β-Lactamase characteristics of oral anaerobes isolated from odontogenic infections were investigated. When 96 specimens from odontogenic infections were studied, the isolation frequencies of Prevotella, Peptostreptococcus and Streptococcus milleri group were 22.6%, 19.8%, and 15.1% respectively. Of 96 specimens, the cases of mixed infection (aerobes + anaerobes) were 63 (65.6%) and the mono-infection by anaerobes was 19 (19.8%) . The percentage of isolation of Prevotella spp. or PeptostreptoGoccusspp. was high in comparison to the mono-infection by anaerobes.
Of these anaerobes, 39% of Prevotella intermedia and 20% of Prevotella melaninogenica were positive for β-lactamase using the acidometry method. Furthermore, in 4 of 11 P. intermedia, β-lactamase activity increased greatly in the strain when ampicillin was used as substrate after the induction by cefoxitin.
Based on these findings, it was suggested that the anaerobes producing β-lactamase may be an indirect pathogen for odontogenic infection.
