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Clinical Laboratory Perspective on Streptococcus halichoeri, an Unusual Nonhemolytic, Lancefield Group B Streptococcus Causing Human Infections

Year: 2021

Type: article

Abstract: S treptococcus halichoeri is a recently identifi ed mem- ber of the genus Streptococcus capable of causing pyogenic human infections.It was fi rst isolated from gray seals (Halichoerus grypus) and formally described in 2004 (1).In 2013, it was reported as the causative organism of empyema in a patient with diabetes (2).S. halichoeri differs from other pyogenic streptococci in that it is nonhemolytic and may exhibit strong catalase activity when grown in blood-containing media such as chocolate and sheep blood agar (SBA).These phenotypic characteristics, along with its colony and Gramstain morphology, may lead to its misidentifi cation as a coagulase-negative Staphylococcus.In addition, S. halichoeri is positive by Lancefi eld group B-typing assays but can be distinguished from S. agalactiae by its gamma hemolysis and negative hippurate hydrolysis results (2).A 2016 study described distinct phenotypic and genetic differences between 6 human clinical isolates and the type strain from a gray seal.The authors proposed distinct subspecies for human (S.halichoeri subspecies hominis) and grey seal isolates (S. halichoeri subsp.halichoeri) (3).Our study examined recent clinical experience with S. halichoeri as a cause of bone and joint infections in patients in the United States with underlying health conditions.We describe phenotypic, genetic, and antimicrobial susceptibility characteristics of S. halichoeri recovered from clinical specimens. Materials and Methods Bacterial IsolatesWe included in this study 45 S. halichoeri isolates from 39 patients identifi ed during 2010-2018 at ARUP Laboratories, a national clinical reference laboratory.Sixteen isolates were identifi ed by DNA sequencing and 39 by matrix-assisted laser desorption/ionization time of fl ight (MALDI-TOF) mass spectrometry.We selected 5 Clinical Laboratory Perspective on Streptococcus halichoeri, an Unusual Nonhemolytic, Lancefi eld Group B Streptococcus Causing Human Infections

Source: Emerging infectious diseases

DOI: 10.3201/eid2705.203428