Bacteriology and treatment of dental infections.

The microbiologic and therapeutic aspects of sixty-one cases of pyogenic dental infection were studied through the use of modern anaerobic culture methods. Forty-five (74 percent) patients had anaerobic infections. Among them, eighteen (29.5 percent) had Bacteroides fragilis, of which six were resistant to penicillin at 16 microgram/ml. but all were susceptible to clindamycin at less than 2 microgram/ml. Of twenty-five patients treated with 4 to 20 million units of penicillin per day, twenty were cured and did not suffer relapse. The five patients in whom treatment failed had mandibular fractures infected with B. fragilis. Of ten patients treated with clindamycin (600 mg. intravenously every 6 hours), which included five patients with B. fragilis infections, all were cured. The presence of B. fragilis in dental infections has not been recognized. Dental infections associated with mandibular fracture that fail to respond to conventional penicillin therapy should be routinely cultured for B. fragilis.