title: Bacteremia due to Streptococcus tigurinus: A case report and literature review.
abstract: Gene sequence analysis methods, including 16S rRNA identification, allows accurate identification of Streptococcus species, which include phenotypically closely related species that are difficult to differentiate using conventional chemical methods. We report a case of bacteremia due to Streptococcus tigurinus, identified by 16S rRNA, in a 72-year-old woman with gastrointestinal cancer and ascites. She was hospitalized to undergo elective tumor-related surgery. Five days prior to undergoing surgery, she developed a fever with no obvious source of infection. Blood cultures identified gram-positive cocci. The patient's bacteremia was initially thought to be caused by an Enterococcus species, given her underlying gastrointestinal disease. However, alpha-hemolytic, mucoid, circular colonies were observed on sheep blood agar the following day. Although matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and biochemical testing suggested Streptococcus pneumoniae, we conducted further investigation to identify the bacterium, as the patient had no symptoms of infections usually related with S. pneumoniae such as pneumonia, meningitis, or sinusitis, and the bacteremia occurred 30 days after hospitalization. Finally, the gram-positive cocci were identified as S. tigurinus, assigned to the Streptococcus mitis group in 2012. Although the origin of infection was unclear, it was suspected that peritonitis or bacterial translocation from the gastrointestinal tract caused the bacteremia. This novel species was recently reported as being extremely pathogenic and different from other Streptococcus species. It has been reported to occur in cases of infectious endocarditis and bacteremia. In this article, we reviewed previous reports of S. tigurinus infection and summarized the clinical and pathogenetic features.
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Japan; Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan; Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Hirai
authors.affiliation: Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sakanashi
authors.affiliation: Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Mao
authors.initials: M
authors.lastname: Hagihara
authors.affiliation: Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Japan.
authors.forename: Shusaku
authors.initials: S
authors.lastname: Haranaga
authors.affiliation: Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Uechi
authors.affiliation: Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hamada
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Japan; Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan; Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Nishiyama
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Japan; Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Koizumi
authors.affiliation: Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Suematsu
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Japan; Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Yamagishi
authors.affiliation: Department of Infectious Diseases, Respiratory, and Digestive Medicine, Graduate School of Medicine, University of the Ryukyus, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Fujita
authors.affiliation: Department of Clinical Infectious Diseases, Aichi Medical University Hospital, Japan; Department of Infection Control and Prevention, Aichi Medical University Hospital, Japan. Electronic address: mikamo@aichi-med-u.ac.jp.
authors.forename: Hiroshige
authors.initials: H
authors.lastname: Mikamo
mesh_terms: D000368:Aged; D016470:Bacteremia / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D006801:Humans; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013290:Streptococcal Infections / Q000382:microbiology*; D013291:Streptococcus / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: 16S rRNA; Bacteremia; Streptococcus tigurinus