Category Archives: Principles of Management and Prevention of Odontogenic Infections

Prophylaxis Against Total Joint Replacement Infection

Prophylaxis Against Total Joint Replacement Infection

Patients who have- undergone total replacement of a joint with a prosthetic joint may be at risk for hematogenous spread of bacteria and subsequent infection. These late. prosthetic joint infections result in severe morbidity,
because the implant is usually lost when infections occur. There has been great concern that the bacteremia caused by ‘.tooth extraction may result in such infection·s. However the recent literature suggests that bacteremias from . oral procedures do not cause prosthetic joint infections.
It appears that the bacteremia after oral surgery is of a transient nature and does not expose the implant and periimplant tissues to bacteria long enough to cause infection. Instead it appears that the hematogenous spread of prosthetic joint infections. is caused by chronic infections elsewhere in the body that result in chronic septicemias. These infections are typically urinary tract infections, pulmonary infections, and skin infections, hut established odontogenic infections may also cause a septicemia of sufficient magnitude to cause a total joint infection. In July of 1997 the American Dental Association (ADA) and the American Academy of Orthopedic  Surgeons (AAOS) issued a joint recommendation concerning the
management of patients with prosthetic total [oints. The recommendations of the ADA and MOS recognize that most patients with a prosthetic joint are not at risk for joint infection after a dental surgical procedure. Instead
the guidelines identify the high-risk patients who are ‘potentially  usceptible to such infections (Box 15-14). Likewise, it Identtfles those procedures that are most likely to cause joint infections and therefore require prophylaxis
(Box IS-IS). Finally, the joint statement recommends a specific antibiotic recommendation to help prevent infection in the susceptible patient who is undergoing one of the procedures that require prophylaxis (Table 15-5).
When the dentist decides to provide antibiotic prophylaxis for a patienf, the recommended antibiotics are first-generation cephalosporin: and ampicillin. For patients who are allergic to penicillin, clindamycin is recommended, ‘As with bacterial endocarditis prophylaxis, only a single preoperative dose is recommended, with no follow-up doses. If patients are unable to take oral rnedication, a parenteral regimen is also sugge-sted (Box 15-16). If a patient who has a total joint replacement needs treatment of an infection, aggressive therapy for’ the. infection is necessary to prevent seeding of the bacteria, causing odontogenic infection to the prosthetic joint . This aggressive treatment should include extraction, I&D, – and the use of high-dose bactericidal antibiotics, probably given IV. The clinician should strongly consider performing C&S testing, because if a prosthetic joint infection does occur, it would. be useful to know which bacteria is likely the culprit and its antibiotic sensitivity.

TABLE 15-5

Antihiotic Reginal Prophylaxis of Total joint Rcplaccrncat Infection

Regl~en Dose
Standard oral prophylaxis
f II \ I’ 111< I:;
First generation cephalosporin
2 G 1 hr before procedure’
Penicillin allergic oral prophylaxis
Parenteral prophylaxis
2 G 1 hr before procedure
600 mg 1 hr before procedure
1 G IV within 1 hr of procedure
IV, Intravenous.
600 mg IV within 1 hr of procedure

BOX 15-16

Indication for Parenteral Regimen

• Patient to have general anesthetic and NPO
• Unable to take oral medications
• High-risk patients, such as those with history of previous
bacterial endocarditis

