syNopsIs Agglutinin titres to Haemophilus influenzae, Streptococcus pneumoniae, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Proteus vulgaris in the serum of patients with acute exacerbations of chronic bronchitis, patients producing mucoid sputum, and healthy controls were determined. Serological evidence of infection with H. influenzae was found in 38 of 57 patients with acute exacerbations, and Str. pneumoniae infection in 10 of the 57 patients, but was generally absent from healthy control subjects and from patients producing mucoid sputum. No serological evidence of infection with other organisms named above was found to be associated with exacerbations of chronic bronchitis. Ten patients with acute exacerbations were without serological evidence of infection by any of the bacteria tested.Antibody response during chronic bronchitis was studied for the purpose of guidance in antibiotic therapy, since isolations of suspected microorganisms do not produce rapid or reliable information. The problem has been investigated by several workers, and, despite the complex antigenic structure of Haemophilus influenzae, most of the earlier workers agreed that bronchitic patients had specific antibodies to this bacterium in their serum, whereas control subjects had not (Faunce, 1958;Murdoch, Leckie, Downie, Swain, and Gould, 1959;Glynn, 1959). Wilson, Dunn, and Blair (1924), studying agglutinins to H. influenzae in the sera of patients suffering from influenza and other respiratory diseases, found that 208 of 220 control sera gave negative results while infected patients had titres above 1/80. These titres were seen to subside rapidly in convalescence. May (1965) found that agglutinins at high titre were commonest in patients with purulent sputum and rare in normal subjects. Burns and May (1968) found precipitins to Streptococcus pneumoniae. May (1965) found inconsistencies in the occurrence of agglutinins and precipitins to H. influenzae, whereas Jenne, MacDonald, Lapinski, Bratberg, and Hall (1970) found that precipitin and passive haemagglutination titres reflected acute infections and exacerbations although 'Present address:

Comparison of the results of cultures from blood and sputum with those of agglutinin response in 40 cases of bacterial pneumonia and 36 controls suggests that a provisional identification of causal bacteria, for purposes of antibiotic therapy, may be made by the serological tests with much greater rapidity and comparable accuracy. A combination of these methods is recommended.