Observation of viral-bacterial coinfection in abscesses may have basically 2 interpretations. Either the theory of viruses causing impaired local host defense and then favoring bacterial overgrowth might be true or occurrence of viruses is just an epiphenomenon to bacterial infection that caused inflammation with consequent influx of virus-infected inflammatory cells to the area. In a study like this with a cross-sectional design, it is not possible to define if each interpretation is true. The fact that there were 11 abscess samples

that tested negative for all target viruses may suggest that the latter explanation would be more appropriate, i.e., viruses accumulate in the lesion as infected defense cells are attracted during inflammation. These negative cases also indicate that patients who are not infected with these DNA-PK inhibitor viruses can also develop acute apical abscess, which is also in favor of the “epiphenomenon” argument. However, one might consider the possibility

that viruses other than those targeted in this study might have been present or that the highly sensitive methods used in this study may have in some way failed to detect the target viruses. Further studies are required to help clarify these important questions. As for specific viral-bacterial interactions, there were many positive albeit weak associations involving HHV-8 and HPV, the 2 most prevalent Selleckchem Luminespib viruses in this study, and the target bacterial species. The nature and consequence of these positive associations, if confirmed, requires further elucidation. Some

authors have suggested a bidirectional interaction between Immune system periodontal bacterial pathogens and herpesviruses, in which bacterial pathogens could promote herpesvirus reactivation, and this active virus infection in turn would impair host defenses and contribute to the increase in numbers and virulence of the bacterial pathogens.12 The low prevalence of the other viruses in the present study does not allow for further comparisons with most findings from periodontal studies in which some viruses, especially HCMV and EBV, have been far more prevalent. Notably, HHV-8 DNA was detected in more than one-half of the cases (54.5%), and showed a weak positive association with 7 of the target bacterial species. Occurrence of this virus in acute endodontic abscesses has been only recently reported22 and almost nothing is known about its role in the disease process. Also, studies in other areas that verified the possibility of coinfection between HHV-8 and bacterial species are scarce.44 Since its discovery, HHV-8 has been related to the development of different pathologies, such as all subtypes of Kaposi’s sarcoma, multicentric Castleman’s disease, primary effusion lymphoma, and body cavity–based lymphoma.45 Given its high prevalence in endodontic abscesses, future studies focusing on this herpesvirus are warranted.