Cutibacterium acnes is a Gram-positive species (Aubin et al., 2017), three subspecies and six phylotypes: C. acnes subsp. acnes (Type I: phylotypes IA1, IA2, IB, IC), C. acnes subsp. defendens (Type II: phylotype II), and C. acnes subsp. elongatum (Type III: phylotype III) (Aubin et al., 2017). This bacterium is a common commensal of the skin and is related to the pathogenesis of acne vulgaris (Aubin et al., 2017, Erbežnik et al., 2023). Historically, its pathogenicity has been restricted to skin conditions (Dréno et al., 2018). Specifically, phylotypes IB and II are associated with implant-associated infections, soft tissue infections and bacteremia (Dréno et al., 2018). On the other hand, although phylotype IA is mainly associated with acne, there are reports of its presence in prosthetic infections. In the case of phylotype III, it has been identified on the trunks (Aubin et al., 2014). However, a variety of studies have shown that this phylotype also colonizes the oral cavity, the gastrointestinal and genitourinary tract (Aubin et al., 2014). Depending on its development and growth, C. acnes has been considered to act as a pathogen or a commensal, simultaneously harboring "beneficial", "neutral" and "harmful" strains in the same host (Achermann et al., 2014).

In addition, C. acnes has been identified in culture studies of the endodontic microbiota (Fitz-Gibbon et al., 2013), specifically in persistent/secondary endodontic infections (Rôcas et al., 2011). Importantly, its relevance as an endodontic pathogen has been ignored due to its presence in the skin; nevertheless, this could lead its presence in the root canal due to health care-associated infections that occur during endodontic treatment (Niazi et al., 2010, Siqueira and Rôçac, 2009).

During the endodontic treatment, the use of sterile supplies and implements is essential, in addition to the proper use of rubber dams and, if possible, sterile gloves (Niazi, Al Kharusi, et al., 2016). These control measures are planned to prevent the entrance of microorganisms to the root canal system, causing cross-infection (Niazi, Al Kharusi, et al., 2016). Currently, there are no protocols or regulations regarding the use of sterile barriers to avoid this phenomenon, such as the mandatory use of disposable sterile surgical drapes to cover the patient's skin (Niazi, Vincer, et al., 2016). Accordingly, there are few reports of Cutibacterium spp. involved in infections. Previously, Ruffier et al., identified a bone superinfection caused by Propionibacterium namnetense (Ruffier d’Epenoux et al., 2020), which was also described in 2016 by Aubin et al., indicating that it most likely belongs to the cutaneous microbiota causing opportunistic infections (Corvec et al., 2018).

Due to the above, the aim of this study was to perform a genomic analysis of three strains of Cutibacterium spp. recovered from health care-associated endodontic infections in Chile.