Streptococcus zooepidemicus

Streptococcus zooepidemicus is a Lancefield group C streptococcus that was first isolated in 1934 by P. R. Edwards, and named Animal pyogens A. It’s a mucosal commensal and opportunistic pathogen that infects several animals and humans, but most commonly isolated from the uterus of Mares. It’s a subspecies of Streptococcus equi, a contagious upper respiratory tract infection of horses, and shares greater than 98% DNA homology, as well as many of the same virulence factors. Streptococcus zooepidemicus are gram-positive, non-sporulating, non-motile, catalase and oxidase negative cocci. S. zooepidemicus is encapsulated, with a capsular polysaccharide containing hyaluronic acid, as well as being facultative anaerobes. The cells usually form in pairs, or as long chains. When plated on agar, colonies are usually 0.5-1.5 mm in diameter, circular, and opaque colored. They also have a smooth surface and a convex elevation. Its optimal temperature of growth is 37 degrees Celsius. Hemolysis on blood agar is beta-hemolytic. It ferments D-glucose, lactose, maltose, sucrose, salicin, D-sorbitol, and starch, but is negative for others like D-mannitol, glycerol, and inulin. S. zooepidemicus is also positive for Ala-Phe-Pro, Leucine, and Tyrosine arylamidase, all of which catalyze hydrolysis of amino acid residues from amino terminus of polypeptide chains. Antibiotic wise, S. zooepidemicus is highly susceptible to Penicillin, usually give for treatment, as well as Ampicillin and Erythromycin, but is extremely resistant to Novobiocin, Optochin, and Tribrissen. The genome of S. zooepidemicus is a single circular chromosome of 2,024,171 base pairs. The G+C content of the genome is 42.59%, very close in value to S. equi, which is at the higher end of the genus for G+C content. It has 1961 predicted protein coding sequences, with an average length of 879 base pairs each, and coding for an approximate value of 292 amino acids. These coding regions make up approximately 85% of the genome. The genome has five ribosomal RNA operons, and 57 tRNAs. The overall similarity between S. zooepidemicus and S. equi, is over 92%. S. zooepidemicus also produces a variety of extracellular proteins, about 100 genes identified so far, making up 5% of the total genome. These genes coding for extracellular proteins are slightly longer in length then others, approximately 478 amino acids each. 44 of these proteins are cell wall anchored surface proteins, which is a high number for Streptococcus species. This is one of the factors that lead to the high pathogenicity of S. zooepidemicus. Known strains include: The by-products of S. zooepidemicus fermentation is hyaluronic and lactic acid. The fermentation process is regulated by the production of hyaluronic acid. When high concentrations of the hyaluronic acid by-product are present, it will inhibit the production of more fermentation product. However, this fermentation process consumes high amounts of energy due to a number of factors. These factors include hyaluronic acid being severely limited, strong competition between hyaluronic synthesis and cell growth, and lactic acid being the main by-product of fermentation; which also will inhibit the overall fermentation process. Since hyaluronic acid is important for the virulence of S. zooepidemicus, as well as a valuable commercial production, hyaluronic acid production is constantly trying to be increased in industry and within the organism. Commercial uses for hyaluronic acid include an ingredient in cosmetics, skin filler for anti-aging and lip injections, in viscosurgery, and a lubricating substance in arthritic joints.