Serologic Studies with Streptococci Isolated in Cases of Myasthenia Gravis

Abstract

Green-producing streptococci from the muscles, foci of infection, and nasopharynges of patients with myasthenia gravis were isolated by methods already described. 2 A carbohydrate was extracted from a number of these freshly-isolated strains by the following method:

The sedimented growth from 3 liters of dextrose-broth was treated by boiling in physiologic salt-solution for one hour and the bacteria were then removed by centrifuging. The supernatant fluid was cooled and proteins were precipitated by adding glacial acetic acid until a cloud appeared. The proteins were then removed by centrifuging and the carbohydrate was precipitated by adding 2 volumes of 95% alcohol and a small amount of sodium acetate. After a good flocculation appeared the mixture was centrifuged. The carbohydrate sediment was then dissolved in water, reprecipitated with alcohol and sodium acetate, and then redissolved in water, this procedure being carried out 5 or 6 times. The final precipitate was dried in a stream of air and dissolved in 10 cc. of physiologic salt-solution; it was then ready for use as antigen. The activity of the carbohydrate was greatest in freshly-made solutions; it decreased about one-fourth when kept at room temperature for 2 weeks.

Precipitation occurred with the carbohydrate from myasthenia gravis strains in 30% of 31 tests made with serums from 15 persons who had myasthenia gravis, in 15% of 20 tests made with serums from 11 persons having disease other than myasthenia gravis, thought to be attributable to green-producing streptococci, and in no instance in 12 tests made with the serums from 7 normal controls. Precipitation occurred with the carbohydrates from strains of green-producing streptococci isolated from persons having disease other than myasthenia gravis in 15% of 32 tests made with the serums from 15 persons who had myasthenia gravis, in 7% of 14 tests made with the serums from 11 persons having disease other than myasthenia gravis, and in no instance in 6 tests made with the serum from 6 normal controls.