Lung abscess caused by Streptococcus pneumoniae type 3. The importance of counterimmunoelectrophoresis in laboratory diagnosis.

We are reporting the case of an 18-month-old girl with a post-pneumonic lung abscess. The counterimmunoelectrophoresis (CIE) of the patient's urine during the bacteremic phase of the disease gave a precipitation line with pneumococcal antiserum. Later in the course of the disease, after the diagnosis of lung abscess had been established, the pus drained from the abscess gave positive reactions with pneumococcal omnivalent serum and type 3 pneumococcal antiserum. At this stage, the pus was sterile and blood cultures were negative. This case demonstrates that the CIE test is a simple procedure which gives a rapid and exact diagnosis up to the serotype level.