Prophylaxis Against Infectious Endocarditis

Prophylaxis Against Infectious Endocarditis

Infectious endocarditis may be caused by bacteria that was ‘introduced into the circulation a~ a result of oral surgery  and that attached to sterile vegetation that exists on an abnormal heart valve. This vegetation can arise because of the turbulent flow around an incompetent heart valve. The turbulent flow causes loss of the surface endocardium, which exposes the underlying collagen. Platelets aggregate on the exposed collagen and, together with precipitated fibrin, form a sterile fibrin-platelet thrombus called This vegetation presents no. problems to the patient until it becomes infected with bacteria and produces bacterial endocarditis. When this occurs the patiemust be treated in the hospital with high doses of intravenous (IV) antibiotics for prolonged periods. Although initial recovery from bacterial endocarditis ‘approaches 100%, jecurrent episodes reduce the 5-year survival rate of patients with this disease to approximately 60%. Bacterial endocarditis resulting from introduction of ‘bacteria from an oral source is almost exclusively the result of alpha-hemolytic streptococci with typical antibiotic sensitivity patterns. Prophylaxis regimens against bacterial endocarditis after dental procedures are directed toward effective killing of Streptococcus organisms. The goals of , antibiotic prophylaxis in this case are to reduce the intensity of the bacteremia, assist the reticuloendothelial system in killing the bacteria, and decrease the bacterial adherence to the damaged heart valves and vegetations. The American Heart Association has had formal recommendations for the prevention of bacterial endocarditis after dental treatments sin ce 1960. The latest formal recommendation’s appeared in June 1997. When treating patients surgically, it is important that the dentist specifically inquire about cardiac valvular lesions that may predispose the patient to bacterial endocarditis. (Box 15-11). Antibiotic prophylaxis should be used when a dental procedure is performed- that will produce bleeding of the mucosa. Some procedures, such as tooth extraction and periodontal surgery, obviously cause’ bacteremias; however, vigorous dental prophylaxis’ should also, be included in this category (Box 15-12). ‘ Some procedures, such as supragingival tooth cleaning, placement and adjustment of orthodontic appliances,  typical restorative tooth preparation procedures, and conservative nonsurgical endodontic therapy,. do not require antibiotic prophylaxis (Box IS-B). These procedures do not cause bacteremias of sufficient intensity to
predispose the patient to endocarditis. Bacterial endocarditis prophylaxis ~ achieved for most routine conditions ~th the administration of 2 G of
amoxlcillln 1 hour before the procedure (Table 15-4). Amoxicillin is the drug of choice, because it is better absorbed from the’ gastrointestinal tract and provides higher and more ‘sustained plasma levels. Amoxicillin is
an effective killer of alpha-hemolytic streptococcus (i.e., Streptococcus viridansi, which is the organism that most commonly causes endocarditis ‘after dental procedures. The decision to recommend amoxicillin was not made to provide a broader antimicrobial spectrum. For patients who are allergic to penicillin, two alternative drugs have been recommended. The first recommended drug is clindamycin, with a dose of 600 mg orally
1 hour before the surgery. If the patient’s allergy topenicillin is mild and not of an anaphylactic type, first-generation cephalosporin can be prescribed. Either cephalexin ‘or cefadroxil is recommended. Although erythromycin is no longer recommended, the newer macrolide antibiotics’, azithromycin or clarithrornycin, are acceptable alternative drugs. Their chief disadvantage
is that they are more expensive than the other regimens. If the patient is unable to take oral medication, parenteral administration can be used.
For the pediatric patient, the dose of the drugs that are given must be reduced. The recommendations include, clear guidelines for these reductions (see Table 15.-4).



Metastatic infection is defined as infection that occurs at a location physically separate from the portal of entry ofthe bacteria. The classic and most widely understood example of this phenomenon is bacterial endocarditis, which arises from bacteria that can be introduced into
the circulation as a result of tooth extraction. The incidenceof metastatic infection can be reduced if antibiotic administration is used to eli minate the bacteria before they can establish an infection at the remote site.
For metastatic infection to’ occur, several conditions, must be met (Box 15-10). The first and most important is that there must be a susceptible location in which an infection can be established. The deformed heart valve
with its altered endothelial surface onto which a sterile vegetation has formed is an example of this. There also must be bacterial seeding of the susceptible area. This seedi. g occurs as the result of a bacteremia in which bacteria from the mouth are carried to the susceptible site. Most likely.a quantitative factor is involved in this seeding process, because the body has multiple episodes of small bacteremias as a result of normal daily
activities. More than likely, bacteremias with large quantities of bacteria are necessary to produce metastatic infection. The duration of the bacteremia may also playa role. In-some situations (e.g., total joint replacement) a prolonged high-level bacteremia, or septicemia, is usually
necessary to es tablish a metastatic infection. It is important to remember that the bacteremia after oral surgery is usually completely eliminated by the body’s reticuloendothelial system within 15 minutes after completion
of the surgery. Also neces sary for the establishment of metastatic
infection is som e impairment of the local host defenses.

