Rôças, Siqueira Jr epigastric pain syndrome, with the bacterium be- ing detected exclusively in the stomach.33 Even so, it remains to be evaluated if this bacterial species occurs in necrotic root canals from patients with es- tablished gastric infection. C. pneumoniae was not detected in any endodon- tic samples either. As for its occurrence in the oral cavity, there are fewer reports as compared to H. pylori and data, while somewhat inconclusive, sug- gest that this species is not a common oral inhabit- ant. Tran et al22 did not detect C. pneumoniae in the subgingival dental plaque, whereas Huovinen et al23 identified it in oropharynx. Mantyla et al24 detected C. pneumoniae RNA in the subgingival plaque sam- ples from only 1 of 12 patients tested. Similar to the present study, Nandakumar et al25 did not find this species in samples from primary and persistent/ secondary endodontic infections using two sensitive molecular methods. Bacteria colonizing the necrotic root canal are usually members of the oral microbiota.34 Absence of both target species in endodontic samples may indicate that either they are not commonly present in the oral cavity or that the root canal environmen- tal conditions are not conducive to their establish- ment. The former is in agreement with some stud- ies mentioned above that reported absence or low prevalence of these species in the oral cavity. The latter may be related, for instance, to ecological conditions established by bacterial interactions in the endodontic bacterial community. Future stud- ies investigating the concomitant presence of these species in saliva or dental plaque and root canal in- fections may help elucidate these questions. In any circumstance, our findings make it rea- sonable to conclude that H. pylori and C. pneumoniae are not candidate endodontic pathogens and that the necrotic root canal does not serve as a reservoir for these two important human pathogens. AKcon WLEGdEMEstn This study was supported by grants from Con- selho Nacional de Desenvolvimento Científico e Tec- nológico (CNPq), and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Brazilian Governmental Institutions. April 2012 - Vol.6 ErFEErEcns 1. Fouad AF. Endodontic infections and systemic disease. In: Fouad AF, ed. Endodontic microbiology. Ames, Iowa: Wiley- Blackwell, 2009: 320-338. 2. Nguyen TN, Barkun AN, Fallone CA. Host determinants of Helicobacter pylori infection and its clinical outcome. Heli- cobacter 1999;4:185-197. 3. Shi R, Xu S, Zhang H, Ding Y, Sun G, Huang X, Chen X, Li X, Yan Z, Zhang G. Prevalence and risk factors for Helico- bacter pylori infection in Chinese populations. Helicobacter 2008;13:157-165. 4. Megraud F, Brassens-Rabbe MP, Denis F, Belbouri A, Hoa DQ. Seroepidemiology of Campylobacter pylori infection in various populations. J Clin Microbiol 1989;27:1870-1873. 5. Peek RMJ, Blaser MJ. Helicobacter pylori: pathogenesis of a "slow" bacterial infection. In: Schaechter M, Engleberg NC, Eisenstein BI, Medoff G, eds. Mechanisms of microbial disease. 3rd ed. Baltimore: Williams & Wilkins, 1998: 224- 229. 6. de Souza Goncalves L, Souto R, Colombo AP. Detection of Helicobacter pylori, Enterococcus faecalis, and Pseudomo- nas aeruginosa in the subgingival biofilm of HIV-infected subjects undergoing HAART with chronic periodontitis. Eur J Clin Microbiol Infect Dis 2009;28:1335-1342. 7. Souto R, Colombo AP. Detection of Helicobacter pylori by polymerase chain reaction in the subgingival biofilm and saliva of non-dyspeptic periodontal patients. J Periodontol 2008;79:97-103. 8. Gebara EC, Pannuti C, Faria CM, Chehter L, Mayer MP, Lima LA. Prevalence of Helicobacter pylori detected by polymerase chain reaction in the oral cavity of periodontitis patients. Oral Microbiol Immunol 2004;19:277-280. 9. Dye BA, Kruszon-Moran D, McQuillan G. The relationship between periodontal disease attributes and Helicobacter pylori infection among adults in the United States. Am J Public Health 2002;92:1809-1815. 10. Song Q, Lange T, Spahr A, Adler G, Bode G. Characteristic distribution pattern of Helicobacter pylori in dental plaque and saliva detected with nested PCR. J Med Microbiol 2000;49:349-353. 11. Riggio MP, Lennon A. Identification by PCR of Helicobacter pylori in subgingival plaque of adult periodontitis patients. J Med Microbiol 1999;48:317-322. 12. Oshowo A, Gillam D, Botha A, Tunio M, Holton J, Boulos P, Hobsley M. Helicobacter pylori: the mouth, stomach, and gut axis. Ann Periodontol 1998;3:276-280. 13. Ferguson DA, Jr., Li C, Patel NR, Mayberry WR, Chi DS, Thomas E. Isolation of Helicobacter pylori from saliva. J Clin Microbiol 1993;31:2802-2804. 161 European Journal of Dentistry