Identification of bacteria in acute endodontic infections and their antimicrobial susceptibility

Saengusa Khemaleelakul, J. Craig Baumgartner, Sumalee Pruksakorn

Research output: Contribution to journalArticlepeer-review

101 Scopus citations


Objective. The purpose of the study was to identify the bacterial composition of the microbiota from acute endodontic abscesses/cellulitis and their antimicrobial susceptibilities. Study design. Purulence from 17 patients with acute endodontic abscesses/cellulitis was obtained by needle aspiration and processed under anaerobic conditions. Bacteria were isolated and identified by biochemical or molecular methods. The antimicrobial susceptibility of isolated bacteria was determined by using the Etest. Results. All 17 aspirates contained a mix of microorganisms. A total of 127 strains of bacteria were isolated. Of 127 strains, 80 strains were anaerobes and 47 strains were aerobes. The mean number of strains per sample was 7.5 (range, 3 to 13). The average number of viable bacteria was 6.37 × 107 (range, 104 to 108) colony-forming units/mL. Strict anaerobes and microaerophiles were the dominant bacteria in 82% (14 of 17) of the cases. The genera of bacteria most frequently encountered were Prevotella and Streptococcus. Prevotella and Peptostreptococcus were frequently found to dominate the mixture. The combination of Prevotella and Streptococcus was found in 53% (9 of 17). The previously reported uncultured Prevotella clone PUS9.180 was frequently identified. The percentage of bacteria susceptible/intermediate for each antibiotic in this study was penicillin V, 81% (95 of 118); metronidazole, 88% (51 of 58); amoxicillin, 85% (100 of 118); amoxicillin + clavulanic acid, 100% (118 of 118); and clindamycin, 89% (105 of 118). Conclusions. The present results confirm the existence of mixed infection with the predominance of anaerobic bacteria in acute endodontic abscesses/cellulitis. The frequency of uncultured Prevotella clone PUS9.180 suggests the possible key role of this Prevotella species in acute endodontic infections. Penicillin V still possesses antimicrobial activity against the majority of bacteria isolated from acute endodontic infections. However, if penicillin V therapy has failed to be effective, the combination of penicillin V with metronidazole or amoxicillin with clavulanic acid is recommended. Switching to clindamycin is another good alternative.

Original languageEnglish (US)
Pages (from-to)746-755
Number of pages10
JournalOral surgery, oral medicine, oral pathology, oral radiology, and endodontics
Issue number6
StatePublished - 2002
Externally publishedYes

ASJC Scopus subject areas

  • Surgery
  • Oral Surgery
  • Otorhinolaryngology
  • Dentistry(all)


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