Phylum Firmicutes, Class Bacilli, Order Lactobacillales, Family Streptococcaceae, Genus Streptococcus, Streptococcus downei
Whiley et al. 1988.
Member of the "Mutans group".
Old synonym: Streptococcus mutans serotype h.
Gram-positive cocci, grouped in chains.
Colonies on 5% sucrose agar (TYC) are large, 2-3 mm in diameter, white, and conical
with an erose edge surrounded by a distinct halo. Colonies on Mitis-Salivarius agar are
small, dark blue, crinkled, up to 1 mm in diameter, with an erose edge, slightly pitting
the agar, easy to entirely remove, but hard to disperse. Growth is present at 37 ºC; no
growth at 45 ºC. No growth at pH 9.6, or in the presence of 6.5% NaCl. Variable growth
on 10% and 40% bile agar. May be non- or alpha-hemolytic.
First isolated from the dental plaque of monkeys (Macaca fascicularis); also reported isolation from human dental plaque.
May be involved in dental plaque forming. Cariogenic for germfree rats fed a high-sucrose diet.
- Robert A. Whiley and Jeremy M. Hardie, 2009. Genus I. Streptococcus Rosenbach 1884, 22AL. In: (Eds.) P.D. Vos, G. Garrity, D.
Jones, N.R. Krieg, W. Ludwig, F.A. Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3: The
Firmicutes, Springer, 655-711.
- Holt J.G., Krieg N.R., Sneath P.H.A., Staley J.T. and Williams S.T., 1994. Bergey's Manual of Determinative Bacteriology, Ninth Edition,
Williams & Wilkins, A Waverly Company, Baltimore, pp 527-558.
- Whiley R.A., Russell R.R.B., Hardie J.M. & Beighton D.: Streptococcus downei sp. nov. for strains previously described as
Streptococcus mutans serotype h. Int. J. Syst. Bacteriol., 1988, 38, 25-29.
- Beighton D, et al. The isolation of characterization of Streptococcus mutans serotype h from dental plaque of monkeys (Macaca
fascicularis). J. Gen. Microbiol. 124: 271-279, 1981.
- Sampo Lahtinen, Arthur C. Ouwehand, Seppo Salminen, Atte von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects,
Fourth Edition CRC Press, 13 dec. 2011, 128-131.
Positive results for Voges-Proskauer reaction, acid production from fructose, glucose, galactose, inulin, lactose, mannose, mannitol,
maltose, salicin, sucrose & trehalose. Extracellular polysaccharide is produced from sucrose.
Negative results for alkaline phosphatase, ammonia production from arginine, catalase, esculin, hydrolysis, hippurate hydrolysis,
starch hydrolysis, acid production from adonitol, arabinose, cellobiose, glycerol, glycogen, inositol, melezitose, melibiose, raffinose
sorbose, soluble starch, sorbitol & xylitol.
(c) Costin Stoica