Searching for Helicobacter pylori and Chlamydia pneumoniae in primary endodontic infections Isabela N. Rôças1 José F. Siqueira Jr1 AbstrA tc Objectives: The purpose of this study was to search samples from primary endodontic infections for the presence of two common human bacterial pathogens - Helicobacter pylori and Chlamydia pneumoniae. Methods: Genomic DNA isolated from samples taken from 25 root canals of teeth with asymptom- atic (chronic) apical periodontitis and 25 aspirates from acute apical abscess was initially amplified by the multiple displacement amplification approach and then used as template in species-specific polymerase chain reaction (PCR) for detection of H. pylori and C. pneumoniae. Results: All clinical samples were positive for the presence of bacterial DNA. However, no clinical sample was positive for either H. pylori or C. pneumoniae. Conclusions: Neither H. pylori nor C. pneumoniae were found in samples from primary endodontic infections. These findings suggest that these species are not candidate endodontic pathogens and that the necrotic root canal does not serve as a reservoir for these human pathogens in healthy pa- tients. (Eur J Dent 2012;6:158-162) Key words: Helicobacter pylori; Chlamydia pneumoniae; apical periodontitis; acute apical abscess; polymerase chain reaction IntroducIon Endodontic infections establish in root canals devoid of vital pulp tissue, which may occur be- cause of pulp necrosis or pulp removal for treat- ment. The infection may spread locally to cause 1 Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, BRAZIL Corresponding author: Dr. José F. Siqueira Jr Faculty of Dentistry, Estácio de Sá University, Av. Alfredo Baltazar da Silveira, 580/cobertura, Recreio, Rio de Janei- ro, 22790-710, RJ, BRAZIL e-mail: jf_siqueira@yahoo.com; siqueira@estacio.br 158 European Journal of Dentistry acute abscesses and the systemic implications of endodontic infections remain to be consistently in- vestigated.1 Because the root canal devoid of pulp tissue is unable to mount an effective inflamma- tory defense against infection, the environment be- comes conducive to the establishment of bacteria that are resident as well as transient in the oral cav- ity. Thus, the possibility exists that some important human pathogens may colonize the pulpless tooth. Helicobacter pylori is a motile non-sporing micro- aerophilic curved or helical gram-negative rod that has been considered an important grastrointestinal