[Detection of bacterial antigens in acute pneumonia: methods of preparing the urine, serum, and pleural fluid samples for immunodiagnostic assays]. / Detecção de antígenos bacterianos em pneumonia aguda: métodos de preparação das amostras de urina, soro e líquido pleural para os testes de imunodiagnóstico.

A method of polysaccharide antigen precipitation in urine treated with 1:1 ethanol-acetone solution, followed by heat treatment with 0.1 M EDTA were developed for detection of S. pneumoniae and H. influenzae type b. Counterimmunoelectrophoresis and latex agglutination were employed to detect the antigens, in paired samples of urine and serum, and also in pleural fluid samples from children with clinical diagnosis of acute pneumonia. Counterimmunoelectrophoresis and latex agglutination showed better results in urine than in serum and also in smaller initial volumes of urine from the onset of illness or during the first days of antibiotic therapy. The results obtained in counterimmunoelectrophoresis and latex agglutination showed that ethanol-acetone solution increased the yield of polysaccharide antigen precipitation while heating with EDTA diminished the probability of false-positive results and cross-reactivity between S. pneumoniae and H. influenzae type b. The results, statistically evaluated, suggest that urine is a body fluid in which the bacterial antigens may be detected in the acute pneumonia. This is of importance in patients previously treated with antibiotics which may inhibit bacterial growth in the culture media.