Principle V: Use Shortest Antibiotic Exposure That Is Effective

Principle V: Use Shortest Antibiotic Exposure That Is Effective 

For the antibiotic prophylaxis to be effective, the antibiotic must be given before the surgery begins, and adequate plasma levels must be maintained during the surgical procedure. Once the surgical procedure is completed, continued antibiotic administration produces no benefit. Therefore the final dose of the antibiotic is usually given after the surgical operation. If the procedure is a short operation, a single preoperative dose of antibiotics is adequate: If the surgery lasts for 1 to 2 hours, the surgeon should give a second dose of antibiotics before the patient leaves the office. A plethora of animal and human clinical data demonstrates that the use of prophylactic antibiotics is necessary only for the time of surgery; after closure of the wounds-and formation of the blood clots, migration of bacteria into the
wound and underlying tissues occurs at such a low level that additional antibiotics are not necessary.

BOX 15-10

Factors Necessary for Metastatic Infection,
.Distant susceptible site
• Hematogenous bacterial seeding
• Impaired local defenses


Principle IV Time Antibiotic Administration Correctly

Principle IV Time Antibiotic Administration Correctly 

For the antibiotic to be maximally effective in preventing postoperative _infection the antibiotic must be given before the surgery begins. This principle has been dearly established in many animal and human clinical trials, ‘Antibiotic administration that occurs after surgery either is markedly decreased in its efficacy or has no effect that all on preventing infection
‘I~the surgery is prolonged and an additional antibiotic dose is required, intraoperative dose intervals should be shorter (i.e., one half the usual therapeutic dose interval). Therefore penicillin should be given every 2 hours,
cephalexin every 2 hours, and dindamycin every 3 hours. This ensures that the peak plasma levels will stay adequately high and avoids periods of inadequate antibiotic levels in the tissue fluids.

.Principle I: Procedure Should Have Significant Risk of Infection

Principle I: Procedure Should Have Significant Risk of Infection

For prophylactic antibiotics to reduce the incidence of infection, the surgical procedure must have a high enough incidence of infection to be reduced with antibiotic therapy. Clean sun.cry done with strict adherence to . basic surgical principles usually has an incidence of infection of about 3%. Infection rates of 10% or more are usually considered unacceptable, and the use of prophylactic antibiotics must be strongly considered. For the dentist doing routine office surgery, this means that most office procedures performed on healthy patients do not require prophylactic antibiotics. The incidence of infection after tooth extraction, frenectomy, biopsy, minor alveoloplasty, and torus reduction is extremely low; therefore antibiotics
would provide no benefit. • liowever, several surgical factors may influence the dentist  o consider strongly the use of antibiotic prophylaxis
(Box 15-9):  The first and most obvious factor that may lead0to infection is a bacterial inoculum of sufficient size. The usual surgical procedure performed in the mouth rarely involves sufficient bacterial inoculation to cause infection. The second factor is surgical procedures that are rather
extensive ami require prolonged surgery. The incidence of infection increases both with the extent of surgery and with longer surgical procedures. A third factor that may suggest the use of antibiotics is the insertion or presenceof a foreign body, most commonly a dental implant.  Most data seem to suggest that the use of antibiotics may decrease the incidence of infection when foreign bodies,  such as dental implants, are inserted into the jaws. The final and most important factor for most dentists
in determining which patients should receive prophylactic antibiotics is whether the patient has depressed host defenses. Patients who have a compromised ability to defend themselves against infection should probably receive prophylactic antibiotics because they are likely to have a higher incidence of more severe infection. All patients receivingcancer chemotherapy or immun suppressives  hould receive prophylactic antibiotics, even

Principle I: Procedure Should Have Significant Risk of Infection

Principle I: Procedure Should Have Significant Risk of Infection

For prophylactic antibiotics to reduce the incidence of infection, the surgical procedure must have a high enough incidence of infection to be reduced with antibiotic therapy. Clean sun.cry done with strict adherence to . basic surgical principles usually has an incidence of infection
of about 3%. Infection rates of 10% or more are usually considered unacceptable, and the use of prophylactic antibiotics must be strongly considered. For the dentist doing routine office surgery, this means that most office procedures performed on healthy patients do not require
prophylactic antibiotics. The incidence of infection after tooth extraction, frenectomy, biopsy, minor alveoloplasty, and torus reduction is extremely low; therefore antibiotics  would provide no benefit. • liowever, several surgical factors may influence the dentist to consider strongly the use of antibiotic prophylaxis (Box 15-9): The first and most obvious factor that may lead to infection is a bacterial inoculum of sufficient size. The
usual surgical procedure performed in the mouth rarely involves sufficient bacterial inoculation to cause infection. The second factor is surgical procedures that are rather extensive ami require prolonged surgery. The incidence of infection increases both with the extent of surgery and
with longer surgical procedures. A third factor that may suggest the use of antibiotics is the insertion or presenceof a foreign body, most commonly a dental implant. Most data seem to suggest that the use of antibiotics may
decrease the incidence of infection when foreign bodies, such as dental implants, are inserted into the jaws. The final and most important factor for most dentists in determining which patients should receive prophylactic
antibiotics is whether the patient has depressed host defenses. Patients who have a compromised ability to defend themselves against infection should probably receive prophylactic antibiotics because they are likely to have a higher incidence of more severe infection. All patients receiving cancer chemotherapy or  supressives should receive prophylactic antibiotics, even when minor surgical procedures are performed. Patientsreceiving immunosupprcsstves for organ transplant will be taking these drugs for the remainder of their lives and should be given preventive antibiotics accordingly. Patients receiving cancer chemotherapy will receive cytotoxic
drugs for 1 year or less but should be given prophylactic antibiotics for at least 1 year after the cessation of their chemotherapy.

