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Ethics approval and consent to participateThis study was conducted according to the prin-ciples of the Declaration of Helsinki, and approved by the Juntendo University ethics committee (JHS 18-060 Juntendo University Hospital Independent Ethics Committee).Written informed consent was obtained from these patients before surgery for publication of this case report. All sequence data of the 16S rRNA sequences for metagenome analysis and two isolates in this study were deposited in the DDBJ/GenBank/EMBL database under accession number DRA007947, DRA007974 and DRA007975, respectively.Not applicable.This work was supported by Asahi Group Hold-ings, Ltd. Japan. The funders had no role in the study design, data collection and analysis, decision to publish, and preparation of the manuscript.MM and AS treated the patient. MT, TK, and AN assessed the bacteriological analysis. DM, SN, and TI assessed the microbial analysis. YF performed pathological evaluation. MM, SW, and TK drafted the manuscript and responsible for study design. All authors read and approved the final manuscript.The authors declare that they have no competing interests. infection associated with acute cholecystitis7), chronic cholecystitis8), and XGC. This study found that A. baumannii and S. capitis were present in the bile samples of two patients with XGC, suggesting that bacteria other than E. coli contribute to patho-logical changes in XGC. To our knowledge, no previous study has reported that other species of bacteria, including A. baumannii and S. capitis, contribute to XGC. Two types of nephritis patho-logically similar to XGC, xanthogranulomatous pyelonephritis and urinary malakoplakia, are caused by Enterobacteriaceae, including E. coli 9, 10). Histo-logic examination of gallbladder samples showed localized accumulation of abundant foamy macro-phages1, 9, 10), with these pathological changes induced by E. coli infection2, 3). A. baumannii is a Gram-negative, opportunistic pathogen that can survive on solid and dry surfaces for up to 5 months. A. baumannii can grow over wide ranges of temperature and pH and forms biofilms on abiotic substrates11). A. baumannii may have been present in bile when Patient 1 was admitted to the ICU.S. capitis is a coagulase-negative staphylococcus with documented potential for both human diseases and nosocomial spread12). S. capitis, which causes prosthetic valve endocarditis and joint infection12), is mainly distributed on the head (primary ears and forehead), arms and occasionally the legs13). The S. capitis isolate obtained from the Patient 2 was multidrug-resistant, suggesting that this patient must have been infected with this pathogen during in-hospital treatment with antibiotics. In addition, the procedures used during ERCP may have been responsible for the entry of this pathogen into the biliary tract.To our knowledge, this is the first report of A. baumannii and S. capitis infections in patients with XGC. Delftia and Anaerobacillus, as well as other several genera, may play a role in the histopatho-logical changes involved in progression from chronic cholecystitis to XGC. However, it is unclear whether these pathogens directly contribute to the patho-logical change of XGC. Further studies are needed to analyze the bacteriology and metagenome involved in gallbladder diseases. Metagenomic analysis is a useful tool for detection of pathogens in chronic cholecystitis such as XGC. 1) Goodman ZD, Ishak KG: Xanthogranulomatous chole-cystitis. The American journal of surgical pathology, 1981; 5: 653-9. 2) Mori M, Watanabe M, Sakuma M, Tsutsumi Y: Infec-tious etiology of xanthogranulomatous cholecystitis: immunohistochemical identification of bacterial anti-287DeclarationsConsent for publicationAvailability of data and materials AcknowledgementsFundingAuthor contributionsConflicts of interest statementReferences