Shunsuke Uemura

Microbiological evaluation of odontogenic infections associated with abscess formation

The microbiological characteristics of 90 patients with odontogenic closed abscesses were studied retrospectively during the 4-year period from January 1992 to December 1995. Of 64 specimens obtained by needle aspiration before antimicrobial therapy, 51 (80%) showed bacterial growth. A total of 279 bacterial strains, consisting of 236 (84.6%) anaerobes and 43 (15.6%) aerobes, were isolated, with an average of 4.7 anaerobes and 0.8 aerobes per specimen. A total of 152 (54.5%) anaerobic gram-negative rods were isolated. Anaerobic bacteria were isolated from 49 (96.1%) of 51 specimens. About 88% of specimens were polymicrobial.The predominant anaerobes isolated were Fusobacterium nucleatum (12.5%), blackpigmented anaerobic gram-negative rods (15.8%), Peptostreptococcus micros (11.1%), and Eubacterium spp.(10.4%). Of 26 specimens obtained after antimicrobial therapy, 22 (85%) had bacterial growth. The bacteria isolated after antimicrobial therapy were almost similar to those isolated before antimicrobial therapy.Susceptibility testing demonstrated that Peptostreptococcus micros and Eubacterium spp. were susceptible to a wide range of antibiotics, including chloramphenicol, minocycline, clindamycin, and β-lactams. Most anaerobic gram-negative rods were sensitive to chloramphenicol, minocycline, and clindamycin, and about 28% were resistant to β-lactams.These results indicate that odontogenic infections associated with abscess formation are usually polymicrobial, caused by mainly anaerobic gram-negative rods, gram-positive cocci, and rods accompanied by aerobic gram-positive cocci.