Principle VIII: Evaluate Patient Frequently

Once the patient has been treated by surgeiy and.antiblotic therapy has been prescribed, the patient” should be 0  followed up carefully to monitor response to treatmentand complications. In most situations the patient should 0be asked to return to the dentist 2 days after the origihal therapy. Typically the patient is much improved. If therapy is successful, swelling and pain decreases dramatically. The dentist should check the I&D site to determine whether the drain should be removed at this time. Other
parameter  s, such as temperature, trismus, swelling, andthe” patient’s subjective feelings of improvement, should also be investigated. ”
“If there is not an adequate response to treatment, the patient should be examined carefully for clues to the reasonfor failure (BOX 15-7). The most common cause of treatment failure is inadequate surgery. A tooth may have
to be reevaluated for extraction, or a fluctuant area not “obvious at the first treatment may have to be incised

BOX 15-7

Reasons for Treatment Failure

• Inadequate surgery
• Depressed host defenses
• Foreign body
• Antibiotic problems
• “p~tient noncompliance
• Drug not reaching site
• Drug dose too low
• Wrong bacterial diagnosis
• Wrong antibiotic •

A second reason for failure is depressed host defense mechanisms. A review of the patient’s medi,cal history should be performed and more careful probing questions asked. Local defense mechanism depression by things
such as dehydration and pain should also be considered and corrected if necessary. A third reason for treatment failure is the presence of a foreign body. Although this is unlikely in an odontogenic infection, the dentist may consider taking a periapical radiograph of the area to help ensure that a foreign .body is not present. . Finally, there may be problems with th. antibiotic that was given to the patient. The dentist firs, ascertains if the
patient has bee n compliant. The patient must have the prescription filled and take the antibiotic according to directions. Many patients fail to follow the orders of their . dentists as carefully as they should. Another problem to
consider is whether the antibiotic reached the infected area. Failure to reach the area may be related to inadequate surgery, inadequate blood supply to the local area, or it dose that is too low to be effective against the bacteria. Another antibiotic-related problem is an incorrect bacterial
diagnosis . If a culture Was not performed ‘at the initial surgical treatment or if no surgical treatment was done at the initial therapy, the dentist should obtain a pus spec. Imen for culture and antibiotic sensitivity testing. Finally, it is possible that the wrong antibiotic was prescribed for
the infection, which’ may be because of an inaccurate bacterial diagnosis or an unusual antibiotic resistance of typical bacteria. For example, Prevotella organisms are usually resistant to penicillin, but rarely cause persistent infection if penicillin 15given and surgery is done. However, if the
patient has a persistent, low-grade infection that does not resolve, prescribing an antianerobic antibiotic such as ctindamycin would be appropriate. • The clinician must also examine the patient to look
specifically for  toxicity reactions and untoward side effects.Patients may report complaints ‘such as nausea and abdominal cramping but may fail to associate watery diarrhea with the drug administration. Specific questioning about the expected toxicities is important to their early recognition. The dentist should also be aware of the possibility of
secondary or superinfections. The most common secondaryinfection encountered by denttsts is oral or vaginal candidiasis. This is the result of an overgrowth of Candida organisms, because the normal oral flora has been altere : by the -antlblotic therapy. Other secoridary infections
may arise as normal host flora is altered, but they are not seen with any degree of frequency in the management of odontogenic infections.
Finally, the dentist should follow the patient carefully once the infection has resolved, to check for recurrent infection. This would be-‘seen in a patient who had incomplete therapy for the infection. A variety of reasons
may acc ount for this. For-example, the patientmay have stopped taking the antibiotics. too early. The drain- may’ have been removed too early and the drainage site sealed too early, which reestablished the infectious process. If
infection does recur , surgical intervention and reinstitutionof antibiotic therapy should be considered.

