ANTIMICROBIAL SUSCEPTIBILITY TESTING,THERAPY Susceptibility to Antimicrobial Agents in Fusobacterium Strains Isolated From Healthy Humans and Patients with Periodontal Disease in Brazil A.C.N.R. Pestana, A.A.P. Oliveira, J.E. Costa, J.R. Nicoli, M.A.R. Carvalho, and L.M. Farias* Laborato Ârio de Microbiologia Oral e Anaero Âbios, Departamento do Microbiologia, Instituto de Cie Ãncias Biolo Âgicas, Universidade Federal de Minas Gerais, Av. Anto Ãnio Carlos 6627, Belo Horizonte, Minas Gerais, Brazil Key Words: Fusobacterium sp., periodontal disease The genus Fusobacterium is among the most common of anaerobes found in the microbiota of humans and animals, being frequently isolated from various sites of the healthy oral cavity. A significant characteristic of indigenous microorganisms is their opportunistic role: they are important in maintaining the health of the host but, on the other hand, may be implicated as opportunistic pathogens, causing infectious diseases. The pathogenicity of Fusobacterium strains is imputed, mainly, to their participation in the development and establishment of periodontal diseases. Among micro- bial groups associated with pathogenesis. The genus Fusobacterium is frequently involved in infectious diseases that occur in other sites of the body [1±3]. Reports concerning antimicrobial agents' susceptibil- ity patterns, occurrence of resistance and specific resistance markers in periodontal pathogens are rare, mainly considering strict anaerobes and the genus Fusobacterium. Based on the need for such knowledge which would help physicians to direct safer anti- microbial therapy in infectious diseases involving these bacteria, this work was carried out to establish susceptibility patterns to relevant drugs in Fusobacter- ium strains isolated from the oral cavity of healthy humans, compared to those isolated from patients with periodontal disease. A total of 62 Fusobacterium strains, isolated on Omata-Disraeli agar [4] from healthy human subgingival plaque (n =30) and from patients with periodontal disease (n = 30) in the Clõ Ânica de Periodontia da Faculdade de Odontologia da UFMGY, identified and kept in our laboratory in the nitrofreezer at 71968C, were tested for susceptibility to clindamycin, metronidazole (Sigma Chemical Co., *Corresponding author. Tel.: +55 31 499 2743; Fax: +55 31 499 2730; E-mail: acnrp@mono.icb.ufmg.br 1075±9964/99/030473 + 03 $30.00/0 # 1999 Academic Press Anaerobe (1999) 5, 473±475 Article No. anae.1999.0265