General Guidelines for Use of Antimicrobial Agents

Since periodontal infections are generally mixed anaerobic and facultative anaerobic infection, identifying the causative organisms in the subgingival flora and determining their antimicrobial susceptibility is helpful in selecting the proper antimicrobial therapy. Identification can be done by culture or DNA probing methods (45). Cultures should also be taken after therapy to ensure eradication of pathogens.

Antimicrobials utilized in odontogenic infections can be divided into broad and narrow spectrum. Many patients can be treated with narrow spectrum antimicrobials. However, three categories of patients need to be treated with broad spectrum antimicrobials to prevent failure and complications: patients infected by resistant bacteria (48,49), and those with underlying serious medical conditions or are suffering from a severe dental infection. The risk factors prompting use of broad spectrum agents are listed in Table 4.

Narrow spectrum antimicrobials include penicillin, amoxicillin, cephalexin, the macro-lides (erythromycin, clarithromycin, and azithromycin), and the tetracyclines (including doxycycline). These agents have a limited antimicrobial efficacy as they are not effective against aerobic and anaerobic beta-lactamase producers as well as other specific organisms.

Broad spectrum antimicrobials or antimicrobial combinations include clindamycin, the combination of a penicillin (i.e., amoxicillin) plus a beta-lactamase inhibitor (i.e., clavulanate), tigecycline and carbapenems and the combination of metronidazole plus penicillin, amoxicillin or a macrolide (31). These possess a broad spectrum of activity against most odontogenic pathogens including aerobic and anaerobic beta-lactamase producers. Furthermore, some of these agents (clindamycin and amoxicillin-clavulante) provide better pharmacokinetic and pharmacodynamic indexes against the odontogenic pathogens compared to the other agents (48,49). Pharmacokinetic and pharmacodynamic indexes of each antimicrobial can predict their clinical efficacy by considering their concentrations at the site of the infection and the susceptibility of the pathogens.

The choice between broad and narrow spectrum antimicrobials should be individualized in each patient. Utilization of broad spectrum antimicrobial can ensure efficacy against all potential pathogens especially those resistant to antimicrobials.

Anti-infectives should be given a chance to work. Improvement may take time and therefore therapy should not be changed until it is given for at least 48 to 72 hours. The short-term

TABLE 4 Risk Factor Prompting Use of Broad Spectrum Agents

Conditions that may increase the risk of infection with antimicrobial resistant organisms Recent antimicrobial therapy or prophylaxis (within the past six weeks)

Close contact with individual(s) recently treated with an antimicrobial. (i.e., household, school, daycare center)

Failure of first line antimicrobial

Direct or indirect exposure to smoking

Antimicrobial resistance high in the community

Winter season

Increased risk of infection due to medical history or condition The young (<2 years) and the old (>55 years) Serious, complicated, or spreading infection

Malignancy (i.e., leukemia, Hodgkin's disease, other hematological malignancies) Metabolic disorder (i.e., out-of-control diabetes mellitus, hemodialysis patients) Immunosupression (congenital or acquired)

Drug-related immunosuppression (i.e., corticosteroids, immunosuppressants, cytotoxic agents, cancer chemotherapy) Other conditions that are associated with immunosuppression (i.e., Radiotherapy/osteoradionecrosis of head and neck, transplant patients, neutropenia, granulocytopenia, patients with an indwelling intravascular catheter, those with immunocompromising procedures)

use of an anti-infective, effective as it may be, may not produce long-term results because the patient may become re-infected.

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