Principle vii: Administer Antibiotic Properly

Principle vii: Administer Antibiotic Properly

Once the decision is made to prescribe an antibiotic to .the patient, the drug should be administered in the proper dose and at the proper dose interval. The manufacturer usuallyrecommends the proper dose. It is adequate to provide plasma levels that are sufficiently high to kill the bacteria that
are sensitive to the antibiotic but are not so high as to causetoxicity. The peak plasma level of the drug should usually be at least 4 or 5 times the minimal inhibitory concentration for the bacteria involved in the infection.
Likewise, the clinician must admin ister the antibioticat the proper interval. This interval is usually recommended by the manufacturer and.Is determined by the plasma half-life of the drug. The interval is usually 4
times the plasma half-life of the drug. Strict adherence to this interval is critical with the bacteriostatic antibiotics but is much less important with bactericidal antibiotics, because bacteria exposed to bactericidal antibiotics will die from a defective cell wall, but those exposed to acteriostatic  antibiotics can resume protein synthesis once the antibiotic is gone. It is clear that patients stop taking their antibiotics after acute symptoms have subsided and rarely take their drugs as prescribed after 5 or 6 days. Despite what the pre~ scription says, patients rarely take antimicrobial agents as.  prescribed longer than 3 or 4 days. Therefore the antibiotic that would have the highest compliance would be the drug that could be given once a day for 4 or 5 days. When antibiotics are given, they should be given for an adequate period. The traditional recommendation has been to continue antibiotic therapy for 2 to 3 days after the infection has resolved. In clinical terms this means that the patient, who has been treated with both surgery “and antibiotics, will usually have dramatic improvement in symptoms by the se{ond day, and by the fourth day
.will be reasonably asymptomatic. Antibiotics should then be administered for an additionaf2 0 days, for a total of 6 days. Most mild odontogenic
infections that are treated on an outpatient basis can usually
be managed with a prescription for antibiotics suffident for 6 or 7 days. ,
In some situations no surgical” therapy (i.e., no endodontics or extraction) is provided. In these situations, resolution of the infection willtake longer. Therefore the prescriptton should be written for 9 or lQ days of
antibiotics. Additional administration of antibiotics may be necessary
in some infections that do not resolve as rapidly. It is important for the clinician to make it clear to the patient that the entire prescription should be taken. If for some reason the patient is advised t~ stop taking the
antibiotic early, all remaining pills or capsules should be discarded. Keeping small amounts of unused antibiotics in medicine cabinets for the anticipated sore throat next winter should be strongly discouraged. Casual selfadministration  of antibiotics is not useful and may be hazardous
to the health of the individual and community.

