patient at risk already receiving penicillin forsome other condition should receive another antibiotic for prophylaxis, such as clindamycin.
Antibiotic prophylaxis is recommended for patients with total jointreplacements that are considered at increased risk of hematogenoustotal joint infection.They are the following: • Previous history of prosthetic joint infection • Immunosuppressed/immunocompromi sed patients • Inflammatory arthorpathies: Rheumatoid arthritis • Disease-, drug- or radiation-induced immunosuppression • Insulin dependent diabetics; Type 1 • Malnourished patients • Hemophiliacs
Antibiotic prophylaxis is not recommended for patients with pins,plates, and screws.In the past, administration of antibiotics prior to dental work was onlyrecommended during the first two years after surgery. Because ofconcerns about the severity of infection of a joint replacement, theAmerican Academy of Orthopaedic Surgeons now recommends thatantibiotics be given before an invasive dental procedure no matter howlong it has been since the joint replacement procedure.
The connection between subacute bacterial endocarditis and dental treatmentsThis infection is affected by two major factors;bacteraemias and cardiac lesions where there isturbulent blood flow. The main type of bacterium involvedwith this infection is Viridans streptococci (found in largenumbers in the mouth, especially abundant with poor oralhygiene) Strep. Mutans and S.sanguis - causing 50% ofcases, and Staphylococcus aureus.
Viridans streptococci can be released into the bloodstreamduring dental treatment such as tooth extraction and scaleand polishes. However it can also enter the blood streamduring home oral care such as flossing and brushing. In themajority of cases this causes no harm and no infection ofthe heart occurs however there are a variety of factors thatincrease the chances of acquiring infective endocarditis;-The number of the bacteria that are entering the bloodstream.-Valvular diseases and cardiovascular diseases that aresuffered.-How well the bacteria adhere to the endocardium.-If prosthetic heart valves are present.
Antibiotic cover is necessary with any tooth extraction, implant surgery,probing, scaling, intraligamental local anaesthesia and endodonticsbeyond the root apex.. It is vital that the patient who is at risk of infective endocarditis is toldto report back immediately if they suffer any symptoms which canappear as late as two months after treatment. If multiple treatments arerequired for a susceptible patient, then they should be at intervals ofnine to fourteen days, this is necessary so as the bacteria does notbecome resistant to the antibiotics.
Dental procedures for which prophylaxis is recommended for highand moderate risk patients:•Dental extractions .•Periodontal procedures including probing, scaling and root planing,surgery and recall maintenance .•Dental implant placement and reimplantation of avulsed teeth .•Endodontic instrumentation or surgery only beyond apex .•Subgingival placement of antibiotic fibers or strips .•Initial placement of orthodontic bands (but not brackets).•Intraligamentary local anesthetic injections .•Prophylactic cleaning of teeth or implants where bleeding isanticipated.
Dental procedures for which prophylaxis is not recommended:• Restorative dentistry (operative and prosthetic) with or without the use of retraction cord (Clinical• judgment may indicate use of prophylaxis if significant bleeding is anticipated)• Local anesthetic injections (other than intraligamentary)• Intracanal endodontic or restorative treatments• Placement of rubber dams• Postoperative suture removal• Placement of removable prosthodontic/orthodontic appliances• Taking of oral impressions• Fluoride treatments• Taking of oral radiographs• Orthodontic appliance adjustment• Shedding of primary teeth
Dental careThe patient should keep his teeth and gums clean and healthy.This will prevent germs from entering the bblood stream through inflamedtissue and will prevent the need for most dental repairs or dentalsurgery.