Characterization of Streptococcus pluranimalium from a cattle with mastitis by whole genome sequencing and functional validation

BACKGROUND: Streptococcus pluranimalium is a new member of the Streptococcus genus isolated from multiple different animal hosts. It has been identified as a pathogen associated with subclinical mastitis, valvular endocarditis and septicaemia in animals. Moreover, this bacterium has emerged as a new pathogen for human infective endocarditis and brain abscess. However, the patho-biological properties of S. pluranimalium remain virtually unknown. The aim of this study was to determine the complete genome sequence of S. pluranimalium strain TH11417 isolated from a cattle with mastitis, and to characterize its antimicrobial resistance, virulence, and carbon catabolism. RESULTS: The genome of S. pluranimalium TH11417, determined by single-molecule real-time (SMRT) sequencing, consists of 2,065,522 base pair (bp) with a G + C content of 38.65%, 2,007 predicted coding sequence (CDS), 58 transfer RNA (tRNA) genes and five ribosome RNA (rRNA) operons. It contains a novel ISSpl1 element (a memeber of the IS3 family) and a Ф11417.1 prophage that carries the mef(A), msr(D) and lnu(C) genes. Consistently, our antimicrobial susceptibility test confirmed that S. pluranimalium TH11417 was resistant to erythromycin and lincomycin. However, this strain did not show virulence in murine pneumonia (intranasal inoculation, 10(7) colony forming unit – CFU) and sepsis (intraperitoneal inoculation, 10(7) CFU) models. Additionally, this strain is able to grow with glucose, lactose or galactose as the sole carbon source, and possesses a lactose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS). CONCLUSIONS: We reported the first whole genome sequence of S. pluranimalium isolated from a cattle with mastitis. It harbors a prophage carrying the mef(A), msr(D) and lnu(C) genes, and is avirulent in the murine infection model.