Principle VI: Choose and Prescribe Appropriate Antibiotic

Principle VI: Choose and Prescribe Appropriate Antibiotic 

Choosing the appropriate antibiotic for treating an odontogenic infection must be done carefully. When all factors are weighed, the clinician may decide that no antibiotic is necessary at all, whereas in other situations, broad-spectrum  or even combination antibiotic therapy may be necessary.
A variety of factors pust be considered when  hoosing an antibiotic from the nearly 70 antibiotics currently available. Antibiotics must be viewed as a
double-edged sword. Although appropriate use may resultin dramatic resolution and cure of patients with infeclions, misuse of antibiotics provides little benefit to offset the associated risks and expense of antibiotic administration.  Therefore the following guidelines are. recommended
for consideration when choosing a specific antibiotic. Determine need for antibiotic admlnlstratlon, It isa common misconception that all infections, by definition, require antibiotic administration; this is not necessarily
the case. In some situations antibiotics are not useful and, in fact, may be contraindicated. In making this determination, three factors must be considered: The first factor is the seriousness of the infection when the
patient comes to the dentist. If the infection has modest swelling, has progressed rapidly, or is a diffuse cellulitis, the evidence would support the use of antibiotics in addition to surgical therapy. The second factor is
whether adequate s urgical treatment can be achieved. In many situations extraction of the offending’ tooth may result in rapid resolution, of the infection. However, in other situations, remoqal of the tooth may not be possible. Antibiotic therapy is important to control the infection
so that the tooth can be removed. The third consideration is the state of the patient’s host defenses. A young, healthy- patient may be able to mobilize host defenses and need less antibiotic therapy for resolution of the infection. On the other hand, patients who have any type of decreased host resistance, such as those with evere metabolic disease or those receiving cancer. chemotherapy, may require vigorous antibiotic therapy
for even minor infections. When these three factors are balanced, several definite indications for antibiotic use in dentistry become clear
(Box 15-3). The first and most common indication is thepresence of an acute-onset infection with diffuse swelling  and msderate-to-severe pain. This intccuon xuxuallv in the cellulitis stage, and, with appropriate .anttbtonc tilerapy and treatment of the offending tooth, rapid resolution
is expected. The second indication is almost any type of infection in a patient who is medically compromised. Such patients who have infections df any severity should be ‘considered candidates for antibiotic administration. The third indication for antibjotic therapy {s the presence
of an infection that has progressed to involvement of extra oral fascial spaces. In these situations the infection is aggressive enough to have spread beyond the mouth, indicating that the host defenses are inadequate to contain the infection. The fourth indication is severe pericoronitis,
with tem peratures higher than 100° F, trismus,and some swelling of the lateral ‘aspect of the face, which occurs most commonly around impacted mandibular third molars. Finally, the patient who has osteomyelitis
requires ant abiotic therapy in additionto surgical therapy to achieve resolution of the infection. Based on the same three criteria, antibiotic therapy would not be indicated or is even contraindicated in other situations (Box 15-4). The first is a minor, chronic, well;localized abscess for which an I&D and ‘treatment of , the offending tooth result in rapid resolution, assuming • that the patient’s host defenses are intact and that the
patient has no other compromising conditions. A second, albeit Similar, contraindication is a very well-localized vestibular abscess, with little or no  ‘facial swelling. In t hese situations the tooth can be opened and necroticpulp removed or the tooth extracted and the abscess incised and drained, which will result in rapid resolution in most patients. Third. is a localized alveolar osteitis, or dry socket. Treatment of the dry socket is primarily palliative, and it is not treated as an infection. Fourth,
patients who have mild pericoronitis with minor gingival edema and mild pain do not require antibiotics for resolution of their infection. Irrigation with hydrogen peroxide or chlorhexidine will result in resolution.
In summary, antibiotics  should be used When clear evidenceexists of bacterial invasion into underlying tissues that is greater than the host defenses can, withstand. Patients who have an impaired ability to defend them  selves against infection and patients who have infectionsthat are not amenable to surgical treatment should be considered for antibiotic therapy. Antibiotics should not be used when no evidence of bacterial involvement is found. Antibiotics do not hasten wound healing and do not ‘provide any benefit- for nonbacterial conditions. ‘Patients who have inflammatory pulpitis will have severe

BOX 15-3

Indications for Use of Antibiotics

• Rapidly progressive swelling
• Diffuse swelling ,
• Compromised host defenses
‘. Involvement of fascial spaces.
• Severe pericoronitis
• Osteomyelitis

BOX 15-4

Situations in Which Use of Antibiotics Is Not Necessary

• Chronic weir-localized abscess
• Minor vestibular abscess
• Dry socket
• Mild pericoronitis

