The Neufeld Method of Pneumococcus Type Determination as Carried Out in a Public Health Laboratory: A Study of 760 Typings 1

As early as 1902 Neufeld (1), in Germany, noticed that when pneumo- cocci are mixed with homologous immune serum, there occurs a pronounced swelling (quellung) of the pneumococcus capsule.In 1931 and 1932, Armstrong (2) (3), in England, reported his results in typing pneumococci in sputum and mouse peritoneal exudate using a method based on this phenomenon: these results were confirmed by Logan and Smeall (4).Last year, Sabin (5) of the Bellevue Hospital, New York, reported his findings -using the Neufeld method for the typing of pneumococci in sputa.During the past 14 months this method has been used as a routine procedure at the Bacteriological Laboratory of the Massachusetts Department of Public Health-and has been found to be simple and accurate.The technic used during this period was demonstrated to us by Dr. Kenneth Goodner of the Hospital of the Rockefeller Institute.His tech- nic has been modified to the extent that plane slide preparations have been -used in preference to hanging drops.Furthermore, we have extended the Neufeld method, previously used only for the determination of Types I, II and III, to the determination of the other 29 specific types of pneumo--cocci.Our technic is as follows: upon receipt of the sputum at the laboratory, stained liquid mounts of the specimen are mixed with rabbit antisera (Types I to XXXII) used undiluted.Combinations of monovalent anti- sera (rabbit) are used instead of making thirty-two preparations of the sputum with the thirty-two monovalent sera.The combinations of sera that we use are the following: Type I A, Types II, IV, V and VII B, " III and VIII C, " IX, XI, XIII and XV D, " VIa, VIb, XVII and XVIII With the financial assistance of the Commonwealth Fund, New York.