Anaerobe 11 (2005) 231–237 Oral and dental bacteriology and infection Characterization of Actinomyces species isolated from failed dental implant fixtures Nanna Sarkonen a,Ã , Eija Ko¨ no¨ nen a,b , Erkki Eerola c , Mauno Ko¨ no¨ nen d,e,b , Hannele Jousimies-Somer a,1 , Pekka Laine d a Anaerobe Reference Laboratory, Department of Microbiology, National Public Health Institute (KTL), Mannerheimintie 166, FIN-00300 Helsinki, Finland b Faculty of Dentistry, Kuwait University, Kuwait c Department of Microbiology, University of Turku, Turku, Finland d Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital e Department of Stomatognathic Physiology and Prosthetic Dentistry, Institute of Dentistry, University of Helsinki, Helsinki Received 6 August 2003; received in revised form 12 October 2004; accepted 8 January 2005 Available online 7 April 2005 Abstract In the oral cavity, Actinomyces form a fundamental component of the indigenous microflora, being among initial colonizers in polymicrobial biofilms. However, some differences may exist between different species in terms of their attachment not only to teeth but also to biomaterials. In this study we investigated the distribution of Actinomyces in 33 dental implant fixtures explanted from 17 patients. The identification was based on comprehensive biochemical testing and gas–liquid chromatography and when needed, 16S rRNA sequencing. Actinomyces was the most prevalent bacterial genus in these failed implants, colonizing 31/33 (94%) of the fixtures. Proportions of Actinomyces growth of the total bacterial growth in the Actinomyces-positive fixtures varied from 0.01% up to 75%. A. odontolyticus was the most common Actinomyces finding, present in 26/31 (84%) Actinomyces-positive fixtures. Actinomyces naeslundii and A. viscosus were both detected in 10/31 (32%) and A. israelii in 7/31 (23%) fixtures. Other Actinomyces species, including A. georgiae, A. gerencseriae and A. graevenitzii, were detected less frequently. Our results suggest that Actinomyces species are frequent colonizers on failed implant surfaces, where A. odontolyticus was the far most prominent Actinomyces species. r 2005 Elsevier Ltd. All rights reserved. Keywords: Actinomyces species; Bacterial colonization; Implant failure 1. Introduction The genus Actinomyces embraces a heterogeneous group of anaerobic and facultatively anaerobic, Gram- positive, mainly branching rods which, on one hand, occur as frequent inhabitants on mucosal surfaces of the human body and, on the other hand, as participants in various infectious processes at different body sites [1,2]. In the oral cavity, Actinomyces are particularly involved in the early plaque development on tooth surfaces [3,4] but also in the developing microbiota of infants [5]. The significance of Actinomyces species is based on their capability of adhering to deposits as well as on their coaggregating properties with other bacteria [6–8]. Early colonization of the tooth surface starts by adhesion of salivary bacteria to the pellicle. Certain Streptococcus and Actinomyces species predominate in this early plaque formation and colonize first on tooth and/or mucosal surfaces providing a substrate for the adherence of more fastidious plaque microbes, including Gram-negative, strictly anaerobic bacteria [8,9]. The ARTICLE IN PRESS www.elsevier.com/locate/anaerobe 1075-9964/$-see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.anaerobe.2005.01.002 Ã Corresponding author. Tel.: +358947448254; fax: +358947448238. E-mail address: nanna.sarkonen@ktl.fi (N. Sarkonen). 1 Deceased in June 2002.