pain. but the pain results from local inflammatory reaction within the pulp. not from bacterial infection. These patients should not be given antibiotic therapy. U\(‘ empirical tilewp)’ routinely. Odontogenic infections are caused by a highly predictable group of bacteria. Additionally, the antibiotic sensitivity of these organisms is well known and consistent. As a result the use of C&S testing is not necessary for routine odontogenic infections. The bacteria that cause more than 90% of odontogenic infections
are aerobic streptococci and anaerobic streptococci, peptostreptococci, Prevotella, and Fusobacterium. Many other species of bacteria are also involved, but they appear to be  opportunistic rather .than causative bacteria. Fortunately the antibiotic susceptibility of the causative bacteria is remarkably consistent. The orally administered antiblotics that are
effective against odontogenic infections include penicillin, amoxicillin, clarithromycin, .clindamycin, cefadroxil, metronidazole, and doxycycline (BOX 15-5). These antibiotics are effective against streptococc i(except metronidazole) and oral anaerobes. Several relatively -important variations can be found within the group. (See Appendix IX for detailed description of the various antibiotics.)  ecause the microbiology and antibiotic sensitivity is well known, it is a reasonable therapeut c maneuver to use one of these antibiotics empirically, that is, to give the  ntibiotic with the assumption that an appropriate.drug is being given. The drug of choice is usually pentcilltn. Alter- -native drugs for use in the penicillin-allergic patient are clarithromycin and clindamycin. The cephalosporin cefadroxil is a useful drug when a broader antibacterial . spectrum is necessary. The cephalosporins should be used with caution in penicillin-allergic patients, because they may also be allergic to the cephalosporins. Doxycycline is
another useful alternative, although some strains of bacteria are resistant to the tetracyclines. Metronidazole is useful only against anaerobic bacteria and should be reserved for situations in which only anaerobic bacteria
are suspected (or in combinatiqn with an antibiotic that has antiaerobic activity such as penicillin). It is ‘clear that patients often, if not usually, fail to take the medication in the way in which it was pre- • s cribed. In fact, Socrates in 400 Be cautioned physiciansto be aware that patients will lie about taking the medications prescribed Hard data exist from many studies that demonstrate that patient compliance decreases with increasing num-

BOX 15-5

Effective Orally Administered Antibiotics Useful for Odontogenic Infections

• Penicillin
• Erythromycin
• Clindamycin
• Cefadroxil
• Metronldazole
• T~tracycline

BOX 15-6

Indications for Culture and Antibiotic Sensitivity Testing

Rapidly spreading infection
• Postoperative infection
• ‘Nonresponsive infection
• Recurrent infectl9n
• Compromised host defenses

penicillin will kill streptococci and oral anaerobic bacteria but will have little effect on the staphylococci of the skin” and almost no effect on gastrointesttnal tract bacteria. As a result, penicillin has little or no effect on the gastrointestirial tract and does not expose a multitude of other bacteria to the opporturrity to develop resistance. By contrast, drugs such as tetracycline are broad spectrum antibiotics, inhibiting not only the streptococd and oral anaerobes bat also a variety of gram-negative
rods. Thus when this antibiotic is given, it has an effect on skin and gastrointestinal bacteria that may result in problems caused by alterations of host flora and overgrowth of resistant bacteria. In addition, broad-spectrum antibiotics provide a multitude of bacteria the opportunity
to develop resistance. In summary, antibiotics that have narrow-spectrum
activity against the causative organisms are just as effective as antibiotics’ that have broad-spectrum activity, without the problems of upsetting normal host microflora populations and increasing the chance of- bacterial
resistance. Use antibiotic with lowestincidence of toxicity and side effects. Most antibiotics have a variety of toxicities and side effects that limit their usefulness. These range from mild to so severe that the antibiotic cannot be used in clinical practice. The antibiotics usually used for odontogenic
infections have a surprisingly low incidence of toxicity-related problems: It is important, however, for the clinician to understand” the probable toxicities and side effects of the drugs they use. Allergy is penicillin’s major side effect. Approximately “2% or 3% of the total population is allergic to penicillin. Patients who have allergic reactions to penicillin, as exhibited by hives, itching, or wheezing, should not be given penicillin again. Penicillin does not have other major side effects or toxicities in the normal dose range
used by dentists. Likewise, clarithromycin, erythromycin, and  .c1indamycin have a low incidence of.toxiciry and side  effects. Clindamycin may cause a severe diarrhea state called pseudomembranous colitis. Several other drugs, such as ampicillin and the oral cephalosporins, also cause this problem. The elimination of much of the anaerobic gut . flora allows the overgrowth of an antibiotic-resistant bacteria, Clostridium difticile. This bacteha produces toxins
that injure the gut wall, which results in colitis. Patients who take clindamycin, amoxicillin, or cefadroxil should be warned of the possibility of profuse watery diarrhea and told to contact their prescribing dentist if it occurs. The oral cephalosporins are associated with only mild
toxicity problems. As with penicillin, the cephalosporins may cause allergic reactions. They should be given cautiously to patients with penicillin allergies, because these patients may be allergic to the cephalosporins also.
Patients who have experienced an anaphylactic type of • reaction to penicillin should not be given a cephalosporin because of increased chance for that life-threatening event to occur again. The tetracycllnes . have minor toxicities’ for most patients (i.e., the commonly encountered gastrointestinal problems of nausea, abdominal cramping, and diarrhea).