Relation of so-called Streptococcus apis to certain Lactic Acid Streptococci

Abstract

ONE of us has previously reported the isolation, from larvae affected with European foul brood, of strains of Str. apis identical in every respect except that of gelatinolysis and caseolysis1. It has now been found that these two Str. apis strains are indistinguishable morphologically, culturally and biochemically from the well-recognized dairy types Str. glycerinaceus and Str. liquefaciens, the former being a non-proteolytic variant of the latter2,3. Thus all four types occur as diplococci and occasionally as short chains. They grow well in litmus milk at 15° and at 45° (the proteolytic Str. apis causing a break-down of the casein similar to that produced by Str. liquefaciens) ; ferment glucose, fructose, lactose, galactose, maltose, mannose, sucrose and salacin strongly; glycerol, dextrin and trehalose slightly; but not arabinose, inulin, starch, xylose, inositol, adonitol or erythritol. Sorbitol and mannitol are usually, and raffinose not usually, fermented. Aesculin is fermented to give a positive reaction with ferric chloride. In glucose broth a final pH of 4.1–4.2 is obtained. All four types also grow in bile salt lactose broth, and resist heating at 60° for 15 minutes in milk at pH 6.6.