Actinomycosis as a Rare Local Manifestation of Severe Periodontitis

TLR2-dependent and independent pyroptosis in dTHP-1 cells induced by Actinomyces oris MG-1

In the immune system, the detection of pathogens through various mechanisms triggers immune responses. Several types of specific programmed cell deaths play a role in the inflammatory reaction. This study emphasizes the inflammatory response induced by Actinomycetes. Actinomyces spp. are resident bacteria in human oral plaque and often serve as a bridge for pathogenic bacteria, which lack affinity to the tooth surface, aiding their colonization of the plaque. We aim to investigate the potential role of Actinomyces oris in the early stages of oral diseases from a new perspective. Actinomyces oris MG-1 (A. oris) was chosen for this research. Differentiated THP-1 (dTHP-1) cells were transiently treated with A. oris to model the inflammatory reaction. Cell viability, as well as relative gene and protein expression levels of dTHP-1 cells, were assessed using CCK-8, quantitative real-time polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay (ELISA), and Western blot assay. The treatment decreased cell viability and increased the expression of inflammatory genes such as IL-1R1 and NLRP3. It was also observed to significantly enhance the release of IL-1β/IL-18 into the supernatant. Immunoblot analysis revealed a notable increase in the expression of N-gasdermin D persisting up to 24 h. Conversely, in models pre-treated with TLR2 inhibitors, N-gasdermin D was detectable only 12 h post-treatment and absent at 24 h. These results suggest that Actinomyces oris MG-1 induces pyroptosis in dTHP-1 cells via TLR2, but the process is not solely dependent on TLR2.

Peri-implantitis as a rare local manifestation of actinomycosis: A case report

BACKGROUND

Actinomycosis can be caused by periapical endodontic infection, trauma, or surgical dental procedures. Due to its rare occurrence in a healthy adult patient, persistent actinomycotic osteomyelitis around implants presenting as severe peri-implantitis may be challenging to diagnose.

METHODS

A 26-year-old male patient with non-contributory medical history presented to the Oral and Maxillofacial Surgery Clinic in 2018 with pain and edema associated with endodontically treated maxillary premolar teeth with poor prognosis. Oral examination revealed fair oral hygiene, heavily restored dentition, multiple carious teeth, failing restorations, endodontic treatments in both maxillary quadrants, and normal periodontal examination.

RESULTS

Two years following extractions and restoration with implants, the patient returned with a bony sequestrum and fistula in the buccal gingiva adjacent to the implants. The patient reported shifting of implants and slight change in his occlusion. Clinical, radiographic, and endodontic examinations did not demonstrate a clear origin of the fistula. A periodontist was consulted regarding the possibility of peri-implantitis and tracing of the fistula suggested intraosseous involvement of the implant surface. Flap surgery, biopsy, culture, implant removal, and surgical debridement were performed. Histologic examination revealed colonies of actinomycotic organisms and confirmed likely diagnosis of actinomycosis. The patient was placed on a long course of penicillin VK.

CONCLUSIONS

The occurrence of actinomycosis in a healthy adult patient is rare. This case report describes persistent actinomycosis presenting as osteomyelitis with severe peri-implantitis in a healthy patient, which may have been associated with a previously existing periapical endodontic infection.