Phenotypic, Genotypic, and Antimicrobial Characteristics of Streptococcus halichoeri Isolates from Humans, Proposal To Rename Streptococcus halichoeri as Streptococcus halichoeri subsp. halichoeri, and Description of Streptococcus halichoeri subsp. hominis subsp. nov., a Bacterium Associated with Human Clinical Infections

Abstract

Phenotypic, genotypic, and antimicrobial characteristics of six phenotypically distinct human clinical isolates that most closely resembled the type strain of Streptococcus halichoeri isolated from a seal are presented. Sequencing of the 16S rRNA, rpoB, sodA, and recN genes; comparative whole-genome analysis; conventional biochemical and Rapid ID 32 Strep identification methods; and antimicrobial susceptibility testing were performed on the human isolates, the type strain of S. halichoeri, and type strains of closely related species. The six human clinical isolates were biochemically indistinguishable from each other and showed 100% 16S rRNA, rpoB, sodA, and recN gene sequence similarity. Comparative 16S rRNA gene sequencing analysis revealed 98.6% similarity to S. halichoeri CCUG 48324 T , 97.9% similarity to S. canis ATCC 43496 T , and 97.8% similarity to S. ictaluri ATCC BAA-1300 T . A 3,530-bp fragment of the rpoB gene was 98.8% similar to the S. halichoeri type strain, 84.6% to the S. canis type strain, and 83.8% to the S. ictaluri type strain. The S. halichoeri type strain and the human clinical isolates were susceptible to the antimicrobials tested based on CLSI guidelines for Streptococcus species viridans group with the exception of tetracycline and erythromycin. The human isolates were phenotypically distinct from the type strain isolated from a seal; comparative whole-genome sequence analysis confirmed that the human isolates were S. halichoeri. On the basis of these results, a novel subspecies, Streptococcus halichoeri subsp. hominis, is proposed for the human isolates and Streptococcus halichoeri subsp. halichoeri is proposed for the gray seal isolates. The type strain of the novel subspecies is SS1844 T ‫؍‬ CCUG 67100 T ‫؍‬ LMG 28801 T .S treptococcus halichoeri was first described in 2004 by Lawson et al.(1). The six isolates described were obtained postmortem from three gray seals in Inverness, Scotland, United Kingdom, and from three gray seals at a rehabilitation center in Cornwall, United Kingdom. Over the past 5 years, five human clinical isolates (4 blood and 1 sinus) have been received at CDC that phenotypically resembled S. halichoeri. An additional human isolate from Sweden was obtained from the Culture Collection, University of Gothenburg, Sweden (CCUG). More recently, in 2014, S. halichoeri was isolated from a 45-year-old male with empyema (2), and in 2015, a case study of S. halichoeri from a European badger with pyogranulomatous pleuropneumonia was described (3). The goal of this study was to evaluate the taxonomic status of S. halichoeri isolates associated with a human clinical source and analyze genetic and phenotypic differences for identification and potential differences in antimicrobial susceptibility patterns. Isolates with phenotypic traits resembling S. halichoeri were evaluated by 16S rRNA, rpoB, sodA, and recN gene sequencing; whole-genome sequence comparison; conventional biochemical testing; Rapid ID 32 Strep panels; and antimicrobial susceptibility patterns. MATERIALS A...

Infectious Cellulitis Caused by Streptococcus halichoeri

“…zooepidemicus, Streptococcus iniae, and Streptococcus suis, are emerging pathogens in humans. On the basis of phenotypic, genotypic and antimicrobial comparison of S. halichoeri characteristics isolated from a seal and from 6 human clinical isolates (4 from blood, 1 from osteitis and 1 from maxillary sinus), Shewmaker et al (13) proposed in a recent study that S. halichoeri should be divided into 2 subspecies; S. halichoeri subsp. hominis, for the human isolates and S. halichoeri subsp.…”

Streptococcus halichoeri: Comparative Genomics of an Emerging Pathogen

“…Findings from Nordgren et al [10] suggest a possible role for S. halichoeri in the pathogenesis of FENP. Also, two reference strains were included, one from a seal (CCUG 48324) [1] and one from human isolate (CCUG 67100) [4]. The origin of the strains and their characteristics are listed in Table 1.…”

“…In addition, several isolates have been obtained from human blood of both septicemic patients and others with unknown symptoms in the United States of America. The bacterium is hence considered an emerging pathogen that can cause serious disease in humans [4]. Subsequently, this bacterium has also been found in Steller sea lion (Eumetopias jubatus) [5] and the European badger (Meles meles) in which it was found to cause serious clinical symptoms [6].…”

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“…Streptococcus halichoeri was originally isolated from gray seals (Halichoerus grypus) in 2004 in the United Kingdom (25). Subsequent to the description of this organism, isolates that were associated with infections in humans (four from blood and one from a sinus) and that were sent to the Centers for Disease Control and Prevention (CDC) were found to be phenotypically similar to S. halichoeri (26). In 2014, an additional isolate was recovered from a man with empyema in Singapore (27).…”