The Normal Bacterial Flora of oral cavity

Flora of the mouth refers to the bacteria and other microorganisms that can and do live inside the mouth. There are literally hundreds of different species of microorganisms that live inside the mouth. Most are relatively harmless. Others have been implicated in a variety of health disorders. The two most common disease states that are attributed primarily to oral flora are dental caries (cavities) and periodontitis (gum disease). Other less common conditions are oral yeast infections and oral herpes.

The presence of nutrients, epithelial debris, and secretions makes the mouth a favorable habitat for a great variety of bacteria. The normal flora occupy available colonization sites which makes it more difficult for other microorganisms (nonindigenous species) to become established. Also, the oral flora contribute to host nutrition through the synthesis of vitamins, and they contribute to immunity by inducing low levels of circulating and secretory antibodies that may cross react with pathogens. Finally, the oral bacteria exert microbial antagonism against nonindigenous species by production of inhibitory substances such as fatty acids, peroxides and bacteriocins.

Oral flora are able to live and thrive in the mouth because the conditions are nearly ideal. The mouth is warm, dark, moist, and usually provides a good food supply to the flora. Most microorganisms live in the periodontal sulcus between the teeth and gums. Others can hide in the small pits and fissures of the teeth where it is difficult to remove them with a toothbrush.If oral streptococci are introduced into wounds created by dental manipulation or treatment, they may adhere to heart valves and initiate subacute bacterial endocarditis.

Subacute Bacterial Endocarditis

Subacute Bacterial Endocarditis (SBE) is a bacterial infection 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 fatal within six weeks to a year.

Causes and Risk Factors of Subacute Bacterial EndocarditisSubacute bacterial endocarditis (SBE) is usually caused by streptococcal species (especially viridans streptococci), and less often by staphylococci. SBE often develops on abnormal valves after asymptomatic bacteremias (bacteria traveling through the bloodstream) from infected gums, or from gastrointestinal, urinary, or pelvic procedures.

Symptoms of Subacute Bacterial EndocarditisMost patients present with a fever that lasts several days to 2 weeks. Nonspecific symptoms are common. Cough, shortness of breath, joint pain, diarrhea, and abdominal or flank pain may be present,anaemiaand blood in urine.About 90 percent of patients will have heart murmurs, but murmurs may be absent in patients with right-sided heart infections. A changing murmur is common only in acute endocarditis.

Diagnosis of Subacute Bacterial EndocarditisEndocarditis is suspected in a patient with a heart murmur and unexplained fever for at least one week, and in an intravenous drug abuser with a fever, even in the absence of hearing a murmur. A definitive clinical diagnosis requires blood cultures that grow bacteria. Echocardiography (ultrasound study of the heart) may visualize vegetations (growths) on heart valves.

Treatment of Subacute Bacterial Endocarditis

Cure of endocarditis requires eradication of all microorganisms from the vegetation(s), usually on the heart valve. Bacterial endocarditis almost always requires hospitalization for antibiotic therapy, generally given intravenously, at least at the outset. Most patients respond rapidly to appropriate antibiotic therapy, with over 70 percent of patients becoming afebrile (without a fever) within one week. Occasionally, therapy with oral antibiotics at home will be successful. Antibiotic therapy must usually continue for at least a month. In unusual cases, surgery may be necessary to repair or replace a damaged 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)

Complications

If bacterial endocarditis is not adequately treated, it can be

fatal. This is dependent on the infecting organism. Even

when treated, further damage to a heart valve may can to

heart failure. In addition, blood clots can form and travel

throughout the bloodstream to the brain or lungs.

In Adults, the new antibiotic regime recommended for the prevention of bacterial endocarditis is: Amoxycillin: 2.0 grams, 1 hour prior to the procedure (Four 500 mg tablets) For those patients allergic to penicillin, Clindamycin: 600 mg, 1 hour to the procedure (Four 150 mg tablets) The guidelines for Children are: Amoxycillin: 50 mg/kg, 1 hour prior to the procedure. For those patients allergic to penicillin, Clindamycin: 20

mg/kg, 1 hour prior to the procedure.

- Cannot use oral medications Ampicillin Adults, 2.0 g IM or IV ;Children, 50 mg/kg IM or IVwithin 30 minutes beforeprocedure.

Cephalexin or cefadroxil Adults, 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 are already receiving an antibiotic for a preexisting condition should receive an antibiotic for prophylaxis from a different classification. For example, a patient at risk already receiving penicillin for some other condition should receive another antibiotic for prophylaxis, such as clindamycin.

Antibiotic prophylaxis is recommended for patients with total joint replacements that are considered at increased risk of hematogenous total joint infection.

They are the following: • Previous history of prosthetic joint

infection • Immunosuppressed/

immunocompromised 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 only recommended during the first two years after surgery. Because of concerns about the severity of infection of a joint replacement, the American Academy of Orthopaedic Surgeons now recommends that antibiotics be given before an invasive dental procedure no matter how

long it has been since the joint replacement procedure.

The connection between subacute bacterial endocarditis and dental treatments

This infection is affected by two major factors; bacteraemias and cardiac lesions where there is turbulent blood flow. The main type of bacterium involved with this infection is Viridans streptococci (found in large numbers in the mouth, especially abundant with poor oral hygiene) Strep. Mutans and S.sanguis - causing 50% of cases, and Staphylococcus aureus.

Viridans streptococci can be released into the bloodstream during dental treatment such as tooth extraction and scale and polishes. However it can also enter the blood stream during home oral care such as flossing and brushing. In the majority of cases this causes no harm and no infection of the heart occurs however there are a variety of factors that increase the chances of acquiring infective endocarditis;-The number of the bacteria that are entering the blood stream.-Valvular diseases and cardiovascular diseases that are suffered.-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 endodontics beyond the root apex.. It is vital that the patient who is at risk of infective endocarditis is told to report back immediately if they suffer any symptoms which can appear as late as two months after treatment. If multiple treatments are required for a susceptible patient, then they should be at intervals of nine to fourteen days, this is necessary so as the bacteria does not become resistant to the antibiotics.

Dental procedures for which prophylaxis is recommended for high and 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 is anticipated.

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 care

The patient should keep his teeth and gums clean and healthy.This will prevent germs from entering the bblood stream through inflamed tissue and will prevent the need for most dental repairs or dentalsurgery.