Pneumococcal typing by polyvalent counterimmunoelectrophoresis (PIE).

A one-step polyvalent counterimmunoelectrophoresis (PIE) method for the typing of pneumococci is describe. Only one antiserum is used (omniserum, containing antibodies to greater than 80 pneumococcal types) and it is not necessary to stock large numbers of monospecific typing sera. By observing reactions of identity between the precipitin lines produced by the pneumococcus under test, and the specific capsular polysaccharide precipitin lines in a reference pattern produced by the polyvalent pneumococcal vaccine 'Pneumovax', a cumulative percentage of 64.6% of pneumococcal types isolated could be typed. The method is simple, reproducible, inexpensive and provides a permanent stained record.