Streptococcus azizii sp. nov., isolated from naïve weanling mice

Isolation and Characterization of a Novel Alpha-Hemolytic Streptococcus spp. from the Oral Cavity and Blood of Septicemic Periparturient Immunodeficient Mice

MISTRG is an immunodeficient mouse strain that expresses multiple human cytokines that support hematopoietic stem cell maintenance and myelopoiesis. While establishing a breeding colony of MISTRG mice in a dedicated barrier room, 6 cases of death or disease occurred in pregnant or postpartum mice. Clinically, this manifested as hunched posture, dyspnea, and 1 case of emaciation with ataxia. Pathologic analysis of 7 mice revealed multisystemic necrosuppurative inflammation variably affecting the uterus and placenta, joints, meninges, inner and middle ears, kidneys, and small intestine. Bacteria cultured from the blood of septic mice were identified with 89% probability by the Vitek 2 identification system as Streptococcus sanguinus with atypical biochemical parameters; the API 20E/NE system fully differentiated the isolates as a novel Streptococcus species. MALDI Biotyper-based mass spectrometry also indicated that the phenotype represented a novel Streptococcus spp. Sequencing revealed that the full-length 16S rRNA gene identity was below 97% with known Streptococcus species, including the 2 closest species Streptococcus acidominimus and Streptococcus azizii. We propose the name Streptococcus murisepticum spp. nov to our novel isolates. All male mice in this colony remained healthy despite their association with diseased female mice. Overall, 19% of the colony carried the novel Streptococcus in their oral cavity, but it could not be detected in feces. The organism was sensitive to amoxicillin, which was administered via drinking water throughout pregnancy and weaning to establish a colony of pathogen-negative future breeders. The colony remained disease-free and culture-negative for Streptococcus murisepticum spp. nov after treatment with amoxicillin. We suspect that oral colonization of MISTRG mice with the novel Streptococcus species and its associated unique pathology in periparturient mice is potentially the principal cause of loss of this strain at several institutions. Therefore, screening the oral cavity for α-hemolytic streptococci followed by targeted antibiotic treatment may be necessary when establishing MISTRG and allied immunodeficient mouse strains.

Vagococcus bubulae sp. nov., isolated from ground beef, and Vagococcus vulneris sp. nov., isolated from a human foot wound

Two unusual catalase-negative, Gram-stain-positive, Vagococcus-like isolates that were referred to the CDC Streptococcus Laboratory for identification are described. Strain SS1994^T was isolated from ground beef and strain SS1995^T was isolated from a human foot wound. Comparative 16S rRNA gene sequence analysis of isolates SS1994^T and SS1995^T against Vagococcus type strain sequences supported their inclusion in the genus Vagococcus. Strain SS1994^T showed high sequence similarity (>97.0 %) to the two most recently proposed species, Vagococcus martis (99.2 %) and Vagococcus teuberi (99.0 %) followed by Vagococcus penaei (98.8 %), strain SS1995^T (98.6 %), Vagococcus carniphilus (98.0 %), Vagococcus acidifermentans (98.0 %) and Vagococcus fluvialis (97.9 %). The 16S rRNA gene sequence of strain SS1995^T was most similar to V. penaei (99.1 %), followed by SS1994^T (98.6 %), V. martis (98.4 %), V. teuberi (98.1 %), V. acidifermentans (97.8 %), and both V. carniphilus and V. fluvialis (97.5 %). A polyphasic taxonomic study using conventional biochemical and the rapid ID 32 STREP system, MALDI-TOF MS, cell fatty acid analysis, pairwise sequence comparisons of the 16S rRNA, rpoA, rpoB, pheS and groL genes, and comparative core and whole genome sequence analyses revealed that strains SS1994^T and SS1995^T were two novel Vagococcus species. The novel taxonomic status of the two isolates was confirmed with core genome phylogeny, average nucleotide identity <84 % and in silico DNA-DNA hybridization <28 % to any other Vagococcus species. The names Vagococcusbubulae SS1994^T=(CCUG 70831^T=LMG 30164^T) and Vagococcusvulneris SS1995^T=(CCUG 70832^T=LMG 30165^T) are proposed.